1 files changed, 104 insertions, 99 deletions

diff --git a/kernel/freezer.c b/kernel/freezer.c
index 7be56c534397..9815b8d1eed5 100644
--- a/kernel/freezer.c
+++ b/kernel/freezer.c
@@ -9,101 +9,114 @@
 #include <linux/export.h>
 #include <linux/syscalls.h>
 #include <linux/freezer.h>
+#include <linux/kthread.h>
 
-/*
- * freezing is complete, mark current process as frozen
+/* total number of freezing conditions in effect */
+atomic_t system_freezing_cnt = ATOMIC_INIT(0);
+EXPORT_SYMBOL(system_freezing_cnt);
+
+/* indicate whether PM freezing is in effect, protected by pm_mutex */
+bool pm_freezing;
+bool pm_nosig_freezing;
+
+/* protects freezing and frozen transitions */
+static DEFINE_SPINLOCK(freezer_lock);
+
+/**
+ * freezing_slow_path - slow path for testing whether a task needs to be frozen
+ * @p: task to be tested
+ *
+ * This function is called by freezing() if system_freezing_cnt isn't zero
+ * and tests whether @p needs to enter and stay in frozen state.  Can be
+ * called under any context.  The freezers are responsible for ensuring the
+ * target tasks see the updated state.
  */
-static inline void frozen_process(void)
+bool freezing_slow_path(struct task_struct *p)
 {
-        if (!unlikely(current->flags & PF_NOFREEZE)) {
-                current->flags |= PF_FROZEN;
-                smp_wmb();
-        }
-        clear_freeze_flag(current);
+        if (p->flags & PF_NOFREEZE)
+                return false;
+
+        if (pm_nosig_freezing || cgroup_freezing(p))
+                return true;
+
+        if (pm_freezing && !(p->flags & PF_KTHREAD))
+                return true;
+
+        return false;
 }
+EXPORT_SYMBOL(freezing_slow_path);
 
 /* Refrigerator is place where frozen processes are stored :-). */
-void refrigerator(void)
+bool __refrigerator(bool check_kthr_stop)
 {
         /* Hmm, should we be allowed to suspend when there are realtime
            processes around? */
-        long save;
+        bool was_frozen = false;
+        long save = current->state;
 
-        task_lock(current);
-        if (freezing(current)) {
-                frozen_process();
-                task_unlock(current);
-        } else {
-                task_unlock(current);
-                return;
-        }
-        save = current->state;
         pr_debug("%s entered refrigerator\n", current->comm);
 
-        spin_lock_irq(&current->sighand->siglock);
-        recalc_sigpending(); /* We sent fake signal, clean it up */
-        spin_unlock_irq(&current->sighand->siglock);
-
-        /* prevent accounting of that task to load */
-        current->flags |= PF_FREEZING;
-
         for (;;) {
                 set_current_state(TASK_UNINTERRUPTIBLE);
-                if (!frozen(current))
+
+                spin_lock_irq(&freezer_lock);
+                current->flags |= PF_FROZEN;
+                if (!freezing(current) ||
+                    (check_kthr_stop && kthread_should_stop()))
+                        current->flags &= ~PF_FROZEN;
+                spin_unlock_irq(&freezer_lock);
+
+                if (!(current->flags & PF_FROZEN))
                         break;
+                was_frozen = true;
                 schedule();
         }
 
-        /* Remove the accounting blocker */
-        current->flags &= ~PF_FREEZING;
-
         pr_debug("%s left refrigerator\n", current->comm);
-        __set_current_state(save);
+
+        /*
+         * Restore saved task state before returning.  The mb'd version
+         * needs to be used; otherwise, it might silently break
+         * synchronization which depends on ordered task state change.
+         */
+        set_current_state(save);
+
+        return was_frozen;
 }
-EXPORT_SYMBOL(refrigerator);
+EXPORT_SYMBOL(__refrigerator);
 
 static void fake_signal_wake_up(struct task_struct *p)
 {
         unsigned long flags;
 
-        spin_lock_irqsave(&p->sighand->siglock, flags);
-        signal_wake_up(p, 0);
-        spin_unlock_irqrestore(&p->sighand->siglock, flags);
+        if (lock_task_sighand(p, &flags)) {
+                signal_wake_up(p, 0);
+                unlock_task_sighand(p, &flags);
+        }
 }
 
