perf: Do the big rename: Performance Counters -> Performance Events

Bye-bye Performance Counters, welcome Performance Events!

In the past few months the perfcounters subsystem has grown out its
initial role of counting hardware events, and has become (and is
becoming) a much broader generic event enumeration, reporting, logging,
monitoring, analysis facility.

Naming its core object 'perf_counter' and naming the subsystem
'perfcounters' has become more and more of a misnomer. With pending
code like hw-breakpoints support the 'counter' name is less and
less appropriate.

All in one, we've decided to rename the subsystem to 'performance
events' and to propagate this rename through all fields, variables
and API names. (in an ABI compatible fashion)

The word 'event' is also a bit shorter than 'counter' - which makes
it slightly more convenient to write/handle as well.

Thanks goes to Stephane Eranian who first observed this misnomer and
suggested a rename.

User-space tooling and ABI compatibility is not affected - this patch
should be function-invariant. (Also, defconfigs were not touched to
keep the size down.)

This patch has been generated via the following script:

  FILES=$(find * -type f | grep -vE 'oprofile|[^K]config')

  sed -i \
    -e 's/PERF_EVENT_/PERF_RECORD_/g' \
    -e 's/PERF_COUNTER/PERF_EVENT/g' \
    -e 's/perf_counter/perf_event/g' \
    -e 's/nb_counters/nb_events/g' \
    -e 's/swcounter/swevent/g' \
    -e 's/tpcounter_event/tp_event/g' \
    $FILES

  for N in $(find . -name perf_counter.[ch]); do
    M=$(echo $N | sed 's/perf_counter/perf_event/g')
    mv $N $M
  done

  FILES=$(find . -name perf_event.*)

  sed -i \
    -e 's/COUNTER_MASK/REG_MASK/g' \
    -e 's/COUNTER/EVENT/g' \
    -e 's/\<event\>/event_id/g' \
    -e 's/counter/event/g' \
    -e 's/Counter/Event/g' \
    $FILES

... to keep it as correct as possible. This script can also be
used by anyone who has pending perfcounters patches - it converts
a Linux kernel tree over to the new naming. We tried to time this
change to the point in time where the amount of pending patches
is the smallest: the end of the merge window.

Namespace clashes were fixed up in a preparatory patch - and some
stylistic fallout will be fixed up in a subsequent patch.

( NOTE: 'counters' are still the proper terminology when we deal
  with hardware registers - and these sed scripts are a bit
  over-eager in renaming them. I've undone some of that, but
  in case there's something left where 'counter' would be
  better than 'event' we can undo that on an individual basis
  instead of touching an otherwise nicely automated patch. )

