Messages in this thread | | | Date | Sun, 11 Oct 2009 13:33:21 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH] sound_core.c: Remove BKL from soundcore_open |
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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 <jkacur@redhat.com> wrote: > > > > > >From 030af455d4f54482130c8eccb47fe90aaba8808c Mon Sep 17 00:00:00 2001 > > > From: John Kacur <jkacur@redhat.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@redhat.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@redhat.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);
Yeah that's tempting, but I fear that also means this mutex will never be removed....
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