/*
 * Performance events 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/slab.h>
#include <linux/hash.h>
#include <linux/sysfs.h>
#include <linux/dcache.h>
#include <linux/percpu.h>
#include <linux/ptrace.h>
#include <linux/vmstat.h>
#include <linux/vmalloc.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 <linux/ftrace_event.h>
#include <linux/hw_breakpoint.h>

#include <asm/irq_regs.h>

atomic_t perf_task_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;

static LIST_HEAD(pmus);
static DEFINE_MUTEX(pmus_lock);
static struct srcu_struct pmus_srcu;

/*
 * 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;

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;

void __weak perf_event_print_debug(void)	{ }

extern __weak const char *perf_pmu_name(void)
{
	return "pmu";
}

void perf_pmu_disable(struct pmu *pmu)
{
	int *count = this_cpu_ptr(pmu->pmu_disable_count);
	if (!(*count)++)
		pmu->pmu_disable(pmu);
}

void perf_pmu_enable(struct pmu *pmu)
{
	int *count = this_cpu_ptr(pmu->pmu_disable_count);
	if (!--(*count))
		pmu->pmu_enable(pmu);
}

static DEFINE_PER_CPU(struct list_head, rotation_list);

/*
 * perf_pmu_rotate_start() and perf_rotate_context() are fully serialized
 * because they're strictly cpu affine and rotate_start is called with IRQs
 * disabled, while rotate_context is called from IRQ context.
 */
static void perf_pmu_rotate_start(struct pmu *pmu)
{
	struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
	struct list_head *head = &__get_cpu_var(rotation_list);

	WARN_ON(!irqs_disabled());

	if (list_empty(&cpuctx->rotation_list))
		list_add(&cpuctx->rotation_list, head);
}

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, int ctxn, unsigned long *flags)
{
	struct perf_event_context *ctx;

	rcu_read_lock();
retry:
	ctx = rcu_dereference(task->perf_event_ctxp[ctxn]);
	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.
		 */
		raw_spin_lock_irqsave(&ctx->lock, *flags);
		if (ctx != rcu_dereference(task->perf_event_ctxp[ctxn])) {
			raw_spin_unlock_irqrestore(&ctx->lock, *flags);
			goto retry;
		}

		if (!atomic_inc_not_zero(&ctx->refcount)) {
			raw_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, int ctxn)
{
	struct perf_event_context *ctx;
	unsigned long flags;

	ctx = perf_lock_task_context(task, ctxn, &flags);
	if (ctx) {
		++ctx->pin_count;
		raw_spin_unlock_irqrestore(&ctx->lock, flags);
	}
	return ctx;
}

static void perf_unpin_context(struct perf_event_context *ctx)
{
	unsigned long flags;

	raw_spin_lock_irqsave(&ctx->lock, flags);
	--ctx->pin_count;
	raw_spin_unlock_irqrestore(&ctx->lock, flags);
	put_ctx(ctx);
}

static inline u64 perf_clock(void)
{
	return local_clock();
}

/*
 * 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;

	if (ctx->is_active)
		run_end = ctx->time;
	else
		run_end = event->tstamp_stopped;

	event->total_time_enabled = run_end - 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);
}

static struct list_head *
ctx_group_list(struct perf_event *event, struct perf_event_context *ctx)
{
	if (event->attr.pinned)
		return &ctx->pinned_groups;
	else
		return &ctx->flexible_groups;
}

/*
 * 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)
{
	WARN_ON_ONCE(event->attach_state & PERF_ATTACH_CONTEXT);
	event->attach_state |= PERF_ATTACH_CONTEXT;

	/*
	 * If we're a stand alone event or group leader, we go to the context
	 * list, group events are kept attached to the group so that
	 * perf_group_detach can, at all times, locate all siblings.
	 */
	if (event->group_leader == event) {
		struct list_head *list;

		if (is_software_event(event))
			event->group_flags |= PERF_GROUP_SOFTWARE;

		list = ctx_group_list(event, ctx);
		list_add_tail(&event->group_entry, list);
	}

	list_add_rcu(&event->event_entry, &ctx->event_list);
	if (!ctx->nr_events)
		perf_pmu_rotate_start(ctx->pmu);
	ctx->nr_events++;
	if (event->attr.inherit_stat)
		ctx->nr_stat++;
}

static void perf_group_attach(struct perf_event *event)
{
	struct perf_event *group_leader = event->group_leader;

	/*
	 * We can have double attach due to group movement in perf_event_open.
	 */
	if (event->attach_state & PERF_ATTACH_GROUP)
		return;

	event->attach_state |= PERF_ATTACH_GROUP;

	if (group_leader == event)
		return;

	if (group_leader->group_flags & PERF_GROUP_SOFTWARE &&
			!is_software_event(event))
		group_leader->group_flags &= ~PERF_GROUP_SOFTWARE;

	list_add_tail(&event->group_entry, &group_leader->sibling_list);
	group_leader->nr_siblings++;
}

/*
 * 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)
{
	/*
	 * We can have double detach due to exit/hot-unplug + close.
	 */
	if (!(event->attach_state & PERF_ATTACH_CONTEXT))
		return;

	event->attach_state &= ~PERF_ATTACH_CONTEXT;

	ctx->nr_events--;
	if (event->attr.inherit_stat)
		ctx->nr_stat--;

	list_del_rcu(&event->event_entry);

	if (event->group_leader == event)
		list_del_init(&event->group_entry);

	update_group_times(event);

