powerpc/xics: Reduce and comment xics IPI use of memory barriers
authorMilton Miller <miltonm@bga.com>
Fri, 10 Oct 2008 01:56:44 +0000 (01:56 +0000)
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>
Mon, 13 Oct 2008 05:24:19 +0000 (16:24 +1100)
commit199f45c45e8d4f58a5f568464be933534460eb82
tree488e5c5e4530313aff840fc5a2074a26f6233172
parent2172fe8704a1df7cbb988ae1ec4edbfef3e28860
powerpc/xics: Reduce and comment xics IPI use of memory barriers

A single full sync (mb()) is requrired to order the mmio to the qirr reg
with the set or clear of the message word.  However, test_and_clear_bit
has the effect of smp_mb() and we are not doing any other io from here,
so we don't need a mb per bit processed.

Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
arch/powerpc/platforms/pseries/xics.c