5 files changed, 972 insertions, 0 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index 19fad003b19d..1f184a1dc406 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -89,6 +89,7 @@ obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o
 obj-$(CONFIG_FUNCTION_TRACER) += trace/
 obj-$(CONFIG_TRACING) += trace/
 obj-$(CONFIG_SMP) += sched_cpupri.o
+obj-$(CONFIG_PERF_COUNTERS) += perf_counter.o
 
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
diff --git a/kernel/fork.c b/kernel/fork.c
index 2a372a0e206f..441fadff1fa4 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -975,6 +975,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
                 goto fork_out;
 
         rt_mutex_init_task(p);
+        perf_counter_init_task(p);
 
 #ifdef CONFIG_PROVE_LOCKING
         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
new file mode 100644
index 000000000000..20508f053658
--- /dev/null
+++ b/kernel/perf_counter.c
@@ -0,0 +1,943 @@
+/*
+ * Performance counter core code
+ *
+ *  Copyright(C) 2008 Thomas Gleixner <tglx@linutronix.de>
+ *  Copyright(C) 2008 Red Hat, Inc., Ingo Molnar
+ *
+ *  For licencing details see kernel-base/COPYING
+ */
+
+#include <linux/fs.h>
+#include <linux/cpu.h>
+#include <linux/smp.h>
+#include <linux/poll.h>
+#include <linux/sysfs.h>
+#include <linux/ptrace.h>
+#include <linux/percpu.h>
+#include <linux/uaccess.h>
+#include <linux/syscalls.h>
+#include <linux/anon_inodes.h>
+#include <linux/perf_counter.h>
+
+/*
+ * Each CPU has a list of per CPU counters:
+ */
+DEFINE_PER_CPU(struct perf_cpu_context, perf_cpu_context);
+
+int perf_max_counters __read_mostly;
+static int perf_reserved_percpu __read_mostly;
+static int perf_overcommit __read_mostly = 1;
+
+/*
+ * Mutex for (sysadmin-configurable) counter reservations:
+ */
+static DEFINE_MUTEX(perf_resource_mutex);
+
+/*
+ * Architecture provided APIs - weak aliases:
+ */
+
+int __weak hw_perf_counter_init(struct perf_counter *counter, u32 hw_event_type)
+{
+        return -EINVAL;
+}
+
+void __weak hw_perf_counter_enable(struct perf_counter *counter)         { }
+void __weak hw_perf_counter_disable(struct perf_counter *counter)        { }
+void __weak hw_perf_counter_read(struct perf_counter *counter)           { }
+void __weak hw_perf_disable_all(void) { }
+void __weak hw_perf_enable_all(void) { }
+void __weak hw_perf_counter_setup(void) { }
+
+#if BITS_PER_LONG == 64
+
+/*
+ * Read the cached counter in counter safe against cross CPU / NMI
+ * modifications. 64 bit version - no complications.
+ */
+static inline u64 perf_read_counter_safe(struct perf_counter *counter)
+{
+        return (u64) atomic64_read(&counter->count);
+}
+
+#else
+
+/*
+ * Read the cached counter in counter safe against cross CPU / NMI
+ * modifications. 32 bit version.
+ */
+static u64 perf_read_counter_safe(struct perf_counter *counter)
+{
+        u32 cntl, cnth;
+
+        local_irq_disable();
+        do {
+                cnth = atomic_read(&counter->count32[1]);
+                cntl = atomic_read(&counter->count32[0]);
+        } while (cnth != atomic_read(&counter->count32[1]));
+
+        local_irq_enable();
+
+        return cntl | ((u64) cnth) << 32;
+}
+
+#endif
+
+/*
+ * Cross CPU call to remove a performance counter
+ *
+ * We disable the counter on the hardware level first. After that we
+ * remove it from the context list.