	/*
	 * If event was in error state, then keep it
	 * that way, otherwise bogus counts will be
	 * returned on read(). The only way to get out
	 * of error state is by explicit re-enabling
	 * of the event
	 */
	if (event->state > PERF_EVENT_STATE_OFF)
		event->state = PERF_EVENT_STATE_OFF;
}

static void perf_group_detach(struct perf_event *event)
{
	struct perf_event *sibling, *tmp;
	struct list_head *list = NULL;

	/*
	 * We can have double detach due to exit/hot-unplug + close.
	 */
	if (!(event->attach_state & PERF_ATTACH_GROUP))
		return;

	event->attach_state &= ~PERF_ATTACH_GROUP;

	/*
	 * If this is a sibling, remove it from its group.
	 */
	if (event->group_leader != event) {
		list_del_init(&event->group_entry);
		event->group_leader->nr_siblings--;
		return;
	}

	if (!list_empty(&event->group_entry))
		list = &event->group_entry;

	/*
	 * If this was a group event with sibling events then
	 * upgrade the siblings to singleton events by adding them
	 * to whatever list we are on.
	 */
	list_for_each_entry_safe(sibling, tmp, &event->sibling_list, group_entry) {
		if (list)
			list_move_tail(&sibling->group_entry, list);
		sibling->group_leader = sibling;

		/* Inherit group flags from the previous leader */
		sibling->group_flags = event->group_flags;
	}
}

static inline int
event_filter_match(struct perf_event *event)
{
	return event->cpu == -1 || event->cpu == smp_processor_id();
}

static void
event_sched_out(struct perf_event *event,
		  struct perf_cpu_context *cpuctx,
		  struct perf_event_context *ctx)
{
	u64 delta;
	/*
	 * An event which could not be activated because of
	 * filter mismatch still needs to have its timings
	 * maintained, otherwise bogus information is return
	 * via read() for time_enabled, time_running:
	 */
	if (event->state == PERF_EVENT_STATE_INACTIVE
	    && !event_filter_match(event)) {
		delta = ctx->time - event->tstamp_stopped;
		event->tstamp_running += delta;
		event->tstamp_stopped = ctx->time;
	}

	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->del(event, 0);
	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;
	int state = group_event->state;

	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 (state == PERF_EVENT_STATE_ACTIVE && group_event->attr.exclusive)
		cpuctx->exclusive = 0;
}

static inline struct perf_cpu_context *
__get_cpu_context(struct perf_event_context *ctx)
{
	return this_cpu_ptr(ctx->pmu->pmu_cpu_context);
}

/*
 * 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_event *event = info;
	struct perf_event_context *ctx = event->ctx;
	struct perf_cpu_context *cpuctx = __get_cpu_context(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;

	raw_spin_lock(&ctx->lock);

	event_sched_out(event, cpuctx, ctx);

	list_del_event(event, ctx);

	raw_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 successful.
		 */
		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);

	raw_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)) {
		raw_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);
	raw_spin_unlock_irq(&ctx->lock);
}

/*
 * Cross CPU call to disable a performance event
 */
static void __perf_event_disable(void *info)
{
	struct perf_event *event = info;
	struct perf_event_context *ctx = event->ctx;
	struct perf_cpu_context *cpuctx = __get_cpu_context(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;

	raw_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;
	}

	raw_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.
 */
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);

	raw_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) {
		raw_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;
	}

	raw_spin_unlock_irq(&ctx->lock);
}

static int
event_sched_in(struct perf_event *event,
		 struct perf_cpu_context *cpuctx,
		 struct perf_event_context *ctx)
{
	if (event->state <= PERF_EVENT_STATE_OFF)
		return 0;

	event->state = PERF_EVENT_STATE_ACTIVE;
	event->oncpu = smp_processor_id();
	/*
	 * The new state must be visible before we turn it on in the hardware:
	 */
	smp_wmb();

	if (event->pmu->add(event, PERF_EF_START)) {
		event->state = PERF_EVENT_STATE_INACTIVE;
		event->oncpu = -1;
		return -EAGAIN;
	}

	event->tstamp_running += ctx->time - event->tstamp_stopped;

	event->shadow_ctx_time = ctx->time - ctx->timestamp;

	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)
{
	struct perf_event *event, *partial_group = NULL;
	struct pmu *pmu = group_event->pmu;
	u64 now = ctx->time;
	bool simulate = false;

	if (group_event->state == PERF_EVENT_STATE_OFF)
		return 0;

	pmu->start_txn(pmu);

	if (event_sched_in(group_event, cpuctx, ctx)) {
		pmu->cancel_txn(pmu);
		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)) {
			partial_group = event;
			goto group_error;
		}
	}

	if (!pmu->commit_txn(pmu))
		return 0;

group_error:
	/*
	 * Groups can be scheduled in as one unit only, so undo any
	 * partial group before returning:
	 * The events up to the failed event are scheduled out normally,
	 * tstamp_stopped will be updated.
	 *
	 * The failed events and the remaining siblings need to have
	 * their timings updated as if they had gone thru event_sched_in()
	 * and event_sched_out(). This is required to get consistent timings
	 * across the group. This also takes care of the case where the group
	 * could never be scheduled by ensuring tstamp_stopped is set to mark
	 * the time the event was actually stopped, such that time delta
	 * calculation in update_event_times() is correct.
	 */
	list_for_each_entry(event, &group_event->sibling_list, group_entry) {
		if (event == partial_group)
			simulate = true;

