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>
3e2e0d2c22