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1cf12e08bc
With the new mechanism which kicks tasks off the outgoing CPU at the end of schedule() the situation on an outgoing CPU right before the stopper thread brings it down completely is: - All user tasks and all unbound kernel threads have either been migrated away or are not running and the next wakeup will move them to a online CPU. - All per CPU kernel threads, except cpu hotplug thread and the stopper thread have either been unbound or parked by the responsible CPU hotplug callback. That means that at the last step before the stopper thread is invoked the cpu hotplug thread is the last legitimate running task on the outgoing CPU. Add a final wait step right before the stopper thread is kicked which ensures that any still running tasks on the way to park or on the way to kick themself of the CPU are either sleeping or gone. This allows to remove the migrate_tasks() crutch in sched_cpu_dying(). If sched_cpu_dying() detects that there is still another running task aside of the stopper thread then it will explode with the appropriate fireworks. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com> Link: https://lkml.kernel.org/r/20201023102346.547163969@infradead.org
27 lines
664 B
C
27 lines
664 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_SCHED_HOTPLUG_H
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#define _LINUX_SCHED_HOTPLUG_H
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/*
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* Scheduler interfaces for hotplug CPU support:
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*/
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extern int sched_cpu_starting(unsigned int cpu);
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extern int sched_cpu_activate(unsigned int cpu);
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extern int sched_cpu_deactivate(unsigned int cpu);
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#ifdef CONFIG_HOTPLUG_CPU
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extern int sched_cpu_wait_empty(unsigned int cpu);
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extern int sched_cpu_dying(unsigned int cpu);
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#else
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# define sched_cpu_wait_empty NULL
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# define sched_cpu_dying NULL
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#endif
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#ifdef CONFIG_HOTPLUG_CPU
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extern void idle_task_exit(void);
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#else
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static inline void idle_task_exit(void) {}
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#endif
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#endif /* _LINUX_SCHED_HOTPLUG_H */
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