![Roland McGrath](/assets/img/avatar_default.png)
Steve Hawkes discovered a problem where recalc_sigpending_tsk was called in do_sigaction but no signal_wake_up call was made, preventing later signals from waking up blocked threads with TIF_SIGPENDING already set. In fact, the few other calls to recalc_sigpending_tsk outside the signals code are also subject to this problem in other race conditions. This change makes recalc_sigpending_tsk private to the signals code. It changes the outside calls, as well as do_sigaction, to use the new recalc_sigpending_and_wake instead. Signed-off-by: Roland McGrath <roland@redhat.com> Cc: <Steve.Hawkes@motorola.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
231 lines
4.9 KiB
C
231 lines
4.9 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_tsk_thread_flag(current, TIF_FREEZE);
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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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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_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 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 (freeze_user_space && !is_user_space(p))
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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 (freeze_user_space && !is_user_space(p))
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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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