From 8adbf57fc4294588e9785069215d445a98e6c23a Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 20 Feb 2014 17:42:07 +0000 Subject: [PATCH] irqchip: gic: use dmb ishst instead of dsb when raising a softirq When sending an SGI to another CPU, we require a barrier to ensure that any pending stores to normal memory are made visible to the recipient before the interrupt arrives. Rather than use a vanilla dsb() (which will soon cause an assembly error on arm64) before the writel_relaxed, we can instead use dsb(ishst), since we just need to ensure that any pending normal writes are visible within the inner-shareable domain before we poke the GIC. With this observation, we can then further weaken the barrier to a dmb(ishst), since other CPUs in the inner-shareable domain must observe the write to the distributor before the SGI is generated. Cc: Thomas Gleixner Acked-by: Marc Zyngier Acked-by: Catalin Marinas Signed-off-by: Will Deacon Signed-off-by: Arnd Bergmann --- drivers/irqchip/irq-gic.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c index 341c601..500e533 100644 --- a/drivers/irqchip/irq-gic.c +++ b/drivers/irqchip/irq-gic.c @@ -661,9 +661,9 @@ void gic_raise_softirq(const struct cpumask *mask, unsigned int irq) /* * Ensure that stores to Normal memory are visible to the - * other CPUs before issuing the IPI. + * other CPUs before they observe us issuing the IPI. */ - dsb(); + dmb(ishst); /* this always happens on GIC0 */ writel_relaxed(map << 16 | irq, gic_data_dist_base(&gic_data[0]) + GIC_DIST_SOFTINT); -- 2.7.4