linux-kernel - Re: [PATCH 12/13][Resubmit][drivers/media] changed ioctls to unlocked

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Date:	Wed, 25 Mar 2009 01:25:35 +0300
From:	Alexey Klimov <klimov.linux@...il.com>
To:	stoyboyker@...il.com
Cc:	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Subject: Re: [PATCH 12/13][Resubmit][drivers/media] changed ioctls to
 unlocked

Hello, Stoyan

On Tue, 2009-03-24 at 16:38 -0500, stoyboyker@...il.com wrote:
> From: Stoyan Gaydarov <stoyboyker@...il.com>
> 
> Signed-off-by: Stoyan Gaydarov <stoyboyker@...il.com>
> ---
>  drivers/media/dvb/bt8xx/dst_ca.c |    7 +++++--
>  drivers/media/video/dabusb.c     |   11 ++++++++---
>  2 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/dvb/bt8xx/dst_ca.c b/drivers/media/dvb/bt8xx/dst_ca.c
> index 0258451..d3487c5 100644
> --- a/drivers/media/dvb/bt8xx/dst_ca.c
> +++ b/drivers/media/dvb/bt8xx/dst_ca.c
> @@ -552,8 +552,10 @@ free_mem_and_exit:
>  	return result;
>  }
>  
> -static int dst_ca_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long ioctl_arg)
> +static long dst_ca_ioctl(struct file *file, unsigned int cmd, unsigned long ioctl_arg)
>  {
> +	lock_kernel();
> +
>  	struct dvb_device* dvbdev = (struct dvb_device*) file->private_data;
>  	struct dst_state* state = (struct dst_state*) dvbdev->priv;
>  	struct ca_slot_info *p_ca_slot_info;
> @@ -647,6 +649,7 @@ static int dst_ca_ioctl(struct inode *inode, struct file *file, unsigned int cmd
>  	kfree (p_ca_slot_info);
>  	kfree (p_ca_caps);
>  
> +	unlock_kernel();
>  	return result;
>  }
>  
> @@ -684,7 +687,7 @@ static ssize_t dst_ca_write(struct file *file, const char __user *buffer, size_t
>  
>  static struct file_operations dst_ca_fops = {
>  	.owner = THIS_MODULE,
> -	.ioctl = dst_ca_ioctl,
> +	.unlocked_ioctl = dst_ca_ioctl,
>  	.open = dst_ca_open,
>  	.release = dst_ca_release,
>  	.read = dst_ca_read,
> diff --git a/drivers/media/video/dabusb.c b/drivers/media/video/dabusb.c
> index 298810d..c31e76f 100644
> --- a/drivers/media/video/dabusb.c
> +++ b/drivers/media/video/dabusb.c
> @@ -657,22 +657,26 @@ static int dabusb_release (struct inode *inode, struct file *file)
>  	return 0;
>  }
>  
> -static int dabusb_ioctl (struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
> +static long dabusb_ioctl (struct file *file, unsigned int cmd, unsigned long arg)
>  {
>  	pdabusb_t s = (pdabusb_t) file->private_data;
>  	pbulk_transfer_t pbulk;
>  	int ret = 0;
>  	int version = DABUSB_VERSION;
>  
> +	lock_kernel();
>  	dbg("dabusb_ioctl");
>  
> -	if (s->remove_pending)
> +	if (s->remove_pending) {
> +		unlock_kernel();
>  		return -EIO;
> +	}
>  
>  	mutex_lock(&s->mutex);
>  
>  	if (!s->usbdev) {
>  		mutex_unlock(&s->mutex);
> +		unlock_kernel();
>  		return -EIO;
>  	}
>  
> @@ -713,6 +717,7 @@ static int dabusb_ioctl (struct inode *inode, struct file *file, unsigned int cm
>  		break;
>  	}
>  	mutex_unlock(&s->mutex);
> +	unlock_kernel();

May i ask why big kernel lock is used here?
Where is an advantage of BKL here?
Why not to use, for example, one more mutex lock?

-- 
Best regards, Klimov Alexey

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