linux/arch/mips/sibyte/bcm1480
Alex Smith 4ace6139bf 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>
2015-08-03 09:25:12 +02:00
..
irq.c MIPS: BCM1480: Remove checks for CONFIG_SIBYTE_BCM1480_PROF 2014-05-23 15:12:40 +02:00
Makefile MIPS: Sibyte: Migrate to new platform makefile style. 2010-08-05 13:25:55 +01:00
setup.c MIPS: Cleanup CP0 PRId and CP1 FPIR register access masks 2013-09-18 20:25:19 +02:00
smp.c MIPS: SMP: Don't increment irq_count multiple times for call function IPIs 2015-08-03 09:25:12 +02:00
time.c [MIPS] Sibyte: Split and move clock code. 2007-11-02 16:13:47 +00:00