aboutsummaryrefslogtreecommitdiff
path: root/kernel/sched_fair.c
diff options
context:
space:
mode:
authorPaul Turner <pjt@google.com>2011-07-21 09:43:37 -0700
committerIngo Molnar <mingo@elte.hu>2011-08-14 12:03:42 +0200
commit5238cdd3873e67a98b28c1161d65d2a615c320a3 (patch)
tree6c0e162a8ef9e0eb4d0099b537cfde5138aeddb4 /kernel/sched_fair.c
parent64660c864f46202b932b911a69deb09805bdbaf8 (diff)
downloadlinux-linaro-stable-5238cdd3873e67a98b28c1161d65d2a615c320a3.tar.gz
sched: Prevent buddy interactions with throttled entities
Buddies allow us to select "on-rq" entities without actually selecting them from a cfs_rq's rb_tree. As a result we must ensure that throttled entities are not falsely nominated as buddies. The fact that entities are dequeued within throttle_entity is not sufficient for clearing buddy status as the nomination may occur after throttling. Signed-off-by: Paul Turner <pjt@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20110721184757.886850167@google.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_fair.c')
-rw-r--r--kernel/sched_fair.c18
1 files changed, 17 insertions, 1 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 5a2089492a98..1d4acbea9e60 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -2348,6 +2348,15 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
if (unlikely(se == pse))
return;
+ /*
+ * This is possible from callers such as pull_task(), in which we
+ * unconditionally check_prempt_curr() after an enqueue (which may have
+ * lead to a throttle). This both saves work and prevents false
+ * next-buddy nomination below.
+ */
+ if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
+ return;
+
if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
set_next_buddy(pse);
next_buddy_marked = 1;
@@ -2356,6 +2365,12 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
/*
* We can come here with TIF_NEED_RESCHED already set from new task
* wake up path.
+ *
+ * Note: this also catches the edge-case of curr being in a throttled
+ * group (e.g. via set_curr_task), since update_curr() (in the
+ * enqueue of curr) will have resulted in resched being set. This
+ * prevents us from potentially nominating it as a false LAST_BUDDY
+ * below.
*/
if (test_tsk_need_resched(curr))
return;
@@ -2474,7 +2489,8 @@ static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preemp
{
struct sched_entity *se = &p->se;
- if (!se->on_rq)
+ /* throttled hierarchies are not runnable */
+ if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
return false;
/* Tell the scheduler that we'd really like pse to run next. */