[PATCH] dabusb: remove the BKL

[PATCH] dabusb: remove the BKL

[Arnd Bergmann]

The dabusb device driver is sufficiently serialized using
its own mutex, no need for the big kernel lock here
in addition.
    
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
---

Hi Mauro,

I just realized that the dabusb driver is not actually a v4l driver,
when I did more test builds with allyesconfig and CONFIG_BKL disabled.

I've added this patch to my bkl/config queue for now, but if you want to carry
it in your tree, I'll drop it from mine.

diff --git a/drivers/media/video/dabusb.c b/drivers/media/video/dabusb.c
index 5b176bd..f3e25e9 100644
--- a/drivers/media/video/dabusb.c
+++ b/drivers/media/video/dabusb.c
@@ -32,7 +32,6 @@
 #include <linux/list.h>
 #include <linux/vmalloc.h>
 #include <linux/slab.h>
-#include <linux/smp_lock.h>
 #include <linux/init.h>
 #include <asm/uaccess.h>
 #include <asm/atomic.h>
@@ -621,7 +620,6 @@ static int dabusb_open (struct inode *inode, struct file *file)
 	if (devnum < DABUSB_MINOR || devnum >= (DABUSB_MINOR + NRDABUSB))
 		return -EIO;
 
-	lock_kernel();
 	s = &dabusb[devnum - DABUSB_MINOR];
 
 	dbg("dabusb_open");
@@ -630,21 +628,17 @@ static int dabusb_open (struct inode *inode, struct file *file)
 	while (!s->usbdev || s->opened) {
 		mutex_unlock(&s->mutex);
 
-		if (file->f_flags & O_NONBLOCK) {
+		if (file->f_flags & O_NONBLOCK)
 			return -EBUSY;
-		}
 		msleep_interruptible(500);
 
-		if (signal_pending (current)) {
-			unlock_kernel();
+		if (signal_pending (current))
 			return -EAGAIN;
-		}
 		mutex_lock(&s->mutex);
 	}
 	if (usb_set_interface (s->usbdev, _DABUSB_IF, 1) < 0) {
 		mutex_unlock(&s->mutex);
 		dev_err(&s->usbdev->dev, "set_interface failed\n");
-		unlock_kernel();
 		return -EINVAL;
 	}
 	s->opened = 1;
@@ -654,7 +648,6 @@ static int dabusb_open (struct inode *inode, struct file *file)
 	file->private_data = s;
 
 	r = nonseekable_open(inode, file);
-	unlock_kernel();
 	return r;
 }
 
@@ -689,17 +682,13 @@ static long dabusb_ioctl (struct file *file, unsigned int cmd, unsigned long arg
 
 	dbg("dabusb_ioctl");
 
-	lock_kernel();
-	if (s->remove_pending) {
-		unlock_kernel();
+	if (s->remove_pending)
 		return -EIO;
-	}
 
 	mutex_lock(&s->mutex);
 
 	if (!s->usbdev) {
 		mutex_unlock(&s->mutex);
-		unlock_kernel();
 		return -EIO;
 	}
 
@@ -735,7 +724,6 @@ static long dabusb_ioctl (struct file *file, unsigned int cmd, unsigned long arg
 		break;
 	}
 	mutex_unlock(&s->mutex);
-	unlock_kernel();
 	return ret;
 }
 

Re: [PATCH] dabusb: remove the BKL

[Mauro Carvalho Chehab]

Em 04-10-2010 16:32, Arnd Bergmann escreveu:
> The dabusb device driver is sufficiently serialized using
> its own mutex, no need for the big kernel lock here
> in addition.
>     
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
> ---
> 
> Hi Mauro,
> 
> I just realized that the dabusb driver is not actually a v4l driver,
> when I did more test builds with allyesconfig and CONFIG_BKL disabled.
> 
> I've added this patch to my bkl/config queue for now, but if you want to carry
> it in your tree, I'll drop it from mine.

Sorry for not handling it sooner... I have a large number of patches in my queue...
I don't have any patch for dabusb on my tree, so, I'm OK if you sent it via your
tree. So,

Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>

---

PS.: I tried to contact the authors a few weeks ago to double check about this driver.
I suspect that it were added for some prototype, based on its help message, and the
links I found about that. So, it could be a good idea to simply move it to staging
and let it die, as maybe nobody has an actual hardware for it... 
Well, I got no answer about that so far.

> 
> diff --git a/drivers/media/video/dabusb.c b/drivers/media/video/dabusb.c
> index 5b176bd..f3e25e9 100644
> --- a/drivers/media/video/dabusb.c
> +++ b/drivers/media/video/dabusb.c
> @@ -32,7 +32,6 @@
>  #include <linux/list.h>
>  #include <linux/vmalloc.h>
>  #include <linux/slab.h>
> -#include <linux/smp_lock.h>
>  #include <linux/init.h>
>  #include <asm/uaccess.h>
>  #include <asm/atomic.h>
> @@ -621,7 +620,6 @@ static int dabusb_open (struct inode *inode, struct file *file)
>  	if (devnum < DABUSB_MINOR || devnum >= (DABUSB_MINOR + NRDABUSB))
>  		return -EIO;
>  
> -	lock_kernel();
>  	s = &dabusb[devnum - DABUSB_MINOR];
>  
>  	dbg("dabusb_open");
> @@ -630,21 +628,17 @@ static int dabusb_open (struct inode *inode, struct file *file)
>  	while (!s->usbdev || s->opened) {
>  		mutex_unlock(&s->mutex);
>  
> -		if (file->f_flags & O_NONBLOCK) {
> +		if (file->f_flags & O_NONBLOCK)
>  			return -EBUSY;
> -		}
>  		msleep_interruptible(500);
>  
> -		if (signal_pending (current)) {
> -			unlock_kernel();
> +		if (signal_pending (current))
>  			return -EAGAIN;
> -		}
>  		mutex_lock(&s->mutex);
>  	}
>  	if (usb_set_interface (s->usbdev, _DABUSB_IF, 1) < 0) {
>  		mutex_unlock(&s->mutex);
>  		dev_err(&s->usbdev->dev, "set_interface failed\n");
> -		unlock_kernel();
>  		return -EINVAL;
>  	}
>  	s->opened = 1;
> @@ -654,7 +648,6 @@ static int dabusb_open (struct inode *inode, struct file *file)
>  	file->private_data = s;
>  
>  	r = nonseekable_open(inode, file);
> -	unlock_kernel();
>  	return r;
>  }
>  
> @@ -689,17 +682,13 @@ static long dabusb_ioctl (struct file *file, unsigned int cmd, unsigned long arg
>  
>  	dbg("dabusb_ioctl");
>  
> -	lock_kernel();
> -	if (s->remove_pending) {
> -		unlock_kernel();
> +	if (s->remove_pending)
>  		return -EIO;
> -	}
>  
>  	mutex_lock(&s->mutex);
>  
>  	if (!s->usbdev) {
>  		mutex_unlock(&s->mutex);
> -		unlock_kernel();
>  		return -EIO;
>  	}
>  
> @@ -735,7 +724,6 @@ static long dabusb_ioctl (struct file *file, unsigned int cmd, unsigned long arg
>  		break;
>  	}
>  	mutex_unlock(&s->mutex);
> -	unlock_kernel();
>  	return ret;
>  }
>