3 files changed, 59 insertions, 6 deletions

diff --git a/kernel/power/power.h b/kernel/power/power.h
index 0c4defe6d3b8..21724eee5206 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -231,8 +231,28 @@ extern int pm_test_level;
 #ifdef CONFIG_SUSPEND_FREEZER
 static inline int suspend_freeze_processes(void)
 {
-	int error = freeze_processes();
-	return error ? : freeze_kernel_threads();
+	int error;
+
+	error = freeze_processes();
+
+	/*
+	 * freeze_processes() automatically thaws every task if freezing
+	 * fails. So we need not do anything extra upon error.
+	 */
+	if (error)
+		goto Finish;
+
+	error = freeze_kernel_threads();
+
+	/*
+	 * freeze_kernel_threads() thaws only kernel threads upon freezing
+	 * failure. So we have to thaw the userspace tasks ourselves.
+	 */
+	if (error)
+		thaw_processes();
+
+ Finish:
+	return error;
 }
 
 static inline void suspend_thaw_processes(void)
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 77274c9ba2f1..7e426459e60a 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -143,7 +143,10 @@ int freeze_processes(void)
 /**
  * freeze_kernel_threads - Make freezable kernel threads go to the refrigerator.
  *
- * On success, returns 0.  On failure, -errno and system is fully thawed.
+ * On success, returns 0.  On failure, -errno and only the kernel threads are
+ * thawed, so as to give a chance to the caller to do additional cleanups
+ * (if any) before thawing the userspace tasks. So, it is the responsibility
+ * of the caller to thaw the userspace tasks, when the time is right.
  */
 int freeze_kernel_threads(void)
 {
@@ -159,7 +162,7 @@ int freeze_kernel_threads(void)
 	BUG_ON(in_atomic());
 
 	if (error)
-		thaw_processes();
+		thaw_kernel_threads();
 	return error;
 }
 
@@ -188,3 +191,22 @@ 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");
+}
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 6b1ab7a88522..3e100075b13c 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -249,13 +249,15 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
 		}
 		pm_restore_gfp_mask();
 		error = hibernation_snapshot(data->platform_support);
-		if (!error) {
+		if (error) {
+			thaw_kernel_threads();
+		} else {
 			error = put_user(in_suspend, (int __user *)arg);
 			if (!error && !freezer_test_done)
 				data->ready = 1;
 			if (freezer_test_done) {
 				freezer_test_done = false;
-				thaw_processes();
+				thaw_kernel_threads();
 			}
 		}
 		break;
@@ -274,6 +276,15 @@ 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: