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![Linus Torvalds](/assets/img/avatar_default.png)
Pull preparatory smp/hotplug patches from Ingo Molnar: "Some early preparatory changes for the WIP hotplug rework by Thomas Gleixner." * 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: stop_machine: Use smpboot threads stop_machine: Store task reference in a separate per cpu variable smpboot: Allow selfparking per cpu threads
737 lines
18 KiB
C
737 lines
18 KiB
C
/* CPU control.
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* (C) 2001, 2002, 2003, 2004 Rusty Russell
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*
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* This code is licenced under the GPL.
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*/
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#include <linux/proc_fs.h>
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#include <linux/smp.h>
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#include <linux/init.h>
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#include <linux/notifier.h>
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#include <linux/sched.h>
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#include <linux/unistd.h>
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#include <linux/cpu.h>
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#include <linux/oom.h>
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#include <linux/rcupdate.h>
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#include <linux/export.h>
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#include <linux/bug.h>
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#include <linux/kthread.h>
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#include <linux/stop_machine.h>
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#include <linux/mutex.h>
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#include <linux/gfp.h>
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#include <linux/suspend.h>
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#include "smpboot.h"
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#ifdef CONFIG_SMP
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/* Serializes the updates to cpu_online_mask, cpu_present_mask */
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static DEFINE_MUTEX(cpu_add_remove_lock);
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/*
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* The following two API's must be used when attempting
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* to serialize the updates to cpu_online_mask, cpu_present_mask.
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*/
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void cpu_maps_update_begin(void)
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{
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mutex_lock(&cpu_add_remove_lock);
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}
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void cpu_maps_update_done(void)
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{
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mutex_unlock(&cpu_add_remove_lock);
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}
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static RAW_NOTIFIER_HEAD(cpu_chain);
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/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
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* Should always be manipulated under cpu_add_remove_lock
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*/
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static int cpu_hotplug_disabled;
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#ifdef CONFIG_HOTPLUG_CPU
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static struct {
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struct task_struct *active_writer;
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struct mutex lock; /* Synchronizes accesses to refcount, */
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/*
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* Also blocks the new readers during
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* an ongoing cpu hotplug operation.
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*/
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int refcount;
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} cpu_hotplug = {
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.active_writer = NULL,
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.lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
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.refcount = 0,
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};
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void get_online_cpus(void)
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{
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might_sleep();
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if (cpu_hotplug.active_writer == current)
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return;
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mutex_lock(&cpu_hotplug.lock);
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cpu_hotplug.refcount++;
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mutex_unlock(&cpu_hotplug.lock);
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}
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EXPORT_SYMBOL_GPL(get_online_cpus);
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void put_online_cpus(void)
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{
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if (cpu_hotplug.active_writer == current)
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return;
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mutex_lock(&cpu_hotplug.lock);
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if (WARN_ON(!cpu_hotplug.refcount))
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cpu_hotplug.refcount++; /* try to fix things up */
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if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
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wake_up_process(cpu_hotplug.active_writer);
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mutex_unlock(&cpu_hotplug.lock);
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}
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EXPORT_SYMBOL_GPL(put_online_cpus);
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/*
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* This ensures that the hotplug operation can begin only when the
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* refcount goes to zero.
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*
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* Note that during a cpu-hotplug operation, the new readers, if any,
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* will be blocked by the cpu_hotplug.lock
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*
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* Since cpu_hotplug_begin() is always called after invoking
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* cpu_maps_update_begin(), we can be sure that only one writer is active.
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*
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* Note that theoretically, there is a possibility of a livelock:
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* - Refcount goes to zero, last reader wakes up the sleeping
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* writer.
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* - Last reader unlocks the cpu_hotplug.lock.
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* - A new reader arrives at this moment, bumps up the refcount.
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* - The writer acquires the cpu_hotplug.lock finds the refcount
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* non zero and goes to sleep again.
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*
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* However, this is very difficult to achieve in practice since
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* get_online_cpus() not an api which is called all that often.
