Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760630AbZJKLeF (ORCPT ); Sun, 11 Oct 2009 07:34:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757135AbZJKLeD (ORCPT ); Sun, 11 Oct 2009 07:34:03 -0400 Received: from mail-ew0-f208.google.com ([209.85.219.208]:61874 "EHLO mail-ew0-f208.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756790AbZJKLeC (ORCPT ); Sun, 11 Oct 2009 07:34:02 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=x6iPqe3kuQifF3zF/m3YqncmDbaqmev0G13IEjYEOOqFPU/BnmiRqNv0sbZTGTPGah WvM+dAgWPGmM6gNTwh9koyauPgKcmX/0dwL44jYbUzr8yNzeSCxudGFAucyCSnWHXqYJ MHxeRz1Hv3qPIntnALWVoROpMucY8JWPWBQqE= Date: Sun, 11 Oct 2009 13:33:21 +0200 From: Frederic Weisbecker To: John Kacur Cc: Alan Cox , linux-kernel@vger.kernel.org, Thomas Gleixner , Jonathan Corbet , Peter Zijlstra , Christoph Hellwig , Andrew Morton , Vincent^M^J Sanders , Ingo Molnar Subject: Re: [PATCH] sound_core.c: Remove BKL from soundcore_open Message-ID: <20091011113317.GA4901@nowhere> References: <20091011004219.74c30f67@lxorguk.ukuu.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3074 Lines: 91 On Sun, Oct 11, 2009 at 02:25:53AM +0200, John Kacur wrote: > > > On Sun, 11 Oct 2009, Alan Cox wrote: > > > On Sun, 11 Oct 2009 01:24:14 +0200 (CEST) > > John Kacur wrote: > > > > > >From 030af455d4f54482130c8eccb47fe90aaba8808c Mon Sep 17 00:00:00 2001 > > > From: John Kacur > > > Date: Sat, 10 Oct 2009 23:39:56 +0200 > > > Subject: [PATCH] This code is already protected by spin_lock, and doesn't require the bkl > > > > Sorry but I don't think that is true becaue of: > > > > spin_unlock(&sound_loader_lock); > > if(file->f_op->open) > > err = file->f_op->open(inode,file); > > > > > > So the underlying driver open method expects lock_kernel status and you > > don't propogate it down. You really need to track down each thing that > > can be called into here and fix it, or maybe just punt for the moment and > > push it down to > > > > { > > lock_kernel() > > err = file-f_op->open ... > > unlock_kernel() > > } > > > > so its obvious to the next person who takes up the war on the BKL what is > > to be tackled. > > > > Yikes, I missed that. Still I'm loath to just push it down like that. I > wonder if I can use a mutex there. What about the following patch? > > From 8b0b91523ee2fcf60ccd82dba44b8da8bad34ce4 Mon Sep 17 00:00:00 2001 > From: John Kacur > Date: Sun, 11 Oct 2009 02:14:44 +0200 > Subject: [PATCH] Remove the bkl in soundcore_open > > Remove the bkl in soundcore_open since it is mostly covered by the sound_loader_lock spin_lock > > Protect the underlying driver open method with a mutex. > > Signed-off-by: John Kacur > --- > sound/sound_core.c | 8 ++++---- > 1 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/sound/sound_core.c b/sound/sound_core.c > index 49c9981..6afb6f1 100644 > --- a/sound/sound_core.c > +++ b/sound/sound_core.c > @@ -14,6 +14,8 @@ > #include > #include > > +static DEFINE_MUTEX(osc_mutex); > + > #ifdef CONFIG_SOUND_OSS_CORE > static int __init init_oss_soundcore(void); > static void cleanup_oss_soundcore(void); > @@ -576,8 +578,6 @@ static int soundcore_open(struct inode *inode, struct file *file) > struct sound_unit *s; > const struct file_operations *new_fops = NULL; > > - lock_kernel (); > - > chain=unit&0x0F; > if(chain==4 || chain==5) /* dsp/audio/dsp16 */ > { > @@ -631,17 +631,17 @@ static int soundcore_open(struct inode *inode, struct file *file) > file->f_op = new_fops; > spin_unlock(&sound_loader_lock); > if(file->f_op->open) > + mutex_lock(&osc_mutex); > err = file->f_op->open(inode,file); > + mutex_unlock(&osc_mutex); Yeah that's tempting, but I fear that also means this mutex will never be removed.... -- 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/