1 files changed, 32 insertions, 0 deletions

diff --git a/kernel/freezer.c b/kernel/freezer.c
index cb0931f89306..ba6248b323ef 100644
--- a/kernel/freezer.c
+++ b/kernel/freezer.c
@@ -120,3 +120,35 @@ void cancel_freezing(struct task_struct *p)
                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
         }
 }
+
+/*
+ * Wake up a frozen process
+ *
+ * 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.
+ */
+int __thaw_process(struct task_struct *p)
+{
+        if (frozen(p)) {
+                p->flags &= ~PF_FROZEN;
+                return 1;
+        }
+        clear_freeze_flag(p);
+        return 0;
+}
+
+int thaw_process(struct task_struct *p)
+{
+        task_lock(p);
+        if (__thaw_process(p) == 1) {
+                task_unlock(p);
+                wake_up_process(p);
+                return 1;
+        }
+        task_unlock(p);
+        return 0;
+}
+EXPORT_SYMBOL(thaw_process);