Suggested-by: Stephane Eranian <eranian@google.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Paul Mackerras <paulus@samba.org>
Reviewed-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: <linux-arch@vger.kernel.org>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5000 insertions, 0 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
new file mode 100644
index 000000000000..6e8b99a04e1e
--- /dev/null
+++ b/kernel/perf_event.c
@@ -0,0 +1,5000 @@
+/*
+ * Performance event core code
+ *
+ *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
+ *  Copyright (C) 2008-2009 Red Hat, Inc., Ingo Molnar
+ *  Copyright (C) 2008-2009 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
+ *  Copyright  ©  2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
+ *
+ *  For licensing details see kernel-base/COPYING
+ */
+
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/cpu.h>
+#include <linux/smp.h>
+#include <linux/file.h>
+#include <linux/poll.h>
+#include <linux/sysfs.h>
+#include <linux/dcache.h>
+#include <linux/percpu.h>
+#include <linux/ptrace.h>
+#include <linux/vmstat.h>
+#include <linux/hardirq.h>
+#include <linux/rculist.h>
+#include <linux/uaccess.h>
+#include <linux/syscalls.h>
+#include <linux/anon_inodes.h>
+#include <linux/kernel_stat.h>
+#include <linux/perf_event.h>
+
+#include <asm/irq_regs.h>
+
+/*
+ * Each CPU has a list of per CPU events:
+ */
+DEFINE_PER_CPU(struct perf_cpu_context, perf_cpu_context);
+
+int perf_max_events __read_mostly = 1;
+static int perf_reserved_percpu __read_mostly;
+static int perf_overcommit __read_mostly = 1;
+
+static atomic_t nr_events __read_mostly;
+static atomic_t nr_mmap_events __read_mostly;
+static atomic_t nr_comm_events __read_mostly;
+static atomic_t nr_task_events __read_mostly;
+
+/*
+ * perf event paranoia level:
+ *  -1 - not paranoid at all
+ *   0 - disallow raw tracepoint access for unpriv
+ *   1 - disallow cpu events for unpriv
+ *   2 - disallow kernel profiling for unpriv
+ */
+int sysctl_perf_event_paranoid __read_mostly = 1;
+
+static inline bool perf_paranoid_tracepoint_raw(void)
+{
+        return sysctl_perf_event_paranoid > -1;
+}
+
+static inline bool perf_paranoid_cpu(void)
+{
+        return sysctl_perf_event_paranoid > 0;
+}
+
+static inline bool perf_paranoid_kernel(void)
+{
+        return sysctl_perf_event_paranoid > 1;
+}
+
+int sysctl_perf_event_mlock __read_mostly = 512; /* 'free' kb per user */
+
+/*
+ * max perf event sample rate
+ */
+int sysctl_perf_event_sample_rate __read_mostly = 100000;
+
+static atomic64_t perf_event_id;
+
+/*
+ * Lock for (sysadmin-configurable) event reservations:
+ */
+static DEFINE_SPINLOCK(perf_resource_lock);
+
+/*
+ * Architecture provided APIs - weak aliases:
+ */
+extern __weak const struct pmu *hw_perf_event_init(struct perf_event *event)
+{
+        return NULL;
+}
+
+void __weak hw_perf_disable(void)               { barrier(); }
+void __weak hw_perf_enable(void)                { barrier(); }
+
+void __weak hw_perf_event_setup(int cpu)        { barrier(); }
+void __weak hw_perf_event_setup_online(int cpu) { barrier(); }
+
+int __weak
+hw_perf_group_sched_in(struct perf_event *group_leader,
+               struct perf_cpu_context *cpuctx,
+               struct perf_event_context *ctx, int cpu)
+{
+        return 0;
+}
+
+void __weak perf_event_print_debug(void)        { }
+
+static DEFINE_PER_CPU(int, perf_disable_count);
+
+void __perf_disable(void)
+{
+        __get_cpu_var(perf_disable_count)++;
+}
+
+bool __perf_enable(void)
+{
+        return !--__get_cpu_var(perf_disable_count);
+}
+
+void perf_disable(void)
+{
+        __perf_disable();
+        hw_perf_disable();
+}
+
+void perf_enable(void)
+{
+        if (__perf_enable())
+                hw_perf_enable();
+}
+
+static void get_ctx(struct perf_event_context *ctx)
+{
+        WARN_ON(!atomic_inc_not_zero(&ctx->refcount));
+}
+
+static void free_ctx(struct rcu_head *head)
+{
+        struct perf_event_context *ctx;
+
+        ctx = container_of(head, struct perf_event_context, rcu_head);
+        kfree(ctx);
+}
+
+static void put_ctx(struct perf_event_context *ctx)
+{
+        if (atomic_dec_and_test(&ctx->refcount)) {
+                if (ctx->parent_ctx)
+                        put_ctx(ctx->parent_ctx);
+                if (ctx->task)
+                        put_task_struct(ctx->task);
+                call_rcu(&ctx->rcu_head, free_ctx);
+        }
+}
+
+static void unclone_ctx(struct perf_event_context *ctx)
+{
+        if (ctx->parent_ctx) {
+                put_ctx(ctx->parent_ctx);
+                ctx->parent_ctx = NULL;
+        }
+}
+
+/*
+ * If we inherit events we want to return the parent event id
+ * to userspace.
+ */
+static u64 primary_event_id(struct perf_event *event)
+{
+        u64 id = event->id;
+
+        if (event->parent)
+                id = event->parent->id;
+
+        return id;
+}
+
+/*
+ * Get the perf_event_context for a task and lock it.
+ * This has to cope with with the fact that until it is locked,
+ * the context could get moved to another task.
+ */
+static struct perf_event_context *
+perf_lock_task_context(struct task_struct *task, unsigned long *flags)
+{
+        struct perf_event_context *ctx;
+
+        rcu_read_lock();
+ retry:
+        ctx = rcu_dereference(task->perf_event_ctxp);
+        if (ctx) {
+                /*
+                 * If this context is a clone of another, it might
+                 * get swapped for another underneath us by
+                 * perf_event_task_sched_out, though the
+                 * rcu_read_lock() protects us from any context
+                 * getting freed.  Lock the context and check if it
+                 * got swapped before we could get the lock, and retry
+                 * if so.  If we locked the right context, then it
+                 * can't get swapped on us any more.
+                 */
+                spin_lock_irqsave(&ctx->lock, *flags);
+                if (ctx != rcu_dereference(task->perf_event_ctxp)) {
+                        spin_unlock_irqrestore(&ctx->lock, *flags);
+                        goto retry;
+                }
+
+                if (!atomic_inc_not_zero(&ctx->refcount)) {
+                        spin_unlock_irqrestore(&ctx->lock, *flags);
+                        ctx = NULL;
+                }
+        }
+        rcu_read_unlock();
+        return ctx;
+}
+
+/*
+ * Get the context for a task and increment its pin_count so it
+ * can't get swapped to another task.  This also increments its
+ * reference count so that the context can't get freed.
+ */
+static struct perf_event_context *perf_pin_task_context(struct task_struct *task)
+{
+        struct perf_event_context *ctx;
+        unsigned long flags;
+
+        ctx = perf_lock_task_context(task, &flags);
+        if (ctx) {
+                ++ctx->pin_count;
+                spin_unlock_irqrestore(&ctx->lock, flags);
+        }
+        return ctx;
+}
+
+static void perf_unpin_context(struct perf_event_context *ctx)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&ctx->lock, flags);
+        --ctx->pin_count;
+        spin_unlock_irqrestore(&ctx->lock, flags);
+        put_ctx(ctx);
+}
+
+/*
+ * Add a event from the lists for its context.
+ * Must be called with ctx->mutex and ctx->lock held.
+ */
+static void
+list_add_event(struct perf_event *event, struct perf_event_context *ctx)
+{
+        struct perf_event *group_leader = event->group_leader;
+
+        /*
+         * Depending on whether it is a standalone or sibling event,
+         * add it straight to the context's event list, or to the group
+         * leader's sibling list:
+         */
+        if (group_leader == event)
+                list_add_tail(&event->group_entry, &ctx->group_list);
+        else {
+                list_add_tail(&event->group_entry, &group_leader->sibling_list);
+                group_leader->nr_siblings++;
+        }
+
+        list_add_rcu(&event->event_entry, &ctx->event_list);
+        ctx->nr_events++;
+        if (event->attr.inherit_stat)
+                ctx->nr_stat++;
+}
+
+/*
+ * Remove a event from the lists for its context.
+ * Must be called with ctx->mutex and ctx->lock held.
+ */
+static void
+list_del_event(struct perf_event *event, struct perf_event_context *ctx)
+{
+        struct perf_event *sibling, *tmp;
+
+        if (list_empty(&event->group_entry))
+                return;
+        ctx->nr_events--;
+        if (event->attr.inherit_stat)
+                ctx->nr_stat--;
+
+        list_del_init(&event->group_entry);
+        list_del_rcu(&event->event_entry);
+
+        if (event->group_leader != event)
+                event->group_leader->nr_siblings--;
+
+        /*
+         * If this was a group event with sibling events then
+         * upgrade the siblings to singleton events by adding them
+         * to the context list directly:
+         */
+        list_for_each_entry_safe(sibling, tmp, &event->sibling_list, group_entry) {
+
+                list_move_tail(&sibling->group_entry, &ctx->group_list);
+                sibling->group_leader = sibling;
+        }
+}
+
+static void
+event_sched_out(struct perf_event *event,
+                  struct perf_cpu_context *cpuctx,
+                  struct perf_event_context *ctx)
+{
+        if (event->state != PERF_EVENT_STATE_ACTIVE)
+                return;
+
+        event->state = PERF_EVENT_STATE_INACTIVE;
+        if (event->pending_disable) {
+                event->pending_disable = 0;
+                event->state = PERF_EVENT_STATE_OFF;
+        }
+        event->tstamp_stopped = ctx->time;
+        event->pmu->disable(event);
+        event->oncpu = -1;
+
+        if (!is_software_event(event))
+                cpuctx->active_oncpu--;
+        ctx->nr_active--;
+        if (event->attr.exclusive || !cpuctx->active_oncpu)
+                cpuctx->exclusive = 0;
+}
+
+static void
+group_sched_out(struct perf_event *group_event,
+                struct perf_cpu_context *cpuctx,
+                struct perf_event_context *ctx)
+{
+        struct perf_event *event;
+
+        if (group_event->state != PERF_EVENT_STATE_ACTIVE)
+                return;
+
+        event_sched_out(group_event, cpuctx, ctx);
+
+        /*
+         * Schedule out siblings (if any):
+         */
+        list_for_each_entry(event, &group_event->sibling_list, group_entry)
+                event_sched_out(event, cpuctx, ctx);
+
+        if (group_event->attr.exclusive)
+                cpuctx->exclusive = 0;
+}
+
+/*
+ * Cross CPU call to remove a performance event
+ *
+ * We disable the event on the hardware level first. After that we
+ * remove it from the context list.
+ */
+static void __perf_event_remove_from_context(void *info)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_event *event = info;
+        struct perf_event_context *ctx = event->ctx;
+
+        /*
+         * If this is a task context, we need to check whether it is
+         * the current task context of this cpu. If not it has been
+         * scheduled out before the smp call arrived.
+         */
+        if (ctx->task && cpuctx->task_ctx != ctx)
+                return;
+
+        spin_lock(&ctx->lock);
+        /*
+         * Protect the list operation against NMI by disabling the
+         * events on a global level.
+         */
+        perf_disable();
+
+        event_sched_out(event, cpuctx, ctx);
+
+        list_del_event(event, ctx);
+
+        if (!ctx->task) {
+                /*
+                 * Allow more per task events with respect to the
+                 * reservation:
+                 */
+                cpuctx->max_pertask =
+                        min(perf_max_events - ctx->nr_events,
+                            perf_max_events - perf_reserved_percpu);
+        }
+
+        perf_enable();
+        spin_unlock(&ctx->lock);
+}
+
+
+/*
+ * Remove the event from a task's (or a CPU's) list of events.
+ *
+ * Must be called with ctx->mutex held.
+ *
+ * CPU events are removed with a smp call. For task events we only
+ * call when the task is on a CPU.
+ *
+ * If event->ctx is a cloned context, callers must make sure that
+ * every task struct that event->ctx->task could possibly point to
+ * remains valid.  This is OK when called from perf_release since
+ * that only calls us on the top-level context, which can't be a clone.
+ * When called from perf_event_exit_task, it's OK because the
+ * context has been detached from its task.
+ */
+static void perf_event_remove_from_context(struct perf_event *event)
+{
+        struct perf_event_context *ctx = event->ctx;
+        struct task_struct *task = ctx->task;
+
+        if (!task) {
+                /*
+                 * Per cpu events are removed via an smp call and
+                 * the removal is always sucessful.
+                 */
+                smp_call_function_single(event->cpu,
+                                         __perf_event_remove_from_context,
+                                         event, 1);
+                return;
+        }
+
+retry:
+        task_oncpu_function_call(task, __perf_event_remove_from_context,
+                                 event);
+
+        spin_lock_irq(&ctx->lock);
+        /*
+         * If the context is active we need to retry the smp call.
+         */
+        if (ctx->nr_active && !list_empty(&event->group_entry)) {
+                spin_unlock_irq(&ctx->lock);
+                goto retry;
+        }
+
+        /*
+         * The lock prevents that this context is scheduled in so we
+         * can remove the event safely, if the call above did not
+         * succeed.
+         */
+        if (!list_empty(&event->group_entry)) {
+                list_del_event(event, ctx);
+        }
+        spin_unlock_irq(&ctx->lock);
+}
+
+static inline u64 perf_clock(void)
+{
+        return cpu_clock(smp_processor_id());
+}
+
+/*
+ * Update the record of the current time in a context.
+ */
+static void update_context_time(struct perf_event_context *ctx)
+{
+        u64 now = perf_clock();
+
+        ctx->time += now - ctx->timestamp;
+        ctx->timestamp = now;
+}
+
+/*
+ * Update the total_time_enabled and total_time_running fields for a event.
+ */
+static void update_event_times(struct perf_event *event)
+{
+        struct perf_event_context *ctx = event->ctx;
+        u64 run_end;
+
+        if (event->state < PERF_EVENT_STATE_INACTIVE ||
+            event->group_leader->state < PERF_EVENT_STATE_INACTIVE)
+                return;
+
+        event->total_time_enabled = ctx->time - event->tstamp_enabled;
+
+        if (event->state == PERF_EVENT_STATE_INACTIVE)
+                run_end = event->tstamp_stopped;
+        else
+                run_end = ctx->time;
+
+        event->total_time_running = run_end - event->tstamp_running;
+}
+
+/*
+ * Update total_time_enabled and total_time_running for all events in a group.
+ */
+static void update_group_times(struct perf_event *leader)
+{
+        struct perf_event *event;
+
+        update_event_times(leader);
+        list_for_each_entry(event, &leader->sibling_list, group_entry)
+                update_event_times(event);
+}
+
+/*
+ * Cross CPU call to disable a performance event
+ */
+static void __perf_event_disable(void *info)
+{
+        struct perf_event *event = info;
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_event_context *ctx = event->ctx;
+
+        /*
+         * If this is a per-task event, need to check whether this
+         * event's task is the current task on this cpu.
+         */
+        if (ctx->task && cpuctx->task_ctx != ctx)
+                return;
+
+        spin_lock(&ctx->lock);
+
+        /*
+         * If the event is on, turn it off.
+         * If it is in error state, leave it in error state.
+         */
+        if (event->state >= PERF_EVENT_STATE_INACTIVE) {
+                update_context_time(ctx);
+                update_group_times(event);
+                if (event == event->group_leader)
+                        group_sched_out(event, cpuctx, ctx);
+                else
+                        event_sched_out(event, cpuctx, ctx);
+                event->state = PERF_EVENT_STATE_OFF;
+        }
+
+        spin_unlock(&ctx->lock);
+}
+
+/*
+ * Disable a event.
+ *
+ * If event->ctx is a cloned context, callers must make sure that
+ * every task struct that event->ctx->task could possibly point to
+ * remains valid.  This condition is satisifed when called through
+ * perf_event_for_each_child or perf_event_for_each because they
+ * hold the top-level event's child_mutex, so any descendant that
+ * goes to exit will block in sync_child_event.
+ * When called from perf_pending_event it's OK because event->ctx
+ * is the current context on this CPU and preemption is disabled,
+ * hence we can't get into perf_event_task_sched_out for this context.
+ */
+static void perf_event_disable(struct perf_event *event)
+{
+        struct perf_event_context *ctx = event->ctx;
+        struct task_struct *task = ctx->task;
+
+        if (!task) {
+                /*
+                 * Disable the event on the cpu that it's on
+                 */
+                smp_call_function_single(event->cpu, __perf_event_disable,
+                                         event, 1);
+                return;
+        }
+
+ retry:
+        task_oncpu_function_call(task, __perf_event_disable, event);
+
+        spin_lock_irq(&ctx->lock);
+        /*
+         * If the event is still active, we need to retry the cross-call.
+         */
+        if (event->state == PERF_EVENT_STATE_ACTIVE) {
+                spin_unlock_irq(&ctx->lock);
+                goto retry;
+        }
+
+        /*
+         * Since we have the lock this context can't be scheduled
+         * in, so we can change the state safely.
+         */
+        if (event->state == PERF_EVENT_STATE_INACTIVE) {
+                update_group_times(event);
+                event->state = PERF_EVENT_STATE_OFF;
+        }
+
+        spin_unlock_irq(&ctx->lock);
+}
+
+static int
+event_sched_in(struct perf_event *event,
+                 struct perf_cpu_context *cpuctx,
+                 struct perf_event_context *ctx,
+                 int cpu)
+{
+        if (event->state <= PERF_EVENT_STATE_OFF)
+                return 0;
+
+        event->state = PERF_EVENT_STATE_ACTIVE;
+        event->oncpu = cpu;     /* TODO: put 'cpu' into cpuctx->cpu */
+        /*
+         * The new state must be visible before we turn it on in the hardware:
+         */
+        smp_wmb();
+
+        if (event->pmu->enable(event)) {
+                event->state = PERF_EVENT_STATE_INACTIVE;
+                event->oncpu = -1;
+                return -EAGAIN;
+        }
+
+        event->tstamp_running += ctx->time - event->tstamp_stopped;
+
+        if (!is_software_event(event))
+                cpuctx->active_oncpu++;
+        ctx->nr_active++;
+
+        if (event->attr.exclusive)
+                cpuctx->exclusive = 1;
+
+        return 0;
+}
+
+static int
+group_sched_in(struct perf_event *group_event,
+               struct perf_cpu_context *cpuctx,
+               struct perf_event_context *ctx,
+               int cpu)
+{
+        struct perf_event *event, *partial_group;
+        int ret;
+
+        if (group_event->state == PERF_EVENT_STATE_OFF)
+                return 0;
+
+        ret = hw_perf_group_sched_in(group_event, cpuctx, ctx, cpu);
+        if (ret)
+                return ret < 0 ? ret : 0;
+
+        if (event_sched_in(group_event, cpuctx, ctx, cpu))
+                return -EAGAIN;
+
+        /*
+         * Schedule in siblings as one group (if any):
+         */
+        list_for_each_entry(event, &group_event->sibling_list, group_entry) {
+                if (event_sched_in(event, cpuctx, ctx, cpu)) {
+                        partial_group = event;
+                        goto group_error;
+                }
+        }
+
+        return 0;
+
+group_error:
+        /*
+         * Groups can be scheduled in as one unit only, so undo any
+         * partial group before returning:
+         */
+        list_for_each_entry(event, &group_event->sibling_list, group_entry) {
+                if (event == partial_group)
+                        break;
+                event_sched_out(event, cpuctx, ctx);
+        }
+        event_sched_out(group_event, cpuctx, ctx);
+
+        return -EAGAIN;
+}
+
+/*
+ * Return 1 for a group consisting entirely of software events,
+ * 0 if the group contains any hardware events.
+ */
+static int is_software_only_group(struct perf_event *leader)
+{
+        struct perf_event *event;
+
+        if (!is_software_event(leader))
+                return 0;
+
+        list_for_each_entry(event, &leader->sibling_list, group_entry)
+                if (!is_software_event(event))
+                        return 0;
+
+        return 1;
+}
+
+/*
+ * Work out whether we can put this event group on the CPU now.
+ */
+static int group_can_go_on(struct perf_event *event,
+                           struct perf_cpu_context *cpuctx,
+                           int can_add_hw)
+{
+        /*
+         * Groups consisting entirely of software events can always go on.
+         */
+        if (is_software_only_group(event))
+                return 1;
+        /*
+         * If an exclusive group is already on, no other hardware
+         * events can go on.
+         */
+        if (cpuctx->exclusive)
+                return 0;
+        /*
+         * If this group is exclusive and there are already
+         * events on the CPU, it can't go on.
+         */
+        if (event->attr.exclusive && cpuctx->active_oncpu)
+                return 0;
+        /*
+         * Otherwise, try to add it if all previous groups were able
+         * to go on.
+         */
+        return can_add_hw;
+}
+
+static void add_event_to_ctx(struct perf_event *event,
+                               struct perf_event_context *ctx)
+{
+        list_add_event(event, ctx);
+        event->tstamp_enabled = ctx->time;
+        event->tstamp_running = ctx->time;
+        event->tstamp_stopped = ctx->time;
+}
+
+/*
+ * Cross CPU call to install and enable a performance event
