[PATCH] swsusp: thaw userspace and kernel space separately

Modify process thawing so that we can thaw kernel space without thawing
userspace, and thaw kernelspace first.  This will be useful in later
patches, where I intend to get swsusp thawing kernel threads only before
seeking to free memory.
Signed-off-by: Nigel Cunningham <nigel@suspend2.net>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/freezer.h

 /* Freezer declarations */
 
+#define FREEZER_KERNEL_THREADS 0
+#define FREEZER_ALL_THREADS 1
+
 #ifdef CONFIG_PM
 /*
  * Check if a process has been frozen
@@ -57,7 +60,8 @@ static inline void frozen_process(struct task_struct *p)
 
 extern void refrigerator(void);
 extern int freeze_processes(void);
-extern void thaw_processes(void);
+#define thaw_processes() do { thaw_some_processes(FREEZER_ALL_THREADS); } while(0)
+#define thaw_kernel_threads() do { thaw_some_processes(FREEZER_KERNEL_THREADS); } while(0)
 
 static inline int try_to_freeze(void)
 {
@@ -67,6 +71,9 @@ static inline int try_to_freeze(void)
 	} else
 		return 0;
 }
+
+extern void thaw_some_processes(int all);
+
 #else
 static inline int frozen(struct task_struct *p) { return 0; }
 static inline int freezing(struct task_struct *p) { return 0; }

kernel/power/process.c

@@ -153,18 +153,29 @@ int freeze_processes(void)
 	return 0;
 }
 
-void thaw_processes(void)
+void thaw_some_processes(int all)
 {
 	struct task_struct *g, *p;
+	int pass = 0; /* Pass 0 = Kernel space, 1 = Userspace */
 
 	printk("Restarting tasks... ");
 	read_lock(&tasklist_lock);
-	do_each_thread(g, p) {
-		if (!freezeable(p))
-			continue;
-		if (!thaw_process(p))
-			printk(KERN_INFO "Strange, %s not stopped\n", p->comm);
-	} while_each_thread(g, p);
+	do {
+		do_each_thread(g, p) {
+			/*
+			 * is_user = 0 if kernel thread or borrowed mm,
+			 * 1 otherwise.
+			 */
+			int is_user = !!(p->mm && !(p->flags & PF_BORROWED_MM));
+			if (!freezeable(p) || (is_user != pass))
+				continue;
+			if (!thaw_process(p))
+				printk(KERN_INFO
+					"Strange, %s not stopped\n", p->comm);
+		} while_each_thread(g, p);
+
+		pass++;
+	} while (pass < 2 && all);
 
 	read_unlock(&tasklist_lock);
 	schedule();