From: Vincent Guittot <vincent.guittot@linaro.org> mainline inclusion from mainline-v5.6-rc2 commit 2a4b03ffc69f2dedc6388e9a6438b5f4c133a40d category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/13564 CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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@... Conflicts: kernel/sched/core.c [Conflicts with set_curr_task(rq, tsk) due to lacking of 03b7fad167ef ("sched: Add task_struct pointer to sched_class::set_curr_task"), but this patch has no relevance to make running state resched_curr(rq).] Signed-off-by: Zicheng Qu <quzicheng@huawei.com> --- kernel/sched/core.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f7fa066b05ba..765e437732be 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6565,8 +6565,15 @@ void sched_move_task(struct task_struct *tsk) if (queued) enqueue_task(rq, tsk, queue_flags); - if (running) + if (running) { set_curr_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); } -- 2.34.1