diff options
authorTakashi Iwai <>2016-04-01 12:28:16 +0200
committerTakashi Iwai <>2016-04-01 12:28:16 +0200
commit4a07083ed613644c96c34a7dd2853dc5d7c70902 (patch)
parente549d190f7b5f94e9ab36bd965028112914d010d (diff)
ALSA: timer: Use mod_timer() for rearming the system timer
ALSA system timer backend stops the timer via del_timer() without sync and leaves del_timer_sync() at the close instead. This is because of the restriction by the design of ALSA timer: namely, the stop callback may be called from the timer handler, and calling the sync shall lead to a hangup. However, this also triggers a kernel BUG() when the timer is rearmed immediately after stopping without sync: kernel BUG at kernel/time/timer.c:966! Call Trace: <IRQ> [<ffffffff8239c94e>] snd_timer_s_start+0x13e/0x1a0 [<ffffffff8239e1f4>] snd_timer_interrupt+0x504/0xec0 [<ffffffff8122fca0>] ? debug_check_no_locks_freed+0x290/0x290 [<ffffffff8239ec64>] snd_timer_s_function+0xb4/0x120 [<ffffffff81296b72>] call_timer_fn+0x162/0x520 [<ffffffff81296add>] ? call_timer_fn+0xcd/0x520 [<ffffffff8239ebb0>] ? snd_timer_interrupt+0xec0/0xec0 .... It's the place where add_timer() checks the pending timer. It's clear that this may happen after the immediate restart without sync in our cases. So, the workaround here is just to use mod_timer() instead of add_timer(). This looks like a band-aid fix, but it's a right move, as snd_timer_interrupt() takes care of the continuous rearm of timer. Reported-by: Jiri Slaby <> Cc: <> Signed-off-by: Takashi Iwai <>
1 files changed, 2 insertions, 2 deletions
diff --git a/sound/core/timer.c b/sound/core/timer.c
index ea4d999113ef..6469bedda2f3 100644
--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -1019,8 +1019,8 @@ static int snd_timer_s_start(struct snd_timer * timer)
njiff += timer->sticks - priv->correction;
priv->correction = 0;
- priv->last_expires = priv->tlist.expires = njiff;
- add_timer(&priv->tlist);
+ priv->last_expires = njiff;
+ mod_timer(&priv->tlist, njiff);
return 0;