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SubjectBig kernel lock in release functions
  I've been looking at use of the big kernel lock in a lot of different
places in the kernel. I've noticed that there are quite a few uses in
devices' release functions, with no obvious purpose. Take a look at
arch/m68k/atari/joystick.c:

lock_kernel();
joystick[minor].active = 0;
joystick[minor].ready = 0;

if ((joystick[0].active == 0) && (joystick[1].active == 0))
ikbd_joystick_disable();
unlock_kernel();

But, there are other places in the same file where the same operations
are performed with no locking at all (except for
ikbd_joystick_disable()). Is there a reason to have locking in the
release function but not in the read or open functions?
This is a quite common practice in release functions throughout the
kernel. In 2.4.10, I counted 108 different places where the BKL is used
in a release function. I'm not claiming that all of these are
unnecessary, but I believe a big chunk of them are.

--
David C. Hansen
haveblue@us.ibm.com
IBM LTC Base/OS Group
(503)578-4080
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