The following commit has been merged into the sched/core branch of tip:
Commit-ID: df16b71c686cb096774e30153c9ce6756450796c
Gitweb: https://git.kernel.org/tip/df16b71c686cb096774e30153c9ce6756450796c
Author: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
AuthorDate: Thu, 18 Aug 2022 20:48:03 +08:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 23 Aug 2022 11:01:19 +02:00
sched/fair: Allow changing cgroup of new forked task
commit 7dc603c9028e ("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@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220818124805.601-8-zhouchengming@xxxxxxxxxxxxx
---
kernel/sched/core.c | 25 +++++--------------------
kernel/sched/fair.c | 7 +++++++
2 files changed, 12 insertions(+), 20 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e74e79f..603a80e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10238,36 +10238,19 @@ static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
sched_unregister_group(tg);
}
+#ifdef CONFIG_RT_GROUP_SCHED
static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
{
struct task_struct *task;
struct cgroup_subsys_state *css;
- int ret = 0;
cgroup_taskset_for_each(task, css, tset) {
-#ifdef CONFIG_RT_GROUP_SCHED
if (!sched_rt_can_attach(css_tg(css), task))
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)
{
@@ -11103,7 +11086,9 @@ struct cgroup_subsys cpu_cgrp_subsys = {
.css_released = cpu_cgroup_css_released,
.css_free = cpu_cgroup_css_free,
.css_extra_stat_show = cpu_extra_stat_show,
+#ifdef CONFIG_RT_GROUP_SCHED
.can_attach = cpu_cgroup_can_attach,
+#endif
.attach = cpu_cgroup_attach,
.legacy_cftypes = cpu_legacy_files,
.dfl_cftypes = cpu_files,
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e92bc05..fd1aa4c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -11676,6 +11676,13 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
#ifdef CONFIG_FAIR_GROUP_SCHED
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);
#ifdef CONFIG_SMP
|