linux/arch/mips/sgi-ip27
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
..
ip27-berr.c
ip27-console.c
ip27-hubio.c
ip27-init.c
ip27-irq-pci.c
ip27-irq.c MIPS: SMP: Don't increment irq_count multiple times for call function IPIs 2015-08-03 09:25:12 +02:00
ip27-irqno.c MIPS: IRQ/IP27: Move IRQ allocation API to platform code. 2015-06-21 21:54:31 +02:00
ip27-klconfig.c
ip27-klnuma.c
ip27-memory.c
ip27-nmi.c
ip27-reset.c
ip27-smp.c
ip27-timer.c MIPS: sgi-ip27: Implement read_sched_clock 2015-04-01 17:21:29 +02:00
ip27-xtalk.c
Kconfig
Makefile MIPS: IRQ/IP27: Move IRQ allocation API to platform code. 2015-06-21 21:54:31 +02:00
Platform
TODO