perf_events: Fix stale ->cgrp pointer in update_cgrp_time_from_cpuctx()

[pandora-kernel.git] / kernel / perf_event.c

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 3472bb1..0c71422 100644 (file)
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -941,6 +941,7 @@ static void perf_group_attach(struct perf_event *event)
 static void
 list_del_event(struct perf_event *event, struct perf_event_context *ctx)
 {
+       struct perf_cpu_context *cpuctx;
        /*
         * We can have double detach due to exit/hot-unplug + close.
         */
@@ -949,8 +950,17 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx)
 
        event->attach_state &= ~PERF_ATTACH_CONTEXT;
 
-       if (is_cgroup_event(event))
+       if (is_cgroup_event(event)) {
                ctx->nr_cgroups--;
+               cpuctx = __get_cpu_context(ctx);
+               /*
+                * if there are no more cgroup events
+                * then cler cgrp to avoid stale pointer
+                * in update_cgrp_time_from_cpuctx()
+                */
+               if (!ctx->nr_cgroups)
+                       cpuctx->cgrp = NULL;
+       }
 
        ctx->nr_events--;
        if (event->attr.inherit_stat)