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SubjectRe: [PATCH v5 7/9] sched/fair: allow changing cgroup of new forked task
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On 2022/8/18 18:36, Peter Zijlstra wrote:
> On Thu, Aug 18, 2022 at 11:43:41AM +0800, Chengming Zhou wrote:
>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index 8e3f1c3f0b2c..157f7461a08a 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -4550,11 +4550,11 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
>> {
>> __sched_fork(clone_flags, p);
>> /*
>> - * We mark the process as NEW here. This guarantees that
>> + * We mark the process as running here. This guarantees that
>> * nobody will actually run it, and a signal or other external
>> * event cannot wake it up and insert it on the runqueue either.
>> */
>> - p->__state = TASK_NEW;
>> + p->__state = TASK_RUNNING;
>>
>> /*
>> * Make sure we do not leak PI boosting priority to the child.
>> @@ -4672,7 +4672,6 @@ void wake_up_new_task(struct task_struct *p)
>> struct rq *rq;
>>
>> raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
>> - WRITE_ONCE(p->__state, TASK_RUNNING);
>> #ifdef CONFIG_SMP
>> /*
>> * Fork balancing, do it here and not earlier because:
>> @@ -10290,36 +10289,19 @@ static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
>> sched_unregister_group(tg);
>> }
>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index eba8a64f905a..e0d34ecdabae 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -11840,6 +11840,13 @@ 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 (!p->on_rq && !p->se.sum_exec_runtime)
>> + return;
>> +
>> detach_task_cfs_rq(p);
>
> Wouldn't that be much clearer when expressed in TASK_NEW ?

Ah, I was stupid, will change to use TASK_NEW.

Thanks for your suggestion!

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