diff options
author | Takashi Iwai <tiwai@suse.de> | 2016-01-18 13:52:47 +0100 |
---|---|---|
committer | Simon Shields <keepcalm444@gmail.com> | 2016-05-05 21:06:11 +1000 |
commit | afe9fd7ee230ab733e6de47f6acfc822f2472ec1 (patch) | |
tree | 2cf91c9dfdd1fbb33216ce5bd63d307fce6911bb /sound/core/hrtimer.c | |
parent | 342ec72c6123f81c16863ba25d57dcf0328104d5 (diff) | |
download | kernel_samsung_smdk4412-afe9fd7ee230ab733e6de47f6acfc822f2472ec1.zip kernel_samsung_smdk4412-afe9fd7ee230ab733e6de47f6acfc822f2472ec1.tar.gz kernel_samsung_smdk4412-afe9fd7ee230ab733e6de47f6acfc822f2472ec1.tar.bz2 |
ALSA: hrtimer: Fix stall by hrtimer_cancel()
hrtimer_cancel() waits for the completion from the callback, thus it
must not be called inside the callback itself. This was already a
problem in the past with ALSA hrtimer driver, and the early commit
[fcfdebe70759: ALSA: hrtimer - Fix lock-up] tried to address it.
However, the previous fix is still insufficient: it may still cause a
lockup when the ALSA timer instance reprograms itself in its callback.
Then it invokes the start function even in snd_timer_interrupt() that
is called in hrtimer callback itself, results in a CPU stall. This is
no hypothetical problem but actually triggered by syzkaller fuzzer.
This patch tries to fix the issue again. Now we call
hrtimer_try_to_cancel() at both start and stop functions so that it
won't fall into a deadlock, yet giving some chance to cancel the queue
if the functions have been called outside the callback. The proper
hrtimer_cancel() is called in anyway at closing, so this should be
enough.
Change-Id: Id6224b2a3ade0d217e891e6af09744df4d0b2e5c
Reported-and-tested-by: Dmitry Vyukov <dvyukov@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/core/hrtimer.c')
-rw-r--r-- | sound/core/hrtimer.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/sound/core/hrtimer.c b/sound/core/hrtimer.c index b8b31c4..14d483d 100644 --- a/sound/core/hrtimer.c +++ b/sound/core/hrtimer.c @@ -90,7 +90,7 @@ static int snd_hrtimer_start(struct snd_timer *t) struct snd_hrtimer *stime = t->private_data; atomic_set(&stime->running, 0); - hrtimer_cancel(&stime->hrt); + hrtimer_try_to_cancel(&stime->hrt); hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution), HRTIMER_MODE_REL); atomic_set(&stime->running, 1); @@ -101,6 +101,7 @@ static int snd_hrtimer_stop(struct snd_timer *t) { struct snd_hrtimer *stime = t->private_data; atomic_set(&stime->running, 0); + hrtimer_try_to_cancel(&stime->hrt); return 0; } |