From 4ace6139bf23ab4f152ba4207fc10b76cc01d2a5 Mon Sep 17 00:00:00 2001 From: Alex Smith Date: Fri, 24 Jul 2015 16:57:49 +0100 Subject: MIPS: SMP: Don't increment irq_count multiple times for call function IPIs The majority of SMP platforms handle their IPIs through do_IRQ() which calls irq_{enter/exit}(). When a call function IPI is received, smp_call_function_interrupt() is called which also calls irq_{enter,exit}(), meaning irq_count is raised twice. When tick broadcasting is used (which is implemented via a call function IPI), this incorrectly causes all CPU idle time on the core receiving broadcast ticks to be accounted as time spent servicing IRQs, as account_process_tick() will account as such if irq_count is greater than 1. This results in 100% CPU usage being reported on a core which receives its ticks via broadcast. This patch removes the SMP smp_call_function_interrupt() wrapper which calls irq_{enter,exit}(). Platforms which handle their IPIs through do_IRQ() now call generic_smp_call_function_interrupt() directly to avoid incrementing irq_count a second time. Platforms which don't (loongson, sgi-ip27, sibyte) call generic_smp_call_function_interrupt() wrapped in irq_{enter,exit}(). Signed-off-by: Alex Smith Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/10770/ Signed-off-by: Ralf Baechle --- arch/mips/pmcs-msp71xx/msp_smp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/mips/pmcs-msp71xx') diff --git a/arch/mips/pmcs-msp71xx/msp_smp.c b/arch/mips/pmcs-msp71xx/msp_smp.c index 10170580a2de..ffa0f7101a97 100644 --- a/arch/mips/pmcs-msp71xx/msp_smp.c +++ b/arch/mips/pmcs-msp71xx/msp_smp.c @@ -44,7 +44,7 @@ static irqreturn_t ipi_resched_interrupt(int irq, void *dev_id) static irqreturn_t ipi_call_interrupt(int irq, void *dev_id) { - smp_call_function_interrupt(); + generic_smp_call_function_interrupt(); return IRQ_HANDLED; } -- cgit v1.2.3