]> git.baikalelectronics.ru Git - kernel.git/commit
x86: Fix and improve cmpxchg_double{,_local}()
authorJan Beulich <JBeulich@suse.com>
Mon, 2 Jan 2012 17:02:18 +0000 (17:02 +0000)
committerIngo Molnar <mingo@elte.hu>
Wed, 4 Jan 2012 14:01:54 +0000 (15:01 +0100)
commit30d44e88fecabd80e97b1ec7ca03d8815a7a941c
tree461087dd5b3d310a7da25021cb4f58270cbb7177
parent2baa8be6e81d73922b93cf0db977c305b9ca540f
x86: Fix and improve cmpxchg_double{,_local}()

Just like the per-CPU ones they had several
problems/shortcomings:

Only the first memory operand was mentioned in the asm()
operands, and the 2x64-bit version didn't have a memory clobber
while the 2x32-bit one did. The former allowed the compiler to
not recognize the need to re-load the data in case it had it
cached in some register, while the latter was overly
destructive.

The types of the local copies of the old and new values were
incorrect (the types of the pointed-to variables should be used
here, to make sure the respective old/new variable types are
compatible).

The __dummy/__junk variables were pointless, given that local
copies of the inputs already existed (and can hence be used for
discarded outputs).

The 32-bit variant of cmpxchg_double_local() referenced
cmpxchg16b_local().

At once also:

 - change the return value type to what it really is: 'bool'
 - unify 32- and 64-bit variants
 - abstract out the common part of the 'normal' and 'local' variants

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/4F01F12A020000780006A19B@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
arch/x86/include/asm/cmpxchg.h
arch/x86/include/asm/cmpxchg_32.h
arch/x86/include/asm/cmpxchg_64.h
mm/slub.c