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*
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*/
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static void cpu_hotplug_begin(void)
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{
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cpu_hotplug.active_writer = current;
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for (;;) {
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mutex_lock(&cpu_hotplug.lock);
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if (likely(!cpu_hotplug.refcount))
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break;
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__set_current_state(TASK_UNINTERRUPTIBLE);
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mutex_unlock(&cpu_hotplug.lock);
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schedule();
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}
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}
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static void cpu_hotplug_done(void)
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{
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cpu_hotplug.active_writer = NULL;
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mutex_unlock(&cpu_hotplug.lock);
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}
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#else /* #if CONFIG_HOTPLUG_CPU */
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static void cpu_hotplug_begin(void) {}
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static void cpu_hotplug_done(void) {}
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#endif /* #else #if CONFIG_HOTPLUG_CPU */
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/* Need to know about CPUs going up/down? */
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int __ref register_cpu_notifier(struct notifier_block *nb)
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{
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int ret;
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cpu_maps_update_begin();
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ret = raw_notifier_chain_register(&cpu_chain, nb);
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cpu_maps_update_done();
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return ret;
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}
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static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
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int *nr_calls)
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{
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int ret;
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ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
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nr_calls);
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return notifier_to_errno(ret);
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}
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static int cpu_notify(unsigned long val, void *v)
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{
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return __cpu_notify(val, v, -1, NULL);
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}
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#ifdef CONFIG_HOTPLUG_CPU
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static void cpu_notify_nofail(unsigned long val, void *v)
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{
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BUG_ON(cpu_notify(val, v));
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}
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EXPORT_SYMBOL(register_cpu_notifier);
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void __ref unregister_cpu_notifier(struct notifier_block *nb)
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{
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cpu_maps_update_begin();
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raw_notifier_chain_unregister(&cpu_chain, nb);
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cpu_maps_update_done();
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}
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EXPORT_SYMBOL(unregister_cpu_notifier);
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/**
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* clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
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* @cpu: a CPU id
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*
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* This function walks all processes, finds a valid mm struct for each one and
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* then clears a corresponding bit in mm's cpumask. While this all sounds
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* trivial, there are various non-obvious corner cases, which this function
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* tries to solve in a safe manner.
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*
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* Also note that the function uses a somewhat relaxed locking scheme, so it may
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* be called only for an already offlined CPU.
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*/
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void clear_tasks_mm_cpumask(int cpu)
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{
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struct task_struct *p;
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/*
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* This function is called after the cpu is taken down and marked
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* offline, so its not like new tasks will ever get this cpu set in
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* their mm mask. -- Peter Zijlstra
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* Thus, we may use rcu_read_lock() here, instead of grabbing
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* full-fledged tasklist_lock.
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*/
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WARN_ON(cpu_online(cpu));
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rcu_read_lock();
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for_each_process(p) {
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struct task_struct *t;
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/*
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* Main thread might exit, but other threads may still have
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* a valid mm. Find one.
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*/
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t = find_lock_task_mm(p);
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if (!t)
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continue;
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cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
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task_unlock(t);
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}
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rcu_read_unlock();
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}
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static inline void check_for_tasks(int cpu)
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{
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struct task_struct *p;
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cputime_t utime, stime;
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write_lock_irq(&tasklist_lock);
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for_each_process(p) {
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task_cputime(p, &utime, &stime);
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if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
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(utime || stime))
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printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
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"(state = %ld, flags = %x)\n",
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p->comm, task_pid_nr(p), cpu,
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p->state, p->flags);
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}
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write_unlock_irq(&tasklist_lock);
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}
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struct take_cpu_down_param {
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unsigned long mod;
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void *hcpu;
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};
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/* Take this CPU down. */
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static int __ref take_cpu_down(void *_param)
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{
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struct take_cpu_down_param *param = _param;
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int err;
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/* Ensure this CPU doesn't handle any more interrupts. */
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err = __cpu_disable();
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if (err < 0)
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return err;
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cpu_notify(CPU_DYING | param->mod, param->hcpu);
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/* Park the stopper thread */
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kthread_park(current);
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return 0;
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}
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/* Requires cpu_add_remove_lock to be held */
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static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
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{
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int err, nr_calls = 0;
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void *hcpu = (void *)(long)cpu;
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unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
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struct take_cpu_down_param tcd_param = {
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.mod = mod,
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.hcpu = hcpu,
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};
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if (num_online_cpus() == 1)
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return -EBUSY;
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if (!cpu_online(cpu))
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return -EINVAL;
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cpu_hotplug_begin();
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err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
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if (err) {
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nr_calls--;
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__cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
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printk("%s: attempt to take down CPU %u failed\n",
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__func__, cpu);
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goto out_release;
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}
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smpboot_park_threads(cpu);
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err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
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if (err) {
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/* CPU didn't die: tell everyone. Can't complain. */
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smpboot_unpark_threads(cpu);
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cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
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goto out_release;
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}
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BUG_ON(cpu_online(cpu));
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/*
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* The migration_call() CPU_DYING callback will have removed all
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* runnable tasks from the cpu, there's only the idle task left now
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* that the migration thread is done doing the stop_machine thing.
