From 0e57779aef22ba4951ea34e9abbdd3f4659d5450 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Fri, 1 Apr 2016 12:28:16 +0200 Subject: [PATCH] ALSA: timer: Use mod_timer() for rearming the system timer commit 4a07083ed613644c96c34a7dd2853dc5d7c70902 upstream. 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: [] snd_timer_s_start+0x13e/0x1a0 [] snd_timer_interrupt+0x504/0xec0 [] ? debug_check_no_locks_freed+0x290/0x290 [] snd_timer_s_function+0xb4/0x120 [] call_timer_fn+0x162/0x520 [] ? call_timer_fn+0xcd/0x520 [] ? 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 Signed-off-by: Willy Tarreau --- sound/core/timer.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/sound/core/timer.c b/sound/core/timer.c index d90d8f4b85fe..38742e826900 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1012,8 +1012,8 @@ 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; } -- 2.20.1