		if (simulate) {
			event->tstamp_running += now - event->tstamp_stopped;
			event->tstamp_stopped = now;
		} else {
			event_sched_out(event, cpuctx, ctx);
		}
	}
	event_sched_out(group_event, cpuctx, ctx);

	pmu->cancel_txn(pmu);

	return -EAGAIN;
}

/*
 * 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 (event->group_flags & PERF_GROUP_SOFTWARE)
		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);
	perf_group_attach(event);
	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_event *event = info;
	struct perf_event_context *ctx = event->ctx;
	struct perf_event *leader = event->group_leader;
	struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
	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;
	}

	raw_spin_lock(&ctx->lock);
	ctx->is_active = 1;
	update_context_time(ctx);

	add_event_to_ctx(event, ctx);

	if (event->cpu != -1 && event->cpu != smp_processor_id())
		goto unlock;

	/*
	 * 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);

	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;
		}
	}

unlock:
	raw_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;

	event->ctx = ctx;

	if (!task) {
		/*
		 * Per cpu events are installed via an smp call and
		 * the install is always successful.
		 */
		smp_call_function_single(cpu, __perf_install_in_context,
					 event, 1);
		return;
	}

retry:
	task_oncpu_function_call(task, __perf_install_in_context,
				 event);

	raw_spin_lock_irq(&ctx->lock);
	/*
	 * we need to retry the smp call.
	 */
	if (ctx->is_active && list_empty(&event->group_entry)) {
		raw_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);
	raw_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_event_context *ctx = event->ctx;
	struct perf_event *leader = event->group_leader;
	struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
	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;
	}

	raw_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 (event->cpu != -1 && event->cpu != smp_processor_id())
		goto unlock;

	/*
	 * 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 {
		if (event == leader)
			err = group_sched_in(event, cpuctx, ctx);
		else
			err = event_sched_in(event, cpuctx, ctx);
	}

	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:
	raw_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.
 */
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;
	}

	raw_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:
	raw_spin_unlock_irq(&ctx->lock);
	task_oncpu_function_call(task, __perf_event_enable, event);

	raw_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:
	raw_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;
}

enum event_type_t {
	EVENT_FLEXIBLE = 0x1,
	EVENT_PINNED = 0x2,
	EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED,
};

static void ctx_sched_out(struct perf_event_context *ctx,
			  struct perf_cpu_context *cpuctx,
			  enum event_type_t event_type)
{
	struct perf_event *event;

	raw_spin_lock(&ctx->lock);
	perf_pmu_disable(ctx->pmu);
	ctx->is_active = 0;
	if (likely(!ctx->nr_events))
		goto out;
	update_context_time(ctx);

	if (!ctx->nr_active)
		goto out;

	if (event_type & EVENT_PINNED) {
		list_for_each_entry(event, &ctx->pinned_groups, group_entry)
			group_sched_out(event, cpuctx, ctx);
	}

	if (event_type & EVENT_FLEXIBLE) {
		list_for_each_entry(event, &ctx->flexible_groups, group_entry)
			group_sched_out(event, cpuctx, ctx);
	}
out:
	perf_pmu_enable(ctx->pmu);
	raw_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_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:
		event->pmu->read(event);
		/* fall-through */

	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 = local64_read(&next_event->count);
	value = local64_xchg(&event->count, value);
	local64_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;

	update_context_time(ctx);

	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);
	}
}

void perf_event_context_sched_out(struct task_struct *task, int ctxn,
				  struct task_struct *next)
{
	struct perf_event_context *ctx = task->perf_event_ctxp[ctxn];
	struct perf_event_context *next_ctx;
	struct perf_event_context *parent;
	struct perf_cpu_context *cpuctx;
	int do_switch = 1;

	if (likely(!ctx))
		return;

	cpuctx = __get_cpu_context(ctx);
	if (!cpuctx->task_ctx)
		return;

	rcu_read_lock();
	parent = rcu_dereference(ctx->parent_ctx);
	next_ctx = next->perf_event_ctxp[ctxn];
	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.
		 */
		raw_spin_lock(&ctx->lock);
		raw_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[ctxn] = next_ctx;
			next->perf_event_ctxp[ctxn] = ctx;
			ctx->task = next;
			next_ctx->task = task;
			do_switch = 0;

			perf_event_sync_stat(ctx, next_ctx);
		}
		raw_spin_unlock(&next_ctx->lock);
		raw_spin_unlock(&ctx->lock);
	}
	rcu_read_unlock();

	if (do_switch) {
		ctx_sched_out(ctx, cpuctx, EVENT_ALL);
		cpuctx->task_ctx = NULL;
	}
}

#define for_each_task_context_nr(ctxn)					\
	for ((ctxn) = 0; (ctxn) < perf_nr_task_contexts; (ctxn)++)

/*
 * 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 ctxn;

	for_each_task_context_nr(ctxn)
		perf_event_context_sched_out(task, ctxn, next);
}

static void task_ctx_sched_out(struct perf_event_context *ctx,
			       enum event_type_t event_type)
{
	struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);

	if (!cpuctx->task_ctx)
		return;

	if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
		return;

	ctx_sched_out(ctx, cpuctx, event_type);
	cpuctx->task_ctx = NULL;
}

/*
 * Called with IRQs disabled
 */
static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx,
			      enum event_type_t event_type)
{
	ctx_sched_out(&cpuctx->ctx, cpuctx, event_type);
}

static void
ctx_pinned_sched_in(struct perf_event_context *ctx,
		    struct perf_cpu_context *cpuctx)
{
	struct perf_event *event;

	list_for_each_entry(event, &ctx->pinned_groups, group_entry) {
		if (event->state <= PERF_EVENT_STATE_OFF)
			continue;
		if (event->cpu != -1 && event->cpu != smp_processor_id())
			continue;

		if (group_can_go_on(event, cpuctx, 1))
			group_sched_in(event, cpuctx, ctx);

