From: Gautham R Shenoy Date: Sat, 6 Sep 2008 09:20:23 +0000 (+0530) Subject: sched: fix __load_balance_iterator() for cfq with only one task X-Git-Tag: v2.6.28-rc1~725^2~2^2~18 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=38736f475071b80b66be28af7b44c854073699cc;p=linux-2.6-omap-h63xx.git sched: fix __load_balance_iterator() for cfq with only one task The __load_balance_iterator() returns a NULL when there's only one sched_entity which is a task. It is caused by the following code-path. /* Skip over entities that are not tasks */ do { se = list_entry(next, struct sched_entity, group_node); next = next->next; } while (next != &cfs_rq->tasks && !entity_is_task(se)); if (next == &cfs_rq->tasks) return NULL; ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This will return NULL even when se is a task. As a side-effect, there was a regression in sched_mc behavior since 2.6.25, since iter_move_one_task() when it calls load_balance_start_fair(), would not get any tasks to move! Fix this by checking if the last entity was a task or not. Signed-off-by: Gautham R Shenoy Acked-by: Peter Zijlstra Signed-off-by: Ingo Molnar --- diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 8264bb5dbd5..a10ac0bcee6 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1458,7 +1458,7 @@ __load_balance_iterator(struct cfs_rq *cfs_rq, struct list_head *next) next = next->next; } while (next != &cfs_rq->tasks && !entity_is_task(se)); - if (next == &cfs_rq->tasks) + if (next == &cfs_rq->tasks && !entity_is_task(se)) return NULL; cfs_rq->balance_iterator = next;