Commit 3f1bc119 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Optimize migration_cpu_stop() 



When the purpose of migration_cpu_stop() is to migrate the task to
'any' valid CPU, don't migrate the task when it's already running on a
valid CPU.

Fixes: 6d337eab ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.569238629@infradead.org
parent 58b1a450

kernel/sched/core.c

+12 −1
Original line number Diff line number Diff line
@@ -1936,14 +1936,25 @@ static int migration_cpu_stop(void *data) 
			complete = true;

		}



		if (dest_cpu < 0)

		if (dest_cpu < 0) {

			if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask))

				goto out;



			dest_cpu = cpumask_any_distribute(&p->cpus_mask);

		}



		if (task_on_rq_queued(p))

			rq = __migrate_task(rq, &rf, p, dest_cpu);

		else

			p->wake_cpu = dest_cpu;



		/*

		 * XXX __migrate_task() can fail, at which point we might end

		 * up running on a dodgy CPU, AFAICT this can only happen

		 * during CPU hotplug, at which point we'll get pushed out

		 * anyway, so it's probably not a big deal.

		 */



	} else if (pending) {

		/*

		 * This happens when we get migrated between migrate_enable()'s