Messages in this thread Patch in this message | | | Date | Wed, 24 Feb 2021 13:24:43 +0100 | From | Peter Zijlstra <> | Subject | [PATCH 4/6] sched: Optimize migration_cpu_stop() |
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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: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- kernel/sched/core.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)
--- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -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
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