+ *
+ * Must be called with ctx->mutex held
+ */
+static void __perf_install_in_context(void *info)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_event *event = info;
+        struct perf_event_context *ctx = event->ctx;
+        struct perf_event *leader = event->group_leader;
+        int cpu = smp_processor_id();
+        int err;
+
+        /*
+         * If this is a task context, we need to check whether it is
+         * the current task context of this cpu. If not it has been
+         * scheduled out before the smp call arrived.
+         * Or possibly this is the right context but it isn't
+         * on this cpu because it had no events.
+         */
+        if (ctx->task && cpuctx->task_ctx != ctx) {
+                if (cpuctx->task_ctx || ctx->task != current)
+                        return;
+                cpuctx->task_ctx = ctx;
+        }
+
+        spin_lock(&ctx->lock);
+        ctx->is_active = 1;
+        update_context_time(ctx);
+
+        /*
+         * Protect the list operation against NMI by disabling the
+         * events on a global level. NOP for non NMI based events.
+         */
+        perf_disable();
+
+        add_event_to_ctx(event, ctx);
+
+        /*
+         * Don't put the event on if it is disabled or if
+         * it is in a group and the group isn't on.
+         */
+        if (event->state != PERF_EVENT_STATE_INACTIVE ||
+            (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE))
+                goto unlock;
+
+        /*
+         * An exclusive event can't go on if there are already active
+         * hardware events, and no hardware event can go on if there
+         * is already an exclusive event on.
+         */
+        if (!group_can_go_on(event, cpuctx, 1))
+                err = -EEXIST;
+        else
+                err = event_sched_in(event, cpuctx, ctx, cpu);
+
+        if (err) {
+                /*
+                 * This event couldn't go on.  If it is in a group
+                 * then we have to pull the whole group off.
+                 * If the event group is pinned then put it in error state.
+                 */
+                if (leader != event)
+                        group_sched_out(leader, cpuctx, ctx);
+                if (leader->attr.pinned) {
+                        update_group_times(leader);
+                        leader->state = PERF_EVENT_STATE_ERROR;
+                }
+        }
+
+        if (!err && !ctx->task && cpuctx->max_pertask)
+                cpuctx->max_pertask--;
+
+ unlock:
+        perf_enable();
+
+        spin_unlock(&ctx->lock);
+}
+
+/*
+ * Attach a performance event to a context
+ *
+ * First we add the event to the list with the hardware enable bit
+ * in event->hw_config cleared.
+ *
+ * If the event is attached to a task which is on a CPU we use a smp
+ * call to enable it in the task context. The task might have been
+ * scheduled away, but we check this in the smp call again.
+ *
+ * Must be called with ctx->mutex held.
+ */
+static void
+perf_install_in_context(struct perf_event_context *ctx,
+                        struct perf_event *event,
+                        int cpu)
+{
+        struct task_struct *task = ctx->task;
+
+        if (!task) {
+                /*
+                 * Per cpu events are installed via an smp call and
+                 * the install is always sucessful.
+                 */
+                smp_call_function_single(cpu, __perf_install_in_context,
+                                         event, 1);
+                return;
+        }
+
+retry:
+        task_oncpu_function_call(task, __perf_install_in_context,
+                                 event);
+
+        spin_lock_irq(&ctx->lock);
+        /*
+         * we need to retry the smp call.
+         */
+        if (ctx->is_active && list_empty(&event->group_entry)) {
+                spin_unlock_irq(&ctx->lock);
+                goto retry;
+        }
+
+        /*
+         * The lock prevents that this context is scheduled in so we
+         * can add the event safely, if it the call above did not
+         * succeed.
+         */
+        if (list_empty(&event->group_entry))
+                add_event_to_ctx(event, ctx);
+        spin_unlock_irq(&ctx->lock);
+}
+
+/*
+ * Put a event into inactive state and update time fields.
+ * Enabling the leader of a group effectively enables all
+ * the group members that aren't explicitly disabled, so we
+ * have to update their ->tstamp_enabled also.
+ * Note: this works for group members as well as group leaders
+ * since the non-leader members' sibling_lists will be empty.
+ */
+static void __perf_event_mark_enabled(struct perf_event *event,
+                                        struct perf_event_context *ctx)
+{
+        struct perf_event *sub;
+
+        event->state = PERF_EVENT_STATE_INACTIVE;
+        event->tstamp_enabled = ctx->time - event->total_time_enabled;
+        list_for_each_entry(sub, &event->sibling_list, group_entry)
+                if (sub->state >= PERF_EVENT_STATE_INACTIVE)
+                        sub->tstamp_enabled =
+                                ctx->time - sub->total_time_enabled;
+}
+
+/*
+ * Cross CPU call to enable a performance event
+ */
+static void __perf_event_enable(void *info)
+{
+        struct perf_event *event = info;
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_event_context *ctx = event->ctx;
+        struct perf_event *leader = event->group_leader;
+        int err;
+
+        /*
+         * If this is a per-task event, need to check whether this
+         * event's task is the current task on this cpu.
+         */
+        if (ctx->task && cpuctx->task_ctx != ctx) {
+                if (cpuctx->task_ctx || ctx->task != current)
+                        return;
+                cpuctx->task_ctx = ctx;
+        }
+
+        spin_lock(&ctx->lock);
+        ctx->is_active = 1;
+        update_context_time(ctx);
+
+        if (event->state >= PERF_EVENT_STATE_INACTIVE)
+                goto unlock;
+        __perf_event_mark_enabled(event, ctx);
+
+        /*
+         * If the event is in a group and isn't the group leader,
+         * then don't put it on unless the group is on.
+         */
+        if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE)
+                goto unlock;
+
+        if (!group_can_go_on(event, cpuctx, 1)) {
+                err = -EEXIST;
+        } else {
+                perf_disable();
+                if (event == leader)
+                        err = group_sched_in(event, cpuctx, ctx,
+                                             smp_processor_id());
+                else
+                        err = event_sched_in(event, cpuctx, ctx,
+                                               smp_processor_id());
+                perf_enable();
+        }
+
+        if (err) {
+                /*
+                 * If this event can't go on and it's part of a
+                 * group, then the whole group has to come off.
+                 */
+                if (leader != event)
+                        group_sched_out(leader, cpuctx, ctx);
+                if (leader->attr.pinned) {
+                        update_group_times(leader);
+                        leader->state = PERF_EVENT_STATE_ERROR;
+                }
+        }
+
+ unlock:
+        spin_unlock(&ctx->lock);
+}
+
+/*
+ * Enable a event.
+ *
+ * If event->ctx is a cloned context, callers must make sure that
+ * every task struct that event->ctx->task could possibly point to
+ * remains valid.  This condition is satisfied when called through
+ * perf_event_for_each_child or perf_event_for_each as described
+ * for perf_event_disable.
+ */
+static void perf_event_enable(struct perf_event *event)
+{
+        struct perf_event_context *ctx = event->ctx;
+        struct task_struct *task = ctx->task;
+
+        if (!task) {
+                /*
+                 * Enable the event on the cpu that it's on
+                 */
+                smp_call_function_single(event->cpu, __perf_event_enable,
+                                         event, 1);
+                return;
+        }
+
+        spin_lock_irq(&ctx->lock);
+        if (event->state >= PERF_EVENT_STATE_INACTIVE)
+                goto out;
+
+        /*
+         * If the event is in error state, clear that first.
+         * That way, if we see the event in error state below, we
+         * know that it has gone back into error state, as distinct
+         * from the task having been scheduled away before the
+         * cross-call arrived.
+         */
+        if (event->state == PERF_EVENT_STATE_ERROR)
+                event->state = PERF_EVENT_STATE_OFF;
+
+ retry:
+        spin_unlock_irq(&ctx->lock);
+        task_oncpu_function_call(task, __perf_event_enable, event);
+
+        spin_lock_irq(&ctx->lock);
+
+        /*
+         * If the context is active and the event is still off,
+         * we need to retry the cross-call.
+         */
+        if (ctx->is_active && event->state == PERF_EVENT_STATE_OFF)
+                goto retry;
+
+        /*
+         * Since we have the lock this context can't be scheduled
+         * in, so we can change the state safely.
+         */
+        if (event->state == PERF_EVENT_STATE_OFF)
+                __perf_event_mark_enabled(event, ctx);
+
+ out:
+        spin_unlock_irq(&ctx->lock);
+}
+
+static int perf_event_refresh(struct perf_event *event, int refresh)
+{
+        /*
+         * not supported on inherited events
+         */
+        if (event->attr.inherit)
+                return -EINVAL;
+
+        atomic_add(refresh, &event->event_limit);
+        perf_event_enable(event);
+
+        return 0;
+}
+
+void __perf_event_sched_out(struct perf_event_context *ctx,
+                              struct perf_cpu_context *cpuctx)
+{
+        struct perf_event *event;
+
+        spin_lock(&ctx->lock);
+        ctx->is_active = 0;
+        if (likely(!ctx->nr_events))
+                goto out;
+        update_context_time(ctx);
+
+        perf_disable();
+        if (ctx->nr_active) {
+                list_for_each_entry(event, &ctx->group_list, group_entry) {
+                        if (event != event->group_leader)
+                                event_sched_out(event, cpuctx, ctx);
+                        else
+                                group_sched_out(event, cpuctx, ctx);
+                }
+        }
+        perf_enable();
+ out:
+        spin_unlock(&ctx->lock);
+}
+
+/*
+ * Test whether two contexts are equivalent, i.e. whether they
+ * have both been cloned from the same version of the same context
+ * and they both have the same number of enabled events.
+ * If the number of enabled events is the same, then the set
+ * of enabled events should be the same, because these are both
+ * inherited contexts, therefore we can't access individual events
+ * in them directly with an fd; we can only enable/disable all
+ * events via prctl, or enable/disable all events in a family
+ * via ioctl, which will have the same effect on both contexts.
+ */
+static int context_equiv(struct perf_event_context *ctx1,
+                         struct perf_event_context *ctx2)
+{
+        return ctx1->parent_ctx && ctx1->parent_ctx == ctx2->parent_ctx
+                && ctx1->parent_gen == ctx2->parent_gen
+                && !ctx1->pin_count && !ctx2->pin_count;
+}
+
+static void __perf_event_read(void *event);
+
+static void __perf_event_sync_stat(struct perf_event *event,
+                                     struct perf_event *next_event)
+{
+        u64 value;
+
+        if (!event->attr.inherit_stat)
+                return;
+
+        /*
+         * Update the event value, we cannot use perf_event_read()
+         * because we're in the middle of a context switch and have IRQs
+         * disabled, which upsets smp_call_function_single(), however
+         * we know the event must be on the current CPU, therefore we
+         * don't need to use it.
+         */
+        switch (event->state) {
+        case PERF_EVENT_STATE_ACTIVE:
+                __perf_event_read(event);
+                break;
+
+        case PERF_EVENT_STATE_INACTIVE:
+                update_event_times(event);
+                break;
+
+        default:
+                break;
+        }
+
+        /*
+         * In order to keep per-task stats reliable we need to flip the event
+         * values when we flip the contexts.
+         */
+        value = atomic64_read(&next_event->count);
+        value = atomic64_xchg(&event->count, value);
+        atomic64_set(&next_event->count, value);
+
+        swap(event->total_time_enabled, next_event->total_time_enabled);
+        swap(event->total_time_running, next_event->total_time_running);
+
+        /*
+         * Since we swizzled the values, update the user visible data too.
+         */
+        perf_event_update_userpage(event);
+        perf_event_update_userpage(next_event);
+}
+
+#define list_next_entry(pos, member) \
+        list_entry(pos->member.next, typeof(*pos), member)
+
+static void perf_event_sync_stat(struct perf_event_context *ctx,
+                                   struct perf_event_context *next_ctx)
+{
+        struct perf_event *event, *next_event;
+
+        if (!ctx->nr_stat)
+                return;
+
+        event = list_first_entry(&ctx->event_list,
+                                   struct perf_event, event_entry);
+
+        next_event = list_first_entry(&next_ctx->event_list,
+                                        struct perf_event, event_entry);
+
+        while (&event->event_entry != &ctx->event_list &&
+               &next_event->event_entry != &next_ctx->event_list) {
+
+                __perf_event_sync_stat(event, next_event);
+
+                event = list_next_entry(event, event_entry);
+                next_event = list_next_entry(next_event, event_entry);
+        }
+}
+
+/*
+ * Called from scheduler to remove the events of the current task,
+ * with interrupts disabled.
+ *
+ * We stop each event and update the event value in event->count.
+ *
+ * This does not protect us against NMI, but disable()
+ * sets the disabled bit in the control field of event _before_
+ * accessing the event control register. If a NMI hits, then it will
+ * not restart the event.
+ */
+void perf_event_task_sched_out(struct task_struct *task,
+                                 struct task_struct *next, int cpu)
+{
+        struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
+        struct perf_event_context *ctx = task->perf_event_ctxp;
+        struct perf_event_context *next_ctx;
+        struct perf_event_context *parent;
+        struct pt_regs *regs;
+        int do_switch = 1;
+
+        regs = task_pt_regs(task);
+        perf_sw_event(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, 1, regs, 0);
+
+        if (likely(!ctx || !cpuctx->task_ctx))
+                return;
+
+        update_context_time(ctx);
+
+        rcu_read_lock();
+        parent = rcu_dereference(ctx->parent_ctx);
+        next_ctx = next->perf_event_ctxp;
+        if (parent && next_ctx &&
+            rcu_dereference(next_ctx->parent_ctx) == parent) {
+                /*
+                 * Looks like the two contexts are clones, so we might be
+                 * able to optimize the context switch.  We lock both
+                 * contexts and check that they are clones under the
+                 * lock (including re-checking that neither has been
+                 * uncloned in the meantime).  It doesn't matter which
+                 * order we take the locks because no other cpu could
+                 * be trying to lock both of these tasks.
+                 */
+                spin_lock(&ctx->lock);
+                spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING);
+                if (context_equiv(ctx, next_ctx)) {
+                        /*
+                         * XXX do we need a memory barrier of sorts
+                         * wrt to rcu_dereference() of perf_event_ctxp
+                         */
+                        task->perf_event_ctxp = next_ctx;
+                        next->perf_event_ctxp = ctx;
+                        ctx->task = next;
+                        next_ctx->task = task;
+                        do_switch = 0;
+
+                        perf_event_sync_stat(ctx, next_ctx);
+                }
+                spin_unlock(&next_ctx->lock);
+                spin_unlock(&ctx->lock);
+        }
+        rcu_read_unlock();
+
+        if (do_switch) {
+                __perf_event_sched_out(ctx, cpuctx);
+                cpuctx->task_ctx = NULL;
+        }
+}
+
+/*
+ * Called with IRQs disabled
+ */
+static void __perf_event_task_sched_out(struct perf_event_context *ctx)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+
+        if (!cpuctx->task_ctx)
+                return;
+
+        if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
+                return;
+
+        __perf_event_sched_out(ctx, cpuctx);
+        cpuctx->task_ctx = NULL;
+}
+
+/*
+ * Called with IRQs disabled
+ */
+static void perf_event_cpu_sched_out(struct perf_cpu_context *cpuctx)
+{
+        __perf_event_sched_out(&cpuctx->ctx, cpuctx);
+}
+
+static void
+__perf_event_sched_in(struct perf_event_context *ctx,
+                        struct perf_cpu_context *cpuctx, int cpu)
+{
+        struct perf_event *event;
+        int can_add_hw = 1;
+
+        spin_lock(&ctx->lock);
+        ctx->is_active = 1;
+        if (likely(!ctx->nr_events))
+                goto out;
+
+        ctx->timestamp = perf_clock();
+
+        perf_disable();
+
+        /*
+         * First go through the list and put on any pinned groups
+         * in order to give them the best chance of going on.
+         */
+        list_for_each_entry(event, &ctx->group_list, group_entry) {
+                if (event->state <= PERF_EVENT_STATE_OFF ||
+                    !event->attr.pinned)
+                        continue;
+                if (event->cpu != -1 && event->cpu != cpu)
+                        continue;
+
+                if (event != event->group_leader)
+                        event_sched_in(event, cpuctx, ctx, cpu);
+                else {
+                        if (group_can_go_on(event, cpuctx, 1))
+                                group_sched_in(event, cpuctx, ctx, cpu);
+                }
+
+                /*
+                 * If this pinned group hasn't been scheduled,
+                 * put it in error state.
+                 */
+                if (event->state == PERF_EVENT_STATE_INACTIVE) {
+                        update_group_times(event);
+                        event->state = PERF_EVENT_STATE_ERROR;
+                }
+        }
+
+        list_for_each_entry(event, &ctx->group_list, group_entry) {
+                /*
+                 * Ignore events in OFF or ERROR state, and
+                 * ignore pinned events since we did them already.
+                 */
+                if (event->state <= PERF_EVENT_STATE_OFF ||
+                    event->attr.pinned)
+                        continue;
+
+                /*
+                 * Listen to the 'cpu' scheduling filter constraint
+                 * of events:
+                 */
+                if (event->cpu != -1 && event->cpu != cpu)
+                        continue;
+
+                if (event != event->group_leader) {
+                        if (event_sched_in(event, cpuctx, ctx, cpu))
+                                can_add_hw = 0;
+                } else {
+                        if (group_can_go_on(event, cpuctx, can_add_hw)) {
+                                if (group_sched_in(event, cpuctx, ctx, cpu))
+                                        can_add_hw = 0;
+                        }
+                }
+        }
+        perf_enable();
+ out:
+        spin_unlock(&ctx->lock);
+}
+
+/*
+ * Called from scheduler to add the events of the current task
+ * with interrupts disabled.
+ *
+ * We restore the event value and then enable it.
+ *
+ * This does not protect us against NMI, but enable()
+ * sets the enabled bit in the control field of event _before_
+ * accessing the event control register. If a NMI hits, then it will
+ * keep the event running.
+ */
+void perf_event_task_sched_in(struct task_struct *task, int cpu)
+{
+        struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
+        struct perf_event_context *ctx = task->perf_event_ctxp;
+
+        if (likely(!ctx))
+                return;
+        if (cpuctx->task_ctx == ctx)
+                return;
+        __perf_event_sched_in(ctx, cpuctx, cpu);
+        cpuctx->task_ctx = ctx;
+}
+
+static void perf_event_cpu_sched_in(struct perf_cpu_context *cpuctx, int cpu)
+{
+        struct perf_event_context *ctx = &cpuctx->ctx;
+
+        __perf_event_sched_in(ctx, cpuctx, cpu);
+}
+
+#define MAX_INTERRUPTS (~0ULL)
+
+static void perf_log_throttle(struct perf_event *event, int enable);
+
+static void perf_adjust_period(struct perf_event *event, u64 events)
+{
+        struct hw_perf_event *hwc = &event->hw;
+        u64 period, sample_period;
+        s64 delta;
+
+        events *= hwc->sample_period;
+        period = div64_u64(events, event->attr.sample_freq);
+
+        delta = (s64)(period - hwc->sample_period);
+        delta = (delta + 7) / 8; /* low pass filter */
+
+        sample_period = hwc->sample_period + delta;
+
+        if (!sample_period)
+                sample_period = 1;
+
+        hwc->sample_period = sample_period;
+}
+
+static void perf_ctx_adjust_freq(struct perf_event_context *ctx)
+{
+        struct perf_event *event;
+        struct hw_perf_event *hwc;
+        u64 interrupts, freq;
+
+        spin_lock(&ctx->lock);
+        list_for_each_entry(event, &ctx->group_list, group_entry) {
+                if (event->state != PERF_EVENT_STATE_ACTIVE)
+                        continue;
+
+                hwc = &event->hw;
+
+                interrupts = hwc->interrupts;
+                hwc->interrupts = 0;
+
+                /*
+                 * unthrottle events on the tick
+                 */
