On 05/29/2014 03:57 AM, Peter Zijlstra wrote: > On Wed, May 28, 2014 at 07:52:07PM -0400, Sasha Levin wrote: >> On 05/14/2014 12:35 PM, Peter Zijlstra wrote: >>> On Wed, May 14, 2014 at 12:32:26PM -0400, Sasha Levin wrote: >>>>> -----BEGIN PGP SIGNED MESSAGE----- >>>>> Hash: SHA1 >>>>> >>>>> On 05/14/2014 12:29 PM, Peter Zijlstra wrote: >>>>>>> On Mon, May 12, 2014 at 11:42:33AM -0400, Sasha Levin wrote: >>>>>>>>> Hi all, >>>>>>>>> >>>>>>>>> While fuzzing with trinity inside a KVM tools guest running the >>>>>>>>> latest -next kernel I've stumbled on the following spew. Maybe >>>>>>>>> related to the very recent change in freeing on task exit? >>>>>>>>> >>>>>>>>> [ 2509.827261] general protection fault: 0000 [#1] PREEMPT SMP >>>>>>>>> DEBUG_PAGEALLOC [ 2509.830379] Dumping ftrace buffer: [ 2509.830379] >>>>>>>>> (ftrace buffer empty) [ 2509.830379] Modules linked in: [ >>>>>>>>> 2509.830379] CPU: 47 PID: 43306 Comm: trinity-c126 Tainted: G >>>>>>>>> W 3.15.0-rc5-next-20140512-sasha-00019-ga20bc00-dirty #456 >>>>>>> >>>>>>> Any particular trinity setup? And would you happen to have the seed of >>>>>>> that run? >>>>> >>>>> Nothing special about trinity options. 400 threads and blacklisting some >>>>> of the >>>>> destructive syscalls (umount, reboot, etc). >>>>> >>>>> I don't have the seed, but that problem did reproduce again tonight so I >>>>> can test >>>>> out debug code if you have something in mind. >>> Nah, I drew a pretty big blank, which is why I wanted to see if I could >>> reproduce. If you could share your trinity cmdline I'd be much obliged. >>> While I did manage to clone (the repo moved since last time) and build >>> it, I'm not really that handy with it and want to avoid destroying my >>> machine if possible ;-) >> >> Anything I could do to help out with this? It reproduces pretty easily on my >> configuration so I'd be happy to test out whatever might help. > > Yeah, it takes me days to test anything, and my last guess panned out to > nothing, at which point I decided I needed to look at the things I'd > neglected for a bit :/ > > Could you see if the below makes any difference? I'll try and get back > to tracking this. > > --- > kernel/events/core.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 9efb1e7858ac..851dc9dc5643 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -7497,8 +7497,10 @@ static void perf_event_exit_task_context(struct > task_struct *child, int ctxn) > */ > mutex_lock(&child_ctx->mutex); > > + rcu_read_lock(); > list_for_each_entry_rcu(child_event, &child_ctx->event_list, > event_entry) > __perf_event_exit_task(child_event, child_ctx, child); > + rcu_read_unlock(); > > mutex_unlock(&child_ctx->mutex); > >
It doesn't work out well because we later lock a mutex in sync_child_event(). Thanks, Sasha -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
