286 lines
6.3 KiB
C
286 lines
6.3 KiB
C
/*
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* drivers/power/process.c - Functions for starting/stopping processes on
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* suspend transitions.
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*
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* Originally from swsusp.
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*/
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#undef DEBUG
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#include <linux/interrupt.h>
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#include <linux/suspend.h>
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#include <linux/module.h>
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#include <linux/syscalls.h>
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#include <linux/freezer.h>
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/*
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* Timeout for stopping processes
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*/
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#define TIMEOUT (20 * HZ)
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#define FREEZER_KERNEL_THREADS 0
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#define FREEZER_USER_SPACE 1
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static inline int freezeable(struct task_struct * p)
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{
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if ((p == current) ||
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(p->flags & PF_NOFREEZE) ||
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(p->exit_state != 0))
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return 0;
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return 1;
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}
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/*
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* freezing is complete, mark current process as frozen
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*/
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static inline void frozen_process(void)
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{
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if (!unlikely(current->flags & PF_NOFREEZE)) {
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current->flags |= PF_FROZEN;
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wmb();
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}
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clear_freeze_flag(current);
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}
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/* Refrigerator is place where frozen processes are stored :-). */
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void refrigerator(void)
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{
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/* Hmm, should we be allowed to suspend when there are realtime
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processes around? */
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long save;
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task_lock(current);
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if (freezing(current)) {
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frozen_process();
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task_unlock(current);
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} else {
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task_unlock(current);
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return;
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}
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save = current->state;
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pr_debug("%s entered refrigerator\n", current->comm);
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spin_lock_irq(¤t->sighand->siglock);
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recalc_sigpending(); /* We sent fake signal, clean it up */
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spin_unlock_irq(¤t->sighand->siglock);
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for (;;) {
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set_current_state(TASK_UNINTERRUPTIBLE);
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if (!frozen(current))
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break;
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schedule();
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}
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pr_debug("%s left refrigerator\n", current->comm);
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__set_current_state(save);
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}
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static void fake_signal_wake_up(struct task_struct *p, int resume)
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{
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unsigned long flags;
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spin_lock_irqsave(&p->sighand->siglock, flags);
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signal_wake_up(p, resume);
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spin_unlock_irqrestore(&p->sighand->siglock, flags);
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}
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static void send_fake_signal(struct task_struct *p)
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{
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if (p->state == TASK_STOPPED)
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force_sig_specific(SIGSTOP, p);
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fake_signal_wake_up(p, p->state == TASK_STOPPED);
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}
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static int has_mm(struct task_struct *p)
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{
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return (p->mm && !(p->flags & PF_BORROWED_MM));
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}
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/**
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* freeze_task - send a freeze request to given task
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* @p: task to send the request to
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* @with_mm_only: if set, the request will only be sent if the task has its
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* own mm
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* Return value: 0, if @with_mm_only is set and the task has no mm of its
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* own or the task is frozen, 1, otherwise
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*
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* The freeze request is sent by seting the tasks's TIF_FREEZE flag and
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* either sending a fake signal to it or waking it up, depending on whether
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* or not it has its own mm (ie. it is a user land task). If @with_mm_only
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* is set and the task has no mm of its own (ie. it is a kernel thread),
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* its TIF_FREEZE flag should not be set.
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*
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* The task_lock() is necessary to prevent races with exit_mm() or
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* use_mm()/unuse_mm() from occuring.
