Re: [PATCH] remove BKL from drivers' release functions

[Russell King]

On Wed, Nov 28, 2001 at 04:26:16PM -0800, David C. Hansen wrote:
> I wrote a quick and dirty char device driver to see if this happened. 
>  If I run two tasks doing a bunch of opens and closes, the -EBUSY 
> condition in the open function does happen.  Is my driver doing 
> something wrong?

What's happening is:

task 1				task 2
-> sys_open
 -> lock_kernel
  -> testdev_open
   -> test_and_set_bit
     return success
    unlock kernel
				-> sys_open
				 -> lock_kernel (blocks on it)
				  -> testdev_open
				   -> test_and_set_bit
				     return -EBUSY
				    unlock kernel
				   return
   return

The BKL is only held for the duration of the open, not until you close the
device.

--
Russell King ([e-mail])                The developer of ARM Linux
             http://www.arm.linux.org.uk/personal/aboutme.html