+                if (interrupts == MAX_INTERRUPTS) {
+                        perf_log_throttle(event, 1);
+                        event->pmu->unthrottle(event);
+                        interrupts = 2*sysctl_perf_event_sample_rate/HZ;
+                }
+
+                if (!event->attr.freq || !event->attr.sample_freq)
+                        continue;
+
+                /*
+                 * if the specified freq < HZ then we need to skip ticks
+                 */
+                if (event->attr.sample_freq < HZ) {
+                        freq = event->attr.sample_freq;
+
+                        hwc->freq_count += freq;
+                        hwc->freq_interrupts += interrupts;
+
+                        if (hwc->freq_count < HZ)
+                                continue;
+
+                        interrupts = hwc->freq_interrupts;
+                        hwc->freq_interrupts = 0;
+                        hwc->freq_count -= HZ;
+                } else
+                        freq = HZ;
+
+                perf_adjust_period(event, freq * interrupts);
+
+                /*
+                 * In order to avoid being stalled by an (accidental) huge
+                 * sample period, force reset the sample period if we didn't
+                 * get any events in this freq period.
+                 */
+                if (!interrupts) {
+                        perf_disable();
+                        event->pmu->disable(event);
+                        atomic64_set(&hwc->period_left, 0);
+                        event->pmu->enable(event);
+                        perf_enable();
+                }
+        }
+        spin_unlock(&ctx->lock);
+}
+
+/*
+ * Round-robin a context's events:
+ */
+static void rotate_ctx(struct perf_event_context *ctx)
+{
+        struct perf_event *event;
+
+        if (!ctx->nr_events)
+                return;
+
+        spin_lock(&ctx->lock);
+        /*
+         * Rotate the first entry last (works just fine for group events too):
+         */
+        perf_disable();
+        list_for_each_entry(event, &ctx->group_list, group_entry) {
+                list_move_tail(&event->group_entry, &ctx->group_list);
+                break;
+        }
+        perf_enable();
+
+        spin_unlock(&ctx->lock);
+}
+
+void perf_event_task_tick(struct task_struct *curr, int cpu)
+{
+        struct perf_cpu_context *cpuctx;
+        struct perf_event_context *ctx;
+
+        if (!atomic_read(&nr_events))
+                return;
+
+        cpuctx = &per_cpu(perf_cpu_context, cpu);
+        ctx = curr->perf_event_ctxp;
+
+        perf_ctx_adjust_freq(&cpuctx->ctx);
+        if (ctx)
+                perf_ctx_adjust_freq(ctx);
+
+        perf_event_cpu_sched_out(cpuctx);
+        if (ctx)
+                __perf_event_task_sched_out(ctx);
+
+        rotate_ctx(&cpuctx->ctx);
+        if (ctx)
+                rotate_ctx(ctx);
+
+        perf_event_cpu_sched_in(cpuctx, cpu);
+        if (ctx)
+                perf_event_task_sched_in(curr, cpu);
+}
+
+/*
+ * Enable all of a task's events that have been marked enable-on-exec.
+ * This expects task == current.
+ */
+static void perf_event_enable_on_exec(struct task_struct *task)
+{
+        struct perf_event_context *ctx;
+        struct perf_event *event;
+        unsigned long flags;
+        int enabled = 0;
+
+        local_irq_save(flags);
+        ctx = task->perf_event_ctxp;
+        if (!ctx || !ctx->nr_events)
+                goto out;
+
+        __perf_event_task_sched_out(ctx);
+
+        spin_lock(&ctx->lock);
+
+        list_for_each_entry(event, &ctx->group_list, group_entry) {
+                if (!event->attr.enable_on_exec)
+                        continue;
+                event->attr.enable_on_exec = 0;
+                if (event->state >= PERF_EVENT_STATE_INACTIVE)
+                        continue;
+                __perf_event_mark_enabled(event, ctx);
+                enabled = 1;
+        }
+
+        /*
+         * Unclone this context if we enabled any event.
+         */
+        if (enabled)
+                unclone_ctx(ctx);
+
+        spin_unlock(&ctx->lock);
+
+        perf_event_task_sched_in(task, smp_processor_id());
+ out:
+        local_irq_restore(flags);
+}
+
+/*
+ * Cross CPU call to read the hardware event
+ */
+static void __perf_event_read(void *info)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_event *event = info;
+        struct perf_event_context *ctx = event->ctx;
+        unsigned long flags;
+
+        /*
+         * If this is a task context, we need to check whether it is
+         * the current task context of this cpu.  If not it has been
+         * scheduled out before the smp call arrived.  In that case
+         * event->count would have been updated to a recent sample
+         * when the event was scheduled out.
+         */
+        if (ctx->task && cpuctx->task_ctx != ctx)
+                return;
+
+        local_irq_save(flags);
+        if (ctx->is_active)
+                update_context_time(ctx);
+        event->pmu->read(event);
+        update_event_times(event);
+        local_irq_restore(flags);
+}
+
+static u64 perf_event_read(struct perf_event *event)
+{
+        /*
+         * If event is enabled and currently active on a CPU, update the
+         * value in the event structure:
+         */
+        if (event->state == PERF_EVENT_STATE_ACTIVE) {
+                smp_call_function_single(event->oncpu,
+                                         __perf_event_read, event, 1);
+        } else if (event->state == PERF_EVENT_STATE_INACTIVE) {
+                update_event_times(event);
+        }
+
+        return atomic64_read(&event->count);
+}
+
+/*
+ * Initialize the perf_event context in a task_struct:
+ */
+static void
+__perf_event_init_context(struct perf_event_context *ctx,
+                            struct task_struct *task)
+{
+        memset(ctx, 0, sizeof(*ctx));
+        spin_lock_init(&ctx->lock);
+        mutex_init(&ctx->mutex);
+        INIT_LIST_HEAD(&ctx->group_list);
+        INIT_LIST_HEAD(&ctx->event_list);
+        atomic_set(&ctx->refcount, 1);
+        ctx->task = task;
+}
+
+static struct perf_event_context *find_get_context(pid_t pid, int cpu)
+{
+        struct perf_event_context *ctx;
+        struct perf_cpu_context *cpuctx;
+        struct task_struct *task;
+        unsigned long flags;
+        int err;
+
+        /*
+         * If cpu is not a wildcard then this is a percpu event:
+         */
+        if (cpu != -1) {
+                /* Must be root to operate on a CPU event: */
+                if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
+                        return ERR_PTR(-EACCES);
+
+                if (cpu < 0 || cpu > num_possible_cpus())
+                        return ERR_PTR(-EINVAL);
+
+                /*
+                 * We could be clever and allow to attach a event to an
+                 * offline CPU and activate it when the CPU comes up, but
+                 * that's for later.
+                 */
+                if (!cpu_isset(cpu, cpu_online_map))
+                        return ERR_PTR(-ENODEV);
+
+                cpuctx = &per_cpu(perf_cpu_context, cpu);
+                ctx = &cpuctx->ctx;
+                get_ctx(ctx);
+
+                return ctx;
+        }
+
+        rcu_read_lock();
+        if (!pid)
+                task = current;
+        else
+                task = find_task_by_vpid(pid);
+        if (task)
+                get_task_struct(task);
+        rcu_read_unlock();
+
+        if (!task)
+                return ERR_PTR(-ESRCH);
+
+        /*
+         * Can't attach events to a dying task.
+         */
+        err = -ESRCH;
+        if (task->flags & PF_EXITING)
+                goto errout;
+
+        /* Reuse ptrace permission checks for now. */
+        err = -EACCES;
+        if (!ptrace_may_access(task, PTRACE_MODE_READ))
+                goto errout;
+
+ retry:
+        ctx = perf_lock_task_context(task, &flags);
+        if (ctx) {
+                unclone_ctx(ctx);
+                spin_unlock_irqrestore(&ctx->lock, flags);
+        }
+
+        if (!ctx) {
+                ctx = kmalloc(sizeof(struct perf_event_context), GFP_KERNEL);
+                err = -ENOMEM;
+                if (!ctx)
+                        goto errout;
+                __perf_event_init_context(ctx, task);
+                get_ctx(ctx);
+                if (cmpxchg(&task->perf_event_ctxp, NULL, ctx)) {
+                        /*
+                         * We raced with some other task; use
+                         * the context they set.
+                         */
+                        kfree(ctx);
+                        goto retry;
+                }
+                get_task_struct(task);
+        }
+
+        put_task_struct(task);
+        return ctx;
+
+ errout:
+        put_task_struct(task);
+        return ERR_PTR(err);
+}
+
+static void free_event_rcu(struct rcu_head *head)
+{
+        struct perf_event *event;
+
+        event = container_of(head, struct perf_event, rcu_head);
+        if (event->ns)
+                put_pid_ns(event->ns);
+        kfree(event);
+}
+
+static void perf_pending_sync(struct perf_event *event);
+
+static void free_event(struct perf_event *event)
+{
+        perf_pending_sync(event);
+
+        if (!event->parent) {
+                atomic_dec(&nr_events);
+                if (event->attr.mmap)
+                        atomic_dec(&nr_mmap_events);
+                if (event->attr.comm)
+                        atomic_dec(&nr_comm_events);
+                if (event->attr.task)
+                        atomic_dec(&nr_task_events);
+        }
+
+        if (event->output) {
+                fput(event->output->filp);
+                event->output = NULL;
+        }
+
+        if (event->destroy)
+                event->destroy(event);
+
+        put_ctx(event->ctx);
+        call_rcu(&event->rcu_head, free_event_rcu);
+}
+
+/*
+ * Called when the last reference to the file is gone.
+ */
+static int perf_release(struct inode *inode, struct file *file)
+{
+        struct perf_event *event = file->private_data;
+        struct perf_event_context *ctx = event->ctx;
+
+        file->private_data = NULL;
+
+        WARN_ON_ONCE(ctx->parent_ctx);
+        mutex_lock(&ctx->mutex);
+        perf_event_remove_from_context(event);
+        mutex_unlock(&ctx->mutex);
+
+        mutex_lock(&event->owner->perf_event_mutex);
+        list_del_init(&event->owner_entry);
+        mutex_unlock(&event->owner->perf_event_mutex);
+        put_task_struct(event->owner);
+
+        free_event(event);
+
+        return 0;
+}
+
+static int perf_event_read_size(struct perf_event *event)
+{
+        int entry = sizeof(u64); /* value */
+        int size = 0;
+        int nr = 1;
+
+        if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
+                size += sizeof(u64);
+
+        if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
+                size += sizeof(u64);
+
+        if (event->attr.read_format & PERF_FORMAT_ID)
+                entry += sizeof(u64);
+
+        if (event->attr.read_format & PERF_FORMAT_GROUP) {
+                nr += event->group_leader->nr_siblings;
+                size += sizeof(u64);
+        }
+
+        size += entry * nr;
+
+        return size;
+}
+
+static u64 perf_event_read_value(struct perf_event *event)
+{
+        struct perf_event *child;
+        u64 total = 0;
+
+        total += perf_event_read(event);
+        list_for_each_entry(child, &event->child_list, child_list)
+                total += perf_event_read(child);
+
+        return total;
+}
+
+static int perf_event_read_entry(struct perf_event *event,
+                                   u64 read_format, char __user *buf)
+{
+        int n = 0, count = 0;
+        u64 values[2];
+
+        values[n++] = perf_event_read_value(event);
+        if (read_format & PERF_FORMAT_ID)
+                values[n++] = primary_event_id(event);
+
+        count = n * sizeof(u64);
+
+        if (copy_to_user(buf, values, count))
+                return -EFAULT;
+
+        return count;
+}
+
+static int perf_event_read_group(struct perf_event *event,
+                                   u64 read_format, char __user *buf)
+{
+        struct perf_event *leader = event->group_leader, *sub;
+        int n = 0, size = 0, err = -EFAULT;
+        u64 values[3];
+
+        values[n++] = 1 + leader->nr_siblings;
+        if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
+                values[n++] = leader->total_time_enabled +
+                        atomic64_read(&leader->child_total_time_enabled);
+        }
+        if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {
+                values[n++] = leader->total_time_running +
+                        atomic64_read(&leader->child_total_time_running);
+        }
+
+        size = n * sizeof(u64);
+
+        if (copy_to_user(buf, values, size))
+                return -EFAULT;
+
+        err = perf_event_read_entry(leader, read_format, buf + size);
+        if (err < 0)
+                return err;
+
+        size += err;
+
+        list_for_each_entry(sub, &leader->sibling_list, group_entry) {
+                err = perf_event_read_entry(sub, read_format,
+                                buf + size);
+                if (err < 0)
+                        return err;
+
+                size += err;
+        }
+
+        return size;
+}
+
+static int perf_event_read_one(struct perf_event *event,
+                                 u64 read_format, char __user *buf)
+{
+        u64 values[4];
+        int n = 0;
+
+        values[n++] = perf_event_read_value(event);
+        if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
+                values[n++] = event->total_time_enabled +
+                        atomic64_read(&event->child_total_time_enabled);
+        }
+        if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {
+                values[n++] = event->total_time_running +
+                        atomic64_read(&event->child_total_time_running);
+        }
+        if (read_format & PERF_FORMAT_ID)
+                values[n++] = primary_event_id(event);
+
+        if (copy_to_user(buf, values, n * sizeof(u64)))
+                return -EFAULT;
+
+        return n * sizeof(u64);
+}
+
+/*
+ * Read the performance event - simple non blocking version for now
+ */
+static ssize_t
+perf_read_hw(struct perf_event *event, char __user *buf, size_t count)
+{
+        u64 read_format = event->attr.read_format;
+        int ret;
+
+        /*
+         * Return end-of-file for a read on a event that is in
+         * error state (i.e. because it was pinned but it couldn't be
+         * scheduled on to the CPU at some point).
+         */
+        if (event->state == PERF_EVENT_STATE_ERROR)
+                return 0;
+
+        if (count < perf_event_read_size(event))
+                return -ENOSPC;
+
+        WARN_ON_ONCE(event->ctx->parent_ctx);
+        mutex_lock(&event->child_mutex);
+        if (read_format & PERF_FORMAT_GROUP)
+                ret = perf_event_read_group(event, read_format, buf);
+        else
+                ret = perf_event_read_one(event, read_format, buf);
+        mutex_unlock(&event->child_mutex);
+
+        return ret;
+}
+
+static ssize_t
+perf_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
+{
+        struct perf_event *event = file->private_data;
+
+        return perf_read_hw(event, buf, count);
+}
+
+static unsigned int perf_poll(struct file *file, poll_table *wait)
+{
+        struct perf_event *event = file->private_data;
+        struct perf_mmap_data *data;
+        unsigned int events = POLL_HUP;
+
+        rcu_read_lock();
+        data = rcu_dereference(event->data);
+        if (data)
+                events = atomic_xchg(&data->poll, 0);
+        rcu_read_unlock();
+
+        poll_wait(file, &event->waitq, wait);
+
+        return events;
+}
+
+static void perf_event_reset(struct perf_event *event)
+{
+        (void)perf_event_read(event);
+        atomic64_set(&event->count, 0);
+        perf_event_update_userpage(event);
+}
+
+/*
+ * Holding the top-level event's child_mutex means that any
+ * descendant process that has inherited this event will block
+ * in sync_child_event if it goes to exit, thus satisfying the
+ * task existence requirements of perf_event_enable/disable.
+ */
+static void perf_event_for_each_child(struct perf_event *event,
+                                        void (*func)(struct perf_event *))
+{
+        struct perf_event *child;
+
+        WARN_ON_ONCE(event->ctx->parent_ctx);
+        mutex_lock(&event->child_mutex);
+        func(event);
+        list_for_each_entry(child, &event->child_list, child_list)
+                func(child);
+        mutex_unlock(&event->child_mutex);
+}
+
+static void perf_event_for_each(struct perf_event *event,
+                                  void (*func)(struct perf_event *))
+{
+        struct perf_event_context *ctx = event->ctx;
+        struct perf_event *sibling;
+
+        WARN_ON_ONCE(ctx->parent_ctx);
+        mutex_lock(&ctx->mutex);
+        event = event->group_leader;
+
+        perf_event_for_each_child(event, func);
+        func(event);
+        list_for_each_entry(sibling, &event->sibling_list, group_entry)
+                perf_event_for_each_child(event, func);
+        mutex_unlock(&ctx->mutex);
+}
+
+static int perf_event_period(struct perf_event *event, u64 __user *arg)
+{
+        struct perf_event_context *ctx = event->ctx;
+        unsigned long size;
+        int ret = 0;
+        u64 value;
+
+        if (!event->attr.sample_period)
+                return -EINVAL;
+
+        size = copy_from_user(&value, arg, sizeof(value));
+        if (size != sizeof(value))
+                return -EFAULT;
+
+        if (!value)
+                return -EINVAL;
+
+        spin_lock_irq(&ctx->lock);
+        if (event->attr.freq) {
+                if (value > sysctl_perf_event_sample_rate) {
+                        ret = -EINVAL;
+                        goto unlock;
+                }
+
+                event->attr.sample_freq = value;
+        } else {
+                event->attr.sample_period = value;
+                event->hw.sample_period = value;
+        }
+unlock:
+        spin_unlock_irq(&ctx->lock);
+
+        return ret;
+}
+
+int perf_event_set_output(struct perf_event *event, int output_fd);
+
+static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+        struct perf_event *event = file->private_data;
+        void (*func)(struct perf_event *);
+        u32 flags = arg;
+
+        switch (cmd) {
+        case PERF_EVENT_IOC_ENABLE:
+                func = perf_event_enable;
+                break;
+        case PERF_EVENT_IOC_DISABLE:
+                func = perf_event_disable;
+                break;
+        case PERF_EVENT_IOC_RESET:
+                func = perf_event_reset;
+                break;
+
+        case PERF_EVENT_IOC_REFRESH:
+                return perf_event_refresh(event, arg);
+
+        case PERF_EVENT_IOC_PERIOD:
+                return perf_event_period(event, (u64 __user *)arg);
+
+        case PERF_EVENT_IOC_SET_OUTPUT:
+                return perf_event_set_output(event, arg);
+
+        default:
+                return -ENOTTY;
+        }
+
+        if (flags & PERF_IOC_FLAG_GROUP)
+                perf_event_for_each(event, func);
+        else
+                perf_event_for_each_child(event, func);
+
+        return 0;
+}
+
+int perf_event_task_enable(void)
+{
+        struct perf_event *event;
+
+        mutex_lock(&current->perf_event_mutex);
+        list_for_each_entry(event, &current->perf_event_list, owner_entry)
+                perf_event_for_each_child(event, perf_event_enable);
+        mutex_unlock(&current->perf_event_mutex);
+
+        return 0;
+}
+
+int perf_event_task_disable(void)
+{
+        struct perf_event *event;
+
+        mutex_lock(&current->perf_event_mutex);
+        list_for_each_entry(event, &current->perf_event_list, owner_entry)
+                perf_event_for_each_child(event, perf_event_disable);
+        mutex_unlock(&current->perf_event_mutex);
+
+        return 0;
+}
+
+#ifndef PERF_EVENT_INDEX_OFFSET
+# define PERF_EVENT_INDEX_OFFSET 0
+#endif
+
+static int perf_event_index(struct perf_event *event)
+{
+        if (event->state != PERF_EVENT_STATE_ACTIVE)
+                return 0;
+
+        return event->hw.idx + 1 - PERF_EVENT_INDEX_OFFSET;
+}
+
+/*
+ * Callers need to ensure there can be no nesting of this function, otherwise
+ * the seqlock logic goes bad. We can not serialize this because the arch
+ * code calls this from NMI context.
+ */
+void perf_event_update_userpage(struct perf_event *event)
+{
+        struct perf_event_mmap_page *userpg;
+        struct perf_mmap_data *data;
+
+        rcu_read_lock();
+        data = rcu_dereference(event->data);
+        if (!data)
+                goto unlock;
+
+        userpg = data->user_page;
+
+        /*
+         * Disable preemption so as to not let the corresponding user-space
+         * spin too long if we get preempted.
+         */
+        preempt_disable();
+        ++userpg->lock;
+        barrier();
+        userpg->index = perf_event_index(event);
+        userpg->offset = atomic64_read(&event->count);
+        if (event->state == PERF_EVENT_STATE_ACTIVE)
+                userpg->offset -= atomic64_read(&event->hw.prev_count);
+
+        userpg->time_enabled = event->total_time_enabled +
+                        atomic64_read(&event->child_total_time_enabled);
+
+        userpg->time_running = event->total_time_running +
+                        atomic64_read(&event->child_total_time_running);
+
+        barrier();
+        ++userpg->lock;
+        preempt_enable();
+unlock:
+        rcu_read_unlock();
+}
+
+static int perf_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+        struct perf_event *event = vma->vm_file->private_data;
+        struct perf_mmap_data *data;
+        int ret = VM_FAULT_SIGBUS;
+
+        if (vmf->flags & FAULT_FLAG_MKWRITE) {
+                if (vmf->pgoff == 0)
+                        ret = 0;
