Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=08ec3df5109e0555da5b9deb4382fd29733c852c
Commit: 08ec3df5109e0555da5b9deb4382fd29733c852c
Parent: 647e7cac2d215fb8890f79252d7eaee3d6743d66
Author: Dmitry Adamushko <[EMAIL PROTECTED]>
AuthorDate: Mon Oct 15 17:00:13 2007 +0200
Committer: Ingo Molnar <[EMAIL PROTECTED]>
CommitDate: Mon Oct 15 17:00:13 2007 +0200
sched: fix __pick_next_entity()
The thing is that __pick_next_entity() must never be called when
first_fair(cfs_rq) == NULL. It wouldn't be a problem, should 'run_node'
be the very first field of 'struct sched_entity' (and it's the second).
The 'nr_running != 0' check is _not_ enough, due to the fact that
'current' is not within the tree. Generic paths are ok (e.g. schedule()
as put_prev_task() is called previously)... I'm more worried about e.g.
migration_call() -> CPU_DEAD_FROZEN -> migrate_dead_tasks()... if
'current' == rq->idle, no problems.. if it's one of the SCHED_NORMAL
tasks (or imagine, some other use-cases in the future -- i.e. we should
not make outer world dependent on internal details of sched_fair class)
-- it may be "Houston, we've got a problem" case.
it's +16 bytes to the ".text". Another variant is to make 'run_node' the
first data member of 'struct sched_entity' but an additional check (se !
= NULL) is still needed in pick_next_entity().
Signed-off-by: Dmitry Adamushko <[EMAIL PROTECTED]>
Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
Reviewed-by: Thomas Gleixner <[EMAIL PROTECTED]>
---
kernel/sched_fair.c | 7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 1f14b56..fa78686 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -600,9 +600,12 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity
*se)
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
{
- struct sched_entity *se = __pick_next_entity(cfs_rq);
+ struct sched_entity *se = NULL;
- set_next_entity(cfs_rq, se);
+ if (first_fair(cfs_rq)) {
+ se = __pick_next_entity(cfs_rq);
+ set_next_entity(cfs_rq, se);
+ }
return se;
}
-
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