perf: Fix EXIT event notification

The perf_event_task_ctx() function needs to be called with
preemption disabled, since it's checking for currently
scheduled cpu against event cpu.

We disable preemption for task related perf event context
if there's one defined, leaving up to the chance which cpu
it gets scheduled in.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/1367857638-27631-2-git-send-email-jolsa@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6b41c1899a8b00acc0ca48ae30b0e8dfbdd2ad9d..38b68a05c3c6ba6cbf57a25c27b28e3075f72e61 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4474,7 +4474,7 @@ static void perf_event_task_ctx(struct perf_event_context *ctx,
 static void perf_event_task_event(struct perf_task_event *task_event)
 {
        struct perf_cpu_context *cpuctx;
-       struct perf_event_context *ctx;
+       struct perf_event_context *ctx, *task_ctx = task_event->task_ctx;
        struct pmu *pmu;
        int ctxn;
 
@@ -4485,20 +4485,22 @@ static void perf_event_task_event(struct perf_task_event *task_event)
                        goto next;
                perf_event_task_ctx(&cpuctx->ctx, task_event);
 
-               ctx = task_event->task_ctx;
-               if (!ctx) {
-                       ctxn = pmu->task_ctx_nr;
-                       if (ctxn < 0)
-                               goto next;
-                       ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);
-                       if (ctx)
-                               perf_event_task_ctx(ctx, task_event);
-               }
+               if (task_ctx)
+                       goto next;
+               ctxn = pmu->task_ctx_nr;
+               if (ctxn < 0)
+                       goto next;
+               ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);
+               if (ctx)
+                       perf_event_task_ctx(ctx, task_event);
 next:
                put_cpu_ptr(pmu->pmu_cpu_context);
        }
-       if (task_event->task_ctx)
-               perf_event_task_ctx(task_event->task_ctx, task_event);
+       if (task_ctx) {
+               preempt_disable();
+               perf_event_task_ctx(task_ctx, task_event);
+               preempt_enable();
+       }
 
        rcu_read_unlock();
 }