+                return ret;
+        }
+
+        rcu_read_lock();
+        data = rcu_dereference(event->data);
+        if (!data)
+                goto unlock;
+
+        if (vmf->pgoff == 0) {
+                vmf->page = virt_to_page(data->user_page);
+        } else {
+                int nr = vmf->pgoff - 1;
+
+                if ((unsigned)nr > data->nr_pages)
+                        goto unlock;
+
+                if (vmf->flags & FAULT_FLAG_WRITE)
+                        goto unlock;
+
+                vmf->page = virt_to_page(data->data_pages[nr]);
+        }
+
+        get_page(vmf->page);
+        vmf->page->mapping = vma->vm_file->f_mapping;
+        vmf->page->index   = vmf->pgoff;
+
+        ret = 0;
+unlock:
+        rcu_read_unlock();
+
+        return ret;
+}
+
+static int perf_mmap_data_alloc(struct perf_event *event, int nr_pages)
+{
+        struct perf_mmap_data *data;
+        unsigned long size;
+        int i;
+
+        WARN_ON(atomic_read(&event->mmap_count));
+
+        size = sizeof(struct perf_mmap_data);
+        size += nr_pages * sizeof(void *);
+
+        data = kzalloc(size, GFP_KERNEL);
+        if (!data)
+                goto fail;
+
+        data->user_page = (void *)get_zeroed_page(GFP_KERNEL);
+        if (!data->user_page)
+                goto fail_user_page;
+
+        for (i = 0; i < nr_pages; i++) {
+                data->data_pages[i] = (void *)get_zeroed_page(GFP_KERNEL);
+                if (!data->data_pages[i])
+                        goto fail_data_pages;
+        }
+
+        data->nr_pages = nr_pages;
+        atomic_set(&data->lock, -1);
+
+        if (event->attr.watermark) {
+                data->watermark = min_t(long, PAGE_SIZE * nr_pages,
+                                      event->attr.wakeup_watermark);
+        }
+        if (!data->watermark)
+                data->watermark = max(PAGE_SIZE, PAGE_SIZE * nr_pages / 4);
+
+        rcu_assign_pointer(event->data, data);
+
+        return 0;
+
+fail_data_pages:
+        for (i--; i >= 0; i--)
+                free_page((unsigned long)data->data_pages[i]);
+
+        free_page((unsigned long)data->user_page);
+
+fail_user_page:
+        kfree(data);
+
+fail:
+        return -ENOMEM;
+}
+
+static void perf_mmap_free_page(unsigned long addr)
+{
+        struct page *page = virt_to_page((void *)addr);
+
+        page->mapping = NULL;
+        __free_page(page);
+}
+
+static void __perf_mmap_data_free(struct rcu_head *rcu_head)
+{
+        struct perf_mmap_data *data;
+        int i;
+
+        data = container_of(rcu_head, struct perf_mmap_data, rcu_head);
+
+        perf_mmap_free_page((unsigned long)data->user_page);
+        for (i = 0; i < data->nr_pages; i++)
+                perf_mmap_free_page((unsigned long)data->data_pages[i]);
+
+        kfree(data);
+}
+
+static void perf_mmap_data_free(struct perf_event *event)
+{
+        struct perf_mmap_data *data = event->data;
+
+        WARN_ON(atomic_read(&event->mmap_count));
+
+        rcu_assign_pointer(event->data, NULL);
+        call_rcu(&data->rcu_head, __perf_mmap_data_free);
+}
+
+static void perf_mmap_open(struct vm_area_struct *vma)
+{
+        struct perf_event *event = vma->vm_file->private_data;
+
+        atomic_inc(&event->mmap_count);
+}
+
+static void perf_mmap_close(struct vm_area_struct *vma)
+{
+        struct perf_event *event = vma->vm_file->private_data;
+
+        WARN_ON_ONCE(event->ctx->parent_ctx);
+        if (atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) {
+                struct user_struct *user = current_user();
+
+                atomic_long_sub(event->data->nr_pages + 1, &user->locked_vm);
+                vma->vm_mm->locked_vm -= event->data->nr_locked;
+                perf_mmap_data_free(event);
+                mutex_unlock(&event->mmap_mutex);
+        }
+}
+
+static struct vm_operations_struct perf_mmap_vmops = {
+        .open           = perf_mmap_open,
+        .close          = perf_mmap_close,
+        .fault          = perf_mmap_fault,
+        .page_mkwrite   = perf_mmap_fault,
+};
+
+static int perf_mmap(struct file *file, struct vm_area_struct *vma)
+{
+        struct perf_event *event = file->private_data;
+        unsigned long user_locked, user_lock_limit;
+        struct user_struct *user = current_user();
+        unsigned long locked, lock_limit;
+        unsigned long vma_size;
+        unsigned long nr_pages;
+        long user_extra, extra;
+        int ret = 0;
+
+        if (!(vma->vm_flags & VM_SHARED))
+                return -EINVAL;
+
+        vma_size = vma->vm_end - vma->vm_start;
+        nr_pages = (vma_size / PAGE_SIZE) - 1;
+
+        /*
+         * If we have data pages ensure they're a power-of-two number, so we
+         * can do bitmasks instead of modulo.
+         */
+        if (nr_pages != 0 && !is_power_of_2(nr_pages))
+                return -EINVAL;
+
+        if (vma_size != PAGE_SIZE * (1 + nr_pages))
+                return -EINVAL;
+
+        if (vma->vm_pgoff != 0)
+                return -EINVAL;
+
+        WARN_ON_ONCE(event->ctx->parent_ctx);
+        mutex_lock(&event->mmap_mutex);
+        if (event->output) {
+                ret = -EINVAL;
+                goto unlock;
+        }
+
+        if (atomic_inc_not_zero(&event->mmap_count)) {
+                if (nr_pages != event->data->nr_pages)
+                        ret = -EINVAL;
+                goto unlock;
+        }
+
+        user_extra = nr_pages + 1;
+        user_lock_limit = sysctl_perf_event_mlock >> (PAGE_SHIFT - 10);
+
+        /*
+         * Increase the limit linearly with more CPUs:
+         */
+        user_lock_limit *= num_online_cpus();
+
+        user_locked = atomic_long_read(&user->locked_vm) + user_extra;
+
+        extra = 0;
+        if (user_locked > user_lock_limit)
+                extra = user_locked - user_lock_limit;
+
+        lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
+        lock_limit >>= PAGE_SHIFT;
+        locked = vma->vm_mm->locked_vm + extra;
+
+        if ((locked > lock_limit) && perf_paranoid_tracepoint_raw() &&
+                !capable(CAP_IPC_LOCK)) {
+                ret = -EPERM;
+                goto unlock;
+        }
+
+        WARN_ON(event->data);
+        ret = perf_mmap_data_alloc(event, nr_pages);
+        if (ret)
+                goto unlock;
+
+        atomic_set(&event->mmap_count, 1);
+        atomic_long_add(user_extra, &user->locked_vm);
+        vma->vm_mm->locked_vm += extra;
+        event->data->nr_locked = extra;
+        if (vma->vm_flags & VM_WRITE)
+                event->data->writable = 1;
+
+unlock:
+        mutex_unlock(&event->mmap_mutex);
+
+        vma->vm_flags |= VM_RESERVED;
+        vma->vm_ops = &perf_mmap_vmops;
+
+        return ret;
+}
+
+static int perf_fasync(int fd, struct file *filp, int on)
+{
+        struct inode *inode = filp->f_path.dentry->d_inode;
+        struct perf_event *event = filp->private_data;
+        int retval;
+
+        mutex_lock(&inode->i_mutex);
+        retval = fasync_helper(fd, filp, on, &event->fasync);
+        mutex_unlock(&inode->i_mutex);
+
+        if (retval < 0)
+                return retval;
+
+        return 0;
+}
+
+static const struct file_operations perf_fops = {
+        .release                = perf_release,
+        .read                   = perf_read,
+        .poll                   = perf_poll,
+        .unlocked_ioctl         = perf_ioctl,
+        .compat_ioctl           = perf_ioctl,
+        .mmap                   = perf_mmap,
+        .fasync                 = perf_fasync,
+};
+
+/*
+ * Perf event wakeup
+ *
+ * If there's data, ensure we set the poll() state and publish everything
+ * to user-space before waking everybody up.
+ */
+
+void perf_event_wakeup(struct perf_event *event)
+{
+        wake_up_all(&event->waitq);
+
+        if (event->pending_kill) {
+                kill_fasync(&event->fasync, SIGIO, event->pending_kill);
+                event->pending_kill = 0;
+        }
+}
+
+/*
+ * Pending wakeups
+ *
+ * Handle the case where we need to wakeup up from NMI (or rq->lock) context.
+ *
+ * The NMI bit means we cannot possibly take locks. Therefore, maintain a
+ * single linked list and use cmpxchg() to add entries lockless.
+ */
+
+static void perf_pending_event(struct perf_pending_entry *entry)
+{
+        struct perf_event *event = container_of(entry,
+                        struct perf_event, pending);
+
+        if (event->pending_disable) {
+                event->pending_disable = 0;
+                __perf_event_disable(event);
+        }
+
+        if (event->pending_wakeup) {
+                event->pending_wakeup = 0;
+                perf_event_wakeup(event);
+        }
+}
+
+#define PENDING_TAIL ((struct perf_pending_entry *)-1UL)
+
+static DEFINE_PER_CPU(struct perf_pending_entry *, perf_pending_head) = {
+        PENDING_TAIL,
+};
+
+static void perf_pending_queue(struct perf_pending_entry *entry,
+                               void (*func)(struct perf_pending_entry *))
+{
+        struct perf_pending_entry **head;
+
+        if (cmpxchg(&entry->next, NULL, PENDING_TAIL) != NULL)
+                return;
+
+        entry->func = func;
+
+        head = &get_cpu_var(perf_pending_head);
+
+        do {
+                entry->next = *head;
+        } while (cmpxchg(head, entry->next, entry) != entry->next);
+
+        set_perf_event_pending();
+
+        put_cpu_var(perf_pending_head);
+}
+
+static int __perf_pending_run(void)
+{
+        struct perf_pending_entry *list;
+        int nr = 0;
+
+        list = xchg(&__get_cpu_var(perf_pending_head), PENDING_TAIL);
+        while (list != PENDING_TAIL) {
+                void (*func)(struct perf_pending_entry *);
+                struct perf_pending_entry *entry = list;
+
+                list = list->next;
+
+                func = entry->func;
+                entry->next = NULL;
+                /*
+                 * Ensure we observe the unqueue before we issue the wakeup,
+                 * so that we won't be waiting forever.
+                 * -- see perf_not_pending().
+                 */
+                smp_wmb();
+
+                func(entry);
+                nr++;
+        }
+
+        return nr;
+}
+
+static inline int perf_not_pending(struct perf_event *event)
+{
+        /*
+         * If we flush on whatever cpu we run, there is a chance we don't
+         * need to wait.
+         */
+        get_cpu();
+        __perf_pending_run();
+        put_cpu();
+
+        /*
+         * Ensure we see the proper queue state before going to sleep
+         * so that we do not miss the wakeup. -- see perf_pending_handle()
+         */
+        smp_rmb();
+        return event->pending.next == NULL;
+}
+
+static void perf_pending_sync(struct perf_event *event)
+{
+        wait_event(event->waitq, perf_not_pending(event));
+}
+
+void perf_event_do_pending(void)
+{
+        __perf_pending_run();
+}
+
+/*
+ * Callchain support -- arch specific
+ */
+
+__weak struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
+{
+        return NULL;
+}
+
+/*
+ * Output
+ */
+static bool perf_output_space(struct perf_mmap_data *data, unsigned long tail,
+                              unsigned long offset, unsigned long head)
+{
+        unsigned long mask;
+
+        if (!data->writable)
+                return true;
+
+        mask = (data->nr_pages << PAGE_SHIFT) - 1;
+
+        offset = (offset - tail) & mask;
+        head   = (head   - tail) & mask;
+
+        if ((int)(head - offset) < 0)
+                return false;
+
+        return true;
+}
+
+static void perf_output_wakeup(struct perf_output_handle *handle)
+{
+        atomic_set(&handle->data->poll, POLL_IN);
+
+        if (handle->nmi) {
+                handle->event->pending_wakeup = 1;
+                perf_pending_queue(&handle->event->pending,
+                                   perf_pending_event);
+        } else
+                perf_event_wakeup(handle->event);
+}
+
+/*
+ * Curious locking construct.
+ *
+ * We need to ensure a later event_id doesn't publish a head when a former
+ * event_id isn't done writing. However since we need to deal with NMIs we
+ * cannot fully serialize things.
+ *
+ * What we do is serialize between CPUs so we only have to deal with NMI
+ * nesting on a single CPU.
+ *
+ * We only publish the head (and generate a wakeup) when the outer-most
+ * event_id completes.
+ */
+static void perf_output_lock(struct perf_output_handle *handle)
+{
+        struct perf_mmap_data *data = handle->data;
+        int cpu;
+
+        handle->locked = 0;
+
+        local_irq_save(handle->flags);
+        cpu = smp_processor_id();
+
+        if (in_nmi() && atomic_read(&data->lock) == cpu)
+                return;
+
+        while (atomic_cmpxchg(&data->lock, -1, cpu) != -1)
+                cpu_relax();
+
+        handle->locked = 1;
+}
+
+static void perf_output_unlock(struct perf_output_handle *handle)
+{
+        struct perf_mmap_data *data = handle->data;
+        unsigned long head;
+        int cpu;
+
+        data->done_head = data->head;
+
+        if (!handle->locked)
+                goto out;
+
+again:
+        /*
+         * The xchg implies a full barrier that ensures all writes are done
+         * before we publish the new head, matched by a rmb() in userspace when
+         * reading this position.
+         */
+        while ((head = atomic_long_xchg(&data->done_head, 0)))
+                data->user_page->data_head = head;
+
+        /*
+         * NMI can happen here, which means we can miss a done_head update.
+         */
+
+        cpu = atomic_xchg(&data->lock, -1);
+        WARN_ON_ONCE(cpu != smp_processor_id());
+
+        /*
+         * Therefore we have to validate we did not indeed do so.
+         */
+        if (unlikely(atomic_long_read(&data->done_head))) {
+                /*
+                 * Since we had it locked, we can lock it again.
+                 */
+                while (atomic_cmpxchg(&data->lock, -1, cpu) != -1)
+                        cpu_relax();
+
+                goto again;
+        }
+
+        if (atomic_xchg(&data->wakeup, 0))
+                perf_output_wakeup(handle);
+out:
+        local_irq_restore(handle->flags);
+}
+
+void perf_output_copy(struct perf_output_handle *handle,
+                      const void *buf, unsigned int len)
+{
+        unsigned int pages_mask;
+        unsigned int offset;
+        unsigned int size;
+        void **pages;
+
+        offset          = handle->offset;
+        pages_mask      = handle->data->nr_pages - 1;
+        pages           = handle->data->data_pages;
+
+        do {
+                unsigned int page_offset;
+                int nr;
+
+                nr          = (offset >> PAGE_SHIFT) & pages_mask;
+                page_offset = offset & (PAGE_SIZE - 1);
+                size        = min_t(unsigned int, PAGE_SIZE - page_offset, len);
+
+                memcpy(pages[nr] + page_offset, buf, size);
+
+                len         -= size;
+                buf         += size;
+                offset      += size;
+        } while (len);
+
+        handle->offset = offset;
+
+        /*
+         * Check we didn't copy past our reservation window, taking the
+         * possible unsigned int wrap into account.
+         */
+        WARN_ON_ONCE(((long)(handle->head - handle->offset)) < 0);
+}
+
+int perf_output_begin(struct perf_output_handle *handle,
+                      struct perf_event *event, unsigned int size,
+                      int nmi, int sample)
+{
+        struct perf_event *output_event;
+        struct perf_mmap_data *data;
+        unsigned long tail, offset, head;
+        int have_lost;
+        struct {
+                struct perf_event_header header;
+                u64                      id;
+                u64                      lost;
+        } lost_event;
+
+        rcu_read_lock();
+        /*
+         * For inherited events we send all the output towards the parent.
+         */
+        if (event->parent)
+                event = event->parent;
+
+        output_event = rcu_dereference(event->output);
+        if (output_event)
+                event = output_event;
+
+        data = rcu_dereference(event->data);
+        if (!data)
+                goto out;
+
+        handle->data    = data;
+        handle->event   = event;
+        handle->nmi     = nmi;
+        handle->sample  = sample;
+
+        if (!data->nr_pages)
+                goto fail;
+
+        have_lost = atomic_read(&data->lost);
+        if (have_lost)
+                size += sizeof(lost_event);
+
+        perf_output_lock(handle);
+
+        do {
+                /*
+                 * Userspace could choose to issue a mb() before updating the
+                 * tail pointer. So that all reads will be completed before the
+                 * write is issued.
+                 */
+                tail = ACCESS_ONCE(data->user_page->data_tail);
+                smp_rmb();
+                offset = head = atomic_long_read(&data->head);
+                head += size;
+                if (unlikely(!perf_output_space(data, tail, offset, head)))
+                        goto fail;
+        } while (atomic_long_cmpxchg(&data->head, offset, head) != offset);
+
+        handle->offset  = offset;
+        handle->head    = head;
+
+        if (head - tail > data->watermark)
+                atomic_set(&data->wakeup, 1);
+
+        if (have_lost) {
+                lost_event.header.type = PERF_RECORD_LOST;
+                lost_event.header.misc = 0;
+                lost_event.header.size = sizeof(lost_event);
+                lost_event.id          = event->id;
+                lost_event.lost        = atomic_xchg(&data->lost, 0);
+
+                perf_output_put(handle, lost_event);
+        }
+
+        return 0;
+
+fail:
+        atomic_inc(&data->lost);
+        perf_output_unlock(handle);
+out:
+        rcu_read_unlock();
+
+        return -ENOSPC;
+}
+
+void perf_output_end(struct perf_output_handle *handle)
+{
+        struct perf_event *event = handle->event;
+        struct perf_mmap_data *data = handle->data;
+
+        int wakeup_events = event->attr.wakeup_events;
+
+        if (handle->sample && wakeup_events) {
+                int events = atomic_inc_return(&data->events);
+                if (events >= wakeup_events) {
+                        atomic_sub(wakeup_events, &data->events);
+                        atomic_set(&data->wakeup, 1);
+                }
+        }
+
+        perf_output_unlock(handle);
+        rcu_read_unlock();
+}
+
+static u32 perf_event_pid(struct perf_event *event, struct task_struct *p)
+{
+        /*
+         * only top level events have the pid namespace they were created in
+         */
+        if (event->parent)
+                event = event->parent;
+
+        return task_tgid_nr_ns(p, event->ns);
+}
+
+static u32 perf_event_tid(struct perf_event *event, struct task_struct *p)
+{
+        /*
+         * only top level events have the pid namespace they were created in
+         */
+        if (event->parent)
+                event = event->parent;
+
+        return task_pid_nr_ns(p, event->ns);
+}
+
+static void perf_output_read_one(struct perf_output_handle *handle,
+                                 struct perf_event *event)
+{
+        u64 read_format = event->attr.read_format;
+        u64 values[4];
+        int n = 0;
+
+        values[n++] = atomic64_read(&event->count);
+        if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
+                values[n++] = event->total_time_enabled +
+                        atomic64_read(&event->child_total_time_enabled);
+        }
+        if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {
+                values[n++] = event->total_time_running +
+                        atomic64_read(&event->child_total_time_running);
+        }
+        if (read_format & PERF_FORMAT_ID)
+                values[n++] = primary_event_id(event);
+
+        perf_output_copy(handle, values, n * sizeof(u64));
+}
+
+/*
+ * XXX PERF_FORMAT_GROUP vs inherited events seems difficult.
+ */
+static void perf_output_read_group(struct perf_output_handle *handle,
+                            struct perf_event *event)
+{
+        struct perf_event *leader = event->group_leader, *sub;
+        u64 read_format = event->attr.read_format;
+        u64 values[5];
+        int n = 0;
+
+        values[n++] = 1 + leader->nr_siblings;
+
+        if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
+                values[n++] = leader->total_time_enabled;
+
+        if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
+                values[n++] = leader->total_time_running;
+
+        if (leader != event)
+                leader->pmu->read(leader);
+
+        values[n++] = atomic64_read(&leader->count);
+        if (read_format & PERF_FORMAT_ID)
+                values[n++] = primary_event_id(leader);
+
+        perf_output_copy(handle, values, n * sizeof(u64));
+
+        list_for_each_entry(sub, &leader->sibling_list, group_entry) {
+                n = 0;
+
+                if (sub != event)
+                        sub->pmu->read(sub);
+
+                values[n++] = atomic64_read(&sub->count);
+                if (read_format & PERF_FORMAT_ID)
+                        values[n++] = primary_event_id(sub);
+
+                perf_output_copy(handle, values, n * sizeof(u64));
+        }
+}
+
+static void perf_output_read(struct perf_output_handle *handle,
+                             struct perf_event *event)
+{
+        if (event->attr.read_format & PERF_FORMAT_GROUP)
+                perf_output_read_group(handle, event);
+        else
+                perf_output_read_one(handle, event);
+}
+
+void perf_output_sample(struct perf_output_handle *handle,
+                        struct perf_event_header *header,
+                        struct perf_sample_data *data,
+                        struct perf_event *event)
+{
+        u64 sample_type = data->type;
+
+        perf_output_put(handle, *header);
+
+        if (sample_type & PERF_SAMPLE_IP)
