Merge tag 'driver-core-3.11-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git...

[firefly-linux-kernel-4.4.55.git] / kernel / events / core.c

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1833bc5a84a73049b6e1f27caed87adfbdf44b2c..f86599e8c12371c7d78248e0c6b2a6869b9122ee 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -947,8 +947,18 @@ perf_lock_task_context(struct task_struct *task, int ctxn, unsigned long *flags)
 {
        struct perf_event_context *ctx;
 
-       rcu_read_lock();
 retry:
+       /*
+        * One of the few rules of preemptible RCU is that one cannot do
+        * rcu_read_unlock() while holding a scheduler (or nested) lock when
+        * part of the read side critical section was preemptible -- see
+        * rcu_read_unlock_special().
+        *
+        * Since ctx->lock nests under rq->lock we must ensure the entire read
+        * side critical section is non-preemptible.
+        */
+       preempt_disable();
+       rcu_read_lock();
        ctx = rcu_dereference(task->perf_event_ctxp[ctxn]);
        if (ctx) {
                /*
@@ -964,6 +974,8 @@ retry:
                raw_spin_lock_irqsave(&ctx->lock, *flags);
                if (ctx != rcu_dereference(task->perf_event_ctxp[ctxn])) {
                        raw_spin_unlock_irqrestore(&ctx->lock, *flags);
+                       rcu_read_unlock();
+                       preempt_enable();
                        goto retry;
                }
 
@@ -973,6 +985,7 @@ retry:
                }
        }
        rcu_read_unlock();
+       preempt_enable();
        return ctx;
 }
 
@@ -1950,7 +1963,16 @@ static int __perf_event_enable(void *info)
        struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
        int err;
 
-       if (WARN_ON_ONCE(!ctx->is_active))
+       /*
+        * There's a time window between 'ctx->is_active' check
+        * in perf_event_enable function and this place having:
+        *   - IRQs on
+        *   - ctx->lock unlocked
+        *
+        * where the task could be killed and 'ctx' deactivated
+        * by perf_event_exit_task.
+        */
+       if (!ctx->is_active)
                return -EINVAL;
 
        raw_spin_lock(&ctx->lock);
@@ -6212,8 +6234,6 @@ perf_event_mux_interval_ms_store(struct device *dev,
        return count;
 }
 
-#define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
-
 static struct device_attribute pmu_dev_attrs[] = {
        __ATTR_RO(type),
        __ATTR_RW(perf_event_mux_interval_ms),
@@ -7465,7 +7485,7 @@ inherit_task_group(struct perf_event *event, struct task_struct *parent,
                 * child.
                 */
 
-               child_ctx = alloc_perf_context(event->pmu, child);
+               child_ctx = alloc_perf_context(parent_ctx->pmu, child);
                if (!child_ctx)
                        return -ENOMEM;
 
@@ -7608,7 +7628,7 @@ static void __init perf_event_init_all_cpus(void)
        }
 }
 
-static void __cpuinit perf_event_init_cpu(int cpu)
+static void perf_event_init_cpu(int cpu)
 {
        struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);
 
@@ -7697,7 +7717,7 @@ static struct notifier_block perf_reboot_notifier = {
        .priority = INT_MIN,
 };
 
-static int __cpuinit
+static int
 perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
 {
        unsigned int cpu = (long)hcpu;