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Commit 199f45c4 authored by Milton Miller's avatar Milton Miller Committed by Benjamin Herrenschmidt
Browse files

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: default avatarMilton Miller <miltonm@bga.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 2172fe87

arch/powerpc/platforms/pseries/xics.c

+1 −4
Original line number Diff line number Diff line
@@ -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