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1142d81029
Implement a simplistic per-cpu maximum priority cpu monopolization mechanism. A non-sleeping callback can be scheduled to run on one or multiple cpus with maximum priority monopolozing those cpus. This is primarily to replace and unify RT workqueue usage in stop_machine and scheduler migration_thread which currently is serving multiple purposes. Four functions are provided - stop_one_cpu(), stop_one_cpu_nowait(), stop_cpus() and try_stop_cpus(). This is to allow clean sharing of resources among stop_cpu and all the migration thread users. One stopper thread per cpu is created which is currently named "stopper/CPU". This will eventually replace the migration thread and take on its name. * This facility was originally named cpuhog and lived in separate files but Peter Zijlstra nacked the name and thus got renamed to cpu_stop and moved into stop_machine.c. * Better reporting of preemption leak as per Peter's suggestion. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Dimitri Sivanich <sivanich@sgi.com>
103 lines
3.3 KiB
C
103 lines
3.3 KiB
C
#ifndef _LINUX_STOP_MACHINE
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#define _LINUX_STOP_MACHINE
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#include <linux/cpu.h>
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#include <linux/cpumask.h>
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#include <linux/list.h>
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#include <asm/system.h>
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#if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)
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/*
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* stop_cpu[s]() is simplistic per-cpu maximum priority cpu
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* monopolization mechanism. The caller can specify a non-sleeping
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* function to be executed on a single or multiple cpus preempting all
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* other processes and monopolizing those cpus until it finishes.
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*
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* Resources for this mechanism are preallocated when a cpu is brought
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* up and requests are guaranteed to be served as long as the target
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* cpus are online.
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*/
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typedef int (*cpu_stop_fn_t)(void *arg);
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struct cpu_stop_work {
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struct list_head list; /* cpu_stopper->works */
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cpu_stop_fn_t fn;
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void *arg;
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struct cpu_stop_done *done;
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};
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int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
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void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
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struct cpu_stop_work *work_buf);
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int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
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int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
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/*
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* stop_machine "Bogolock": stop the entire machine, disable
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* interrupts. This is a very heavy lock, which is equivalent to
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* grabbing every spinlock (and more). So the "read" side to such a
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* lock is anything which disables preeempt.
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*/
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/**
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* stop_machine: freeze the machine on all CPUs and run this function
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* @fn: the function to run
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* @data: the data ptr for the @fn()
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* @cpus: the cpus to run the @fn() on (NULL = any online cpu)
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*
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* Description: This causes a thread to be scheduled on every cpu,
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* each of which disables interrupts. The result is that noone is
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* holding a spinlock or inside any other preempt-disabled region when
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* @fn() runs.
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*
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* This can be thought of as a very heavy write lock, equivalent to
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* grabbing every spinlock in the kernel. */
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int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus);
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/**
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* __stop_machine: freeze the machine on all CPUs and run this function
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* @fn: the function to run
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* @data: the data ptr for the @fn
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* @cpus: the cpus to run the @fn() on (NULL = any online cpu)
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*
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* Description: This is a special version of the above, which assumes cpus
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* won't come or go while it's being called. Used by hotplug cpu.
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*/
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int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus);
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/**
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* stop_machine_create: create all stop_machine threads
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*
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* Description: This causes all stop_machine threads to be created before
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* stop_machine actually gets called. This can be used by subsystems that
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* need a non failing stop_machine infrastructure.
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*/
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int stop_machine_create(void);
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/**
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* stop_machine_destroy: destroy all stop_machine threads
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*
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* Description: This causes all stop_machine threads which were created with
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* stop_machine_create to be destroyed again.
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*/
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void stop_machine_destroy(void);
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#else
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static inline int stop_machine(int (*fn)(void *), void *data,
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const struct cpumask *cpus)
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{
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int ret;
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local_irq_disable();
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ret = fn(data);
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local_irq_enable();
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return ret;
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}
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static inline int stop_machine_create(void) { return 0; }
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static inline void stop_machine_destroy(void) { }
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#endif /* CONFIG_SMP */
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#endif /* _LINUX_STOP_MACHINE */
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