		/*
		 * 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;
		}
	}
}

static void
ctx_flexible_sched_in(struct perf_event_context *ctx,
		      struct perf_cpu_context *cpuctx)
{
	struct perf_event *event;
	int can_add_hw = 1;

	list_for_each_entry(event, &ctx->flexible_groups, group_entry) {
		/* Ignore events in OFF or ERROR state */
		if (event->state <= PERF_EVENT_STATE_OFF)
			continue;
		/*
		 * Listen to the 'cpu' scheduling filter constraint
		 * of events:
		 */
		if (event->cpu != -1 && event->cpu != smp_processor_id())
			continue;

		if (group_can_go_on(event, cpuctx, can_add_hw)) {
			if (group_sched_in(event, cpuctx, ctx))
				can_add_hw = 0;
		}
	}
}

static void
ctx_sched_in(struct perf_event_context *ctx,
	     struct perf_cpu_context *cpuctx,
	     enum event_type_t event_type)
{
	raw_spin_lock(&ctx->lock);
	ctx->is_active = 1;
	if (likely(!ctx->nr_events))
		goto out;

	ctx->timestamp = perf_clock();

	/*
	 * First go through the list and put on any pinned groups
	 * in order to give them the best chance of going on.
	 */
	if (event_type & EVENT_PINNED)
		ctx_pinned_sched_in(ctx, cpuctx);

	/* Then walk through the lower prio flexible groups */
	if (event_type & EVENT_FLEXIBLE)
		ctx_flexible_sched_in(ctx, cpuctx);

out:
	raw_spin_unlock(&ctx->lock);
}

static void cpu_ctx_sched_in(struct perf_cpu_context *cpuctx,
			     enum event_type_t event_type)
{
	struct perf_event_context *ctx = &cpuctx->ctx;

	ctx_sched_in(ctx, cpuctx, event_type);
}

static void task_ctx_sched_in(struct perf_event_context *ctx,
			      enum event_type_t event_type)
{
	struct perf_cpu_context *cpuctx;

       	cpuctx = __get_cpu_context(ctx);
	if (cpuctx->task_ctx == ctx)
		return;

	ctx_sched_in(ctx, cpuctx, event_type);
	cpuctx->task_ctx = ctx;
}

void perf_event_context_sched_in(struct perf_event_context *ctx)
{
	struct perf_cpu_context *cpuctx;

	cpuctx = __get_cpu_context(ctx);
	if (cpuctx->task_ctx == ctx)
		return;

	perf_pmu_disable(ctx->pmu);
	/*
	 * We want to keep the following priority order:
	 * cpu pinned (that don't need to move), task pinned,
	 * cpu flexible, task flexible.
	 */
	cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);

	ctx_sched_in(ctx, cpuctx, EVENT_PINNED);
	cpu_ctx_sched_in(cpuctx, EVENT_FLEXIBLE);
	ctx_sched_in(ctx, cpuctx, EVENT_FLEXIBLE);

	cpuctx->task_ctx = ctx;

	/*
	 * Since these rotations are per-cpu, we need to ensure the
	 * cpu-context we got scheduled on is actually rotating.
	 */
	perf_pmu_rotate_start(ctx->pmu);
	perf_pmu_enable(ctx->pmu);
}

/*
 * 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)
{
	struct perf_event_context *ctx;
	int ctxn;

	for_each_task_context_nr(ctxn) {
		ctx = task->perf_event_ctxp[ctxn];
		if (likely(!ctx))
			continue;

		perf_event_context_sched_in(ctx);
	}
}

#define MAX_INTERRUPTS (~0ULL)

static void perf_log_throttle(struct perf_event *event, int enable);

static u64 perf_calculate_period(struct perf_event *event, u64 nsec, u64 count)
{
	u64 frequency = event->attr.sample_freq;
	u64 sec = NSEC_PER_SEC;
	u64 divisor, dividend;

	int count_fls, nsec_fls, frequency_fls, sec_fls;

	count_fls = fls64(count);
	nsec_fls = fls64(nsec);
	frequency_fls = fls64(frequency);
	sec_fls = 30;

	/*
	 * We got @count in @nsec, with a target of sample_freq HZ
	 * the target period becomes:
	 *
	 *             @count * 10^9
	 * period = -------------------
	 *          @nsec * sample_freq
	 *
	 */

	/*
	 * Reduce accuracy by one bit such that @a and @b converge
	 * to a similar magnitude.
	 */
#define REDUCE_FLS(a, b) 		\
do {					\
	if (a##_fls > b##_fls) {	\
		a >>= 1;		\
		a##_fls--;		\
	} else {			\
		b >>= 1;		\
		b##_fls--;		\
	}				\
} while (0)

