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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>
105 lines
2.8 KiB
C
105 lines
2.8 KiB
C
/*
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* This file is subject to the terms and conditions of the GNU General
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* Public License. See the file "COPYING" in the main directory of this
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* archive for more details.
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*
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* Copyright (C) 2000 - 2001 by Kanoj Sarcar (kanoj@sgi.com)
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* Copyright (C) 2000 - 2001 by Silicon Graphics, Inc.
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* Copyright (C) 2000, 2001, 2002 Ralf Baechle
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* Copyright (C) 2000, 2001 Broadcom Corporation
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*/
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#ifndef __ASM_SMP_H
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#define __ASM_SMP_H
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#include <linux/bitops.h>
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#include <linux/linkage.h>
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#include <linux/smp.h>
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#include <linux/threads.h>
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#include <linux/cpumask.h>
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#include <linux/atomic.h>
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#include <asm/smp-ops.h>
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extern int smp_num_siblings;
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extern cpumask_t cpu_sibling_map[];
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extern cpumask_t cpu_core_map[];
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extern cpumask_t cpu_foreign_map;
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#define raw_smp_processor_id() (current_thread_info()->cpu)
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/* Map from cpu id to sequential logical cpu number. This will only
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not be idempotent when cpus failed to come on-line. */
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extern int __cpu_number_map[NR_CPUS];
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#define cpu_number_map(cpu) __cpu_number_map[cpu]
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/* The reverse map from sequential logical cpu number to cpu id. */
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extern int __cpu_logical_map[NR_CPUS];
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#define cpu_logical_map(cpu) __cpu_logical_map[cpu]
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#define NO_PROC_ID (-1)
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#define SMP_RESCHEDULE_YOURSELF 0x1 /* XXX braindead */
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#define SMP_CALL_FUNCTION 0x2
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/* Octeon - Tell another core to flush its icache */
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#define SMP_ICACHE_FLUSH 0x4
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/* Used by kexec crashdump to save all cpu's state */
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#define SMP_DUMP 0x8
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#define SMP_ASK_C0COUNT 0x10
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extern cpumask_t cpu_callin_map;
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/* Mask of CPUs which are currently definitely operating coherently */
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extern cpumask_t cpu_coherent_mask;
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extern void asmlinkage smp_bootstrap(void);
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/*
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* this function sends a 'reschedule' IPI to another CPU.
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* it goes straight through and wastes no time serializing
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* anything. Worst case is that we lose a reschedule ...
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*/
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static inline void smp_send_reschedule(int cpu)
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{
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extern struct plat_smp_ops *mp_ops; /* private */
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mp_ops->send_ipi_single(cpu, SMP_RESCHEDULE_YOURSELF);
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}
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#ifdef CONFIG_HOTPLUG_CPU
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static inline int __cpu_disable(void)
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{
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extern struct plat_smp_ops *mp_ops; /* private */
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return mp_ops->cpu_disable();
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}
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static inline void __cpu_die(unsigned int cpu)
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{
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extern struct plat_smp_ops *mp_ops; /* private */
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mp_ops->cpu_die(cpu);
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}
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extern void play_dead(void);
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#endif
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static inline void arch_send_call_function_single_ipi(int cpu)
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{
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extern struct plat_smp_ops *mp_ops; /* private */
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mp_ops->send_ipi_mask(cpumask_of(cpu), SMP_CALL_FUNCTION);
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}
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static inline void arch_send_call_function_ipi_mask(const struct cpumask *mask)
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{
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extern struct plat_smp_ops *mp_ops; /* private */
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mp_ops->send_ipi_mask(mask, SMP_CALL_FUNCTION);
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}
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#if defined(CONFIG_KEXEC)
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extern void (*dump_ipi_function_ptr)(void *);
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void dump_send_ipi(void (*dump_ipi_callback)(void *));
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#endif
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#endif /* __ASM_SMP_H */
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