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sched/fair: Remove redundant cpu_cgrp_subsys->fork()

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We use cpu_cgrp_subsys->fork() to set task group for the new fair task
in cgroup_post_fork().

Since commit b1e8206582 ("sched: Fix yet more sched_fork() races")
has already set_task_rq() for the new fair task in sched_cgroup_fork(),
so cpu_cgrp_subsys->fork() can be removed.

  cgroup_can_fork()	--> pin parent's sched_task_group
  sched_cgroup_fork()
    __set_task_cpu()
      set_task_rq()
  cgroup_post_fork()
    ss->fork() := cpu_cgroup_fork()
      sched_change_group(..., TASK_SET_GROUP)
        task_set_group_fair()
          set_task_rq()  --> can be removed

After this patch's change, task_change_group_fair() only need to
care about task cgroup migration, make the code much simplier.

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>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/20220818124805.601-3-zhouchengming@bytedance.com
This commit is contained in:
Chengming Zhou 2022-08-18 20:47:58 +08:00 committed by Peter Zijlstra
parent 78b6b15770
commit 39c4261191
3 changed files with 6 additions and 49 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
kernel/sched/core.c
View File

@ -481,8 +481,7 @@ sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) { }
* p->se.load, p->rt_priority,
* p->dl.dl_{runtime, deadline, period, flags, bw, density}
* - sched_setnuma(): p->numa_preferred_nid
* - sched_move_task()/
* cpu_cgroup_fork(): p->sched_task_group
* - sched_move_task(): p->sched_task_group
* - uclamp_update_active() p->uclamp*
*
* p->state <- TASK_*:
@ -10114,7 +10113,7 @@ void sched_release_group(struct task_group *tg)
spin_unlock_irqrestore(&task_group_lock, flags);
}
static void sched_change_group(struct task_struct *tsk, int type)
static void sched_change_group(struct task_struct *tsk)
{
struct task_group *tg;
@ -10130,7 +10129,7 @@ static void sched_change_group(struct task_struct *tsk, int type)
#ifdef CONFIG_FAIR_GROUP_SCHED
if (tsk->sched_class->task_change_group)
tsk->sched_class->task_change_group(tsk, type);
tsk->sched_class->task_change_group(tsk);
else
#endif
set_task_rq(tsk, task_cpu(tsk));
@ -10161,7 +10160,7 @@ void sched_move_task(struct task_struct *tsk)
if (running)
put_prev_task(rq, tsk);
sched_change_group(tsk, TASK_MOVE_GROUP);
sched_change_group(tsk);
if (queued)
enqueue_task(rq, tsk, queue_flags);
@ -10239,23 +10238,6 @@ static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
sched_unregister_group(tg);
}
/*
* This is called before wake_up_new_task(), therefore we really only
* have to set its group bits, all the other stuff does not apply.
*/
static void cpu_cgroup_fork(struct task_struct *task)
{
struct rq_flags rf;
struct rq *rq;
rq = task_rq_lock(task, &rf);
update_rq_clock(rq);
sched_change_group(task, TASK_SET_GROUP);
task_rq_unlock(rq, task, &rf);
}
static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
{
struct task_struct *task;
@ -11121,7 +11103,6 @@ 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,
.fork = cpu_cgroup_fork,
.can_attach = cpu_cgroup_can_attach,
.attach = cpu_cgroup_attach,
.legacy_cftypes = cpu_legacy_files,

23
kernel/sched/fair.c
View File

@ -11657,15 +11657,7 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
}
#ifdef CONFIG_FAIR_GROUP_SCHED
static void task_set_group_fair(struct task_struct *p)
{
struct sched_entity *se = &p->se;
set_task_rq(p, task_cpu(p));
se->depth = se->parent ? se->parent->depth + 1 : 0;
}
static void task_move_group_fair(struct task_struct *p)
static void task_change_group_fair(struct task_struct *p)
{
detach_task_cfs_rq(p);
set_task_rq(p, task_cpu(p));
@ -11677,19 +11669,6 @@ static void task_move_group_fair(struct task_struct *p)
attach_task_cfs_rq(p);
}
static void task_change_group_fair(struct task_struct *p, int type)
{
switch (type) {
case TASK_SET_GROUP:
task_set_group_fair(p);
break;
case TASK_MOVE_GROUP:
task_move_group_fair(p);
break;
}
}
void free_fair_sched_group(struct task_group *tg)
{
int i;

5
kernel/sched/sched.h
View File

@ -2193,11 +2193,8 @@ struct sched_class {
void (*update_curr)(struct rq *rq);
#define TASK_SET_GROUP 0
#define TASK_MOVE_GROUP 1
#ifdef CONFIG_FAIR_GROUP_SCHED
void (*task_change_group)(struct task_struct *p, int type);
void (*task_change_group)(struct task_struct *p);
#endif
};