	/*
	 * Reduce accuracy until either term fits in a u64, then proceed with
	 * the other, so that finally we can do a u64/u64 division.
	 */
	while (count_fls + sec_fls > 64 && nsec_fls + frequency_fls > 64) {
		REDUCE_FLS(nsec, frequency);
		REDUCE_FLS(sec, count);
	}

	if (count_fls + sec_fls > 64) {
		divisor = nsec * frequency;

		while (count_fls + sec_fls > 64) {
			REDUCE_FLS(count, sec);
			divisor >>= 1;
		}

		dividend = count * sec;
	} else {
		dividend = count * sec;

		while (nsec_fls + frequency_fls > 64) {
			REDUCE_FLS(nsec, frequency);
			dividend >>= 1;
		}

		divisor = nsec * frequency;
	}

	if (!divisor)
		return dividend;

	return div64_u64(dividend, divisor);
}

static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count)
{
	struct hw_perf_event *hwc = &event->hw;
	s64 period, sample_period;
	s64 delta;

	period = perf_calculate_period(event, nsec, count);

	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;

	if (local64_read(&hwc->period_left) > 8*sample_period) {
		event->pmu->stop(event, PERF_EF_UPDATE);
		local64_set(&hwc->period_left, 0);
		event->pmu->start(event, PERF_EF_RELOAD);
	}
}

static void perf_ctx_adjust_freq(struct perf_event_context *ctx, u64 period)
{
	struct perf_event *event;
	struct hw_perf_event *hwc;
	u64 interrupts, now;
	s64 delta;

	raw_spin_lock(&ctx->lock);
	list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
		if (event->state != PERF_EVENT_STATE_ACTIVE)
			continue;

		if (event->cpu != -1 && event->cpu != smp_processor_id())
			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->start(event, 0);
		}

		if (!event->attr.freq || !event->attr.sample_freq)
			continue;

		event->pmu->read(event);
		now = local64_read(&event->count);
		delta = now - hwc->freq_count_stamp;
		hwc->freq_count_stamp = now;

		if (delta > 0)
			perf_adjust_period(event, period, delta);
	}
	raw_spin_unlock(&ctx->lock);
}

/*
 * Round-robin a context's events:
 */
static void rotate_ctx(struct perf_event_context *ctx)
{
	raw_spin_lock(&ctx->lock);

	/*
	 * Rotate the first entry last of non-pinned groups. Rotation might be
	 * disabled by the inheritance code.
	 */
	if (!ctx->rotate_disable)
		list_rotate_left(&ctx->flexible_groups);

	raw_spin_unlock(&ctx->lock);
}

/*
 * perf_pmu_rotate_start() and perf_rotate_context() are fully serialized
 * because they're strictly cpu affine and rotate_start is called with IRQs
 * disabled, while rotate_context is called from IRQ context.
 */
static void perf_rotate_context(struct perf_cpu_context *cpuctx)
{
	u64 interval = (u64)cpuctx->jiffies_interval * TICK_NSEC;
	struct perf_event_context *ctx = NULL;
	int rotate = 0, remove = 1;

	if (cpuctx->ctx.nr_events) {
		remove = 0;
		if (cpuctx->ctx.nr_events != cpuctx->ctx.nr_active)
			rotate = 1;
	}

	ctx = cpuctx->task_ctx;
	if (ctx && ctx->nr_events) {
		remove = 0;
		if (ctx->nr_events != ctx->nr_active)
			rotate = 1;
	}

	perf_pmu_disable(cpuctx->ctx.pmu);
	perf_ctx_adjust_freq(&cpuctx->ctx, interval);
	if (ctx)
		perf_ctx_adjust_freq(ctx, interval);

	if (!rotate)
		goto done;

	cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);
	if (ctx)
		task_ctx_sched_out(ctx, EVENT_FLEXIBLE);

	rotate_ctx(&cpuctx->ctx);
	if (ctx)
		rotate_ctx(ctx);

	cpu_ctx_sched_in(cpuctx, EVENT_FLEXIBLE);
	if (ctx)
		task_ctx_sched_in(ctx, EVENT_FLEXIBLE);

done:
	if (remove)
		list_del_init(&cpuctx->rotation_list);

	perf_pmu_enable(cpuctx->ctx.pmu);
}

void perf_event_task_tick(void)
{
	struct list_head *head = &__get_cpu_var(rotation_list);
	struct perf_cpu_context *cpuctx, *tmp;

	WARN_ON(!irqs_disabled());

	list_for_each_entry_safe(cpuctx, tmp, head, rotation_list) {
		if (cpuctx->jiffies_interval == 1 ||
				!(jiffies % cpuctx->jiffies_interval))
			perf_rotate_context(cpuctx);
	}
}

static int event_enable_on_exec(struct perf_event *event,
				struct perf_event_context *ctx)
{
	if (!event->attr.enable_on_exec)
		return 0;

	event->attr.enable_on_exec = 0;
	if (event->state >= PERF_EVENT_STATE_INACTIVE)
		return 0;

	__perf_event_mark_enabled(event, ctx);

	return 1;
}

/*
 * 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 perf_event_context *ctx)
{
	struct perf_event *event;
	unsigned long flags;
	int enabled = 0;
	int ret;

	local_irq_save(flags);
	if (!ctx || !ctx->nr_events)
		goto out;

	task_ctx_sched_out(ctx, EVENT_ALL);

	raw_spin_lock(&ctx->lock);

	list_for_each_entry(event, &ctx->pinned_groups, group_entry) {
		ret = event_enable_on_exec(event, ctx);
		if (ret)
			enabled = 1;
	}

	list_for_each_entry(event, &ctx->flexible_groups, group_entry) {
		ret = event_enable_on_exec(event, ctx);
		if (ret)
			enabled = 1;
	}

