perf: Remove WARN_ON_ONCE() check in __perf_event_enable() for valid scenario

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

diff --git a/kernel/events/core.c b/kernel/events/core.c
index b391907d53520cb4a126bc8e3e0a2d5a64ade54d..cb8744a1b120673d981d20c4c85188839698c33e 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1761,7 +1761,16 @@ 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);
@@ -7228,7 +7237,7 @@ 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;