summaryrefslogtreecommitdiffstats
path: root/kernel
diff options
context:
space:
mode:
authorVincent Guittot <vincent.guittot@linaro.org>2020-01-14 15:13:56 +0100
committerIngo Molnar <mingo@kernel.org>2020-01-28 21:36:58 +0100
commit2a4b03ffc69f2dedc6388e9a6438b5f4c133a40d (patch)
tree505945ec9db4bdb8fa441a381c50a8ccdcdb1d73 /kernel
parente938b9c94164e4d981039f1cf6007d7453883e5a (diff)
downloadlinux-2a4b03ffc69f2dedc6388e9a6438b5f4c133a40d.tar.gz
linux-2a4b03ffc69f2dedc6388e9a6438b5f4c133a40d.tar.bz2
linux-2a4b03ffc69f2dedc6388e9a6438b5f4c133a40d.zip
sched/fair: Prevent unlimited runtime on throttled group
When a running task is moved on a throttled task group and there is no other task enqueued on the CPU, the task can keep running using 100% CPU whatever the allocated bandwidth for the group and although its cfs rq is throttled. Furthermore, the group entity of the cfs_rq and its parents are not enqueued but only set as curr on their respective cfs_rqs. We have the following sequence: sched_move_task -dequeue_task: dequeue task and group_entities. -put_prev_task: put task and group entities. -sched_change_group: move task to new group. -enqueue_task: enqueue only task but not group entities because cfs_rq is throttled. -set_next_task : set task and group_entities as current sched_entity of their cfs_rq. Another impact is that the root cfs_rq runnable_load_avg at root rq stays null because the group_entities are not enqueued. This situation will stay the same until an "external" event triggers a reschedule. Let trigger it immediately instead. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Ben Segall <bsegall@google.com> Link: https://lkml.kernel.org/r/1579011236-31256-1-git-send-email-vincent.guittot@linaro.org
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched/core.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a8a5d5b6f5cf..89e54f3ed571 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7072,8 +7072,15 @@ void sched_move_task(struct task_struct *tsk)
if (queued)
enqueue_task(rq, tsk, queue_flags);
- if (running)
+ if (running) {
set_next_task(rq, tsk);
+ /*
+ * After changing group, the running task may have joined a
+ * throttled one but it's still the running task. Trigger a
+ * resched to make sure that task can still run.
+ */
+ resched_curr(rq);
+ }
task_rq_unlock(rq, tsk, &rf);
}