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/kernel/smp.c | 10 ---------- 1 file changed, 10 deletions(-) (limited to 'arch/mips/kernel/smp.c') diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c index d0744cc77ea7..a31896c33716 100644 --- a/arch/mips/kernel/smp.c +++ b/arch/mips/kernel/smp.c @@ -192,16 +192,6 @@ asmlinkage void start_secondary(void) cpu_startup_entry(CPUHP_ONLINE); } -/* - * Call into both interrupt handlers, as we share the IPI for them - */ -void __irq_entry smp_call_function_interrupt(void) -{ - irq_enter(); - generic_smp_call_function_interrupt(); - irq_exit(); -} - static void stop_this_cpu(void *dummy) { /* -- cgit v1.2.3