Merge tag 'pm-fix-for-3.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Power management fix for 3.3-rc2

Fix for a hibernate (s2disk) regression introduced during the 3.2
merge window that causes s2disk to trigger BUG_ON() in
freeze_workqueues_begin() if there is not enough swap space to save
the image.

* tag 'pm-fix-for-3.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  PM / Hibernate: Fix s2disk regression related to freezing workqueues

include/linux/freezer.h

@@ -39,6 +39,7 @@ extern bool __refrigerator(bool check_kthr_stop);
 extern int freeze_processes(void);
 extern int freeze_kernel_threads(void);
 extern void thaw_processes(void);
+extern void thaw_kernel_threads(void);
 
 static inline bool try_to_freeze(void)
 {
@@ -174,6 +175,7 @@ static inline bool __refrigerator(bool check_kthr_stop) { return false; }
 static inline int freeze_processes(void) { return -ENOSYS; }
 static inline int freeze_kernel_threads(void) { return -ENOSYS; }
 static inline void thaw_processes(void) {}
+static inline void thaw_kernel_threads(void) {}
 
 static inline bool try_to_freeze(void) { return false; }
 

kernel/power/process.c

@@ -188,3 +188,22 @@ void thaw_processes(void)
 	printk("done.\n");
 }
 
+void thaw_kernel_threads(void)
+{
+	struct task_struct *g, *p;
+
+	pm_nosig_freezing = false;
+	printk("Restarting kernel threads ... ");
+
+	thaw_workqueues();
+
+	read_lock(&tasklist_lock);
+	do_each_thread(g, p) {
+		if (p->flags & (PF_KTHREAD | PF_WQ_WORKER))
+			__thaw_task(p);
+	} while_each_thread(g, p);
+	read_unlock(&tasklist_lock);
+
+	schedule();
+	printk("done.\n");
+}

kernel/power/user.c

@@ -274,6 +274,15 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
 		swsusp_free();
 		memset(&data->handle, 0, sizeof(struct snapshot_handle));
 		data->ready = 0;
+		/*
+		 * It is necessary to thaw kernel threads here, because
+		 * SNAPSHOT_CREATE_IMAGE may be invoked directly after
+		 * SNAPSHOT_FREE.  In that case, if kernel threads were not
+		 * thawed, the preallocation of memory carried out by
+		 * hibernation_snapshot() might run into problems (i.e. it
+		 * might fail or even deadlock).
+		 */
+		thaw_kernel_threads();
 		break;
 
 	case SNAPSHOT_PREF_IMAGE_SIZE: