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Date: Sun, 11 Oct 2009 02:25:53 +0200 (CEST) From: John Kacur <jkacur@...hat.com> To: Alan Cox <alan@...rguk.ukuu.org.uk> cc: linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, Jonathan Corbet <corbet@....net>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Frederic Weisbecker <fweisbec@...il.com>, Christoph Hellwig <hch@...radead.org>, Andrew Morton <akpm@...ux-foundation.org>, Vincent^M^J Sanders <vince@...tec.co.uk>, Ingo Molnar <mingo@...e.hu> Subject: Re: [PATCH] sound_core.c: Remove BKL from soundcore_open On Sun, 11 Oct 2009, Alan Cox wrote: > On Sun, 11 Oct 2009 01:24:14 +0200 (CEST) > John Kacur <jkacur@...hat.com> wrote: > > > >From 030af455d4f54482130c8eccb47fe90aaba8808c Mon Sep 17 00:00:00 2001 > > From: John Kacur <jkacur@...hat.com> > > 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 <jkacur@...hat.com> 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 <jkacur@...hat.com> --- 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 <linux/major.h> #include <sound/core.h> +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); if (err) { fops_put(file->f_op); file->f_op = fops_get(old_fops); } fops_put(old_fops); - unlock_kernel(); return err; } spin_unlock(&sound_loader_lock); - unlock_kernel(); return -ENODEV; } -- 1.6.0.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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