tile: comment assumption about __insn_mtspr for <asm/irqflags.h>
authorChris Metcalf <cmetcalf@tilera.com>
Tue, 9 Apr 2013 16:33:07 +0000 (12:33 -0400)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 9 Apr 2013 17:08:14 +0000 (10:08 -0700)
commit3e2e0d2c222bdf5bafd722dec1618fa6073ef372
tree04ea03bb23d59080ce52012095591874cad6cf49
parent84ee9805bc7406bee35f2d62001440c81059f073
tile: comment assumption about __insn_mtspr for <asm/irqflags.h>

The arch_local_irq_save(), etc., routines are required to function
as compiler barriers.  They do, but it's subtle and requires knowing
that the gcc builtin __insn_mtspr() is marked as a memory clobber.
Provide a comment explaining the assumption.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
[ This came about from me wondering about the synchronization rules of
  __insn_mtspr()   - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
arch/tile/include/asm/irqflags.h