Commit 277e0909 authored by Michal Koutný's avatar Michal Koutný Committed by Peter Zijlstra
Browse files

sched: Bypass bandwitdh checks with runtime disabled RT_GROUP_SCHED 



When RT_GROUPs are compiled but not exposed, their bandwidth cannot
be configured (and it is not initialized for non-root task_groups neither).
Therefore bypass any checks of task vs task_group bandwidth.

This will achieve behavior very similar to setups that have
!CONFIG_RT_GROUP_SCHED and attach cpu controller to cgroup v2 hierarchy.
(On a related note, this may allow having RT tasks with
CONFIG_RT_GROUP_SCHED and cgroup v2 hierarchy.)

Signed-off-by: default avatarMichal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250310170442.504716-7-mkoutny@suse.com
parent 61d3164f

kernel/sched/core.c

+5 −1
Original line number Diff line number Diff line
@@ -9206,11 +9206,15 @@ static int cpu_cgroup_can_attach(struct cgroup_taskset *tset) 
	struct task_struct *task;

	struct cgroup_subsys_state *css;



	if (!rt_group_sched_enabled())

		goto scx_check;



	cgroup_taskset_for_each(task, css, tset) {

		if (!sched_rt_can_attach(css_tg(css), task))

			return -EINVAL;

	}

#endif

scx_check:

#endif /* CONFIG_RT_GROUP_SCHED */

	return scx_cgroup_can_attach(tset);

}

kernel/sched/rt.c

+1 −1
Original line number Diff line number Diff line
@@ -2864,7 +2864,7 @@ static int sched_rt_global_constraints(void) 
int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)

{

	/* Don't accept real-time tasks when there is no way for them to run */

	if (rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0)

	if (rt_group_sched_enabled() && rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0)

		return 0;



	return 1;

kernel/sched/syscalls.c

+2 −1
Original line number Diff line number Diff line
@@ -634,7 +634,8 @@ int __sched_setscheduler(struct task_struct *p, 
		 * Do not allow real-time tasks into groups that have no runtime

		 * assigned.

		 */

		if (rt_bandwidth_enabled() && rt_policy(policy) &&

		if (rt_group_sched_enabled() &&

				rt_bandwidth_enabled() && rt_policy(policy) &&

				task_group(p)->rt_bandwidth.rt_runtime == 0 &&

				!task_group_is_autogroup(task_group(p))) {

			retval = -EPERM;