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b5242e98c1
This patch series allows the watchdog to run by default only on the housekeeping cores when nohz_full is in effect; this seems to be a good compromise short of turning it off completely (since the nohz_full cores can't tolerate a watchdog). To provide customizability, we add /proc/sys/kernel/watchdog_cpumask so that the set of cores running the watchdog can be tuned to different values after bootup. To implement this customizability, we add a new smpboot_update_cpumask_percpu_thread() API to the smpboot_thread subsystem that lets us park or unpark "unwanted" threads. And now that threads can be parked for long periods of time, we tweak the /proc/<pid>/stat and /proc/<pid>/status code so parked threads aren't reported as running, which is otherwise confusing. This patch (of 3): This change allows some cores to be excluded from running the smp_hotplug_thread tasks. The following commit to update kernel/watchdog.c to use this functionality is the motivating example, and more information on the motivation is provided there. A new smp_hotplug_thread field is introduced, "cpumask", which is cpumask field managed by the smpboot subsystem that indicates whether or not the given smp_hotplug_thread should run on that core; the cpumask is checked when deciding whether to unpark the thread. To limit the cpumask to less than cpu_possible, you must call smpboot_update_cpumask_percpu_thread() after registering. Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com> Cc: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Ulrich Obergfell <uobergfe@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
56 lines
2.1 KiB
C
56 lines
2.1 KiB
C
#ifndef _LINUX_SMPBOOT_H
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#define _LINUX_SMPBOOT_H
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#include <linux/types.h>
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struct task_struct;
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/* Cookie handed to the thread_fn*/
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struct smpboot_thread_data;
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/**
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* struct smp_hotplug_thread - CPU hotplug related thread descriptor
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* @store: Pointer to per cpu storage for the task pointers
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* @list: List head for core management
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* @thread_should_run: Check whether the thread should run or not. Called with
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* preemption disabled.
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* @thread_fn: The associated thread function
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* @create: Optional setup function, called when the thread gets
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* created (Not called from the thread context)
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* @setup: Optional setup function, called when the thread gets
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* operational the first time
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* @cleanup: Optional cleanup function, called when the thread
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* should stop (module exit)
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* @park: Optional park function, called when the thread is
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* parked (cpu offline)
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* @unpark: Optional unpark function, called when the thread is
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* unparked (cpu online)
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* @pre_unpark: Optional unpark function, called before the thread is
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* unparked (cpu online). This is not guaranteed to be
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* called on the target cpu of the thread. Careful!
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* @cpumask: Internal state. To update which threads are unparked,
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* call smpboot_update_cpumask_percpu_thread().
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* @selfparking: Thread is not parked by the park function.
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* @thread_comm: The base name of the thread
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*/
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struct smp_hotplug_thread {
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struct task_struct __percpu **store;
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struct list_head list;
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int (*thread_should_run)(unsigned int cpu);
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void (*thread_fn)(unsigned int cpu);
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void (*create)(unsigned int cpu);
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void (*setup)(unsigned int cpu);
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void (*cleanup)(unsigned int cpu, bool online);
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void (*park)(unsigned int cpu);
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void (*unpark)(unsigned int cpu);
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void (*pre_unpark)(unsigned int cpu);
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cpumask_var_t cpumask;
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bool selfparking;
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const char *thread_comm;
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};
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int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread);
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void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread);
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int smpboot_update_cpumask_percpu_thread(struct smp_hotplug_thread *plug_thread,
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const struct cpumask *);
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#endif
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