Commit 78e4690d authored by Tejun Heo's avatar Tejun Heo
Browse files

Merge branch 'for-6.14-fixes' into for-6.15 

Pull to receive f3f08c3a ("sched_ext: Fix incorrect assumption about
migration disabled tasks in task_can_run_on_remote_rq()") which conflicts
with 26176116 ("sched_ext: Count SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE in
the right spot") in for-6.15.
parents 2e7df12b f3f08c3a

kernel/sched/ext.c

+21 −8
Original line number Diff line number Diff line
@@ -2446,6 +2446,25 @@ static bool task_can_run_on_remote_rq(struct task_struct *p, struct rq *rq, 


	SCHED_WARN_ON(task_cpu(p) == cpu);



	/*

	 * If @p has migration disabled, @p->cpus_ptr is updated to contain only

	 * the pinned CPU in migrate_disable_switch() while @p is being switched

	 * out. However, put_prev_task_scx() is called before @p->cpus_ptr is

	 * updated and thus another CPU may see @p on a DSQ inbetween leading to

	 * @p passing the below task_allowed_on_cpu() check while migration is

	 * disabled.

	 *

	 * Test the migration disabled state first as the race window is narrow

	 * and the BPF scheduler failing to check migration disabled state can

	 * easily be masked if task_allowed_on_cpu() is done first.

	 */

	if (unlikely(is_migration_disabled(p))) {

		if (enforce)

			scx_ops_error("SCX_DSQ_LOCAL[_ON] cannot move migration disabled %s[%d] from CPU %d to %d",

				      p->comm, p->pid, task_cpu(p), cpu);

		return false;

	}



	/*

	 * We don't require the BPF scheduler to avoid dispatching to offline

	 * CPUs mostly for convenience but also because CPUs can go offline
@@ -2454,17 +2473,11 @@ static bool task_can_run_on_remote_rq(struct task_struct *p, struct rq *rq, 
	 */

	if (!task_allowed_on_cpu(p, cpu)) {

		if (enforce)

			scx_ops_error("SCX_DSQ_LOCAL[_ON] verdict target cpu %d not allowed for %s[%d]",

				      cpu_of(rq), p->comm, p->pid);

			scx_ops_error("SCX_DSQ_LOCAL[_ON] target CPU %d not allowed for %s[%d]",

				      cpu, p->comm, p->pid);

		return false;

	}



	/*

	 * If @p has migration disabled, @p->cpus_ptr only contains its current

	 * CPU and the above task_allowed_on_cpu() test should have failed.

	 */

	SCHED_WARN_ON(is_migration_disabled(p));



	if (!scx_rq_online(rq)) {

		if (enforce)

			__scx_add_event(SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE, 1);