From 199f45c45e8d4f58a5f568464be933534460eb82 Mon Sep 17 00:00:00 2001 From: Milton Miller Date: Fri, 10 Oct 2008 01:56:44 +0000 Subject: [PATCH] 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 Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/platforms/pseries/xics.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/arch/powerpc/platforms/pseries/xics.c b/arch/powerpc/platforms/pseries/xics.c index 62b0400577de..e1904774a70f 100644 --- a/arch/powerpc/platforms/pseries/xics.c +++ b/arch/powerpc/platforms/pseries/xics.c @@ -498,26 +498,23 @@ static irqreturn_t xics_ipi_dispatch(int cpu) { WARN_ON(cpu_is_offline(cpu)); + mb(); /* order mmio clearing qirr */ while (xics_ipi_message[cpu].value) { if (test_and_clear_bit(PPC_MSG_CALL_FUNCTION, &xics_ipi_message[cpu].value)) { - mb(); smp_message_recv(PPC_MSG_CALL_FUNCTION); } if (test_and_clear_bit(PPC_MSG_RESCHEDULE, &xics_ipi_message[cpu].value)) { - mb(); smp_message_recv(PPC_MSG_RESCHEDULE); } if (test_and_clear_bit(PPC_MSG_CALL_FUNC_SINGLE, &xics_ipi_message[cpu].value)) { - mb(); smp_message_recv(PPC_MSG_CALL_FUNC_SINGLE); } #if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC) if (test_and_clear_bit(PPC_MSG_DEBUGGER_BREAK, &xics_ipi_message[cpu].value)) { - mb(); smp_message_recv(PPC_MSG_DEBUGGER_BREAK); } #endif -- 2.20.1