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*
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* Wait for the stop thread to go away.
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*/
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while (!idle_cpu(cpu))
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cpu_relax();
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/* This actually kills the CPU. */
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__cpu_die(cpu);
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/* CPU is completely dead: tell everyone. Too late to complain. */
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cpu_notify_nofail(CPU_DEAD | mod, hcpu);
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check_for_tasks(cpu);
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out_release:
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cpu_hotplug_done();
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if (!err)
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cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
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return err;
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}
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int __ref cpu_down(unsigned int cpu)
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{
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int err;
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cpu_maps_update_begin();
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if (cpu_hotplug_disabled) {
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err = -EBUSY;
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goto out;
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}
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err = _cpu_down(cpu, 0);
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out:
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cpu_maps_update_done();
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return err;
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}
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EXPORT_SYMBOL(cpu_down);
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#endif /*CONFIG_HOTPLUG_CPU*/
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/* Requires cpu_add_remove_lock to be held */
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static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
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{
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int ret, nr_calls = 0;
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void *hcpu = (void *)(long)cpu;
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unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
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struct task_struct *idle;
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cpu_hotplug_begin();
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if (cpu_online(cpu) || !cpu_present(cpu)) {
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ret = -EINVAL;
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goto out;
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}
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idle = idle_thread_get(cpu);
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if (IS_ERR(idle)) {
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ret = PTR_ERR(idle);
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goto out;
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}
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ret = smpboot_create_threads(cpu);
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if (ret)
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goto out;
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ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
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if (ret) {
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nr_calls--;
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printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
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__func__, cpu);
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goto out_notify;
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}
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/* Arch-specific enabling code. */
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ret = __cpu_up(cpu, idle);
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if (ret != 0)
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goto out_notify;
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BUG_ON(!cpu_online(cpu));
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/* Wake the per cpu threads */
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smpboot_unpark_threads(cpu);
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/* Now call notifier in preparation. */
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cpu_notify(CPU_ONLINE | mod, hcpu);
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out_notify:
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if (ret != 0)
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__cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
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out:
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cpu_hotplug_done();
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return ret;
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}
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int __cpuinit cpu_up(unsigned int cpu)
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{
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int err = 0;
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#ifdef CONFIG_MEMORY_HOTPLUG
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int nid;
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pg_data_t *pgdat;
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#endif
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if (!cpu_possible(cpu)) {
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printk(KERN_ERR "can't online cpu %d because it is not "
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"configured as may-hotadd at boot time\n", cpu);
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#if defined(CONFIG_IA64)
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printk(KERN_ERR "please check additional_cpus= boot "
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"parameter\n");
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#endif
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return -EINVAL;
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}
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#ifdef CONFIG_MEMORY_HOTPLUG
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nid = cpu_to_node(cpu);
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if (!node_online(nid)) {
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err = mem_online_node(nid);
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if (err)
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return err;
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}
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pgdat = NODE_DATA(nid);
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if (!pgdat) {
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printk(KERN_ERR
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"Can't online cpu %d due to NULL pgdat\n", cpu);
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return -ENOMEM;
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}
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if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
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mutex_lock(&zonelists_mutex);
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build_all_zonelists(NULL, NULL);
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mutex_unlock(&zonelists_mutex);
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}
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#endif
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cpu_maps_update_begin();
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if (cpu_hotplug_disabled) {
