linux-kernel - Re: [PATCH] sound_core.c: Remove BKL from soundcore

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Date:	Mon, 12 Oct 2009 10:37:05 +0200 (CEST)
From:	John Kacur <jkacur@...hat.com>
To:	Takashi Iwai <tiwai@...e.de>
cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Jonathan Corbet <corbet@....net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	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 Mon, 12 Oct 2009, Takashi Iwai wrote:

> At Sun, 11 Oct 2009 14:41:15 +0200 (CEST),
> John Kacur wrote:
> > 
> > @@ -631,17 +629,17 @@ 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)
> > +			lock_kernel();
> >  			err = file->f_op->open(inode,file);
> > +			unlock_kernel();
> 
> You certainly want braces around here, no?
> 

Oh, I don't know, I was kinda hoping that the spaces would magically 
impart bracketnishish to the whole thing. My God yes we want the brackets -
Thank you Takashi!

What follows is version four.

>From 90f527d2ae660a3a0e712075479a4cc24504ad45 Mon Sep 17 00:00:00 2001
From: John Kacur <jkacur@...hat.com>
Date: Sun, 11 Oct 2009 14:25:46 +0200
Subject: [PATCH] soundcore_open: Reduce the area BKL coverage in this function.

Most of this function is protected by the sound_loader_lock.
We can push down the BKL to this call out err = file->f_op->open(inode,file);

Signed-off-by: John Kacur <jkacur@...hat.com>
Acked-by: Alan Cox <alan@...ux.intel.com>
---
 sound/sound_core.c |   10 ++++------
 1 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/sound/sound_core.c b/sound/sound_core.c
index 49c9981..643a61f 100644
--- a/sound/sound_core.c
+++ b/sound/sound_core.c
@@ -576,8 +576,6 @@ 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 */
 	{
@@ -630,18 +628,18 @@ static int soundcore_open(struct inode *inode, struct file *file)
 		const struct file_operations *old_fops = file->f_op;
 		file->f_op = new_fops;
 		spin_unlock(&sound_loader_lock);
-		if(file->f_op->open)
+		if(file->f_op->open) {
+			lock_kernel();
 			err = file->f_op->open(inode,file);
-		if (err) {
+			unlock_kernel();
+		} 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

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