+ */
+static void __perf_remove_from_context(void *info)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_counter *counter = info;
+        struct perf_counter_context *ctx = counter->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);
+
+        if (counter->active) {
+                hw_perf_counter_disable(counter);
+                counter->active = 0;
+                ctx->nr_active--;
+                cpuctx->active_oncpu--;
+                counter->task = NULL;
+        }
+        ctx->nr_counters--;
+
+        /*
+         * Protect the list operation against NMI by disabling the
+         * counters on a global level. NOP for non NMI based counters.
+         */
+        hw_perf_disable_all();
+        list_del_init(&counter->list);
+        hw_perf_enable_all();
+
+        if (!ctx->task) {
+                /*
+                 * Allow more per task counters with respect to the
+                 * reservation:
+                 */
+                cpuctx->max_pertask =
+                        min(perf_max_counters - ctx->nr_counters,
+                            perf_max_counters - perf_reserved_percpu);
+        }
+
+        spin_unlock(&ctx->lock);
+}
+
+
+/*
+ * Remove the counter from a task's (or a CPU's) list of counters.
+ *
+ * Must be called with counter->mutex held.
+ *
+ * CPU counters are removed with a smp call. For task counters we only
+ * call when the task is on a CPU.
+ */
+static void perf_remove_from_context(struct perf_counter *counter)
+{
+        struct perf_counter_context *ctx = counter->ctx;
+        struct task_struct *task = ctx->task;
+
+        if (!task) {
+                /*
+                 * Per cpu counters are removed via an smp call and
+                 * the removal is always sucessful.
+                 */
+                smp_call_function_single(counter->cpu,
+                                         __perf_remove_from_context,
+                                         counter, 1);
+                return;
+        }
+
+retry:
+        task_oncpu_function_call(task, __perf_remove_from_context,
+                                 counter);
+
+        spin_lock_irq(&ctx->lock);
+        /*
+         * If the context is active we need to retry the smp call.
+         */
+        if (ctx->nr_active && !list_empty(&counter->list)) {
+                spin_unlock_irq(&ctx->lock);
+                goto retry;
+        }
+
+        /*
+         * The lock prevents that this context is scheduled in so we
+         * can remove the counter safely, if it the call above did not
+         * succeed.
+         */
+        if (!list_empty(&counter->list)) {
+                ctx->nr_counters--;
+                list_del_init(&counter->list);
+                counter->task = NULL;
+        }
+        spin_unlock_irq(&ctx->lock);
+}
+
+/*
+ * Cross CPU call to install and enable a preformance counter
+ */
+static void __perf_install_in_context(void *info)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_counter *counter = info;
+        struct perf_counter_context *ctx = counter->ctx;
+        int cpu = smp_processor_id();
+
+        /*
+         * 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
+         * counters on a global level. NOP for non NMI based counters.
+         */
+        hw_perf_disable_all();
+        list_add_tail(&counter->list, &ctx->counters);
+        hw_perf_enable_all();
+
+        ctx->nr_counters++;
+
+        if (cpuctx->active_oncpu < perf_max_counters) {
+                hw_perf_counter_enable(counter);
+                counter->active = 1;
+                counter->oncpu = cpu;
+                ctx->nr_active++;
+                cpuctx->active_oncpu++;
+        }
+
+        if (!ctx->task && cpuctx->max_pertask)
+                cpuctx->max_pertask--;
+
+        spin_unlock(&ctx->lock);
+}
+
+/*
+ * Attach a performance counter to a context
+ *
+ * First we add the counter to the list with the hardware enable bit
+ * in counter->hw_config cleared.
+ *
+ * If the counter 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.
+ */
+static void
+perf_install_in_context(struct perf_counter_context *ctx,
+                        struct perf_counter *counter,
+                        int cpu)
+{
+        struct task_struct *task = ctx->task;
+
+        counter->ctx = ctx;
+        if (!task) {
+                /*
+                 * Per cpu counters are installed via an smp call and
+                 * the install is always sucessful.
