From b1353ab8df1e6dd3bf9afaef3096749db2a193f1 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 8 Jun 2021 00:37:33 -0400 Subject: [PATCH 292/323] sched: Optimize migration_cpu_stop() Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz commit 3f1bc119cd7fc987c8ed25ffb717f99403bb308c upstream. 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()") Cc: stable@kernel.org Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Valentin Schneider Link: https://lkml.kernel.org/r/20210224131355.569238629@infradead.org Signed-off-by: Paul Gortmaker Signed-off-by: Steven Rostedt (VMware) --- kernel/sched/core.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 3130289baf79..e28fb33afa95 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1988,14 +1988,25 @@ 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 -- 2.43.0