	/*
	 * Unclone this context if we enabled any event.
	 */
	if (enabled)
		unclone_ctx(ctx);

	raw_spin_unlock(&ctx->lock);

	perf_event_context_sched_in(ctx);
out:
	local_irq_restore(flags);
}

/*
 * Cross CPU call to read the hardware event
 */
static void __perf_event_read(void *info)
{
	struct perf_event *event = info;
	struct perf_event_context *ctx = event->ctx;
	struct perf_cpu_context *cpuctx = __get_cpu_context(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.  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;

	raw_spin_lock(&ctx->lock);
	update_context_time(ctx);
	update_event_times(event);
	raw_spin_unlock(&ctx->lock);

	event->pmu->read(event);
}

static inline u64 perf_event_count(struct perf_event *event)
{
	return local64_read(&event->count) + atomic64_read(&event->child_count);
}

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) {
		struct perf_event_context *ctx = event->ctx;
		unsigned long flags;

		raw_spin_lock_irqsave(&ctx->lock, flags);
		/*
		 * may read while context is not active
		 * (e.g., thread is blocked), in that case
		 * we cannot update context time
		 */
		if (ctx->is_active)
			update_context_time(ctx);
		update_event_times(event);
		raw_spin_unlock_irqrestore(&ctx->lock, flags);
	}

	return perf_event_count(event);
}

/*
 * Callchain support
 */

struct callchain_cpus_entries {
	struct rcu_head			rcu_head;
	struct perf_callchain_entry	*cpu_entries[0];
};

static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]);
static atomic_t nr_callchain_events;
static DEFINE_MUTEX(callchain_mutex);
struct callchain_cpus_entries *callchain_cpus_entries;


__weak void perf_callchain_kernel(struct perf_callchain_entry *entry,
				  struct pt_regs *regs)
{
}

__weak void perf_callchain_user(struct perf_callchain_entry *entry,
				struct pt_regs *regs)
{
}

static void release_callchain_buffers_rcu(struct rcu_head *head)
{
	struct callchain_cpus_entries *entries;
	int cpu;

	entries = container_of(head, struct callchain_cpus_entries, rcu_head);

	for_each_possible_cpu(cpu)
		kfree(entries->cpu_entries[cpu]);

	kfree(entries);
}

static void release_callchain_buffers(void)
{
	struct callchain_cpus_entries *entries;

	entries = callchain_cpus_entries;
	rcu_assign_pointer(callchain_cpus_entries, NULL);
	call_rcu(&entries->rcu_head, release_callchain_buffers_rcu);
}

static int alloc_callchain_buffers(void)
{
	int cpu;
	int size;
	struct callchain_cpus_entries *entries;

	/*
	 * We can't use the percpu allocation API for data that can be
	 * accessed from NMI. Use a temporary manual per cpu allocation
	 * until that gets sorted out.
	 */
	size = sizeof(*entries) + sizeof(struct perf_callchain_entry *) *
		num_possible_cpus();

	entries = kzalloc(size, GFP_KERNEL);
	if (!entries)
		return -ENOMEM;

	size = sizeof(struct perf_callchain_entry) * PERF_NR_CONTEXTS;

	for_each_possible_cpu(cpu) {
		entries->cpu_entries[cpu] = kmalloc_node(size, GFP_KERNEL,
							 cpu_to_node(cpu));
		if (!entries->cpu_entries[cpu])
			goto fail;
	}

	rcu_assign_pointer(callchain_cpus_entries, entries);

	return 0;

fail:
	for_each_possible_cpu(cpu)
		kfree(entries->cpu_entries[cpu]);
	kfree(entries);

	return -ENOMEM;
}

static int get_callchain_buffers(void)
{
	int err = 0;
	int count;

	mutex_lock(&callchain_mutex);

	count = atomic_inc_return(&nr_callchain_events);
	if (WARN_ON_ONCE(count < 1)) {
		err = -EINVAL;
		goto exit;
	}

	if (count > 1) {
		/* If the allocation failed, give up */
		if (!callchain_cpus_entries)
			err = -ENOMEM;
		goto exit;
	}

	err = alloc_callchain_buffers();
	if (err)
		release_callchain_buffers();
exit:
	mutex_unlock(&callchain_mutex);

	return err;
}

static void put_callchain_buffers(void)
{
	if (atomic_dec_and_mutex_lock(&nr_callchain_events, &callchain_mutex)) {
		release_callchain_buffers();
		mutex_unlock(&callchain_mutex);
	}
}

static int get_recursion_context(int *recursion)
{
	int rctx;

	if (in_nmi())
		rctx = 3;
	else if (in_irq())
		rctx = 2;
	else if (in_softirq())
		rctx = 1;
	else
		rctx = 0;

	if (recursion[rctx])
		return -1;

	recursion[rctx]++;
	barrier();

	return rctx;
}

static inline void put_recursion_context(int *recursion, int rctx)
{
	barrier();
	recursion[rctx]--;
}

static struct perf_callchain_entry *get_callchain_entry(int *rctx)
{
	int cpu;
	struct callchain_cpus_entries *entries;