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err = -EBUSY;
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goto out;
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}
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err = _cpu_up(cpu, 0);
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out:
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cpu_maps_update_done();
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return err;
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}
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EXPORT_SYMBOL_GPL(cpu_up);
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#ifdef CONFIG_PM_SLEEP_SMP
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static cpumask_var_t frozen_cpus;
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int disable_nonboot_cpus(void)
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{
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int cpu, first_cpu, error = 0;
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cpu_maps_update_begin();
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first_cpu = cpumask_first(cpu_online_mask);
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/*
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* We take down all of the non-boot CPUs in one shot to avoid races
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* with the userspace trying to use the CPU hotplug at the same time
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*/
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cpumask_clear(frozen_cpus);
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printk("Disabling non-boot CPUs ...\n");
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for_each_online_cpu(cpu) {
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if (cpu == first_cpu)
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continue;
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error = _cpu_down(cpu, 1);
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if (!error)
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cpumask_set_cpu(cpu, frozen_cpus);
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else {
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printk(KERN_ERR "Error taking CPU%d down: %d\n",
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cpu, error);
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break;
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}
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}
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if (!error) {
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BUG_ON(num_online_cpus() > 1);
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/* Make sure the CPUs won't be enabled by someone else */
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cpu_hotplug_disabled = 1;
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} else {
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printk(KERN_ERR "Non-boot CPUs are not disabled\n");
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}
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cpu_maps_update_done();
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return error;
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}
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void __weak arch_enable_nonboot_cpus_begin(void)
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{
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}
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void __weak arch_enable_nonboot_cpus_end(void)
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{
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}
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void __ref enable_nonboot_cpus(void)
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{
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int cpu, error;
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/* Allow everyone to use the CPU hotplug again */
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cpu_maps_update_begin();
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cpu_hotplug_disabled = 0;
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if (cpumask_empty(frozen_cpus))
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goto out;
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printk(KERN_INFO "Enabling non-boot CPUs ...\n");
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arch_enable_nonboot_cpus_begin();
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for_each_cpu(cpu, frozen_cpus) {
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error = _cpu_up(cpu, 1);
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if (!error) {
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printk(KERN_INFO "CPU%d is up\n", cpu);
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continue;
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}
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printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
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}
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arch_enable_nonboot_cpus_end();
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cpumask_clear(frozen_cpus);
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out:
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cpu_maps_update_done();
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}
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static int __init alloc_frozen_cpus(void)
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{
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if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
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return -ENOMEM;
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return 0;
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}
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core_initcall(alloc_frozen_cpus);
|
|
|
|
/*
|
|
* Prevent regular CPU hotplug from racing with the freezer, by disabling CPU
|
|
* hotplug when tasks are about to be frozen. Also, don't allow the freezer
|
|
* to continue until any currently running CPU hotplug operation gets
|
|
* completed.
|
|
* To modify the 'cpu_hotplug_disabled' flag, we need to acquire the
|
|
* 'cpu_add_remove_lock'. And this same lock is also taken by the regular
|
|
* CPU hotplug path and released only after it is complete. Thus, we
|
|
* (and hence the freezer) will block here until any currently running CPU
|
|
* hotplug operation gets completed.
|
|
*/
|
|
void cpu_hotplug_disable_before_freeze(void)
|
|
{
|
|
cpu_maps_update_begin();
|
|
cpu_hotplug_disabled = 1;
|
|
cpu_maps_update_done();
|
|
}
|
|
|
|
|
|
/*
|
|
* When tasks have been thawed, re-enable regular CPU hotplug (which had been
|
|
* disabled while beginning to freeze tasks).
|
|
*/
|
|
void cpu_hotplug_enable_after_thaw(void)
|
|
{
|
|
cpu_maps_update_begin();
|
|
cpu_hotplug_disabled = 0;
|
|
cpu_maps_update_done();
|
|
}
|
|
|
|
/*
|
|
* When callbacks for CPU hotplug notifications are being executed, we must
|
|
* ensure that the state of the system with respect to the tasks being frozen
|
|
* or not, as reported by the notification, remains unchanged *throughout the
|
|
* duration* of the execution of the callbacks.
|
|
* Hence we need to prevent the freezer from racing with regular CPU hotplug.
|
|
*
|
|
* This synchronization is implemented by mutually excluding regular CPU
|
|
* hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
|
|
* Hibernate notifications.
|
|
*/
|
|
static int
|
|
cpu_hotplug_pm_callback(struct notifier_block *nb,
|
|
unsigned long action, void *ptr)
|
|
{
|
|
switch (action) {
|
|
|
|
case PM_SUSPEND_PREPARE:
|
|
case PM_HIBERNATION_PREPARE:
|
|
cpu_hotplug_disable_before_freeze();
|
|
break;
|
|
|
|
case PM_POST_SUSPEND:
|
|
case PM_POST_HIBERNATION:
|
|
cpu_hotplug_enable_after_thaw();
|
|
break;
|
|
|
|
default:
|
|
return NOTIFY_DONE;
|
|
}
|
|
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
|
|
static int __init cpu_hotplug_pm_sync_init(void)
|
|
{
|
|
/*
|
|
* cpu_hotplug_pm_callback has higher priority than x86
|
|
* bsp_pm_callback which depends on cpu_hotplug_pm_callback
|
|
* to disable cpu hotplug to avoid cpu hotplug race.
