Messages in this thread | | | Date | Mon, 8 Aug 2022 22:57:24 +0800 | Subject | Re: [PATCH v4 7/9] sched/fair: allow changing cgroup of new forked task | From | Chengming Zhou <> |
| |
On 2022/8/8 20:57, Chengming Zhou wrote: > 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@bytedance.com> > --- > include/linux/sched.h | 5 ++--- > kernel/sched/core.c | 30 +++++++----------------------- > kernel/sched/fair.c | 7 +++++++ > 3 files changed, 16 insertions(+), 26 deletions(-) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 88b8817b827d..b504e55bbf7a 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -95,10 +95,9 @@ struct task_group; > #define TASK_WAKEKILL 0x0100 > #define TASK_WAKING 0x0200 > #define TASK_NOLOAD 0x0400 > -#define TASK_NEW 0x0800 > /* RT specific auxilliary flag to mark RT lock waiters */ > -#define TASK_RTLOCK_WAIT 0x1000 > -#define TASK_STATE_MAX 0x2000 > +#define TASK_RTLOCK_WAIT 0x0800 > +#define TASK_STATE_MAX 0x1000 > > /* Convenience macros for the sake of set_current_state: */ > #define TASK_KILLABLE (TASK_WAKEKILL | TASK_UNINTERRUPTIBLE) > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index e74e79f783af..d5faa1700bd7 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -4500,11 +4500,11 @@ 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. > @@ -4622,7 +4622,6 @@ 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: > @@ -10238,36 +10237,19 @@ 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 +11085,9 @@ 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 4bc76d95a99d..90aba33a3780 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -11669,6 +11669,13 @@ 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 && !se->sum_exec_runtime)
should be: if (!p->on_rq && !p->se.sum_exec_runtime) sorry for my carelessness...
> + return; > + > detach_task_cfs_rq(p); > > #ifdef CONFIG_SMP
| |