	*rctx = get_recursion_context(__get_cpu_var(callchain_recursion));
	if (*rctx == -1)
		return NULL;

	entries = rcu_dereference(callchain_cpus_entries);
	if (!entries)
		return NULL;

	cpu = smp_processor_id();

	return &entries->cpu_entries[cpu][*rctx];
}

static void
put_callchain_entry(int rctx)
{
	put_recursion_context(__get_cpu_var(callchain_recursion), rctx);
}

static struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
{
	int rctx;
	struct perf_callchain_entry *entry;


	entry = get_callchain_entry(&rctx);
	if (rctx == -1)
		return NULL;

	if (!entry)
		goto exit_put;

	entry->nr = 0;

	if (!user_mode(regs)) {
		perf_callchain_store(entry, PERF_CONTEXT_KERNEL);
		perf_callchain_kernel(entry, regs);
		if (current->mm)
			regs = task_pt_regs(current);
		else
			regs = NULL;
	}

	if (regs) {
		perf_callchain_store(entry, PERF_CONTEXT_USER);
		perf_callchain_user(entry, regs);
	}

exit_put:
	put_callchain_entry(rctx);

	return entry;
}

/*
 * Initialize the perf_event context in a task_struct:
 */
static void __perf_event_init_context(struct perf_event_context *ctx)
{
	raw_spin_lock_init(&ctx->lock);
	mutex_init(&ctx->mutex);
	INIT_LIST_HEAD(&ctx->pinned_groups);
	INIT_LIST_HEAD(&ctx->flexible_groups);
	INIT_LIST_HEAD(&ctx->event_list);
	atomic_set(&ctx->refcount, 1);
}

static struct perf_event_context *
alloc_perf_context(struct pmu *pmu, struct task_struct *task)
{
	struct perf_event_context *ctx;

	ctx = kzalloc(sizeof(struct perf_event_context), GFP_KERNEL);
	if (!ctx)
		return NULL;

	__perf_event_init_context(ctx);
	if (task) {
		ctx->task = task;
		get_task_struct(task);
	}
	ctx->pmu = pmu;

	return ctx;
}

static struct task_struct *
find_lively_task_by_vpid(pid_t vpid)
{
	struct task_struct *task;
	int err;

	rcu_read_lock();
	if (!vpid)
		task = current;
	else
		task = find_task_by_vpid(vpid);
	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;

	return task;
errout:
	put_task_struct(task);
	return ERR_PTR(err);

}

static struct perf_event_context *
find_get_context(struct pmu *pmu, struct task_struct *task, int cpu)
{
	struct perf_event_context *ctx;
	struct perf_cpu_context *cpuctx;
	unsigned long flags;
	int ctxn, err;

	if (!task && 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 >= nr_cpumask_bits)
			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_online(cpu))
			return ERR_PTR(-ENODEV);

		cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
		ctx = &cpuctx->ctx;
		get_ctx(ctx);

		return ctx;
	}

	err = -EINVAL;
	ctxn = pmu->task_ctx_nr;
	if (ctxn < 0)
		goto errout;

retry:
	ctx = perf_lock_task_context(task, ctxn, &flags);
	if (ctx) {
		unclone_ctx(ctx);
		raw_spin_unlock_irqrestore(&ctx->lock, flags);
	}

	if (!ctx) {
		ctx = alloc_perf_context(pmu, task);
		err = -ENOMEM;
		if (!ctx)
			goto errout;

		get_ctx(ctx);

		if (cmpxchg(&task->perf_event_ctxp[ctxn], NULL, ctx)) {
			/*
			 * We raced with some other task; use
			 * the context they set.
			 */
			put_task_struct(task);
			kfree(ctx);
			goto retry;
		}
	}

	return ctx;

errout:
	return ERR_PTR(err);
}

static void perf_event_free_filter(struct perf_event *event);

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);
	perf_event_free_filter(event);
	kfree(event);
}

static void perf_buffer_put(struct perf_buffer *buffer);

static void free_event(struct perf_event *event)
{
	irq_work_sync(&event->pending);

	if (!event->parent) {
		if (event->attach_state & PERF_ATTACH_TASK)
			jump_label_dec(&perf_task_events);
		if (event->attr.mmap || event->attr.mmap_data)
			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->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
			put_callchain_buffers();
	}

	if (event->buffer) {
		perf_buffer_put(event->buffer);
		event->buffer = NULL;
	}

	if (event->destroy)
		event->destroy(event);

	if (event->ctx)
		put_ctx(event->ctx);

	call_rcu(&event->rcu_head, free_event_rcu);
}

int perf_event_release_kernel(struct perf_event *event)
{
	struct perf_event_context *ctx = event->ctx;

	/*
	 * Remove from the PMU, can't get re-enabled since we got
	 * here because the last ref went.
	 */
	perf_event_disable(event);

	WARN_ON_ONCE(ctx->parent_ctx);
	/*
	 * There are two ways this annotation is useful:
	 *
	 *  1) there is a lock recursion from perf_event_exit_task
	 *     see the comment there.
	 *
	 *  2) there is a lock-inversion with mmap_sem through
	 *     perf_event_read_group(), which takes faults while
	 *     holding ctx->mutex, however this is called after
	 *     the last filedesc died, so there is no possibility
	 *     to trigger the AB-BA case.
	 */
	mutex_lock_nested(&ctx->mutex, SINGLE_DEPTH_NESTING);
	raw_spin_lock_irq(&ctx->lock);
	perf_group_detach(event);
	list_del_event(event, ctx);
	raw_spin_unlock_irq(&ctx->lock);
	mutex_unlock(&ctx->mutex);

	free_event(event);

	return 0;
}
EXPORT_SYMBOL_GPL(perf_event_release_kernel);

/*
 * 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 task_struct *owner;

	file->private_data = NULL;

	rcu_read_lock();
	owner = ACCESS_ONCE(event->owner);
	/*
	 * Matches the smp_wmb() in perf_event_exit_task(). If we observe
	 * !owner it means the list deletion is complete and we can indeed
	 * free this event, otherwise we need to serialize on
	 * owner->perf_event_mutex.
	 */
	smp_read_barrier_depends();
	if (owner) {
		/*
		 * Since delayed_put_task_struct() also drops the last
		 * task reference we can safely take a new reference
		 * while holding the rcu_read_lock().
		 */
		get_task_struct(owner);
	}
	rcu_read_unlock();

	if (owner) {
		mutex_lock(&owner->perf_event_mutex);
		/*
		 * We have to re-check the event->owner field, if it is cleared
		 * we raced with perf_event_exit_task(), acquiring the mutex
		 * ensured they're done, and we can proceed with freeing the
		 * event.
		 */
		if (event->owner)
			list_del_init(&event->owner_entry);
		mutex_unlock(&owner->perf_event_mutex);
		put_task_struct(owner);
	}

	return perf_event_release_kernel(event);
}

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;
}

u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
{
	struct perf_event *child;
	u64 total = 0;

	*enabled = 0;
	*running = 0;

	mutex_lock(&event->child_mutex);
	total += perf_event_read(event);
	*enabled += event->total_time_enabled +
			atomic64_read(&event->child_total_time_enabled);
	*running += event->total_time_running +
			atomic64_read(&event->child_total_time_running);

	list_for_each_entry(child, &event->child_list, child_list) {
		total += perf_event_read(child);
		*enabled += child->total_time_enabled;
		*running += child->total_time_running;
	}
	mutex_unlock(&event->child_mutex);

	return total;
}
EXPORT_SYMBOL_GPL(perf_event_read_value);

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, ret = -EFAULT;
	struct perf_event_context *ctx = leader->ctx;
	u64 values[5];
	u64 count, enabled, running;

	mutex_lock(&ctx->mutex);
	count = perf_event_read_value(leader, &enabled, &running);

	values[n++] = 1 + leader->nr_siblings;
	if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
		values[n++] = enabled;
	if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
		values[n++] = running;
	values[n++] = count;
	if (read_format & PERF_FORMAT_ID)
		values[n++] = primary_event_id(leader);

	size = n * sizeof(u64);

	if (copy_to_user(buf, values, size))
		goto unlock;

	ret = size;

	list_for_each_entry(sub, &leader->sibling_list, group_entry) {
		n = 0;

		values[n++] = perf_event_read_value(sub, &enabled, &running);
		if (read_format & PERF_FORMAT_ID)
			values[n++] = primary_event_id(sub);

		size = n * sizeof(u64);

		if (copy_to_user(buf + ret, values, size)) {
			ret = -EFAULT;
			goto unlock;
		}

		ret += size;
	}
unlock:
	mutex_unlock(&ctx->mutex);

	return ret;
}

static int perf_event_read_one(struct perf_event *event,
				 u64 read_format, char __user *buf)
{
	u64 enabled, running;
	u64 values[4];
	int n = 0;

	values[n++] = perf_event_read_value(event, &enabled, &running);
	if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
		values[n++] = enabled;
	if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
		values[n++] = 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);
	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);

	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_buffer *buffer;
	unsigned int events = POLL_HUP;

	rcu_read_lock();
	buffer = rcu_dereference(event->buffer);
	if (buffer)
		events = atomic_xchg(&buffer->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);
	local64_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;
	int ret = 0;
	u64 value;

	if (!event->attr.sample_period)
		return -EINVAL;

	if (copy_from_user(&value, arg, sizeof(value)))
		return -EFAULT;

	if (!value)
		return -EINVAL;

	raw_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:
	raw_spin_unlock_irq(&ctx->lock);

	return ret;
}

static const struct file_operations perf_fops;

static struct perf_event *perf_fget_light(int fd, int *fput_needed)
{
	struct file *file;

	file = fget_light(fd, fput_needed);
	if (!file)
		return ERR_PTR(-EBADF);

	if (file->f_op != &perf_fops) {
		fput_light(file, *fput_needed);
		*fput_needed = 0;
		return ERR_PTR(-EBADF);
	}

	return file->private_data;
}

static int perf_event_set_output(struct perf_event *event,
				 struct perf_event *output_event);
static int perf_event_set_filter(struct perf_event *event, void __user *arg);

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:
	{
		struct perf_event *output_event = NULL;
		int fput_needed = 0;
		int ret;

		if (arg != -1) {
			output_event = perf_fget_light(arg, &fput_needed);
			if (IS_ERR(output_event))
				return PTR_ERR(output_event);
		}

		ret = perf_event_set_output(event, output_event);
		if (output_event)
			fput_light(output_event->filp, fput_needed);

		return ret;
	}

	case PERF_EVENT_IOC_SET_FILTER:
		return perf_event_set_filter(event, (void __user *)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->hw.state & PERF_HES_STOPPED)
		return 0;

	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_buffer *buffer;

	rcu_read_lock();
	buffer = rcu_dereference(event->buffer);
	if (!buffer)
		goto unlock;

	userpg = buffer->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 = perf_event_count(event);
	if (event->state == PERF_EVENT_STATE_ACTIVE)
		userpg->offset -= local64_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 unsigned long perf_data_size(struct perf_buffer *buffer);

static void
perf_buffer_init(struct perf_buffer *buffer, long watermark, int flags)
{
	long max_size = perf_data_size(buffer);

	if (watermark)
		buffer->