From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Vyukov Subject: Re: sound: deadlock involving snd_hrtimer_callback Date: Wed, 4 May 2016 10:34:33 +0200 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-wm0-f42.google.com (mail-wm0-f42.google.com [74.125.82.42]) by alsa0.perex.cz (Postfix) with ESMTP id EDD10260542 for ; Wed, 4 May 2016 10:34:53 +0200 (CEST) Received: by mail-wm0-f42.google.com with SMTP id a17so80185492wme.0 for ; Wed, 04 May 2016 01:34:53 -0700 (PDT) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Takashi Iwai Cc: alsa-devel@alsa-project.org, LKML , Kostya Serebryany , syzkaller , Alexander Potapenko , Sasha Levin List-Id: alsa-devel@alsa-project.org On Mon, May 2, 2016 at 1:54 PM, Dmitry Vyukov wrote: > On Sun, Apr 24, 2016 at 11:31 PM, Takashi Iwai wrote: >> On Sun, 24 Apr 2016 19:09:48 +0200, >> Dmitry Vyukov wrote: >>> >>> On Sun, Apr 24, 2016 at 6:16 PM, Takashi Iwai wrote: >>> > On Sun, 24 Apr 2016 17:16:32 +0200, >>> > Dmitry Vyukov wrote: >>> >> >>> >> On Sat, Apr 23, 2016 at 11:02 PM, Takashi Iwai 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: [] >>> >> >> snd_timer_interrupt+0xa9/0xd30 sound/core/timer.c:701 >>> >> >> >>> >> >> but task is already holding lock: >>> >> >> (&(&stime->lock)->rlock){-.....}, at: [] >>> >> >> 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/raw/20891f7e87fe9af3967565559d465d296469244b/gistfile1.txt >>> >> https://gist.githubusercontent.com/dvyukov/7f397ea4aeb9e35596e0c8053cf35a11/raw/3fc22f24f7bab5941e47bab604f96487b5f1944d/gistfile1.txt >>> > >>> > 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". >>> >>> Done. I will let you know if I see any failures. >> >> After reconsideration, I rewrote the whole patchset again. >> Could you scratch all the previous three patches and replace with the >> single patch below? Sorry for inconvenience! > > Reapplied. > I will let you know if I see any crashes in sound. No crashes over two nights. We can consider it as fixed.