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authorTakashi Iwai <tiwai@suse.de>2016-01-18 13:52:47 +0100
committerTakashi Iwai <tiwai@suse.de>2016-01-18 14:33:30 +0100
commit2ba1fe7a06d3624f9a7586d672b55f08f7c670f3 (patch)
tree18d95fff22f412e9bab6689314ac4a815551efd1 /sound/core/pcm_compat.c
parentdb8948e653e12b218058bb6696f4a33fa7845f64 (diff)
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. 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/pcm_compat.c')
0 files changed, 0 insertions, 0 deletions