From: Rafael J. Wysocki <rjw@sisk.pl>
Date: Sun, 6 May 2007 21:50:48 +0000 (-0700)
Subject: freezer: fix racy usage of try_to_freeze in kswapd
X-Git-Tag: v2.6.22-rc1~898
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=b1296cc48b39355241470ef934a5e2270e3f23bd;p=linux-2.6-omap-h63xx.git

freezer: fix racy usage of try_to_freeze in kswapd

Currently we can miss freeze_process()->signal_wake_up() in kswapd() if it
happens between try_to_freeze() and prepare_to_wait().  To prevent this
from happening we should check freezing(current) before calling schedule().

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/vmscan.c b/mm/vmscan.c
index db023e2ff38..56651a10c36 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1323,8 +1323,6 @@ static int kswapd(void *p)
 	for ( ; ; ) {
 		unsigned long new_order;
 
-		try_to_freeze();
-
 		prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
 		new_order = pgdat->kswapd_max_order;
 		pgdat->kswapd_max_order = 0;
@@ -1335,12 +1333,19 @@ static int kswapd(void *p)
 			 */
 			order = new_order;
 		} else {
-			schedule();
+			if (!freezing(current))
+				schedule();
+
 			order = pgdat->kswapd_max_order;
 		}
 		finish_wait(&pgdat->kswapd_wait, &wait);
 
-		balance_pgdat(pgdat, order);
+		if (!try_to_freeze()) {
+			/* We can speed up thawing tasks if we don't call
+			 * balance_pgdat after returning from the refrigerator
+			 */
+			balance_pgdat(pgdat, order);
+		}
 	}
 	return 0;
 }