Commit a9c1fbbd authored by Tejun Heo's avatar Tejun Heo
Browse files

sched_ext: Don't kick CPUs running higher classes 



When a sched_ext scheduler tries to kick a CPU, the CPU may be running a
higher class task. sched_ext has no control over such CPUs. A sched_ext
scheduler couldn't have expected to get access to the CPU after kicking it
anyway. Skip kicking when the target CPU is running a higher class.

Reviewed-by: default avatarAndrea Righi <arighi@nvidia.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 2dbbdeda

kernel/sched/ext.c

+8 −3
Original line number Diff line number Diff line
@@ -5122,18 +5122,23 @@ static bool kick_one_cpu(s32 cpu, struct rq *this_rq, unsigned long *pseqs) 
{

	struct rq *rq = cpu_rq(cpu);

	struct scx_rq *this_scx = &this_rq->scx;

	const struct sched_class *cur_class;

	bool should_wait = false;

	unsigned long flags;



	raw_spin_rq_lock_irqsave(rq, flags);

	cur_class = rq->curr->sched_class;



	/*

	 * During CPU hotplug, a CPU may depend on kicking itself to make

	 * forward progress. Allow kicking self regardless of online state.

	 * forward progress. Allow kicking self regardless of online state. If

	 * @cpu is running a higher class task, we have no control over @cpu.

	 * Skip kicking.

	 */

	if (cpu_online(cpu) || cpu == cpu_of(this_rq)) {

	if ((cpu_online(cpu) || cpu == cpu_of(this_rq)) &&

	    !sched_class_above(cur_class, &ext_sched_class)) {

		if (cpumask_test_cpu(cpu, this_scx->cpus_to_preempt)) {

			if (rq->curr->sched_class == &ext_sched_class)

			if (cur_class == &ext_sched_class)

				rq->curr->scx.slice = 0;

			cpumask_clear_cpu(cpu, this_scx->cpus_to_preempt);

		}