Currently try_to_freeze_tasks() has to wait until all of the vforked processes exit and for this reason every user can make it fail. To fix this problem we can introduce the additional process flag PF_FREEZER_SKIP to be used by tasks that do not want to be counted as freezable by the freezer and want to have TIF_FREEZE set nevertheless. Then, this flag can be set by tasks using sys_vfork() before they call wait_for_completion(&vfork) and cleared after they have woken up. After clearing it, the tasks should call try_to_freeze() as soon as possible. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Cc: Gautham R Shenoy <ego@in.ibm.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Pavel Machek <pavel@ucw.cz> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
219 lines
4.6 KiB
C
219 lines
4.6 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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/* 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(current);
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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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current->state = save;
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}
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static inline void freeze_process(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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rmb();
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if (!frozen(p)) {
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if (p->state == TASK_STOPPED)
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force_sig_specific(SIGSTOP, p);
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freeze(p);
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spin_lock_irqsave(&p->sighand->siglock, flags);
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signal_wake_up(p, p->state == TASK_STOPPED);
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spin_unlock_irqrestore(&p->sighand->siglock, flags);
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}
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}
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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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do_not_freeze(p);
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spin_lock_irqsave(&p->sighand->siglock, flags);
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recalc_sigpending_tsk(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 inline int is_user_space(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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static unsigned 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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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 (!freezeable(p))
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continue;
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if (frozen(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 (is_user_space(p) == !freeze_user_space)
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continue;
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freeze_process(p);
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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 (todo && time_after(jiffies, end_time))
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break;
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} while (todo);
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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 "Stopping %s timed out after %d seconds "
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"(%d tasks refusing to freeze):\n",
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freeze_user_space ? "user space processes" :
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"kernel threads",
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TIMEOUT / HZ, todo);
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read_lock(&tasklist_lock);
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do_each_thread(g, p) {
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if (is_user_space(p) == !freeze_user_space)
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continue;
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task_lock(p);
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if (freezeable(p) && !frozen(p) &&
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!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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}
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return todo;
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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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* Returns 0 on success, or the number of processes that didn't freeze,
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* although they were told to.
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*/
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int freeze_processes(void)
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{
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unsigned int nr_unfrozen;
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printk("Stopping tasks ... ");
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nr_unfrozen = try_to_freeze_tasks(FREEZER_USER_SPACE);
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if (nr_unfrozen)
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return nr_unfrozen;
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sys_sync();
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nr_unfrozen = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
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if (nr_unfrozen)
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return nr_unfrozen;
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printk("done.\n");
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BUG_ON(in_atomic());
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return 0;
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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 (is_user_space(p) == !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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