On Tue, 01 Mar 2016 16:04:43 +0100, Dmitry Vyukov wrote: > > On Tue, Mar 1, 2016 at 4:01 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > > On Tue, Mar 1, 2016 at 3:44 PM, Takashi Iwai <tiwai@xxxxxxx> wrote: > >> On Tue, 01 Mar 2016 13:33:27 +0100, > >> Dmitry Vyukov wrote: > >>> > >>> Hello, > >>> > >>> The following program creates an unkillable process: > >> ..... > >>> The hang stack is: > >>> > >>> [<ffffffff85309f77>] snd_seq_oss_writeq_sync+0x327/0x790 > >>> sound/core/seq/oss/seq_oss_writeq.c:121 > >> > >> This is > >> wait_event_interruptible_timeout(q->sync_sleep, ! q->sync_event_put, HZ); > >> > >> and this should return zero > >> if (signal_pending(current)) > >> /* interrupted - return 0 to finish sync */ > >> q->sync_event_put = 0; > >> if (! q->sync_event_put || q->sync_time >= time) > >> return 0; > >> return 1; > >> > >>> [<ffffffff852fa353>] snd_seq_oss_drain_write+0x113/0x160 > >> > >> ... and this loop should break: > >> while (snd_seq_oss_writeq_sync(dp->writeq)) > >> ; > >> > >> So, I see no obvious error in the code, so far. > >> > >> I'm running your test program now with 8 parallel runs, but I couldn't > >> reproduce it. Any other specifics? > > > Hummm.. for me this process hangs every time, even if I just run it > once from console. > I've now retested in on clean commit > fc77dbd34c5c99bce46d40a2491937c3bcbd10af (without KASAN/KCOV and with > release gcc) and also got the same hang. > I can only think of a different config. I've attached mine, please try with it. > > Are signals delivered if we are already in process of dying? > When I kill -9 this process it does not react, so presumably wait is > not unblocked... Good point. But above all, it doesn't make much sense to loop this sync call. When wait_event*() returns, it should go out. So, the patch like below should be good enough and fix your issue, too. Takashi --- diff --git a/sound/core/seq/oss/seq_oss_writeq.c b/sound/core/seq/oss/seq_oss_writeq.c index 1f6788a18444..4014a5469d1a 100644 --- a/sound/core/seq/oss/seq_oss_writeq.c +++ b/sound/core/seq/oss/seq_oss_writeq.c @@ -119,12 +119,7 @@ snd_seq_oss_writeq_sync(struct seq_oss_writeq *q) } wait_event_interruptible_timeout(q->sync_sleep, ! q->sync_event_put, HZ); - if (signal_pending(current)) - /* interrupted - return 0 to finish sync */ - q->sync_event_put = 0; - if (! q->sync_event_put || q->sync_time >= time) - return 0; - return 1; + return 0; } /* _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel