Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932902Ab2KNKou (ORCPT ); Wed, 14 Nov 2012 05:44:50 -0500 Received: from co202.xi-lite.net ([149.6.83.202]:58013 "EHLO co202.xi-lite.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932095Ab2KNKos (ORCPT ); Wed, 14 Nov 2012 05:44:48 -0500 Message-ID: <50A3761C.6090101@parrot.com> Date: Wed, 14 Nov 2012 11:44:44 +0100 From: Matthieu CASTET User-Agent: Thunderbird 2.0.0.24 (X11/20100228) MIME-Version: 1.0 To: Ben Hutchings , Takashi Iwai , "linux-kernel@vger.kernel.org" , Subject: Re : Re: Sound+USB: deadlock problem References: <50A20429.3020109@suse.cz> <50A20512.10805@suse.cz> <50A21542.2090102@suse.cz> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3450 Lines: 111 A deadlock was detected with this patch. You need the following patch [1] Matthieu > 3.2-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Takashi Iwai > > commit 34f3c89fda4fba9fe689db22253ca8db2f5e6386 upstream. > > Replace mutex with rwsem for codec->shutdown protection so that > concurrent accesses are allowed. > > Also add the protection to snd_usb_autosuspend() and > snd_usb_autoresume(), too. > > Reported-by: Matthieu CASTET > Signed-off-by: Takashi Iwai > Signed-off-by: Ben Hutchings > --- > sound/usb/card.c | 12 ++++++++---- > sound/usb/mixer.c | 12 ++++++------ > sound/usb/pcm.c | 12 ++++++------ > sound/usb/usbaudio.h | 2 +- > 4 files changed, 21 insertions(+), 17 deletions(-) [1] Takashi Iwai a ?crit : > At Tue, 13 Nov 2012 10:39:14 +0100, > Jiri Slaby wrote: >> On 11/13/2012 09:45 AM, Takashi Iwai wrote: >>> At Tue, 13 Nov 2012 09:30:10 +0100, >>> Jiri Slaby wrote: >>>> On 11/13/2012 09:28 AM, Takashi Iwai wrote: >>>>> At Tue, 13 Nov 2012 09:26:17 +0100, >>>>> Jiri Slaby wrote: >>>>>> Hello, >>>>>> >>>>>> I've just plugged+unplugged+plugged my USB audio card and the audio >>>>>> subsystem got stuck: >>>>> Which kernel? If it's older than 3.7-rc5, could you try 3.7-rc5? >>>> Oh, forgot to mention: >>>> 3.7.0-rc5-next-20121112_64+ >>> Through a quick glance, one of mutex locks seems stuck. >>> Just a blind short -- does the patch below cure the problem? >> Yes, this helps. >> >> Adding a LOCKDEP splash _before_ applying the patch: > > Thanks, this helps much for understanding the cause. > It's a new rwsem in the usb-audio driver that deadlocks. > > Although the previous patch fixes the deadlock it opens the race > again. > > Could you try the patch below instead? The rwsem above doesn't have > to be taken for the whole operation, but just needs to protect for > turning on the flag. The patch below should suffice for protecting > races but avoids the deadlock. > > > Takashi > > --- > diff --git a/sound/usb/card.c b/sound/usb/card.c > index 282f0fc..dbf7999 100644 > --- a/sound/usb/card.c > +++ b/sound/usb/card.c > @@ -559,9 +559,11 @@ static void snd_usb_audio_disconnect(struct usb_device *dev, > return; > > card = chip->card; > - mutex_lock(®ister_mutex); > down_write(&chip->shutdown_rwsem); > chip->shutdown = 1; > + up_write(&chip->shutdown_rwsem); > + > + mutex_lock(®ister_mutex); > chip->num_interfaces--; > if (chip->num_interfaces <= 0) { > snd_card_disconnect(card); > @@ -582,11 +584,9 @@ static void snd_usb_audio_disconnect(struct usb_device *dev, > snd_usb_mixer_disconnect(p); > } > usb_chip[chip->index] = NULL; > - up_write(&chip->shutdown_rwsem); > mutex_unlock(®ister_mutex); > snd_card_free_when_closed(card); > } else { > - up_write(&chip->shutdown_rwsem); > mutex_unlock(®ister_mutex); > } > } > -- > To unsubscribe from this list: send the line "unsubscribe linux-usb" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/