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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>
78 lines
2.1 KiB
C
78 lines
2.1 KiB
C
/*
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* Copyright (C) 2000, 2001, 2004 MIPS Technologies, Inc.
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* Copyright (C) 2001 Ralf Baechle
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* Copyright (C) 2010 PMC-Sierra, Inc.
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*
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* VSMP support for MSP platforms . Derived from malta vsmp support.
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*
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* This program is free software; you can distribute it and/or modify it
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* under the terms of the GNU General Public License (Version 2) as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
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*
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*/
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#include <linux/smp.h>
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#include <linux/interrupt.h>
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#ifdef CONFIG_MIPS_MT_SMP
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#define MIPS_CPU_IPI_RESCHED_IRQ 0 /* SW int 0 for resched */
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#define MIPS_CPU_IPI_CALL_IRQ 1 /* SW int 1 for call */
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static void ipi_resched_dispatch(void)
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{
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do_IRQ(MIPS_CPU_IPI_RESCHED_IRQ);
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}
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static void ipi_call_dispatch(void)
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{
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do_IRQ(MIPS_CPU_IPI_CALL_IRQ);
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}
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static irqreturn_t ipi_resched_interrupt(int irq, void *dev_id)
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{
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return IRQ_HANDLED;
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}
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static irqreturn_t ipi_call_interrupt(int irq, void *dev_id)
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{
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generic_smp_call_function_interrupt();
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return IRQ_HANDLED;
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}
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static struct irqaction irq_resched = {
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.handler = ipi_resched_interrupt,
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.flags = IRQF_PERCPU,
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.name = "IPI_resched"
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};
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static struct irqaction irq_call = {
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.handler = ipi_call_interrupt,
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.flags = IRQF_PERCPU,
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.name = "IPI_call"
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};
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void __init arch_init_ipiirq(int irq, struct irqaction *action)
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{
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setup_irq(irq, action);
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irq_set_handler(irq, handle_percpu_irq);
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}
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void __init msp_vsmp_int_init(void)
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{
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set_vi_handler(MIPS_CPU_IPI_RESCHED_IRQ, ipi_resched_dispatch);
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set_vi_handler(MIPS_CPU_IPI_CALL_IRQ, ipi_call_dispatch);
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arch_init_ipiirq(MIPS_CPU_IPI_RESCHED_IRQ, &irq_resched);
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arch_init_ipiirq(MIPS_CPU_IPI_CALL_IRQ, &irq_call);
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}
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#endif /* CONFIG_MIPS_MT_SMP */
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