On Fri, Jul 27, 2018 at 07:20:30AM +0200, Takashi Iwai wrote: I think there is a mistake on the reported-by tag. The reported-by tag (e4c8abb920ef...) is for WARNING in port_delete. I guess the tag below is correct. Reported-by: [email protected] Could you please make sure that the reported-by tag is correct?
By the way, I can't reproduce the crash WARNING in port_delete so far. I feel sad for saying this.. I really want to reproduce the crash and thus, to help to fix the crash. If there is any progress on it, I will let you know immediately. Best regards, Dae R. Jeong > On Fri, 27 Jul 2018 06:13:22 +0200, > Dae R. Jeong wrote: > > > > I tested it and it worked. > > Thanks a lot! > > Good to hear. Below is the final patch with a proper comment (and > with syzbot reported-by, too) I'm going to queue to sound.git tree. > > > thanks, > > Takashi > > -- 8< -- > > From: Takashi Iwai <[email protected]> > Subject: [PATCH v2] ALSA: virmidi: Fix too long output trigger loop > > The virmidi output trigger tries to parse the all available bytes and > process sequencer events as much as possible. In a normal situation, > this is supposed to be relatively short, but a program may give a huge > buffer and it'll take a long time in a single spin lock, which may > eventually lead to a soft lockup. > > This patch simply adds a workaround, a cond_resched() call in the loop > if applicable. A better solution would be to move the event processor > into a work, but let's put a duct-tape quickly at first. > > Reported-and-tested-by: Dae R. Jeong <[email protected]> > Reported-by: [email protected] > Cc: <[email protected]> > Signed-off-by: Takashi Iwai <[email protected]> > --- > sound/core/seq/seq_virmidi.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/sound/core/seq/seq_virmidi.c b/sound/core/seq/seq_virmidi.c > index 289ae6bb81d9..8ebbca554e99 100644 > --- a/sound/core/seq/seq_virmidi.c > +++ b/sound/core/seq/seq_virmidi.c > @@ -163,6 +163,7 @@ static void snd_virmidi_output_trigger(struct > snd_rawmidi_substream *substream, > int count, res; > unsigned char buf[32], *pbuf; > unsigned long flags; > + bool check_resched = !in_atomic(); > > if (up) { > vmidi->trigger = 1; > @@ -200,6 +201,15 @@ static void snd_virmidi_output_trigger(struct > snd_rawmidi_substream *substream, > vmidi->event.type = > SNDRV_SEQ_EVENT_NONE; > } > } > + if (!check_resched) > + continue; > + /* do temporary unlock & cond_resched() for avoiding > + * CPU soft lockup, which may happen via a write from > + * a huge rawmidi buffer > + */ > + spin_unlock_irqrestore(&substream->runtime->lock, > flags); > + cond_resched(); > + spin_lock_irqsave(&substream->runtime->lock, flags); > } > out: > spin_unlock_irqrestore(&substream->runtime->lock, flags); > -- > 2.18.0 >
