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sched/fair: Allow changing cgroup of new forked task

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commit 7dc603c902 ("sched/fair: Fix PELT integrity for new tasks")
introduce a TASK_NEW state and an unnessary limitation that would fail
when changing cgroup of new forked task.

Because at that time, we can't handle task_change_group_fair() for new
forked fair task which hasn't been woken up by wake_up_new_task(),
which will cause detach on an unattached task sched_avg problem.

This patch delete this unnessary limitation by adding check before do
detach or attach in task_change_group_fair().

So cpu_cgrp_subsys.can_attach() has nothing to do for fair tasks,
only define it in #ifdef CONFIG_RT_GROUP_SCHED.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20220818124805.601-8-zhouchengming@bytedance.com
This commit is contained in:
Chengming Zhou
2022-08-18 20:48:03 +08:00
committed by Peter Zijlstra
parent 7e2edaf618
commit df16b71c68
2 changed files with 12 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

25
kernel/sched/core.c
View File

@ -10238,36 +10238,19 @@ static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
sched_unregister_group(tg); sched_unregister_group(tg);
} }
#ifdef CONFIG_RT_GROUP_SCHED
static int cpu_cgroup_can_attach(struct cgroup_taskset *tset) static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
{ {
struct task_struct *task; struct task_struct *task;
struct cgroup_subsys_state *css; struct cgroup_subsys_state *css;
int ret = 0;
cgroup_taskset_for_each(task, css, tset) { cgroup_taskset_for_each(task, css, tset) {
#ifdef CONFIG_RT_GROUP_SCHED
if (!sched_rt_can_attach(css_tg(css), task)) if (!sched_rt_can_attach(css_tg(css), task))
return -EINVAL; return -EINVAL;
#endif
/*
* Serialize against wake_up_new_task() such that if it's
* running, we're sure to observe its full state.
*/
raw_spin_lock_irq(&task->pi_lock);
/*
* Avoid calling sched_move_task() before wake_up_new_task()
* has happened. This would lead to problems with PELT, due to
* move wanting to detach+attach while we're not attached yet.
*/
if (READ_ONCE(task->__state) == TASK_NEW)
ret = -EINVAL;
raw_spin_unlock_irq(&task->pi_lock);
if (ret)
break;
} }
return ret; return 0;
} }
#endif
static void cpu_cgroup_attach(struct cgroup_taskset *tset) static void cpu_cgroup_attach(struct cgroup_taskset *tset)
{ {
@ -11103,7 +11086,9 @@ struct cgroup_subsys cpu_cgrp_subsys = {
.css_released = cpu_cgroup_css_released, .css_released = cpu_cgroup_css_released,
.css_free = cpu_cgroup_css_free, .css_free = cpu_cgroup_css_free,
.css_extra_stat_show = cpu_extra_stat_show, .css_extra_stat_show = cpu_extra_stat_show,
#ifdef CONFIG_RT_GROUP_SCHED
.can_attach = cpu_cgroup_can_attach, .can_attach = cpu_cgroup_can_attach,
#endif
.attach = cpu_cgroup_attach, .attach = cpu_cgroup_attach,
.legacy_cftypes = cpu_legacy_files, .legacy_cftypes = cpu_legacy_files,
.dfl_cftypes = cpu_files, .dfl_cftypes = cpu_files,

7
kernel/sched/fair.c
View File

@ -11676,6 +11676,13 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
#ifdef CONFIG_FAIR_GROUP_SCHED #ifdef CONFIG_FAIR_GROUP_SCHED
static void task_change_group_fair(struct task_struct *p) static void task_change_group_fair(struct task_struct *p)
{ {
/*
* We couldn't detach or attach a forked task which
* hasn't been woken up by wake_up_new_task().
*/
if (READ_ONCE(p->__state) == TASK_NEW)
return;
detach_task_cfs_rq(p); detach_task_cfs_rq(p);
#ifdef CONFIG_SMP #ifdef CONFIG_SMP