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authorAlex Smith <alex.smith@imgtec.com>2015-07-24 16:57:49 +0100
committerRalf Baechle <ralf@linux-mips.org>2015-08-03 09:25:12 +0200
commit4ace6139bf23ab4f152ba4207fc10b76cc01d2a5 (patch)
tree8a4682b3460ebd05961e402bc1bb353b74ec97ff /arch/mips/loongson64
parent55fdcb2d56b6edc027657fde9da0c4f224d32303 (diff)
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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 <alex.smith@imgtec.com> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/10770/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/loongson64')
-rw-r--r--arch/mips/loongson64/loongson-3/smp.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/arch/mips/loongson64/loongson-3/smp.c b/arch/mips/loongson64/loongson-3/smp.c
index 509877c6e9d9..1a4738a8f2d3 100644
--- a/arch/mips/loongson64/loongson-3/smp.c
+++ b/arch/mips/loongson64/loongson-3/smp.c
@@ -266,8 +266,11 @@ void loongson3_ipi_interrupt(struct pt_regs *regs)
if (action & SMP_RESCHEDULE_YOURSELF)
scheduler_ipi();
- if (action & SMP_CALL_FUNCTION)
- smp_call_function_interrupt();
+ if (action & SMP_CALL_FUNCTION) {
+ irq_enter();
+ generic_smp_call_function_interrupt();
+ irq_exit();
+ }
if (action & SMP_ASK_C0COUNT) {
BUG_ON(cpu != 0);