Commit 938dd9ab authored by Tejun Heo's avatar Tejun Heo
Browse files

sched_ext: Inline scx_init_task() and move RESET_RUNNABLE_AT into scx_set_task_state() 



Prepare for the SCX_TASK_INIT_BEGIN/DEAD work that follows by collapsing the
scx_init_task() helper. Move the SCX_TASK_RESET_RUNNABLE_AT setting into
scx_set_task_state() on the INIT transition (it was set unconditionally at
every INIT site through the scx_init_task() helper), inline scx_init_task()
into scx_fork() and scx_root_enable_workfn(), and drop the helper.

As a side effect, scx_sub_disable() migration sequence now also sets
RESET_RUNNABLE_AT (it previously wrote INIT directly without going through
scx_init_task()). The flag triggers a runnable_at reset on the next
set_task_runnable(), which is harmless on a task that has just been moved
between scheds.

On root-enable, p->scx.flags is written without the task's rq lock. The task
isn't visible to scx yet, and a follow-up patch restores the lock-held
write.

v2: Note p->scx.flags rq-lock relaxation on root-enable path. (Andrea)

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarAndrea Righi <arighi@nvidia.com>
parent 6947bea4

kernel/sched/ext.c

+9 −22
Original line number Diff line number Diff line
@@ -726,6 +726,7 @@ static void scx_set_task_state(struct task_struct *p, u32 state) 
		break;

	case SCX_TASK_INIT:

		warn = prev_state != SCX_TASK_NONE;

		p->scx.flags |= SCX_TASK_RESET_RUNNABLE_AT;

		break;

	case SCX_TASK_READY:

		warn = prev_state == SCX_TASK_NONE;
@@ -3585,22 +3586,6 @@ static int __scx_init_task(struct scx_sched *sch, struct task_struct *p, bool fo 
	return 0;

}



static int scx_init_task(struct scx_sched *sch, struct task_struct *p, bool fork)

{

	int ret;



	ret = __scx_init_task(sch, p, fork);

	if (!ret) {

		/*

		 * While @p's rq is not locked. @p is not visible to the rest of

		 * SCX yet and it's safe to update the flags and state.

		 */

		p->scx.flags |= SCX_TASK_RESET_RUNNABLE_AT;

		scx_set_task_state(p, SCX_TASK_INIT);

	}

	return ret;

}



static void __scx_enable_task(struct scx_sched *sch, struct task_struct *p)

{

	struct rq *rq = task_rq(p);
@@ -3763,10 +3748,11 @@ int scx_fork(struct task_struct *p, struct kernel_clone_args *kargs) 
#else

		struct scx_sched *sch = scx_root;

#endif

		ret = scx_init_task(sch, p, true);

		if (!ret)

			scx_set_task_sched(p, sch);

		ret = __scx_init_task(sch, p, true);

		if (unlikely(ret))

			return ret;

		scx_set_task_state(p, SCX_TASK_INIT);

		scx_set_task_sched(p, sch);

	}



	return 0;
@@ -6897,8 +6883,8 @@ static void scx_root_enable_workfn(struct kthread_work *work) 


		scx_task_iter_unlock(&sti);



		ret = scx_init_task(sch, p, false);

		if (ret) {

		ret = __scx_init_task(sch, p, false);

		if (unlikely(ret)) {

			put_task_struct(p);

			scx_task_iter_stop(&sti);

			scx_error(sch, "ops.init_task() failed (%d) for %s[%d]",
@@ -6906,6 +6892,7 @@ static void scx_root_enable_workfn(struct kthread_work *work) 
			goto err_disable_unlock_all;

		}



		scx_set_task_state(p, SCX_TASK_INIT);

		scx_set_task_sched(p, sch);

		scx_set_task_state(p, SCX_TASK_READY);