kernel/cred.c: remove unnecessary kdebug atomic reads
authorJoe Perches <joe@perches.com>
Wed, 9 Sep 2015 22:36:09 +0000 (15:36 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 10 Sep 2015 20:29:01 +0000 (13:29 -0700)
commit52aa8536f8f41367d5f2938ad67aa87957e70010
tree55070d401000b7ab501b3b4a51883401f3a8adc3
parent2307e1a3c0780d7b908f6809f34034a04f954806
kernel/cred.c: remove unnecessary kdebug atomic reads

Commit e0e817392b9a ("CRED: Add some configurable debugging [try #6]")
added the kdebug mechanism to this file back in 2009.

The kdebug macro calls no_printk which always evaluates arguments.

Most of the kdebug uses have an unnecessary call of
atomic_read(&cred->usage)

Make the kdebug macro do nothing by defining it with
do { if (0) no_printk(...); } while (0)
when not enabled.

$ size kernel/cred.o* (defconfig x86-64)
   text    data     bss     dec     hex filename
   2748     336       8    3092     c14 kernel/cred.o.new
   2788     336       8    3132     c3c kernel/cred.o.old

Miscellanea:
o Neaten the #define kdebug macros while there

Signed-off-by: Joe Perches <joe@perches.com>
Cc: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kernel/cred.c