+                perf_output_put(handle, data->ip);
+
+        if (sample_type & PERF_SAMPLE_TID)
+                perf_output_put(handle, data->tid_entry);
+
+        if (sample_type & PERF_SAMPLE_TIME)
+                perf_output_put(handle, data->time);
+
+        if (sample_type & PERF_SAMPLE_ADDR)
+                perf_output_put(handle, data->addr);
+
+        if (sample_type & PERF_SAMPLE_ID)
+                perf_output_put(handle, data->id);
+
+        if (sample_type & PERF_SAMPLE_STREAM_ID)
+                perf_output_put(handle, data->stream_id);
+
+        if (sample_type & PERF_SAMPLE_CPU)
+                perf_output_put(handle, data->cpu_entry);
+
+        if (sample_type & PERF_SAMPLE_PERIOD)
+                perf_output_put(handle, data->period);
+
+        if (sample_type & PERF_SAMPLE_READ)
+                perf_output_read(handle, event);
+
+        if (sample_type & PERF_SAMPLE_CALLCHAIN) {
+                if (data->callchain) {
+                        int size = 1;
+
+                        if (data->callchain)
+                                size += data->callchain->nr;
+
+                        size *= sizeof(u64);
+
+                        perf_output_copy(handle, data->callchain, size);
+                } else {
+                        u64 nr = 0;
+                        perf_output_put(handle, nr);
+                }
+        }
+
+        if (sample_type & PERF_SAMPLE_RAW) {
+                if (data->raw) {
+                        perf_output_put(handle, data->raw->size);
+                        perf_output_copy(handle, data->raw->data,
+                                         data->raw->size);
+                } else {
+                        struct {
+                                u32     size;
+                                u32     data;
+                        } raw = {
+                                .size = sizeof(u32),
+                                .data = 0,
+                        };
+                        perf_output_put(handle, raw);
+                }
+        }
+}
+
+void perf_prepare_sample(struct perf_event_header *header,
+                         struct perf_sample_data *data,
+                         struct perf_event *event,
+                         struct pt_regs *regs)
+{
+        u64 sample_type = event->attr.sample_type;
+
+        data->type = sample_type;
+
+        header->type = PERF_RECORD_SAMPLE;
+        header->size = sizeof(*header);
+
+        header->misc = 0;
+        header->misc |= perf_misc_flags(regs);
+
+        if (sample_type & PERF_SAMPLE_IP) {
+                data->ip = perf_instruction_pointer(regs);
+
+                header->size += sizeof(data->ip);
+        }
+
+        if (sample_type & PERF_SAMPLE_TID) {
+                /* namespace issues */
+                data->tid_entry.pid = perf_event_pid(event, current);
+                data->tid_entry.tid = perf_event_tid(event, current);
+
+                header->size += sizeof(data->tid_entry);
+        }
+
+        if (sample_type & PERF_SAMPLE_TIME) {
+                data->time = perf_clock();
+
+                header->size += sizeof(data->time);
+        }
+
+        if (sample_type & PERF_SAMPLE_ADDR)
+                header->size += sizeof(data->addr);
+
+        if (sample_type & PERF_SAMPLE_ID) {
+                data->id = primary_event_id(event);
+
+                header->size += sizeof(data->id);
+        }
+
+        if (sample_type & PERF_SAMPLE_STREAM_ID) {
+                data->stream_id = event->id;
+
+                header->size += sizeof(data->stream_id);
+        }
+
+        if (sample_type & PERF_SAMPLE_CPU) {
+                data->cpu_entry.cpu             = raw_smp_processor_id();
+                data->cpu_entry.reserved        = 0;
+
+                header->size += sizeof(data->cpu_entry);
+        }
+
+        if (sample_type & PERF_SAMPLE_PERIOD)
+                header->size += sizeof(data->period);
+
+        if (sample_type & PERF_SAMPLE_READ)
+                header->size += perf_event_read_size(event);
+
+        if (sample_type & PERF_SAMPLE_CALLCHAIN) {
+                int size = 1;
+
+                data->callchain = perf_callchain(regs);
+
+                if (data->callchain)
+                        size += data->callchain->nr;
+
+                header->size += size * sizeof(u64);
+        }
+
+        if (sample_type & PERF_SAMPLE_RAW) {
+                int size = sizeof(u32);
+
+                if (data->raw)
+                        size += data->raw->size;
+                else
+                        size += sizeof(u32);
+
+                WARN_ON_ONCE(size & (sizeof(u64)-1));
+                header->size += size;
+        }
+}
+
+static void perf_event_output(struct perf_event *event, int nmi,
+                                struct perf_sample_data *data,
+                                struct pt_regs *regs)
+{
+        struct perf_output_handle handle;
+        struct perf_event_header header;
+
+        perf_prepare_sample(&header, data, event, regs);
+
+        if (perf_output_begin(&handle, event, header.size, nmi, 1))
+                return;
+
+        perf_output_sample(&handle, &header, data, event);
+
+        perf_output_end(&handle);
+}
+
+/*
+ * read event_id
+ */
+
+struct perf_read_event {
+        struct perf_event_header        header;
+
+        u32                             pid;
+        u32                             tid;
+};
+
+static void
+perf_event_read_event(struct perf_event *event,
+                        struct task_struct *task)
+{
+        struct perf_output_handle handle;
+        struct perf_read_event read_event = {
+                .header = {
+                        .type = PERF_RECORD_READ,
+                        .misc = 0,
+                        .size = sizeof(read_event) + perf_event_read_size(event),
+                },
+                .pid = perf_event_pid(event, task),
+                .tid = perf_event_tid(event, task),
+        };
+        int ret;
+
+        ret = perf_output_begin(&handle, event, read_event.header.size, 0, 0);
+        if (ret)
+                return;
+
+        perf_output_put(&handle, read_event);
+        perf_output_read(&handle, event);
+
+        perf_output_end(&handle);
+}
+
+/*
+ * task tracking -- fork/exit
+ *
+ * enabled by: attr.comm | attr.mmap | attr.task
+ */
+
+struct perf_task_event {
+        struct task_struct              *task;
+        struct perf_event_context       *task_ctx;
+
+        struct {
+                struct perf_event_header        header;
+
+                u32                             pid;
+                u32                             ppid;
+                u32                             tid;
+                u32                             ptid;
+                u64                             time;
+        } event_id;
+};
+
+static void perf_event_task_output(struct perf_event *event,
+                                     struct perf_task_event *task_event)
+{
+        struct perf_output_handle handle;
+        int size;
+        struct task_struct *task = task_event->task;
+        int ret;
+
+        size  = task_event->event_id.header.size;
+        ret = perf_output_begin(&handle, event, size, 0, 0);
+
+        if (ret)
+                return;
+
+        task_event->event_id.pid = perf_event_pid(event, task);
+        task_event->event_id.ppid = perf_event_pid(event, current);
+
+        task_event->event_id.tid = perf_event_tid(event, task);
+        task_event->event_id.ptid = perf_event_tid(event, current);
+
+        task_event->event_id.time = perf_clock();
+
+        perf_output_put(&handle, task_event->event_id);
+
+        perf_output_end(&handle);
+}
+
+static int perf_event_task_match(struct perf_event *event)
+{
+        if (event->attr.comm || event->attr.mmap || event->attr.task)
+                return 1;
+
+        return 0;
+}
+
+static void perf_event_task_ctx(struct perf_event_context *ctx,
+                                  struct perf_task_event *task_event)
+{
+        struct perf_event *event;
+
+        if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
+                return;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
+                if (perf_event_task_match(event))
+                        perf_event_task_output(event, task_event);
+        }
+        rcu_read_unlock();
+}
+
+static void perf_event_task_event(struct perf_task_event *task_event)
+{
+        struct perf_cpu_context *cpuctx;
+        struct perf_event_context *ctx = task_event->task_ctx;
+
+        cpuctx = &get_cpu_var(perf_cpu_context);
+        perf_event_task_ctx(&cpuctx->ctx, task_event);
+        put_cpu_var(perf_cpu_context);
+
+        rcu_read_lock();
+        if (!ctx)
+                ctx = rcu_dereference(task_event->task->perf_event_ctxp);
+        if (ctx)
+                perf_event_task_ctx(ctx, task_event);
+        rcu_read_unlock();
+}
+
+static void perf_event_task(struct task_struct *task,
+                              struct perf_event_context *task_ctx,
+                              int new)
+{
+        struct perf_task_event task_event;
+
+        if (!atomic_read(&nr_comm_events) &&
+            !atomic_read(&nr_mmap_events) &&
+            !atomic_read(&nr_task_events))
+                return;
+
+        task_event = (struct perf_task_event){
+                .task     = task,
+                .task_ctx = task_ctx,
+                .event_id    = {
+                        .header = {
+                                .type = new ? PERF_RECORD_FORK : PERF_RECORD_EXIT,
+                                .misc = 0,
+                                .size = sizeof(task_event.event_id),
+                        },
+                        /* .pid  */
+                        /* .ppid */
+                        /* .tid  */
+                        /* .ptid */
+                },
+        };
+
+        perf_event_task_event(&task_event);
+}
+
+void perf_event_fork(struct task_struct *task)
+{
+        perf_event_task(task, NULL, 1);
+}
+
+/*
+ * comm tracking
+ */
+
+struct perf_comm_event {
+        struct task_struct      *task;
+        char                    *comm;
+        int                     comm_size;
+
+        struct {
+                struct perf_event_header        header;
+
+                u32                             pid;
+                u32                             tid;
+        } event_id;
+};
+
+static void perf_event_comm_output(struct perf_event *event,
+                                     struct perf_comm_event *comm_event)
+{
+        struct perf_output_handle handle;
+        int size = comm_event->event_id.header.size;
+        int ret = perf_output_begin(&handle, event, size, 0, 0);
+
+        if (ret)
+                return;
+
+        comm_event->event_id.pid = perf_event_pid(event, comm_event->task);
+        comm_event->event_id.tid = perf_event_tid(event, comm_event->task);
+
+        perf_output_put(&handle, comm_event->event_id);
+        perf_output_copy(&handle, comm_event->comm,
+                                   comm_event->comm_size);
+        perf_output_end(&handle);
+}
+
+static int perf_event_comm_match(struct perf_event *event)
+{
+        if (event->attr.comm)
+                return 1;
+
+        return 0;
+}
+
+static void perf_event_comm_ctx(struct perf_event_context *ctx,
+                                  struct perf_comm_event *comm_event)
+{
+        struct perf_event *event;
+
+        if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
+                return;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
+                if (perf_event_comm_match(event))
+                        perf_event_comm_output(event, comm_event);
+        }
+        rcu_read_unlock();
+}
+
+static void perf_event_comm_event(struct perf_comm_event *comm_event)
+{
+        struct perf_cpu_context *cpuctx;
+        struct perf_event_context *ctx;
+        unsigned int size;
+        char comm[TASK_COMM_LEN];
+
+        memset(comm, 0, sizeof(comm));
+        strncpy(comm, comm_event->task->comm, sizeof(comm));
+        size = ALIGN(strlen(comm)+1, sizeof(u64));
+
+        comm_event->comm = comm;
+        comm_event->comm_size = size;
+
+        comm_event->event_id.header.size = sizeof(comm_event->event_id) + size;
+
+        cpuctx = &get_cpu_var(perf_cpu_context);
+        perf_event_comm_ctx(&cpuctx->ctx, comm_event);
+        put_cpu_var(perf_cpu_context);
+
+        rcu_read_lock();
+        /*
+         * doesn't really matter which of the child contexts the
+         * events ends up in.
+         */
+        ctx = rcu_dereference(current->perf_event_ctxp);
+        if (ctx)
+                perf_event_comm_ctx(ctx, comm_event);
+        rcu_read_unlock();
+}
+
+void perf_event_comm(struct task_struct *task)
+{
+        struct perf_comm_event comm_event;
+
+        if (task->perf_event_ctxp)
+                perf_event_enable_on_exec(task);
+
+        if (!atomic_read(&nr_comm_events))
+                return;
+
+        comm_event = (struct perf_comm_event){
+                .task   = task,
+                /* .comm      */
+                /* .comm_size */
+                .event_id  = {
+                        .header = {
+                                .type = PERF_RECORD_COMM,
+                                .misc = 0,
+                                /* .size */
+                        },
+                        /* .pid */
+                        /* .tid */
+                },
+        };
+
+        perf_event_comm_event(&comm_event);
+}
+
+/*
+ * mmap tracking
+ */
+
+struct perf_mmap_event {
+        struct vm_area_struct   *vma;
+
+        const char              *file_name;
+        int                     file_size;
+
+        struct {
+                struct perf_event_header        header;
+
+                u32                             pid;
+                u32                             tid;
+                u64                             start;
+                u64                             len;
+                u64                             pgoff;
+        } event_id;
+};
+
+static void perf_event_mmap_output(struct perf_event *event,
+                                     struct perf_mmap_event *mmap_event)
+{
+        struct perf_output_handle handle;
+        int size = mmap_event->event_id.header.size;
+        int ret = perf_output_begin(&handle, event, size, 0, 0);
+
+        if (ret)
+                return;
+
+        mmap_event->event_id.pid = perf_event_pid(event, current);
+        mmap_event->event_id.tid = perf_event_tid(event, current);
+
+        perf_output_put(&handle, mmap_event->event_id);
+        perf_output_copy(&handle, mmap_event->file_name,
+                                   mmap_event->file_size);
+        perf_output_end(&handle);
+}
+
+static int perf_event_mmap_match(struct perf_event *event,
+                                   struct perf_mmap_event *mmap_event)
+{
+        if (event->attr.mmap)
+                return 1;
+
+        return 0;
+}
+
+static void perf_event_mmap_ctx(struct perf_event_context *ctx,
+                                  struct perf_mmap_event *mmap_event)
+{
+        struct perf_event *event;
+
+        if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
+                return;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
+                if (perf_event_mmap_match(event, mmap_event))
+                        perf_event_mmap_output(event, mmap_event);
+        }
+        rcu_read_unlock();
+}
+
+static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
+{
+        struct perf_cpu_context *cpuctx;
+        struct perf_event_context *ctx;
+        struct vm_area_struct *vma = mmap_event->vma;
+        struct file *file = vma->vm_file;
+        unsigned int size;
+        char tmp[16];
+        char *buf = NULL;
+        const char *name;
+
+        memset(tmp, 0, sizeof(tmp));
+
+        if (file) {
+                /*
+                 * d_path works from the end of the buffer backwards, so we
+                 * need to add enough zero bytes after the string to handle
+                 * the 64bit alignment we do later.
+                 */
+                buf = kzalloc(PATH_MAX + sizeof(u64), GFP_KERNEL);
+                if (!buf) {
+                        name = strncpy(tmp, "//enomem", sizeof(tmp));
+                        goto got_name;
+                }
+                name = d_path(&file->f_path, buf, PATH_MAX);
+                if (IS_ERR(name)) {
+                        name = strncpy(tmp, "//toolong", sizeof(tmp));
+                        goto got_name;
+                }
+        } else {
+                if (arch_vma_name(mmap_event->vma)) {
+                        name = strncpy(tmp, arch_vma_name(mmap_event->vma),
+                                       sizeof(tmp));
+                        goto got_name;
+                }
+
+                if (!vma->vm_mm) {
+                        name = strncpy(tmp, "[vdso]", sizeof(tmp));
+                        goto got_name;
+                }
+
+                name = strncpy(tmp, "//anon", sizeof(tmp));
+                goto got_name;
+        }
+
+got_name:
+        size = ALIGN(strlen(name)+1, sizeof(u64));
+
+        mmap_event->file_name = name;
+        mmap_event->file_size = size;
+
+        mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;
+
+        cpuctx = &get_cpu_var(perf_cpu_context);
+        perf_event_mmap_ctx(&cpuctx->ctx, mmap_event);
+        put_cpu_var(perf_cpu_context);
+
+        rcu_read_lock();
+        /*
+         * doesn't really matter which of the child contexts the
+         * events ends up in.
+         */
+        ctx = rcu_dereference(current->perf_event_ctxp);
+        if (ctx)
+                perf_event_mmap_ctx(ctx, mmap_event);
+        rcu_read_unlock();
+
+        kfree(buf);
+}
+
+void __perf_event_mmap(struct vm_area_struct *vma)
+{
+        struct perf_mmap_event mmap_event;
+
+        if (!atomic_read(&nr_mmap_events))
+                return;
+
+        mmap_event = (struct perf_mmap_event){
+                .vma    = vma,
+                /* .file_name */
+                /* .file_size */
+                .event_id  = {
+                        .header = {
+                                .type = PERF_RECORD_MMAP,
+                                .misc = 0,
+                                /* .size */
+                        },
+                        /* .pid */
+                        /* .tid */
+                        .start  = vma->vm_start,
+                        .len    = vma->vm_end - vma->vm_start,
+                        .pgoff  = vma->vm_pgoff,
+                },
+        };
+
+        perf_event_mmap_event(&mmap_event);
+}
+
+/*
+ * IRQ throttle logging
+ */
+
+static void perf_log_throttle(struct perf_event *event, int enable)
+{
+        struct perf_output_handle handle;
+        int ret;
+
+        struct {
+                struct perf_event_header        header;
+                u64                             time;
+                u64                             id;
+                u64                             stream_id;
+        } throttle_event = {
+                .header = {
+                        .type = PERF_RECORD_THROTTLE,
+                        .misc = 0,
+                        .size = sizeof(throttle_event),
+                },
+                .time           = perf_clock(),
+                .id             = primary_event_id(event),
+                .stream_id      = event->id,
+        };
+
+        if (enable)
+                throttle_event.header.type = PERF_RECORD_UNTHROTTLE;
+
+        ret = perf_output_begin(&handle, event, sizeof(throttle_event), 1, 0);
+        if (ret)
+                return;
+
+        perf_output_put(&handle, throttle_event);
+        perf_output_end(&handle);
+}
+
+/*
+ * Generic event overflow handling, sampling.
+ */
+
+static int __perf_event_overflow(struct perf_event *event, int nmi,
+                                   int throttle, struct perf_sample_data *data,
+                                   struct pt_regs *regs)
+{
+        int events = atomic_read(&event->event_limit);
+        struct hw_perf_event *hwc = &event->hw;
+        int ret = 0;
+
+        throttle = (throttle && event->pmu->unthrottle != NULL);
+
+        if (!throttle) {
+                hwc->interrupts++;
+        } else {
+                if (hwc->interrupts != MAX_INTERRUPTS) {
+                        hwc->interrupts++;
+                        if (HZ * hwc->interrupts >
+                                        (u64)sysctl_perf_event_sample_rate) {
+                                hwc->interrupts = MAX_INTERRUPTS;
+                                perf_log_throttle(event, 0);
+                                ret = 1;
+                        }
+                } else {
+                        /*
+                         * Keep re-disabling events even though on the previous
+                         * pass we disabled it - just in case we raced with a
+                         * sched-in and the event got enabled again:
+                         */
+                        ret = 1;
+                }
+        }
+
+        if (event->attr.freq) {
+                u64 now = perf_clock();
+                s64 delta = now - hwc->freq_stamp;
+
+                hwc->freq_stamp = now;
+
+                if (delta > 0 && delta < TICK_NSEC)
+                        perf_adjust_period(event, NSEC_PER_SEC / (int)delta);
+        }
+
+        /*
+         * XXX event_limit might not quite work as expected on inherited
+         * events
+         */
+
+        event->pending_kill = POLL_IN;
+        if (events && atomic_dec_and_test(&event->event_limit)) {
+                ret = 1;
+                event->pending_kill = POLL_HUP;
+                if (nmi) {
+                        event->pending_disable = 1;
+                        perf_pending_queue(&event->pending,
+                                           perf_pending_event);
+                } else
+                        perf_event_disable(event);
+        }
+