+                 */
+                smp_call_function_single(cpu, __perf_install_in_context,
+                                         counter, 1);
+                return;
+        }
+
+        counter->task = task;
+retry:
+        task_oncpu_function_call(task, __perf_install_in_context,
+                                 counter);
+
+        spin_lock_irq(&ctx->lock);
+        /*
+         * If the context is active and the counter has not been added
+         * we need to retry the smp call.
+         */
+        if (ctx->nr_active && list_empty(&counter->list)) {
+                spin_unlock_irq(&ctx->lock);
+                goto retry;
+        }
+
+        /*
+         * The lock prevents that this context is scheduled in so we
+         * can add the counter safely, if it the call above did not
+         * succeed.
+         */
+        if (list_empty(&counter->list)) {
+                list_add_tail(&counter->list, &ctx->counters);
+                ctx->nr_counters++;
+        }
+        spin_unlock_irq(&ctx->lock);
+}
+
+/*
+ * Called from scheduler to remove the counters of the current task,
+ * with interrupts disabled.
+ *
+ * We stop each counter and update the counter value in counter->count.
+ *
+ * This does not protect us against NMI, but hw_perf_counter_disable()
+ * sets the disabled bit in the control field of counter _before_
+ * accessing the counter control register. If a NMI hits, then it will
+ * not restart the counter.
+ */
+void perf_counter_task_sched_out(struct task_struct *task, int cpu)
+{
+        struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
+        struct perf_counter_context *ctx = &task->perf_counter_ctx;
+        struct perf_counter *counter;
+
+        if (likely(!cpuctx->task_ctx))
+                return;
+
+        spin_lock(&ctx->lock);
+        list_for_each_entry(counter, &ctx->counters, list) {
+                if (!ctx->nr_active)
+                        break;
+                if (counter->active) {
+                        hw_perf_counter_disable(counter);
+                        counter->active = 0;
+                        counter->oncpu = -1;
+                        ctx->nr_active--;
+                        cpuctx->active_oncpu--;
+                }
+        }
+        spin_unlock(&ctx->lock);
+        cpuctx->task_ctx = NULL;
+}
+
+/*
+ * Called from scheduler to add the counters of the current task
+ * with interrupts disabled.
+ *
+ * We restore the counter value and then enable it.
+ *
+ * This does not protect us against NMI, but hw_perf_counter_enable()
+ * sets the enabled bit in the control field of counter _before_
+ * accessing the counter control register. If a NMI hits, then it will
+ * keep the counter running.
+ */
+void perf_counter_task_sched_in(struct task_struct *task, int cpu)
+{
+        struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
+        struct perf_counter_context *ctx = &task->perf_counter_ctx;
+        struct perf_counter *counter;
+
+        if (likely(!ctx->nr_counters))
+                return;
+
+        spin_lock(&ctx->lock);
+        list_for_each_entry(counter, &ctx->counters, list) {
+                if (ctx->nr_active == cpuctx->max_pertask)
+                        break;
+                if (counter->cpu != -1 && counter->cpu != cpu)
+                        continue;
+
+                hw_perf_counter_enable(counter);
+                counter->active = 1;
+                counter->oncpu = cpu;
+                ctx->nr_active++;
+                cpuctx->active_oncpu++;
+        }
+        spin_unlock(&ctx->lock);
+        cpuctx->task_ctx = ctx;
+}
+
+void perf_counter_task_tick(struct task_struct *curr, int cpu)
+{
+        struct perf_counter_context *ctx = &curr->perf_counter_ctx;
+        struct perf_counter *counter;
+
+        if (likely(!ctx->nr_counters))
+                return;
+
+        perf_counter_task_sched_out(curr, cpu);
+
+        spin_lock(&ctx->lock);
+
+        /*
+         * Rotate the first entry last:
+         */
+        hw_perf_disable_all();
+        list_for_each_entry(counter, &ctx->counters, list) {
+                list_del(&counter->list);