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*/
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static int freeze_task(struct task_struct *p, int with_mm_only)
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{
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int ret = 1;
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task_lock(p);
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if (freezing(p)) {
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if (has_mm(p)) {
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if (!signal_pending(p))
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fake_signal_wake_up(p, 0);
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} else {
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if (with_mm_only)
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ret = 0;
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else
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wake_up_state(p, TASK_INTERRUPTIBLE);
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}
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} else {
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rmb();
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if (frozen(p)) {
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ret = 0;
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} else {
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if (has_mm(p)) {
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set_freeze_flag(p);
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send_fake_signal(p);
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} else {
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if (with_mm_only) {
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ret = 0;
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} else {
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set_freeze_flag(p);
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wake_up_state(p, TASK_INTERRUPTIBLE);
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}
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}
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}
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}
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task_unlock(p);
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return ret;
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}
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static void cancel_freezing(struct task_struct *p)
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{
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unsigned long flags;
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if (freezing(p)) {
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pr_debug(" clean up: %s\n", p->comm);
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clear_freeze_flag(p);
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spin_lock_irqsave(&p->sighand->siglock, flags);
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recalc_sigpending_and_wake(p);
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spin_unlock_irqrestore(&p->sighand->siglock, flags);
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}
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}
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static int try_to_freeze_tasks(int freeze_user_space)
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{
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struct task_struct *g, *p;
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unsigned long end_time;
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unsigned int todo;
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struct timeval start, end;
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s64 elapsed_csecs64;
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unsigned int elapsed_csecs;
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do_gettimeofday(&start);
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end_time = jiffies + TIMEOUT;
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do {
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todo = 0;
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read_lock(&tasklist_lock);
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do_each_thread(g, p) {
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if (frozen(p) || !freezeable(p))
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continue;
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if (p->state == TASK_TRACED && frozen(p->parent)) {
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cancel_freezing(p);
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continue;
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}
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if (!freeze_task(p, freeze_user_space))
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continue;
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if (!freezer_should_skip(p))
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todo++;
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} while_each_thread(g, p);
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read_unlock(&tasklist_lock);
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yield(); /* Yield is okay here */
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if (time_after(jiffies, end_time))
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break;
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} while (todo);
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do_gettimeofday(&end);
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elapsed_csecs64 = timeval_to_ns(&end) - timeval_to_ns(&start);
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do_div(elapsed_csecs64, NSEC_PER_SEC / 100);
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elapsed_csecs = elapsed_csecs64;
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if (todo) {
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/* This does not unfreeze processes that are already frozen
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* (we have slightly ugly calling convention in that respect,
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* and caller must call thaw_processes() if something fails),
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* but it cleans up leftover PF_FREEZE requests.
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*/
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printk("\n");
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printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
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"(%d tasks refusing to freeze):\n",
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elapsed_csecs / 100, elapsed_csecs % 100, todo);
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show_state();
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read_lock(&tasklist_lock);
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do_each_thread(g, p) {
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task_lock(p);
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if (freezing(p) && !freezer_should_skip(p))
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printk(KERN_ERR " %s\n", p->comm);
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cancel_freezing(p);
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task_unlock(p);
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} while_each_thread(g, p);
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read_unlock(&tasklist_lock);
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} else {
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printk("(elapsed %d.%02d seconds) ", elapsed_csecs / 100,
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elapsed_csecs % 100);
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}
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return todo ? -EBUSY : 0;
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}
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/**
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* freeze_processes - tell processes to enter the refrigerator
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*/
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int freeze_processes(void)
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{
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int error;
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printk("Freezing user space processes ... ");
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error = try_to_freeze_tasks(FREEZER_USER_SPACE);
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if (error)
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goto Exit;
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printk("done.\n");
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printk("Freezing remaining freezable tasks ... ");
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error = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
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if (error)
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goto Exit;
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printk("done.");
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Exit:
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BUG_ON(in_atomic());
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printk("\n");
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return error;
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}
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static void thaw_tasks(int thaw_user_space)
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{
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struct task_struct *g, *p;
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read_lock(&tasklist_lock);
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do_each_thread(g, p) {
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if (!freezeable(p))
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continue;
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if (!p->mm == thaw_user_space)
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continue;
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thaw_process(p);
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} while_each_thread(g, p);
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read_unlock(&tasklist_lock);
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}
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void thaw_processes(void)
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{
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printk("Restarting tasks ... ");
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thaw_tasks(FREEZER_KERNEL_THREADS);
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thaw_tasks(FREEZER_USER_SPACE);
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schedule();
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printk("done.\n");
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}
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EXPORT_SYMBOL(refrigerator);
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