|
|
*/
|
|
pm_notifier(cpu_hotplug_pm_callback, 0);
|
|
return 0;
|
|
}
|
|
core_initcall(cpu_hotplug_pm_sync_init);
|
|
|
|
#endif /* CONFIG_PM_SLEEP_SMP */
|
|
|
|
/**
|
|
* notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
|
|
* @cpu: cpu that just started
|
|
*
|
|
* This function calls the cpu_chain notifiers with CPU_STARTING.
|
|
* It must be called by the arch code on the new cpu, before the new cpu
|
|
* enables interrupts and before the "boot" cpu returns from __cpu_up().
|
|
*/
|
|
void __cpuinit notify_cpu_starting(unsigned int cpu)
|
|
{
|
|
unsigned long val = CPU_STARTING;
|
|
|
|
#ifdef CONFIG_PM_SLEEP_SMP
|
|
if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
|
|
val = CPU_STARTING_FROZEN;
|
|
#endif /* CONFIG_PM_SLEEP_SMP */
|
|
cpu_notify(val, (void *)(long)cpu);
|
|
}
|
|
|
|
#endif /* CONFIG_SMP */
|
|
|
|
/*
|
|
* cpu_bit_bitmap[] is a special, "compressed" data structure that
|
|
* represents all NR_CPUS bits binary values of 1<<nr.
|
|
*
|
|
* It is used by cpumask_of() to get a constant address to a CPU
|
|
* mask value that has a single bit set only.
|
|
*/
|
|
|
|
/* cpu_bit_bitmap[0] is empty - so we can back into it */
|
|
#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
|
|
#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
|
|
#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
|
|
#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
|
|
|
|
const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
|
|
|
|
MASK_DECLARE_8(0), MASK_DECLARE_8(8),
|
|
MASK_DECLARE_8(16), MASK_DECLARE_8(24),
|
|
#if BITS_PER_LONG > 32
|
|
MASK_DECLARE_8(32), MASK_DECLARE_8(40),
|
|
MASK_DECLARE_8(48), MASK_DECLARE_8(56),
|
|
#endif
|
|
};
|
|
EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
|
|
|
|
const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
|
|
EXPORT_SYMBOL(cpu_all_bits);
|
|
|
|
#ifdef CONFIG_INIT_ALL_POSSIBLE
|
|
static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
|
|
= CPU_BITS_ALL;
|
|
#else
|
|
static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
|
|
#endif
|
|
const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
|
|
EXPORT_SYMBOL(cpu_possible_mask);
|
|
|
|
static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
|
|
const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
|
|
EXPORT_SYMBOL(cpu_online_mask);
|
|
|
|
static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
|
|
const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
|
|
EXPORT_SYMBOL(cpu_present_mask);
|
|
|
|
static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
|
|
const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
|
|
EXPORT_SYMBOL(cpu_active_mask);
|
|
|
|
void set_cpu_possible(unsigned int cpu, bool possible)
|
|
{
|
|
if (possible)
|
|
cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
|
|
else
|
|
cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
|
|
}
|
|
|
|
void set_cpu_present(unsigned int cpu, bool present)
|
|
{
|
|
if (present)
|
|
cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
|
|
else
|
|
cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
|
|
}
|
|
|
|
void set_cpu_online(unsigned int cpu, bool online)
|
|
{
|
|
if (online)
|
|
cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
|
|
else
|
|
cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
|
|
}
|
|
|
|
void set_cpu_active(unsigned int cpu, bool active)
|
|
{
|
|
if (active)
|
|
cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
|
|
else
|
|
cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
|
|
}
|
|
|
|
void init_cpu_present(const struct cpumask *src)
|
|
{
|
|
cpumask_copy(to_cpumask(cpu_present_bits), src);
|
|
}
|
|
|
|
void init_cpu_possible(const struct cpumask *src)
|
|
{
|
|
cpumask_copy(to_cpumask(cpu_possible_bits), src);
|
|
}
|
|
|
|
void init_cpu_online(const struct cpumask *src)
|
|
{
|
|
cpumask_copy(to_cpumask(cpu_online_bits), src);
|
|
}
|