From: Alex,Shi Date: Wed, 28 Sep 2011 00:50:19 +0000 (+1000) Subject: kswapd: assign new_order and new_classzone_idx after wakeup in sleeping X-Git-Tag: next-20110929~2^2~147 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=3a46fa967ae9a5bd48e42146cfc16fc34f09557e;p=karo-tx-linux.git kswapd: assign new_order and new_classzone_idx after wakeup in sleeping There 2 places to read pgdat in kswapd. One is return from a successful balance, another is waked up from kswapd sleeping. The new_order and new_classzone_idx represent the balance input order and classzone_idx. But current new_order and new_classzone_idx are not assigned after kswapd_try_to_sleep(), that will cause a bug in the following scenario. 1: after a successful balance, kswapd goes to sleep, and new_order = 0; new_classzone_idx = __MAX_NR_ZONES - 1; 2: kswapd waked up with order = 3 and classzone_idx = ZONE_NORMAL 3: in the balance_pgdat() running, a new balance wakeup happened with order = 5, and classzone_idx = ZONE_NORMAL 4: the first wakeup(order = 3) finished successufly, return order = 3 but, the new_order is still 0, so, this balancing will be treated as a failed balance. And then the second tighter balancing will be missed. So, to avoid the above problem, the new_order and new_classzone_idx need to be assigned for later successful comparison. Signed-off-by: Alex Shi Acked-by: Mel Gorman Reviewed-by: Minchan Kim Tested-by: Pádraig Brady Signed-off-by: Andrew Morton <> --- diff --git a/mm/vmscan.c b/mm/vmscan.c index ec83496ff754..f94eb0b628f0 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2870,6 +2870,8 @@ static int kswapd(void *p) balanced_classzone_idx); order = pgdat->kswapd_max_order; classzone_idx = pgdat->classzone_idx; + new_order = order; + new_classzone_idx = classzone_idx; pgdat->kswapd_max_order = 0; pgdat->classzone_idx = pgdat->nr_zones - 1; }