On Sun, 24 Apr 2016 17:16:32 +0200, Dmitry Vyukov wrote:
On Sat, Apr 23, 2016 at 11:02 PM, Takashi Iwai tiwai@suse.de wrote:
On Sat, 23 Apr 2016 15:40:21 +0200, Dmitry Vyukov wrote:
Hi Takashi,
I've incorporated your hrtimer fixes (but also updated to ddce192106e4f984123884f8e878f66ace94b573) and now I am seeing lots of the following deadlock messages:
[ INFO: possible circular locking dependency detected ] 4.6.0-rc4+ #351 Not tainted
swapper/0/0 is trying to acquire lock: (&(&timer->lock)->rlock){-.-...}, at: [<ffffffff8537a749>] snd_timer_interrupt+0xa9/0xd30 sound/core/timer.c:701
but task is already holding lock: (&(&stime->lock)->rlock){-.....}, at: [<ffffffff85383d3f>] snd_hrtimer_callback+0x4f/0x2b0 sound/core/hrtimer.c:54
which lock already depends on the new lock.
Oh crap, my second patch is buggy, it leads to ABBA lock, indeed. The first patch is still OK, as it just adds a new behavior mode.
Could you replace the second patch with the below one?
I've replaced the second path with this one. The deadlocks has gone, but I've hit these two hangs that look related:
https://gist.githubusercontent.com/dvyukov/805718ea249c49d17ae759d1b0160684/... https://gist.githubusercontent.com/dvyukov/7f397ea4aeb9e35596e0c8053cf35a11/...
Hmm, so it wasn't a good idea to call hrtimer_cancel() in the spinlock, in anyway. Scratch the previous one.
OK, below is the yet revised two patches. One is the simplified version of the patch, and another is to call hrtimer_cancel() in a new timer op without spinlock. Apply these after the first patch "ALSA: timer: Allow backend disabling start/stop from handler".
thanks,
Takashi