On Wed, Jan 13, 2016 at 5:53 PM, Takashi Iwai <tiwai@xxxxxxx> wrote: > This and your other relevant reports seem pointing the race of timer > ioctls. Although snd_timer_close() itself calls snd_timer_stop(), > there is no other protection against the concurrent execution. > > If my guess is correct, a simplistic fix like below should work. It > basically serializes the timer ioctl by using a new mutex (and > replacing the old tread_sem mutex). They are no longtime blocking > calls, so this shouldn't be a big problem. But certainly there can be > a less intrusive way to paper over this if this really matters. > > In this case for timer.c, I'd leave the final decision rather to > Jaroslav. Jaroslav, what do you think? After applying this patch I still see the following WARNINGS: ------------[ cut here ]------------ WARNING: CPU: 2 PID: 30398 at lib/list_debug.c:53 __list_del_entry+0x10b/0x1e0() list_del corruption, ffff880032d933b0->next is LIST_POISON1 (dead000000000100) Modules linked in: CPU: 2 PID: 30398 Comm: syz-executor Not tainted 4.4.0+ #241 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 00000000ffffffff ffff8800627778d8 ffffffff82926eed ffff880062777948 ffff880061c2af80 ffffffff8660b640 ffff880062777918 ffffffff81350c89 ffffffff8298e77b ffffed000c4eef25 ffffffff8660b640 0000000000000035 Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [<ffffffff82926eed>] dump_stack+0x6f/0xa2 lib/dump_stack.c:50 [<ffffffff81350c89>] warn_slowpath_common+0xd9/0x140 kernel/panic.c:483 [<ffffffff81350d99>] warn_slowpath_fmt+0xa9/0xd0 kernel/panic.c:495 [<ffffffff8298e77b>] __list_del_entry+0x10b/0x1e0 lib/list_debug.c:51 [< inline >] list_del_init include/linux/list.h:145 [<ffffffff84ebd199>] _snd_timer_stop+0x119/0x450 sound/core/timer.c:501 [<ffffffff84ebd4f4>] snd_timer_stop+0x24/0x140 sound/core/timer.c:535 [<ffffffff84ebd648>] snd_timer_close+0x38/0x5f0 sound/core/timer.c:317 [< inline >] snd_timer_user_tselect sound/core/timer.c:1518 [< inline >] __snd_timer_user_ioctl sound/core/timer.c:1803 [<ffffffff84ec4362>] snd_timer_user_ioctl+0x7b2/0x25c0 sound/core/timer.c:1833 [< inline >] vfs_ioctl fs/ioctl.c:43 [<ffffffff817cbd3c>] do_vfs_ioctl+0x18c/0xfa0 fs/ioctl.c:674 [< inline >] SYSC_ioctl fs/ioctl.c:689 [<ffffffff817ccbdf>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:680 [<ffffffff86273076>] entry_SYSCALL_64_fastpath+0x16/0x7a arch/x86/entry/entry_64.S:185 ---[ end trace bfebf27b922184a1 ]--- _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