+                list_add_tail(&counter->list, &ctx->counters);
+                break;
+        }
+        hw_perf_enable_all();
+
+        spin_unlock(&ctx->lock);
+
+        perf_counter_task_sched_in(curr, cpu);
+}
+
+/*
+ * Initialize the perf_counter context in task_struct
+ */
+void perf_counter_init_task(struct task_struct *task)
+{
+        struct perf_counter_context *ctx = &task->perf_counter_ctx;
+
+        spin_lock_init(&ctx->lock);
+        INIT_LIST_HEAD(&ctx->counters);
+        ctx->nr_counters = 0;
+        ctx->task = task;
+}
+
+/*
+ * Cross CPU call to read the hardware counter
+ */
+static void __hw_perf_counter_read(void *info)
+{
+        hw_perf_counter_read(info);
+}
+
+static u64 perf_read_counter(struct perf_counter *counter)
+{
+        /*
+         * If counter is enabled and currently active on a CPU, update the
+         * value in the counter structure:
+         */
+        if (counter->active) {
+                smp_call_function_single(counter->oncpu,
+                                         __hw_perf_counter_read, counter, 1);
+        }
+
+        return perf_read_counter_safe(counter);
+}
+
+/*
+ * Cross CPU call to switch performance data pointers
+ */
+static void __perf_switch_irq_data(void *info)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_counter *counter = info;
+        struct perf_counter_context *ctx = counter->ctx;
+        struct perf_data *oldirqdata = counter->irqdata;
+
+        /*
+         * 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) {
+                if (cpuctx->task_ctx != ctx)
+                        return;
+                spin_lock(&ctx->lock);
+        }
+
+        /* Change the pointer NMI safe */
+        atomic_long_set((atomic_long_t *)&counter->irqdata,
+                        (unsigned long) counter->usrdata);
+        counter->usrdata = oldirqdata;
+
+        if (ctx->task)
+                spin_unlock(&ctx->lock);
+}
+
+static struct perf_data *perf_switch_irq_data(struct perf_counter *counter)
+{
+        struct perf_counter_context *ctx = counter->ctx;
+        struct perf_data *oldirqdata = counter->irqdata;
+        struct task_struct *task = ctx->task;
+
+        if (!task) {
+                smp_call_function_single(counter->cpu,
+                                         __perf_switch_irq_data,
+                                         counter, 1);
+                return counter->usrdata;
+        }
+
+retry:
+        spin_lock_irq(&ctx->lock);
+        if (!counter->active) {
+                counter->irqdata = counter->usrdata;
+                counter->usrdata = oldirqdata;
+                spin_unlock_irq(&ctx->lock);
+                return oldirqdata;
+        }
+        spin_unlock_irq(&ctx->lock);
+        task_oncpu_function_call(task, __perf_switch_irq_data, counter);
+        /* Might have failed, because task was scheduled out */
+        if (counter->irqdata == oldirqdata)
+                goto retry;
+
+        return counter->usrdata;
+}
+
+static void put_context(struct perf_counter_context *ctx)
+{
+        if (ctx->task)
+                put_task_struct(ctx->task);
+}
+
+static struct perf_counter_context *find_get_context(pid_t pid, int cpu)
+{
+        struct perf_cpu_context *cpuctx;
+        struct perf_counter_context *ctx;
+        struct task_struct *task;
+
+        /*
+         * If cpu is not a wildcard then this is a percpu counter:
+         */
+        if (cpu != -1) {
+                /* Must be root to operate on a CPU counter: */
+                if (!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 counter 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;
+
+                WARN_ON_ONCE(ctx->task);
+                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);
+
+        ctx = &task->perf_counter_ctx;
+        ctx->task = task;
+
+        /* Reuse ptrace permission checks for now. */
+        if (!ptrace_may_access(task, PTRACE_MODE_READ)) {
+                put_context(ctx);
+                return ERR_PTR(-EACCES);
+        }
+
+        return ctx;
+}
+
+/*
+ * Called when the last reference to the file is gone.