+        perf_event_output(event, nmi, data, regs);
+        return ret;
+}
+
+int perf_event_overflow(struct perf_event *event, int nmi,
+                          struct perf_sample_data *data,
+                          struct pt_regs *regs)
+{
+        return __perf_event_overflow(event, nmi, 1, data, regs);
+}
+
+/*
+ * Generic software event infrastructure
+ */
+
+/*
+ * We directly increment event->count and keep a second value in
+ * event->hw.period_left to count intervals. This period event
+ * is kept in the range [-sample_period, 0] so that we can use the
+ * sign as trigger.
+ */
+
+static u64 perf_swevent_set_period(struct perf_event *event)
+{
+        struct hw_perf_event *hwc = &event->hw;
+        u64 period = hwc->last_period;
+        u64 nr, offset;
+        s64 old, val;
+
+        hwc->last_period = hwc->sample_period;
+
+again:
+        old = val = atomic64_read(&hwc->period_left);
+        if (val < 0)
+                return 0;
+
+        nr = div64_u64(period + val, period);
+        offset = nr * period;
+        val -= offset;
+        if (atomic64_cmpxchg(&hwc->period_left, old, val) != old)
+                goto again;
+
+        return nr;
+}
+
+static void perf_swevent_overflow(struct perf_event *event,
+                                    int nmi, struct perf_sample_data *data,
+                                    struct pt_regs *regs)
+{
+        struct hw_perf_event *hwc = &event->hw;
+        int throttle = 0;
+        u64 overflow;
+
+        data->period = event->hw.last_period;
+        overflow = perf_swevent_set_period(event);
+
+        if (hwc->interrupts == MAX_INTERRUPTS)
+                return;
+
+        for (; overflow; overflow--) {
+                if (__perf_event_overflow(event, nmi, throttle,
+                                            data, regs)) {
+                        /*
+                         * We inhibit the overflow from happening when
+                         * hwc->interrupts == MAX_INTERRUPTS.
+                         */
+                        break;
+                }
+                throttle = 1;
+        }
+}
+
+static void perf_swevent_unthrottle(struct perf_event *event)
+{
+        /*
+         * Nothing to do, we already reset hwc->interrupts.
+         */
+}
+
+static void perf_swevent_add(struct perf_event *event, u64 nr,
+                               int nmi, struct perf_sample_data *data,
+                               struct pt_regs *regs)
+{
+        struct hw_perf_event *hwc = &event->hw;
+
+        atomic64_add(nr, &event->count);
+
+        if (!hwc->sample_period)
+                return;
+
+        if (!regs)
+                return;
+
+        if (!atomic64_add_negative(nr, &hwc->period_left))
+                perf_swevent_overflow(event, nmi, data, regs);
+}
+
+static int perf_swevent_is_counting(struct perf_event *event)
+{
+        /*
+         * The event is active, we're good!
+         */
+        if (event->state == PERF_EVENT_STATE_ACTIVE)
+                return 1;
+
+        /*
+         * The event is off/error, not counting.
+         */
+        if (event->state != PERF_EVENT_STATE_INACTIVE)
+                return 0;
+
+        /*
+         * The event is inactive, if the context is active
+         * we're part of a group that didn't make it on the 'pmu',
+         * not counting.
+         */
+        if (event->ctx->is_active)
+                return 0;
+
+        /*
+         * We're inactive and the context is too, this means the
+         * task is scheduled out, we're counting events that happen
+         * to us, like migration events.
+         */
+        return 1;
+}
+
+static int perf_swevent_match(struct perf_event *event,
+                                enum perf_type_id type,
+                                u32 event_id, struct pt_regs *regs)
+{
+        if (!perf_swevent_is_counting(event))
+                return 0;
+
+        if (event->attr.type != type)
+                return 0;
+        if (event->attr.config != event_id)
+                return 0;
+
+        if (regs) {
+                if (event->attr.exclude_user && user_mode(regs))
+                        return 0;
+
+                if (event->attr.exclude_kernel && !user_mode(regs))
+                        return 0;
+        }
+
+        return 1;
+}
+
+static void perf_swevent_ctx_event(struct perf_event_context *ctx,
+                                     enum perf_type_id type,
+                                     u32 event_id, u64 nr, int nmi,
+                                     struct perf_sample_data *data,
+                                     struct pt_regs *regs)
+{
+        struct perf_event *event;
+
+        if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
+                return;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
+                if (perf_swevent_match(event, type, event_id, regs))
+                        perf_swevent_add(event, nr, nmi, data, regs);
+        }
+        rcu_read_unlock();
+}
+
+static int *perf_swevent_recursion_context(struct perf_cpu_context *cpuctx)
+{
+        if (in_nmi())
+                return &cpuctx->recursion[3];
+
+        if (in_irq())
+                return &cpuctx->recursion[2];
+
+        if (in_softirq())
+                return &cpuctx->recursion[1];
+
+        return &cpuctx->recursion[0];
+}
+
+static void do_perf_sw_event(enum perf_type_id type, u32 event_id,
+                                    u64 nr, int nmi,
+                                    struct perf_sample_data *data,
+                                    struct pt_regs *regs)
+{
+        struct perf_cpu_context *cpuctx = &get_cpu_var(perf_cpu_context);
+        int *recursion = perf_swevent_recursion_context(cpuctx);
+        struct perf_event_context *ctx;
+
+        if (*recursion)
+                goto out;
+
+        (*recursion)++;
+        barrier();
+
+        perf_swevent_ctx_event(&cpuctx->ctx, type, event_id,
+                                 nr, nmi, data, regs);
+        rcu_read_lock();
+        /*
+         * doesn't really matter which of the child contexts the
+         * events ends up in.
+         */
+        ctx = rcu_dereference(current->perf_event_ctxp);
+        if (ctx)
+                perf_swevent_ctx_event(ctx, type, event_id, nr, nmi, data, regs);
+        rcu_read_unlock();
+
+        barrier();
+        (*recursion)--;
+
+out:
+        put_cpu_var(perf_cpu_context);
+}
+
+void __perf_sw_event(u32 event_id, u64 nr, int nmi,
+                            struct pt_regs *regs, u64 addr)
+{
+        struct perf_sample_data data = {
+                .addr = addr,
+        };
+
+        do_perf_sw_event(PERF_TYPE_SOFTWARE, event_id, nr, nmi,
+                                &data, regs);
+}
+
+static void perf_swevent_read(struct perf_event *event)
+{
+}
+
+static int perf_swevent_enable(struct perf_event *event)
+{
+        struct hw_perf_event *hwc = &event->hw;
+
+        if (hwc->sample_period) {
+                hwc->last_period = hwc->sample_period;
+                perf_swevent_set_period(event);
+        }
+        return 0;
+}
+
+static void perf_swevent_disable(struct perf_event *event)
+{
+}
+
+static const struct pmu perf_ops_generic = {
+        .enable         = perf_swevent_enable,
+        .disable        = perf_swevent_disable,
+        .read           = perf_swevent_read,
+        .unthrottle     = perf_swevent_unthrottle,
+};
+
+/*
+ * hrtimer based swevent callback
+ */
+
+static enum hrtimer_restart perf_swevent_hrtimer(struct hrtimer *hrtimer)
+{
+        enum hrtimer_restart ret = HRTIMER_RESTART;
+        struct perf_sample_data data;
+        struct pt_regs *regs;
+        struct perf_event *event;
+        u64 period;
+
+        event   = container_of(hrtimer, struct perf_event, hw.hrtimer);
+        event->pmu->read(event);
+
+        data.addr = 0;
+        regs = get_irq_regs();
+        /*
+         * In case we exclude kernel IPs or are somehow not in interrupt
+         * context, provide the next best thing, the user IP.
+         */
+        if ((event->attr.exclude_kernel || !regs) &&
+                        !event->attr.exclude_user)
+                regs = task_pt_regs(current);
+
+        if (regs) {
+                if (perf_event_overflow(event, 0, &data, regs))
+                        ret = HRTIMER_NORESTART;
+        }
+
+        period = max_t(u64, 10000, event->hw.sample_period);
+        hrtimer_forward_now(hrtimer, ns_to_ktime(period));
+
+        return ret;
+}
+
+/*
+ * Software event: cpu wall time clock
+ */
+
+static void cpu_clock_perf_event_update(struct perf_event *event)
+{
+        int cpu = raw_smp_processor_id();
+        s64 prev;
+        u64 now;
+
+        now = cpu_clock(cpu);
+        prev = atomic64_read(&event->hw.prev_count);
+        atomic64_set(&event->hw.prev_count, now);
+        atomic64_add(now - prev, &event->count);
+}
+
+static int cpu_clock_perf_event_enable(struct perf_event *event)
+{
+        struct hw_perf_event *hwc = &event->hw;
+        int cpu = raw_smp_processor_id();
+
+        atomic64_set(&hwc->prev_count, cpu_clock(cpu));
+        hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+        hwc->hrtimer.function = perf_swevent_hrtimer;
+        if (hwc->sample_period) {
+                u64 period = max_t(u64, 10000, hwc->sample_period);
+                __hrtimer_start_range_ns(&hwc->hrtimer,
+                                ns_to_ktime(period), 0,
+                                HRTIMER_MODE_REL, 0);
+        }
+
+        return 0;
+}
+
+static void cpu_clock_perf_event_disable(struct perf_event *event)
+{
+        if (event->hw.sample_period)
+                hrtimer_cancel(&event->hw.hrtimer);
+        cpu_clock_perf_event_update(event);
+}
+
+static void cpu_clock_perf_event_read(struct perf_event *event)
+{
+        cpu_clock_perf_event_update(event);
+}
+
+static const struct pmu perf_ops_cpu_clock = {
+        .enable         = cpu_clock_perf_event_enable,
+        .disable        = cpu_clock_perf_event_disable,
+        .read           = cpu_clock_perf_event_read,
+};
+
+/*
+ * Software event: task time clock
+ */
+
+static void task_clock_perf_event_update(struct perf_event *event, u64 now)
+{
+        u64 prev;
+        s64 delta;
+
+        prev = atomic64_xchg(&event->hw.prev_count, now);
+        delta = now - prev;
+        atomic64_add(delta, &event->count);
+}
+
+static int task_clock_perf_event_enable(struct perf_event *event)
+{
+        struct hw_perf_event *hwc = &event->hw;
+        u64 now;
+
+        now = event->ctx->time;
+
+        atomic64_set(&hwc->prev_count, now);
+        hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+        hwc->hrtimer.function = perf_swevent_hrtimer;
+        if (hwc->sample_period) {
+                u64 period = max_t(u64, 10000, hwc->sample_period);
+                __hrtimer_start_range_ns(&hwc->hrtimer,
+                                ns_to_ktime(period), 0,
+                                HRTIMER_MODE_REL, 0);
+        }
+
+        return 0;
+}
+
+static void task_clock_perf_event_disable(struct perf_event *event)
+{
+        if (event->hw.sample_period)
+                hrtimer_cancel(&event->hw.hrtimer);
+        task_clock_perf_event_update(event, event->ctx->time);
+
+}
+
+static void task_clock_perf_event_read(struct perf_event *event)
+{
+        u64 time;
+
+        if (!in_nmi()) {
+                update_context_time(event->ctx);
+                time = event->ctx->time;
+        } else {
+                u64 now = perf_clock();
+                u64 delta = now - event->ctx->timestamp;
+                time = event->ctx->time + delta;
+        }
+
+        task_clock_perf_event_update(event, time);
+}
+
+static const struct pmu perf_ops_task_clock = {
+        .enable         = task_clock_perf_event_enable,
+        .disable        = task_clock_perf_event_disable,
+        .read           = task_clock_perf_event_read,
+};
+
+#ifdef CONFIG_EVENT_PROFILE
+void perf_tp_event(int event_id, u64 addr, u64 count, void *record,
+                          int entry_size)
+{
+        struct perf_raw_record raw = {
+                .size = entry_size,
+                .data = record,
+        };
+
+        struct perf_sample_data data = {
+                .addr = addr,
+                .raw = &raw,
+        };
+
+        struct pt_regs *regs = get_irq_regs();
+
+        if (!regs)
+                regs = task_pt_regs(current);
+
+        do_perf_sw_event(PERF_TYPE_TRACEPOINT, event_id, count, 1,
+                                &data, regs);
+}
+EXPORT_SYMBOL_GPL(perf_tp_event);
+
+extern int ftrace_profile_enable(int);
+extern void ftrace_profile_disable(int);
+
+static void tp_perf_event_destroy(struct perf_event *event)
+{
+        ftrace_profile_disable(event->attr.config);
+}
+
+static const struct pmu *tp_perf_event_init(struct perf_event *event)
+{
+        /*
+         * Raw tracepoint data is a severe data leak, only allow root to
+         * have these.
+         */
+        if ((event->attr.sample_type & PERF_SAMPLE_RAW) &&
+                        perf_paranoid_tracepoint_raw() &&
+                        !capable(CAP_SYS_ADMIN))
+                return ERR_PTR(-EPERM);
+
+        if (ftrace_profile_enable(event->attr.config))
+                return NULL;
+
+        event->destroy = tp_perf_event_destroy;
+
+        return &perf_ops_generic;
+}
+#else
+static const struct pmu *tp_perf_event_init(struct perf_event *event)
+{
+        return NULL;
+}
+#endif
+
+atomic_t perf_swevent_enabled[PERF_COUNT_SW_MAX];
+
+static void sw_perf_event_destroy(struct perf_event *event)
+{
+        u64 event_id = event->attr.config;
+
+        WARN_ON(event->parent);
+
+        atomic_dec(&perf_swevent_enabled[event_id]);
+}
+
+static const struct pmu *sw_perf_event_init(struct perf_event *event)
+{
+        const struct pmu *pmu = NULL;
+        u64 event_id = event->attr.config;
+
+        /*
+         * Software events (currently) can't in general distinguish
+         * between user, kernel and hypervisor events.
+         * However, context switches and cpu migrations are considered
+         * to be kernel events, and page faults are never hypervisor
+         * events.
+         */
+        switch (event_id) {
+        case PERF_COUNT_SW_CPU_CLOCK:
+                pmu = &perf_ops_cpu_clock;
+
+                break;
+        case PERF_COUNT_SW_TASK_CLOCK:
+                /*
+                 * If the user instantiates this as a per-cpu event,
+                 * use the cpu_clock event instead.
+                 */
+                if (event->ctx->task)
+                        pmu = &perf_ops_task_clock;
+                else
+                        pmu = &perf_ops_cpu_clock;
+
+                break;
+        case PERF_COUNT_SW_PAGE_FAULTS:
+        case PERF_COUNT_SW_PAGE_FAULTS_MIN:
+        case PERF_COUNT_SW_PAGE_FAULTS_MAJ:
+        case PERF_COUNT_SW_CONTEXT_SWITCHES:
+        case PERF_COUNT_SW_CPU_MIGRATIONS:
+                if (!event->parent) {
+                        atomic_inc(&perf_swevent_enabled[event_id]);
+                        event->destroy = sw_perf_event_destroy;
+                }
+                pmu = &perf_ops_generic;
+                break;
+        }
+
+        return pmu;
+}
+
+/*
+ * Allocate and initialize a event structure
+ */
+static struct perf_event *
+perf_event_alloc(struct perf_event_attr *attr,
+                   int cpu,
+                   struct perf_event_context *ctx,
+                   struct perf_event *group_leader,
+                   struct perf_event *parent_event,
+                   gfp_t gfpflags)
+{
+        const struct pmu *pmu;
+        struct perf_event *event;
+        struct hw_perf_event *hwc;
+        long err;
+
+        event = kzalloc(sizeof(*event), gfpflags);
+        if (!event)
+                return ERR_PTR(-ENOMEM);
+
+        /*
+         * Single events are their own group leaders, with an
+         * empty sibling list:
+         */
+        if (!group_leader)
+                group_leader = event;
+
+        mutex_init(&event->child_mutex);
+        INIT_LIST_HEAD(&event->child_list);
+
+        INIT_LIST_HEAD(&event->group_entry);
+        INIT_LIST_HEAD(&event->event_entry);
+        INIT_LIST_HEAD(&event->sibling_list);
+        init_waitqueue_head(&event->waitq);
+
+        mutex_init(&event->mmap_mutex);
+
+        event->cpu              = cpu;
+        event->attr             = *attr;
+        event->group_leader     = group_leader;
+        event->pmu              = NULL;
+        event->ctx              = ctx;
+        event->oncpu            = -1;
+
+        event->parent           = parent_event;
+
+        event->ns               = get_pid_ns(current->nsproxy->pid_ns);
+        event->id               = atomic64_inc_return(&perf_event_id);
+
+        event->state            = PERF_EVENT_STATE_INACTIVE;
+
+        if (attr->disabled)
+                event->state = PERF_EVENT_STATE_OFF;
+
+        pmu = NULL;
+
+        hwc = &event->hw;
+        hwc->sample_period = attr->sample_period;
+        if (attr->freq && attr->sample_freq)
+                hwc->sample_period = 1;
+        hwc->last_period = hwc->sample_period;
+
+        atomic64_set(&hwc->period_left, hwc->sample_period);
+
+        /*
+         * we currently do not support PERF_FORMAT_GROUP on inherited events
+         */
+        if (attr->inherit && (attr->read_format & PERF_FORMAT_GROUP))
+                goto done;
+
+        switch (attr->type) {
+        case PERF_TYPE_RAW:
+        case PERF_TYPE_HARDWARE:
+        case PERF_TYPE_HW_CACHE:
+                pmu = hw_perf_event_init(event);
+                break;
+
+        case PERF_TYPE_SOFTWARE:
+                pmu = sw_perf_event_init(event);
+                break;
+
+        case PERF_TYPE_TRACEPOINT:
+                pmu = tp_perf_event_init(event);
+                break;
+
+        default:
+                break;
+        }
+done:
+        err = 0;
+        if (!pmu)
+                err = -EINVAL;
+        else if (IS_ERR(pmu))
+                err = PTR_ERR(pmu);
+
+        if (err) {
+                if (event->ns)
+                        put_pid_ns(event->ns);
+                kfree(event);
+                return ERR_PTR(err);
+        }
+
+        event->pmu = pmu;
+
+        if (!event->parent) {
+                atomic_inc(&nr_events);
+                if (event->attr.mmap)
+                        atomic_inc(&nr_mmap_events);
+                if (event->attr.comm)
+                        atomic_inc(&nr_comm_events);
+                if (event->attr.task)
+                        atomic_inc(&nr_task_events);
+        }
+
+        return event;
+}
+
+static int perf_copy_attr(struct perf_event_attr __user *uattr,
+                          struct perf_event_attr *attr)
+{
+        u32 size;
+        int ret;
+
+        if (!access_ok(VERIFY_WRITE, uattr, PERF_ATTR_SIZE_VER0))
+                return -EFAULT;
+
+        /*
+         * zero the full structure, so that a short copy will be nice.
+         */
+        memset(attr, 0, sizeof(*attr));
+
+        ret = get_user(size, &uattr->size);
+        if (ret)
+                return ret;
+
+        if (size > PAGE_SIZE)   /* silly large */
+                goto err_size;
+
+        if (!size)              /* abi compat */
+                size = PERF_ATTR_SIZE_VER0;
+
+        if (size < PERF_ATTR_SIZE_VER0)
+                goto err_size;
+
+        /*
+         * If we're handed a bigger struct than we know of,
+         * ensure all the unknown bits are 0 - i.e. new
+         * user-space does not rely on any kernel feature
+         * extensions we dont know about yet.
+         */
+        if (size > sizeof(*attr)) {
+                unsigned char __user *addr;
+                unsigned char __user *end;
+                unsigned char val;
+
+                addr = (void __user *)uattr + sizeof(*attr);
+                end  = (void __user *)uattr + size;
+
+                for (; addr < end; addr++) {
+                        ret = get_user(val, addr);
+                        if (ret)
+                                return ret;
+                        if (val)
+                                goto err_size;
+                }
+                size = sizeof(*attr);
+        }
+
+        ret = copy_from_user(attr, uattr, size);
+        if (ret)
+                return -EFAULT;
+
+        /*
+         * If the type exists, the corresponding creation will verify
+         * the attr->config.
+         */
+        if (attr->type >= PERF_TYPE_MAX)
+                return -EINVAL;
+
+        if (attr->__reserved_1 || attr->__reserved_2 || attr->__reserved_3)
+                return -EINVAL;
+
+        if (attr->sample_type & ~(PERF_SAMPLE_MAX-1))
+                return -EINVAL;
+
+        if (attr->read_format & ~(PERF_FORMAT_MAX-1))
+                return -EINVAL;
+
+out:
+        return ret;
+
+err_size:
+        put_user(sizeof(*attr), &uattr->size);
+        ret = -E2BIG;
+        goto out;
+}
+
+int perf_event_set_output(struct perf_event *event, int output_fd)
+{
+        struct perf_event *output_event = NULL;
+        struct file *output_file = NULL;
+        struct perf_event *old_output;
+        int fput_needed = 0;
+        int ret = -EINVAL;
+
+        if (!output_fd)
+                goto set;
+
+        output_file = fget_light(output_fd, &fput_needed);
+        if (!output_file)
+                return -EBADF;
+
+        if (output_file->f_op != &perf_fops)
+                goto out;
+
+        output_event = output_file->private_data;
+
+        /* Don't chain output fds */
+        if (output_event->output)
+                goto out;
+
+        /* Don't set an output fd when we already have an output channel */
+        if (event->data)
+                goto out;
+
+        atomic_long_inc(&output_file->f_count);
+
+set:
+        mutex_lock(&event->mmap_mutex);
+        old_output = event->output;
+        rcu_assign_pointer(event->output, output_event);
+        mutex_unlock(&event->mmap_mutex);
+
+        if (old_output) {
+                /*
+                 * we need to make sure no existing perf_output_*()
