linux-kernel - Re: [PATCH 7/8] soundcore_open: Reduce the area BKL coverage

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Date:	Mon, 05 Jul 2010 18:09:16 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-kernel@...r.kernel.org, John Kacur <jkacur@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 7/8] soundcore_open: Reduce the area BKL coverage

At Sun,  4 Jul 2010 00:02:31 +0200,
Arnd Bergmann wrote:
> 
> From: John Kacur <jkacur@...hat.com>
> 
> 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);
> 
> In order to build the sound core without the BKL, we
> will need to push the lock_kernel() call into the ~20
> device drivers that register their file operations.
> 
> Signed-off-by: John Kacur <jkacur@...hat.com>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Acked-by: Alan Cox <alan@...ux.intel.com>
> Cc: Takashi Iwai <tiwai@...e.de>

I applied this one to sound git tree now.  Thanks!


Takashi

> ---
>  sound/sound_core.c |   13 ++++++++-----
>  1 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/sound/sound_core.c b/sound/sound_core.c
> index 7c2d677..c8627fc 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 +628,23 @@ 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) {
> +			/* TODO: push down BKL into indivial open functions */
> +			lock_kernel();
>  			err = file->f_op->open(inode,file);
> +			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;
>  }
>  
> -- 
> 1.7.1
> 
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