+ */
+static int perf_release(struct inode *inode, struct file *file)
+{
+        struct perf_counter *counter = file->private_data;
+        struct perf_counter_context *ctx = counter->ctx;
+
+        file->private_data = NULL;
+
+        mutex_lock(&counter->mutex);
+
+        perf_remove_from_context(counter);
+        put_context(ctx);
+
+        mutex_unlock(&counter->mutex);
+
+        kfree(counter);
+
+        return 0;
+}
+
+/*
+ * Read the performance counter - simple non blocking version for now
+ */
+static ssize_t
+perf_read_hw(struct perf_counter *counter, char __user *buf, size_t count)
+{
+        u64 cntval;
+
+        if (count != sizeof(cntval))
+                return -EINVAL;
+
+        mutex_lock(&counter->mutex);
+        cntval = perf_read_counter(counter);
+        mutex_unlock(&counter->mutex);
+
+        return put_user(cntval, (u64 __user *) buf) ? -EFAULT : sizeof(cntval);
+}
+
+static ssize_t
+perf_copy_usrdata(struct perf_data *usrdata, char __user *buf, size_t count)
+{
+        if (!usrdata->len)
+                return 0;
+
+        count = min(count, (size_t)usrdata->len);
+        if (copy_to_user(buf, usrdata->data + usrdata->rd_idx, count))
+                return -EFAULT;
+
+        /* Adjust the counters */
+        usrdata->len -= count;
+        if (!usrdata->len)
+                usrdata->rd_idx = 0;
+        else
+                usrdata->rd_idx += count;
+
+        return count;
+}
+
+static ssize_t
+perf_read_irq_data(struct perf_counter  *counter,
+                   char __user          *buf,
+                   size_t               count,
+                   int                  nonblocking)
+{
+        struct perf_data *irqdata, *usrdata;
+        DECLARE_WAITQUEUE(wait, current);
+        ssize_t res;
+
+        irqdata = counter->irqdata;
+        usrdata = counter->usrdata;
+
+        if (usrdata->len + irqdata->len >= count)
+                goto read_pending;
+
+        if (nonblocking)
+                return -EAGAIN;
+
+        spin_lock_irq(&counter->waitq.lock);
+        __add_wait_queue(&counter->waitq, &wait);
+        for (;;) {
+                set_current_state(TASK_INTERRUPTIBLE);
+                if (usrdata->len + irqdata->len >= count)
+                        break;
+
+                if (signal_pending(current))
+                        break;
+
+                spin_unlock_irq(&counter->waitq.lock);
+                schedule();
+                spin_lock_irq(&counter->waitq.lock);
+        }
+        __remove_wait_queue(&counter->waitq, &wait);
+        __set_current_state(TASK_RUNNING);
+        spin_unlock_irq(&counter->waitq.lock);
+
+        if (usrdata->len + irqdata->len < count)
+                return -ERESTARTSYS;
+read_pending:
+        mutex_lock(&counter->mutex);
+
+        /* Drain pending data first: */
+        res = perf_copy_usrdata(usrdata, buf, count);
+        if (res < 0 || res == count)
+                goto out;
+
+        /* Switch irq buffer: */
+        usrdata = perf_switch_irq_data(counter);
+        if (perf_copy_usrdata(usrdata, buf + res, count - res) < 0) {
+                if (!res)
+                        res = -EFAULT;
+        } else {
+                res = count;
+        }
+out:
+        mutex_unlock(&counter->mutex);
+
+        return res;
+}
+
+static ssize_t
+perf_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
+{
+        struct perf_counter *counter = file->private_data;
+
+        switch (counter->record_type) {
+        case PERF_RECORD_SIMPLE:
+                return perf_read_hw(counter, buf, count);
+
+        case PERF_RECORD_IRQ:
+        case PERF_RECORD_GROUP:
+                return perf_read_irq_data(counter, buf, count,
+                                          file->f_flags & O_NONBLOCK);
+        }
+        return -EINVAL;
