On Mon, 08 Jan 2018 20:21:00 +0100, Lars-Peter Clausen wrote: > > On 01/08/2018 05:00 PM, Lars-Peter Clausen wrote: > > On 01/08/2018 04:40 PM, Takashi Iwai wrote: > >> On Mon, 08 Jan 2018 16:37:32 +0100, > >> Lars-Peter Clausen wrote: > >>> > >>> On 01/08/2018 04:05 PM, Takashi Iwai wrote: > >>>> On Mon, 08 Jan 2018 15:58:47 +0100, > >>>> Lars-Peter Clausen wrote: > >>>>> > >>>>> On 01/08/2018 03:25 PM, Takashi Iwai wrote: > >>>>>> Hi, > >>>>>> > >>>>>> this contains two fixes for PCM OSS bugs that have been triggered by > >>>>>> syzbot. These are simple and straightforward, and I'm going to queue > >>>>>> for 4.15-rc8. > >>>>> > >>>>> I tried to reproduce the issue as well with the reproducer generated by > >>>>> syzbot. But what syzbot reported was that the CPU didn't sleep for 140 > >>>>> seconds. But with a long write() we'll go to sleep in between frames. So > >>>>> when I tried the lockup detector never triggered. > >>>>> > >>>>> Were you able to reproduce the same CPU lockup as syzbot? > >>>> > >>>> Yes, I could reproduce RCU stalls with two reproducers > >>>> (001a113ece5c2b600d05620b097a@xxxxxxxxxx and > >>>> 001a1147e1988b160a05620552eb@xxxxxxxxxx) > >>>> > >>>> The patches seem curing them, so far, in combination with other > >>>> patches in for-linus branch of sound.git tree. > >>>> > >>> > >>> Hm, interesting. Are you using aloop for the backend or real hardware? > >> > >> The RCU stall happened also with dummy driver. Just feeding a GB of > >> chunk to /dev/audio and aborting the stream concurrently, then it > >> stalls at that point. > > > > Hm, does that mean that snd_pcm_playback_avail() is never 0 for the dummy > > driver? Usually we should catch the signal_pending() in wait_for_avail(). > > Even with the dummy driver I'm not able to reproduce it. wait_for_avail() > gets called, thread goes to sleep and a Ctrl+C wakes it up with > signal_pending() set and it exits the syscall. Is the machine too fast? But mine isn't that slow, either. FWIW, below is the kconfig I'm using. I ran KVM with -smp 2. Takashi
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config-syz-4.15
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