PM: introduce hibernation and suspend notifiers

Make it possible to register hibernation and suspend notifiers, so that
subsystems can perform hibernation-related or suspend-related operations that
should not be carried out by device drivers' .suspend() and .resume()
routines.

[akpm@linux-foundation.org: build fixes]
[akpm@linux-foundation.org: cleanups]
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Cc: Nigel Cunningham <nigel@nigel.suspend2.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 1f24f30..7f19afe 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -151,10 +151,14 @@
 		if (data->frozen)
 			break;
 		mutex_lock(&pm_mutex);
-		if (freeze_processes()) {
-			thaw_processes();
-			error = -EBUSY;
+		error = pm_notifier_call_chain(PM_HIBERNATION_PREPARE);
+		if (!error) {
+			error = freeze_processes();
+			if (error)
+				thaw_processes();
 		}
+		if (error)
+			pm_notifier_call_chain(PM_POST_HIBERNATION);
 		mutex_unlock(&pm_mutex);
 		if (!error)
 			data->frozen = 1;
@@ -165,6 +169,7 @@
 			break;
 		mutex_lock(&pm_mutex);
 		thaw_processes();
+		pm_notifier_call_chain(PM_POST_HIBERNATION);
 		mutex_unlock(&pm_mutex);
 		data->frozen = 0;
 		break;