Re: [tip:perf/urgent] perf: Fix perf_event_exit_task() race
From: Peter Zijlstra
Date: Mon Jan 25 2016 - 08:08:55 EST
---
Subject: perf: Fix orphan hole
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Fri Jan 22 22:13:41 CET 2016
We should set event->owner before we install the event, otherwise
there is a hole where the target task can fork() and we'll not inherit
the event because it thinks the event is orphaned.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
kernel/events/core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8489,6 +8489,8 @@ SYSCALL_DEFINE5(perf_event_open,
perf_event__header_size(event);
perf_event__id_header_size(event);
+ event->owner = current;
+
perf_install_in_context(ctx, event, event->cpu);
perf_unpin_context(ctx);
@@ -8498,8 +8500,6 @@ SYSCALL_DEFINE5(perf_event_open,
put_online_cpus();
- event->owner = current;
-
mutex_lock(¤t->perf_event_mutex);
list_add_tail(&event->owner_entry, ¤t->perf_event_list);
mutex_unlock(¤t->perf_event_mutex);