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freezer: fix racy usage of try_to_freeze in kswapd

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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>
This commit is contained in:
Rafael J. Wysocki 2007-05-06 14:50:48 -07:00 committed by Linus Torvalds
parent d1d241cc2c
commit b1296cc48b
1 changed files with 9 additions and 4 deletions
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13
mm/vmscan.c
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@ -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;
}