From adc8a43a6d6688272ebffa81789fa857e603dec6 Mon Sep 17 00:00:00 2001 From: Andrej Krutak Date: Thu, 18 Aug 2016 23:52:11 +0200 Subject: [PATCH] ALSA: line6: Give up on the lock while URBs are released. Done, because line6_stream_stop() locks and calls line6_unlink_audio_urbs(), which in turn invokes audio_out_callback(), which tries to lock 2nd time. Fixes: ============================================= [ INFO: possible recursive locking detected ] 4.4.15+ #15 Not tainted --------------------------------------------- mplayer/3591 is trying to acquire lock: (&(&line6pcm->out.lock)->rlock){-.-...}, at: [] audio_out_callback+0x70/0x110 [snd_usb_line6] but task is already holding lock: (&(&line6pcm->out.lock)->rlock){-.-...}, at: [] line6_stream_stop+0x24/0x5c [snd_usb_line6] other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&(&line6pcm->out.lock)->rlock); lock(&(&line6pcm->out.lock)->rlock); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by mplayer/3591: #0: (snd_pcm_link_rwlock){.-.-..}, at: [] snd_pcm_stream_lock+0x1e/0x40 [snd_pcm] #1: (&(&substream->self_group.lock)->rlock){-.-...}, at: [] snd_pcm_stream_lock+0x26/0x40 [snd_pcm] #2: (&(&line6pcm->out.lock)->rlock){-.-...}, at: [] line6_stream_stop+0x24/0x5c [snd_usb_line6] stack backtrace: CPU: 0 PID: 3591 Comm: mplayer Not tainted 4.4.15+ #15 Hardware name: Generic AM33XX (Flattened Device Tree) [] (unwind_backtrace) from [] (show_stack+0x11/0x14) [] (show_stack) from [] (dump_stack+0x8b/0xac) [] (dump_stack) from [] (__lock_acquire+0xc8b/0x1780) [] (__lock_acquire) from [] (lock_acquire+0x99/0x1c0) [] (lock_acquire) from [] (_raw_spin_lock_irqsave+0x3f/0x4c) [] (_raw_spin_lock_irqsave) from [] (audio_out_callback+0x70/0x110 [snd_usb_line6]) [] (audio_out_callback [snd_usb_line6]) from [] (__usb_hcd_giveback_urb+0x53/0xd0) [] (__usb_hcd_giveback_urb) from [] (musb_giveback+0x3d/0x98) [] (musb_giveback) from [] (musb_urb_dequeue+0x6d/0x114) [] (musb_urb_dequeue) from [] (usb_hcd_unlink_urb+0x39/0x98) [] (usb_hcd_unlink_urb) from [] (line6_unlink_audio_urbs+0x6a/0x6c [snd_usb_line6]) [] (line6_unlink_audio_urbs [snd_usb_line6]) from [] (line6_stream_stop+0x42/0x5c [snd_usb_line6]) [] (line6_stream_stop [snd_usb_line6]) from [] (snd_line6_trigger+0xb6/0xf4 [snd_usb_line6]) [] (snd_line6_trigger [snd_usb_line6]) from [] (snd_pcm_do_stop+0x36/0x38 [snd_pcm]) [] (snd_pcm_do_stop [snd_pcm]) from [] (snd_pcm_action_single+0x22/0x40 [snd_pcm]) [] (snd_pcm_action_single [snd_pcm]) from [] (snd_pcm_action+0xac/0xb0 [snd_pcm]) [] (snd_pcm_action [snd_pcm]) from [] (snd_pcm_drop+0x38/0x64 [snd_pcm]) [] (snd_pcm_drop [snd_pcm]) from [] (snd_pcm_common_ioctl1+0x7fe/0xbe8 [snd_pcm]) [] (snd_pcm_common_ioctl1 [snd_pcm]) from [] (snd_pcm_playback_ioctl1+0x15c/0x51c [snd_pcm]) [] (snd_pcm_playback_ioctl1 [snd_pcm]) from [] (snd_pcm_playback_ioctl+0x20/0x28 [snd_pcm]) [] (snd_pcm_playback_ioctl [snd_pcm]) from [] (do_vfs_ioctl+0x3af/0x5c8) Fixes: 63e20df1e5b2 ('ALSA: line6: Reorganize PCM stream handling') Cc: # v4.0+ Reviewed-by: Stefan Hajnoczi Signed-off-by: Andrej Krutak Signed-off-by: Takashi Iwai --- sound/usb/line6/pcm.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/sound/usb/line6/pcm.c b/sound/usb/line6/pcm.c index 2bc8879757f9..41aa3355e920 100644 --- a/sound/usb/line6/pcm.c +++ b/sound/usb/line6/pcm.c @@ -210,7 +210,9 @@ static void line6_stream_stop(struct snd_line6_pcm *line6pcm, int direction, spin_lock_irqsave(&pstr->lock, flags); clear_bit(type, &pstr->running); if (!pstr->running) { + spin_unlock_irqrestore(&pstr->lock, flags); line6_unlink_audio_urbs(line6pcm, pstr); + spin_lock_irqsave(&pstr->lock, flags); if (direction == SNDRV_PCM_STREAM_CAPTURE) { line6pcm->prev_fbuf = NULL; line6pcm->prev_fsize = 0; -- 2.20.1