On Tue, Mar 1, 2016 at 4:31 PM, Takashi Iwai <tiwai@xxxxxxx> wrote: > 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. The patch fixes the hang for me. There is a second delay at exit, but otherwise the process exits fine. Tested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Thanks for quick fix! > --- > 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