+}
+
+static unsigned int perf_poll(struct file *file, poll_table *wait)
+{
+        struct perf_counter *counter = file->private_data;
+        unsigned int events = 0;
+        unsigned long flags;
+
+        poll_wait(file, &counter->waitq, wait);
+
+        spin_lock_irqsave(&counter->waitq.lock, flags);
+        if (counter->usrdata->len || counter->irqdata->len)
+                events |= POLLIN;
+        spin_unlock_irqrestore(&counter->waitq.lock, flags);
+
+        return events;
+}
+
+static const struct file_operations perf_fops = {
+        .release                = perf_release,
+        .read                   = perf_read,
+        .poll                   = perf_poll,
+};
+
+/*
+ * Allocate and initialize a counter structure
+ */
+static struct perf_counter *
+perf_counter_alloc(u32 hw_event_period, int cpu, u32 record_type)
+{
+        struct perf_counter *counter = kzalloc(sizeof(*counter), GFP_KERNEL);
+
+        if (!counter)
+                return NULL;
+
+        mutex_init(&counter->mutex);
+        INIT_LIST_HEAD(&counter->list);
+        init_waitqueue_head(&counter->waitq);
+
+        counter->irqdata        = &counter->data[0];
+        counter->usrdata        = &counter->data[1];
+        counter->cpu            = cpu;
+        counter->record_type    = record_type;
+        counter->__irq_period   = hw_event_period;
+        counter->wakeup_pending = 0;
+
+        return counter;
+}
+
+/**
+ * sys_perf_task_open - open a performance counter associate it to a task
+ * @hw_event_type:      event type for monitoring/sampling...
+ * @pid:                target pid
+ */
+asmlinkage int
+sys_perf_counter_open(u32 hw_event_type,
+                      u32 hw_event_period,
+                      u32 record_type,
+                      pid_t pid,
+                      int cpu)
+{
+        struct perf_counter_context *ctx;
+        struct perf_counter *counter;
+        int ret;
+
+        ctx = find_get_context(pid, cpu);
+        if (IS_ERR(ctx))
+                return PTR_ERR(ctx);
+
+        ret = -ENOMEM;
+        counter = perf_counter_alloc(hw_event_period, cpu, record_type);
+        if (!counter)
+                goto err_put_context;
+
+        ret = hw_perf_counter_init(counter, hw_event_type);
+        if (ret)
+                goto err_free_put_context;
+
+        perf_install_in_context(ctx, counter, cpu);
+
+        ret = anon_inode_getfd("[perf_counter]", &perf_fops, counter, 0);
+        if (ret < 0)
+                goto err_remove_free_put_context;
+
+        return ret;
+
+err_remove_free_put_context:
+        mutex_lock(&counter->mutex);
+        perf_remove_from_context(counter);
+        mutex_unlock(&counter->mutex);
+
+err_free_put_context:
+        kfree(counter);
+
+err_put_context:
+        put_context(ctx);
+
+        return ret;
+}
+
+static void __cpuinit perf_init_cpu(int cpu)
+{
+        struct perf_cpu_context *ctx;
+
+        ctx = &per_cpu(perf_cpu_context, cpu);
+        spin_lock_init(&ctx->ctx.lock);
+        INIT_LIST_HEAD(&ctx->ctx.counters);
+
+        mutex_lock(&perf_resource_mutex);
+        ctx->max_pertask = perf_max_counters - perf_reserved_percpu;
+        mutex_unlock(&perf_resource_mutex);
+        hw_perf_counter_setup();
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static void __perf_exit_cpu(void *info)
+{
+        struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
+        struct perf_counter_context *ctx = &cpuctx->ctx;
+        struct perf_counter *counter, *tmp;
+
+        list_for_each_entry_safe(counter, tmp, &ctx->counters, list)
+                __perf_remove_from_context(counter);
+
+}
+static void perf_exit_cpu(int cpu)
+{
+        smp_call_function_single(cpu, __perf_exit_cpu, NULL, 1);
+}
+#else
+static inline void perf_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_init_cpu(cpu);