+                 * is still referencing this event.
+                 */
+                synchronize_rcu();
+                fput(old_output->filp);
+        }
+
+        ret = 0;
+out:
+        fput_light(output_file, fput_needed);
+        return ret;
+}
+
+/**
+ * sys_perf_event_open - open a performance event, associate it to a task/cpu
+ *
+ * @attr_uptr:  event_id type attributes for monitoring/sampling
+ * @pid:                target pid
+ * @cpu:                target cpu
+ * @group_fd:           group leader event fd
+ */
+SYSCALL_DEFINE5(perf_event_open,
+                struct perf_event_attr __user *, attr_uptr,
+                pid_t, pid, int, cpu, int, group_fd, unsigned long, flags)
+{
+        struct perf_event *event, *group_leader;
+        struct perf_event_attr attr;
+        struct perf_event_context *ctx;
+        struct file *event_file = NULL;
+        struct file *group_file = NULL;
+        int fput_needed = 0;
+        int fput_needed2 = 0;
+        int err;
+
+        /* for future expandability... */
+        if (flags & ~(PERF_FLAG_FD_NO_GROUP | PERF_FLAG_FD_OUTPUT))
+                return -EINVAL;
+
+        err = perf_copy_attr(attr_uptr, &attr);
+        if (err)
+                return err;
+
+        if (!attr.exclude_kernel) {
+                if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
+                        return -EACCES;
+        }
+
+        if (attr.freq) {
+                if (attr.sample_freq > sysctl_perf_event_sample_rate)
+                        return -EINVAL;
+        }
+
+        /*
+         * Get the target context (task or percpu):
+         */
+        ctx = find_get_context(pid, cpu);
+        if (IS_ERR(ctx))
+                return PTR_ERR(ctx);
+
+        /*
+         * Look up the group leader (we will attach this event to it):
+         */
+        group_leader = NULL;
+        if (group_fd != -1 && !(flags & PERF_FLAG_FD_NO_GROUP)) {
+                err = -EINVAL;
+                group_file = fget_light(group_fd, &fput_needed);
+                if (!group_file)
+                        goto err_put_context;
+                if (group_file->f_op != &perf_fops)
+                        goto err_put_context;
+
+                group_leader = group_file->private_data;
+                /*
+                 * Do not allow a recursive hierarchy (this new sibling
+                 * becoming part of another group-sibling):
+                 */
+                if (group_leader->group_leader != group_leader)
+                        goto err_put_context;
+                /*
+                 * Do not allow to attach to a group in a different
+                 * task or CPU context:
+                 */
+                if (group_leader->ctx != ctx)
+                        goto err_put_context;
+                /*
+                 * Only a group leader can be exclusive or pinned
+                 */
+                if (attr.exclusive || attr.pinned)
+                        goto err_put_context;
+        }
+
+        event = perf_event_alloc(&attr, cpu, ctx, group_leader,
+                                     NULL, GFP_KERNEL);
+        err = PTR_ERR(event);
+        if (IS_ERR(event))
+                goto err_put_context;
+
+        err = anon_inode_getfd("[perf_event]", &perf_fops, event, 0);
+        if (err < 0)
+                goto err_free_put_context;
+
+        event_file = fget_light(err, &fput_needed2);
+        if (!event_file)
+                goto err_free_put_context;
+
+        if (flags & PERF_FLAG_FD_OUTPUT) {
+                err = perf_event_set_output(event, group_fd);
+                if (err)
+                        goto err_fput_free_put_context;
+        }
+
+        event->filp = event_file;
+        WARN_ON_ONCE(ctx->parent_ctx);
+        mutex_lock(&ctx->mutex);
+        perf_install_in_context(ctx, event, cpu);
+        ++ctx->generation;
+        mutex_unlock(&ctx->mutex);
+
+        event->owner = current;
+        get_task_struct(current);
+        mutex_lock(&current->perf_event_mutex);
+        list_add_tail(&event->owner_entry, &current->perf_event_list);
+        mutex_unlock(&current->perf_event_mutex);
+
+err_fput_free_put_context:
+        fput_light(event_file, fput_needed2);
+
+err_free_put_context:
+        if (err < 0)
+                kfree(event);
+
+err_put_context:
+        if (err < 0)
+                put_ctx(ctx);
+
+        fput_light(group_file, fput_needed);
+
+        return err;
+}
+
+/*
+ * inherit a event from parent task to child task:
+ */
+static struct perf_event *
+inherit_event(struct perf_event *parent_event,
+              struct task_struct *parent,
+              struct perf_event_context *parent_ctx,
+              struct task_struct *child,
+              struct perf_event *group_leader,
+              struct perf_event_context *child_ctx)
+{
+        struct perf_event *child_event;
+
+        /*
+         * Instead of creating recursive hierarchies of events,
+         * we link inherited events back to the original parent,
+         * which has a filp for sure, which we use as the reference
+         * count:
+         */
+        if (parent_event->parent)
+                parent_event = parent_event->parent;
+
+        child_event = perf_event_alloc(&parent_event->attr,
+                                           parent_event->cpu, child_ctx,
+                                           group_leader, parent_event,
+                                           GFP_KERNEL);
+        if (IS_ERR(child_event))
+                return child_event;
+        get_ctx(child_ctx);
+
+        /*
+         * Make the child state follow the state of the parent event,
+         * not its attr.disabled bit.  We hold the parent's mutex,
+         * so we won't race with perf_event_{en, dis}able_family.
+         */
+        if (parent_event->state >= PERF_EVENT_STATE_INACTIVE)
+                child_event->state = PERF_EVENT_STATE_INACTIVE;
+        else
+                child_event->state = PERF_EVENT_STATE_OFF;
+
+        if (parent_event->attr.freq)
+                child_event->hw.sample_period = parent_event->hw.sample_period;
+
+        /*
+         * Link it up in the child's context:
+         */
+        add_event_to_ctx(child_event, child_ctx);
+
+        /*
+         * Get a reference to the parent filp - we will fput it
+         * when the child event exits. This is safe to do because
+         * we are in the parent and we know that the filp still
+         * exists and has a nonzero count:
+         */
+        atomic_long_inc(&parent_event->filp->f_count);
+
+        /*
+         * Link this into the parent event's child list
+         */
+        WARN_ON_ONCE(parent_event->ctx->parent_ctx);
+        mutex_lock(&parent_event->child_mutex);
+        list_add_tail(&child_event->child_list, &parent_event->child_list);
+        mutex_unlock(&parent_event->child_mutex);
+
+        return child_event;
+}
+
+static int inherit_group(struct perf_event *parent_event,
+              struct task_struct *parent,
+              struct perf_event_context *parent_ctx,
+              struct task_struct *child,
+              struct perf_event_context *child_ctx)
+{
+        struct perf_event *leader;
+        struct perf_event *sub;
+        struct perf_event *child_ctr;
+
+        leader = inherit_event(parent_event, parent, parent_ctx,
+                                 child, NULL, child_ctx);
+        if (IS_ERR(leader))
+                return PTR_ERR(leader);
+        list_for_each_entry(sub, &parent_event->sibling_list, group_entry) {
+                child_ctr = inherit_event(sub, parent, parent_ctx,
+                                            child, leader, child_ctx);
+                if (IS_ERR(child_ctr))
+                        return PTR_ERR(child_ctr);
+        }
+        return 0;
+}
+
+static void sync_child_event(struct perf_event *child_event,
+                               struct task_struct *child)
+{
+        struct perf_event *parent_event = child_event->parent;
+        u64 child_val;
+
+        if (child_event->attr.inherit_stat)
+                perf_event_read_event(child_event, child);
+
+        child_val = atomic64_read(&child_event->count);
+
+        /*
+         * Add back the child's count to the parent's count:
+         */
+        atomic64_add(child_val, &parent_event->count);
+        atomic64_add(child_event->total_time_enabled,
+                     &parent_event->child_total_time_enabled);
+        atomic64_add(child_event->total_time_running,
+                     &parent_event->child_total_time_running);
+
+        /*
+         * Remove this event from the parent's list
+         */
+        WARN_ON_ONCE(parent_event->ctx->parent_ctx);
+        mutex_lock(&parent_event->child_mutex);
+        list_del_init(&child_event->child_list);
+        mutex_unlock(&parent_event->child_mutex);
+
+        /*
+         * Release the parent event, if this was the last
+         * reference to it.
+         */
+        fput(parent_event->filp);
+}
+
+static void
+__perf_event_exit_task(struct perf_event *child_event,
+                         struct perf_event_context *child_ctx,
+                         struct task_struct *child)
+{
+        struct perf_event *parent_event;
+
+        update_event_times(child_event);
+        perf_event_remove_from_context(child_event);
+
+        parent_event = child_event->parent;
+        /*
+         * It can happen that parent exits first, and has events
+         * that are still around due to the child reference. These
+         * events need to be zapped - but otherwise linger.
+         */
+        if (parent_event) {
+                sync_child_event(child_event, child);
+                free_event(child_event);
+        }
+}
+
+/*
+ * When a child task exits, feed back event values to parent events.
+ */
+void perf_event_exit_task(struct task_struct *child)
+{
+        struct perf_event *child_event, *tmp;
+        struct perf_event_context *child_ctx;
+        unsigned long flags;
+
+        if (likely(!child->perf_event_ctxp)) {
+                perf_event_task(child, NULL, 0);
+                return;
+        }
+
+        local_irq_save(flags);
+        /*
+         * We can't reschedule here because interrupts are disabled,
+         * and either child is current or it is a task that can't be
+         * scheduled, so we are now safe from rescheduling changing
+         * our context.
+         */
+        child_ctx = child->perf_event_ctxp;
+        __perf_event_task_sched_out(child_ctx);
+
+        /*
+         * Take the context lock here so that if find_get_context is
+         * reading child->perf_event_ctxp, we wait until it has
+         * incremented the context's refcount before we do put_ctx below.
+         */
+        spin_lock(&child_ctx->lock);
+        child->perf_event_ctxp = NULL;
+        /*
+         * If this context is a clone; unclone it so it can't get
+         * swapped to another process while we're removing all
+         * the events from it.
+         */
+        unclone_ctx(child_ctx);
+        spin_unlock_irqrestore(&child_ctx->lock, flags);
+
+        /*
+         * Report the task dead after unscheduling the events so that we
+         * won't get any samples after PERF_RECORD_EXIT. We can however still
+         * get a few PERF_RECORD_READ events.
+         */
+        perf_event_task(child, child_ctx, 0);
+
+        /*
+         * We can recurse on the same lock type through:
+         *
+         *   __perf_event_exit_task()
+         *     sync_child_event()
+         *       fput(parent_event->filp)
+         *         perf_release()
+         *           mutex_lock(&ctx->mutex)
+         *
+         * But since its the parent context it won't be the same instance.
+         */
+        mutex_lock_nested(&child_ctx->mutex, SINGLE_DEPTH_NESTING);
+
+again:
+        list_for_each_entry_safe(child_event, tmp, &child_ctx->group_list,
+                                 group_entry)
+                __perf_event_exit_task(child_event, child_ctx, child);
+
+        /*
+         * If the last event was a group event, it will have appended all
+         * its siblings to the list, but we obtained 'tmp' before that which
+         * will still point to the list head terminating the iteration.
+         */
+        if (!list_empty(&child_ctx->group_list))
+                goto again;
+
+        mutex_unlock(&child_ctx->mutex);
+
+        put_ctx(child_ctx);
+}
+
+/*
+ * free an unexposed, unused context as created by inheritance by
+ * init_task below, used by fork() in case of fail.
+ */
+void perf_event_free_task(struct task_struct *task)
+{
+        struct perf_event_context *ctx = task->perf_event_ctxp;
+        struct perf_event *event, *tmp;
+
+        if (!ctx)
+                return;
+
+        mutex_lock(&ctx->mutex);
+again:
+        list_for_each_entry_safe(event, tmp, &ctx->group_list, group_entry) {
+                struct perf_event *parent = event->parent;
+
+                if (WARN_ON_ONCE(!parent))
+                        continue;
+
+                mutex_lock(&parent->child_mutex);
+                list_del_init(&event->child_list);
+                mutex_unlock(&parent->child_mutex);
+
+                fput(parent->filp);
+
+                list_del_event(event, ctx);
+                free_event(event);
+        }
+
+        if (!list_empty(&ctx->group_list))
+                goto again;
+
+        mutex_unlock(&ctx->mutex);
+
+        put_ctx(ctx);
+}
+
+/*
+ * Initialize the perf_event context in task_struct
+ */
+int perf_event_init_task(struct task_struct *child)
+{
+        struct perf_event_context *child_ctx, *parent_ctx;
+        struct perf_event_context *cloned_ctx;
+        struct perf_event *event;
+        struct task_struct *parent = current;
+        int inherited_all = 1;
+        int ret = 0;
+
+        child->perf_event_ctxp = NULL;
+
+        mutex_init(&child->perf_event_mutex);
+        INIT_LIST_HEAD(&child->perf_event_list);
+
+        if (likely(!parent->perf_event_ctxp))
+                return 0;
+
+        /*
+         * This is executed from the parent task context, so inherit
+         * events that have been marked for cloning.
+         * First allocate and initialize a context for the child.
+         */
+
+        child_ctx = kmalloc(sizeof(struct perf_event_context), GFP_KERNEL);
+        if (!child_ctx)
+                return -ENOMEM;
+
+        __perf_event_init_context(child_ctx, child);
+        child->perf_event_ctxp = child_ctx;
+        get_task_struct(child);
+
+        /*
+         * If the parent's context is a clone, pin it so it won't get
+         * swapped under us.
+         */
+        parent_ctx = perf_pin_task_context(parent);
+
+        /*
+         * No need to check if parent_ctx != NULL here; since we saw
+         * it non-NULL earlier, the only reason for it to become NULL
+         * is if we exit, and since we're currently in the middle of
+         * a fork we can't be exiting at the same time.
+         */
+
+        /*
+         * Lock the parent list. No need to lock the child - not PID
+         * hashed yet and not running, so nobody can access it.
+         */
+        mutex_lock(&parent_ctx->mutex);
+
+        /*
+         * We dont have to disable NMIs - we are only looking at
+         * the list, not manipulating it:
+         */
+        list_for_each_entry_rcu(event, &parent_ctx->event_list, event_entry) {
+                if (event != event->group_leader)
+                        continue;
+
+                if (!event->attr.inherit) {
+                        inherited_all = 0;
+                        continue;
+                }
+
+                ret = inherit_group(event, parent, parent_ctx,
+                                             child, child_ctx);
+                if (ret) {
+                        inherited_all = 0;
+                        break;
+                }
+        }
+
+        if (inherited_all) {
+                /*
+                 * Mark the child context as a clone of the parent
+                 * context, or of whatever the parent is a clone of.
+                 * Note that if the parent is a clone, it could get
+                 * uncloned at any point, but that doesn't matter
+                 * because the list of events and the generation
+                 * count can't have changed since we took the mutex.
+                 */
+                cloned_ctx = rcu_dereference(parent_ctx->parent_ctx);
+                if (cloned_ctx) {
+                        child_ctx->parent_ctx = cloned_ctx;
+                        child_ctx->parent_gen = parent_ctx->parent_gen;
+                } else {
+                        child_ctx->parent_ctx = parent_ctx;
+                        child_ctx->parent_gen = parent_ctx->generation;
+                }
+                get_ctx(child_ctx->parent_ctx);
+        }
+
+        mutex_unlock(&parent_ctx->mutex);
+
+        perf_unpin_context(parent_ctx);
+
+        return ret;
+}
+
+static void __cpuinit perf_event_init_cpu(int cpu)
+{
+        struct perf_cpu_context *cpuctx;
+
+        cpuctx = &per_cpu(perf_cpu_context, cpu);
+        __perf_event_init_context(&cpuctx->ctx, NULL);
+
+        spin_lock(&perf_resource_lock);
+        cpuctx->max_pertask = perf_max_events - perf_reserved_percpu;
+        spin_unlock(&perf_resource_lock);
+
+        hw_perf_event_setup(cpu);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static void __perf_event_exit_cpu(void *info)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_event_context *ctx = &cpuctx->ctx;
+        struct perf_event *event, *tmp;
+
+        list_for_each_entry_safe(event, tmp, &ctx->group_list, group_entry)
+                __perf_event_remove_from_context(event);
+}
+static void perf_event_exit_cpu(int cpu)
+{
+        struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
+        struct perf_event_context *ctx = &cpuctx->ctx;
+
+        mutex_lock(&ctx->mutex);
+        smp_call_function_single(cpu, __perf_event_exit_cpu, NULL, 1);
+        mutex_unlock(&ctx->mutex);
+}
+#else
+static inline void perf_event_exit_cpu(int cpu) { }
+#endif
+
+static int __cpuinit
+perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
+{
+        unsigned int cpu = (long)hcpu;
+
+        switch (action) {
+
+        case CPU_UP_PREPARE:
+        case CPU_UP_PREPARE_FROZEN:
+                perf_event_init_cpu(cpu);
+                break;
+
+        case CPU_ONLINE:
+        case CPU_ONLINE_FROZEN:
+                hw_perf_event_setup_online(cpu);
+                break;
+
+        case CPU_DOWN_PREPARE:
+        case CPU_DOWN_PREPARE_FROZEN:
+                perf_event_exit_cpu(cpu);
+                break;
+
+        default:
+                break;
+        }
+
+        return NOTIFY_OK;
+}
+
+/*
+ * This has to have a higher priority than migration_notifier in sched.c.
+ */
+static struct notifier_block __cpuinitdata perf_cpu_nb = {
+        .notifier_call          = perf_cpu_notify,
+        .priority               = 20,
+};
+
+void __init perf_event_init(void)
+{
+        perf_cpu_notify(&perf_cpu_nb, (unsigned long)CPU_UP_PREPARE,
+                        (void *)(long)smp_processor_id());
+        perf_cpu_notify(&perf_cpu_nb, (unsigned long)CPU_ONLINE,
+                        (void *)(long)smp_processor_id());
+        register_cpu_notifier(&perf_cpu_nb);
+}
+
+static ssize_t perf_show_reserve_percpu(struct sysdev_class *class, char *buf)
+{
+        return sprintf(buf, "%d\n", perf_reserved_percpu);
+}
+
+static ssize_t
+perf_set_reserve_percpu(struct sysdev_class *class,
+                        const char *buf,
+                        size_t count)
+{
+        struct perf_cpu_context *cpuctx;
+        unsigned long val;
+        int err, cpu, mpt;
+
+        err = strict_strtoul(buf, 10, &val);
+        if (err)
+                return err;
+        if (val > perf_max_events)
+                return -EINVAL;
+
+        spin_lock(&perf_resource_lock);
+        perf_reserved_percpu = val;
+        for_each_online_cpu(cpu) {
+                cpuctx = &per_cpu(perf_cpu_context, cpu);
+                spin_lock_irq(&cpuctx->ctx.lock);
+                mpt = min(perf_max_events - cpuctx->ctx.nr_events,
+                          perf_max_events - perf_reserved_percpu);
+                cpuctx->max_pertask = mpt;
+                spin_unlock_irq(&cpuctx->ctx.lock);
+        }
+        spin_unlock(&perf_resource_lock);
+
+        return count;
+}
+
+static ssize_t perf_show_overcommit(struct sysdev_class *class, char *buf)
+{
+        return sprintf(buf, "%d\n", perf_overcommit);
+}
+
+static ssize_t
+perf_set_overcommit(struct sysdev_class *class, const char *buf, size_t count)
+{
+        unsigned long val;
+        int err;
+
+        err = strict_strtoul(buf, 10, &val);
+        if (err)
+                return err;
+        if (val > 1)
+                return -EINVAL;
+
+        spin_lock(&perf_resource_lock);
+        perf_overcommit = val;
+        spin_unlock(&perf_resource_lock);
+
+        return count;
+}
+
+static SYSDEV_CLASS_ATTR(
+                                reserve_percpu,
+                                0644,
+                                perf_show_reserve_percpu,
+                                perf_set_reserve_percpu
+                        );
+
+static SYSDEV_CLASS_ATTR(
+                                overcommit,
+                                0644,
+                                perf_show_overcommit,
+                                perf_set_overcommit
+                        );
+
+static struct attribute *perfclass_attrs[] = {
+        &attr_reserve_percpu.attr,
+        &attr_overcommit.attr,
+        NULL
+};
+
+static struct attribute_group perfclass_attr_group = {
+        .attrs                  = perfclass_attrs,
+        .name                   = "perf_events",
+};
+
+static int __init perf_event_sysfs_init(void)
+{
+        return sysfs_create_group(&cpu_sysdev_class.kset.kobj,
+                                  &perfclass_attr_group);
+}
+device_initcall(perf_event_sysfs_init);