diff options
| author | Takashi Iwai <tiwai@suse.de> | 2016-01-18 15:52:47 +0300 |
|---|---|---|
| committer | Luis Henriques <luis.henriques@canonical.com> | 2016-02-02 22:09:58 +0300 |
| commit | 4238f492b693a43607f7a02007421d954769531a (patch) | |
| tree | 9544736c9bd14dd990e3379e1055ebec41dcb3fe | |
| parent | 88dd6606685b44773613be5b9bef2dfe5bf5d601 (diff) | |
| download | linux-4238f492b693a43607f7a02007421d954769531a.tar.xz | |
ALSA: hrtimer: Fix stall by hrtimer_cancel()
commit 2ba1fe7a06d3624f9a7586d672b55f08f7c670f3 upstream.
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.
Reported-and-tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
| -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 886be7da989d..38514ed6e55c 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; } |