+                break;
+
+        case CPU_DOWN_PREPARE:
+        case CPU_DOWN_PREPARE_FROZEN:
+                perf_exit_cpu(cpu);
+                break;
+
+        default:
+                break;
+        }
+
+        return NOTIFY_OK;
+}
+
+static struct notifier_block __cpuinitdata perf_cpu_nb = {
+        .notifier_call          = perf_cpu_notify,
+};
+
+static int __init perf_counter_init(void)
+{
+        perf_cpu_notify(&perf_cpu_nb, (unsigned long)CPU_UP_PREPARE,
+                        (void *)(long)smp_processor_id());
+        register_cpu_notifier(&perf_cpu_nb);
+
+        return 0;
+}
+early_initcall(perf_counter_init);
+
+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_counters)
+                return -EINVAL;
+
+        mutex_lock(&perf_resource_mutex);
+        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_counters - cpuctx->ctx.nr_counters,
+                          perf_max_counters - perf_reserved_percpu);
+                cpuctx->max_pertask = mpt;
+                spin_unlock_irq(&cpuctx->ctx.lock);
+        }
+        mutex_unlock(&perf_resource_mutex);
+
+        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;
+
+        mutex_lock(&perf_resource_mutex);
+        perf_overcommit = val;
+        mutex_unlock(&perf_resource_mutex);
+
+        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_counters",
+};
+
+static int __init perf_counter_sysfs_init(void)
+{
+        return sysfs_create_group(&cpu_sysdev_class.kset.kobj,
+                                  &perfclass_attr_group);
+}
+device_initcall(perf_counter_sysfs_init);
+
diff --git a/kernel/sched.c b/kernel/sched.c
index b7480fb5c3dc..254d56de2548 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2212,6 +2212,27 @@ static int sched_balance_self(int cpu, int flag)
 
 #endif /* CONFIG_SMP */
 
+/**
+ * task_oncpu_function_call - call a function on the cpu on which a task runs
+ * @p:          the task to evaluate
+ * @func:       the function to be called
+ * @info:       the function call argument
+ *
+ * Calls the function @func when the task is currently running. This might
+ * be on the current CPU, which just calls the function directly
+ */
+void task_oncpu_function_call(struct task_struct *p,
+                              void (*func) (void *info), void *info)
+{
+        int cpu;
+
+        preempt_disable();
+        cpu = task_cpu(p);
+        if (task_curr(p))
+                smp_call_function_single(cpu, func, info, 1);
+        preempt_enable();
+}
+
 /***
  * try_to_wake_up - wake up a thread
  * @p: the to-be-woken-up thread
@@ -2534,6 +2555,7 @@ prepare_task_switch(struct rq *rq, struct task_struct *prev,
                     struct task_struct *next)
 {
         fire_sched_out_preempt_notifiers(prev, next);
+        perf_counter_task_sched_out(prev, cpu_of(rq));
         prepare_lock_switch(rq, next);
         prepare_arch_switch(next);
 }
@@ -2574,6 +2596,7 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
          */
         prev_state = prev->state;
         finish_arch_switch(prev);
+        perf_counter_task_sched_in(current, cpu_of(rq));
         finish_lock_switch(rq, prev);
 #ifdef CONFIG_SMP
         if (current->sched_class->post_schedule)
@@ -4296,6 +4319,7 @@ void scheduler_tick(void)
         rq->idle_at_tick = idle_cpu(cpu);
         trigger_load_balance(rq, cpu);
 #endif
+        perf_counter_task_tick(curr, cpu);
 }
 
 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index e14a23281707..4be8bbc7577c 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -174,3 +174,6 @@ cond_syscall(compat_sys_timerfd_settime);
 cond_syscall(compat_sys_timerfd_gettime);
 cond_syscall(sys_eventfd);
 cond_syscall(sys_eventfd2);
+
+/* performance counters: */
+cond_syscall(sys_perf_counter_open);