[alsa-devel] sound: another deadlock in snd_seq_pool_done

[Dmitry Vyukov]

On Sat, Mar 4, 2017 at 5:31 PM, Dmitry Vyukov <dvyukov at google.com> wrote:
> Hello,
>
> The following program creates processes deadlocked in snd_seq_pool_done:
>
> https://gist.githubusercontent.com/dvyukov/97efc9cb6d63b1b2c7b737b82cc8b0d6/raw/3546b133ae0b2d3e1190ae7c1f4e240ce7ce132e/gistfile1.txt
>
> After few seconds I get:
>
> # ps afxu | grep a.out
> root      8660  2.0  0.0      0     0 pts/0    Zl   16:27   0:00
> [a.out] <defunct>
>
> # kill -9 8660
>
> # cat /proc/8660/status
> Name: a.out
> State: Z (zombie)
> Tgid: 8660
> Ngid: 0
> Pid: 8660
> PPid: 1
> TracerPid: 0
> Uid: 0 0 0 0
> Gid: 0 0 0 0
> FDSize: 0
> Groups: 0
> NStgid: 8660
> NSpid: 8660
> NSpgid: 8660
> NSsid: 2971
> Threads: 2
> SigQ: 1/3304
> SigPnd: 0000000000000000
> ShdPnd: 0000000000000100
> SigBlk: 0000000000000000
> SigIgn: 0000000180000000
> SigCgt: 0000000000000440
> CapInh: 0000000000000000
> CapPrm: 0000003fffffffff
> CapEff: 0000003fffffffff
> CapBnd: 0000003fffffffff
> CapAmb: 0000000000000000
> NoNewPrivs: 0
> Seccomp: 0
> Cpus_allowed: f
> Cpus_allowed_list: 0-3
> Mems_allowed: 00000000,00000001
> Mems_allowed_list: 0
> voluntary_ctxt_switches: 12
> nonvoluntary_ctxt_switches: 0
>
> # cat /proc/8660/task/*/stack
> [<ffffffff835406db>] snd_seq_pool_done+0x31b/0x620
> sound/core/seq/seq_memory.c:436
> [<ffffffff8353a11e>] snd_seq_ioctl_set_client_pool+0x1ae/0x600
> sound/core/seq/seq_clientmgr.c:1836
> [<ffffffff835382ba>] snd_seq_ioctl+0x2da/0x4d0
> sound/core/seq/seq_clientmgr.c:2130
> [<ffffffff81aced2f>] vfs_ioctl fs/ioctl.c:45 [inline]
> [<ffffffff81aced2f>] do_vfs_ioctl+0x1bf/0x1790 fs/ioctl.c:685
> [<ffffffff81ad038f>] SYSC_ioctl fs/ioctl.c:700 [inline]
> [<ffffffff81ad038f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
> [<ffffffff8457dc41>] entry_SYSCALL_64_fastpath+0x1f/0xc2


A friendly ping.