On Thu, May 29, 2014 at 12:44:23PM -0400, Sasha Levin wrote: > On 05/29/2014 11:07 AM, Peter Zijlstra wrote: > > On Thu, May 29, 2014 at 10:47:09AM -0400, Sasha Levin wrote: > >> It doesn't work out well because we later lock a mutex in > >> sync_child_event(). > >> > > > > Urgh, right you are. I'll go stare at it more. It shouldn't have > > mattered, because the mutex we take just before should ensure existence, > > but.. you know.. :-) > > > > So the only caller to sync_child_event() is that loop. According to what you > said > it should be safe to remove that mutex lock, but doing that triggers a list > corruption: > > [ 1204.341887] WARNING: CPU: 20 PID: 12839 at lib/list_debug.c:62 > __list_del_entry+0xa1/0xe0() > [ 1204.347597] list_del corruption. next->prev should be ffff8806ca68b108, > but was ffff88051a67c398 > [...] > > I don't see how that would happen :/
No, what I said is that the mutex in perf_event_exit_task() should be sufficient to guard the list iteration calling __perf_event_exit_task(). Ading the RCU was a bit of paranoia.. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