 /**
- *      freeze_task - send a freeze request to given task
- *      @p: task to send the request to
- *      @sig_only: if set, the request will only be sent if the task has the
- *              PF_FREEZER_NOSIG flag unset
- *      Return value: 'false', if @sig_only is set and the task has
- *              PF_FREEZER_NOSIG set or the task is frozen, 'true', otherwise
+ * freeze_task - send a freeze request to given task
+ * @p: task to send the request to
+ *
+ * If @p is freezing, the freeze request is sent by setting %TIF_FREEZE
+ * flag and either sending a fake signal to it or waking it up, depending
+ * on whether it has %PF_FREEZER_NOSIG set.
  *
- *      The freeze request is sent by setting the tasks's TIF_FREEZE flag and
- *      either sending a fake signal to it or waking it up, depending on whether
- *      or not it has PF_FREEZER_NOSIG set.  If @sig_only is set and the task
- *      has PF_FREEZER_NOSIG set (ie. it is a typical kernel thread), its
- *      TIF_FREEZE flag will not be set.
+ * RETURNS:
+ * %false, if @p is not freezing or already frozen; %true, otherwise
  */
-bool freeze_task(struct task_struct *p, bool sig_only)
+bool freeze_task(struct task_struct *p)
 {
-        /*
-         * We first check if the task is freezing and next if it has already
-         * been frozen to avoid the race with frozen_process() which first marks
-         * the task as frozen and next clears its TIF_FREEZE.
-         */
-        if (!freezing(p)) {
-                smp_rmb();
-                if (frozen(p))
-                        return false;
-
-                if (!sig_only || should_send_signal(p))
-                        set_freeze_flag(p);
-                else
-                        return false;
+        unsigned long flags;
+
+        spin_lock_irqsave(&freezer_lock, flags);
+        if (!freezing(p) || frozen(p)) {
+                spin_unlock_irqrestore(&freezer_lock, flags);
+                return false;
         }
 
-        if (should_send_signal(p)) {
+        if (!(p->flags & PF_KTHREAD)) {
                 fake_signal_wake_up(p);
                 /*
                  * fake_signal_wake_up() goes through p's scheduler
@@ -111,56 +124,48 @@ bool freeze_task(struct task_struct *p, bool sig_only)
                  * TASK_RUNNING transition can't race with task state
                  * testing in try_to_freeze_tasks().
                  */
-        } else if (sig_only) {
-                return false;
         } else {
                 wake_up_state(p, TASK_INTERRUPTIBLE);
         }
 
+        spin_unlock_irqrestore(&freezer_lock, flags);
         return true;
 }
 
-void cancel_freezing(struct task_struct *p)
+void __thaw_task(struct task_struct *p)
 {
         unsigned long flags;
 
-        if (freezing(p)) {
-                pr_debug("  clean up: %s\n", p->comm);
-                clear_freeze_flag(p);
-                spin_lock_irqsave(&p->sighand->siglock, flags);
-                recalc_sigpending_and_wake(p);
-                spin_unlock_irqrestore(&p->sighand->siglock, flags);
-        }
-}
-
-static int __thaw_process(struct task_struct *p)
-{
-        if (frozen(p)) {
-                p->flags &= ~PF_FROZEN;
-                return 1;
-        }
-        clear_freeze_flag(p);
-        return 0;
+        /*
+         * Clear freezing and kick @p if FROZEN.  Clearing is guaranteed to
+         * be visible to @p as waking up implies wmb.  Waking up inside
+         * freezer_lock also prevents wakeups from leaking outside
+         * refrigerator.
+         */
+        spin_lock_irqsave(&freezer_lock, flags);
+        if (frozen(p))
+                wake_up_process(p);
+        spin_unlock_irqrestore(&freezer_lock, flags);
 }
 
-/*
- * Wake up a frozen process
+/**
+ * set_freezable - make %current freezable
  *
- * task_lock() is needed to prevent the race with refrigerator() which may
- * occur if the freezing of tasks fails.  Namely, without the lock, if the
- * freezing of tasks failed, thaw_tasks() might have run before a task in
- * refrigerator() could call frozen_process(), in which case the task would be
- * frozen and no one would thaw it.
+ * Mark %current freezable and enter refrigerator if necessary.
  */
-int thaw_process(struct task_struct *p)
+bool set_freezable(void)
 {
-        task_lock(p);
-        if (__thaw_process(p) == 1) {
-                task_unlock(p);
-                wake_up_process(p);
-                return 1;
-        }
-        task_unlock(p);
-        return 0;
+        might_sleep();
+
+        /*
+         * Modify flags while holding freezer_lock.  This ensures the
+         * freezer notices that we aren't frozen yet or the freezing
+         * condition is visible to try_to_freeze() below.
+         */
+        spin_lock_irq(&freezer_lock);
+        current->flags &= ~PF_NOFREEZE;
+        spin_unlock_irq(&freezer_lock);
+
+        return try_to_freeze();
 }
-EXPORT_SYMBOL(thaw_process);
+EXPORT_SYMBOL(set_freezable);