[tip: sched/core] sched: Collate affine_move_task() stoppers

tip-bot2 for Peter Zijlstra
2021-03-06T11:43:32Z

The following commit has been merged into the sched/core branch of tip:

Commit-ID: 58b1a45086b5f80f2b2842aa7ed0da51a64a302b
Gitweb: https://git.kernel.org/tip/58b1a45086b5f80f2b2842aa7ed0da51a64a302b
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Wed, 24 Feb 2021 11:15:23 +01:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 06 Mar 2021 12:40:21 +01:00

sched: Collate affine_move_task() stoppers

The SCA_MIGRATE_ENABLE and task_running() cases are almost identical,
collapse them to avoid further duplication.

Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.500108964@infradead.org
---
kernel/sched/core.c | 23 ++++++++---------------
1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 088e8f4..84b657f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2239,30 +2239,23 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag
return -EINVAL;
}

- if (flags & SCA_MIGRATE_ENABLE) {
-
- refcount_inc(&pending->refs); /* pending->{arg,stop_work} */
- p->migration_flags &= ~MDF_PUSH;
- task_rq_unlock(rq, p, rf);
-
- stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
- &pending->arg, &pending->stop_work);
-
- return 0;
- }
-
if (task_running(rq, p) || p->state == TASK_WAKING) {
/*
- * Lessen races (and headaches) by delegating
- * is_migration_disabled(p) checks to the stopper, which will
- * run on the same CPU as said p.
+ * MIGRATE_ENABLE gets here because 'p == current', but for
+ * anything else we cannot do is_migration_disabled(), punt
+ * and have the stopper function handle it all race-free.
*/
+
refcount_inc(&pending->refs); /* pending->{arg,stop_work} */
+ if (flags & SCA_MIGRATE_ENABLE)
+ p->migration_flags &= ~MDF_PUSH;
task_rq_unlock(rq, p, rf);

stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
&pending->arg, &pending->stop_work);

+ if (flags & SCA_MIGRATE_ENABLE)
+ return 0;
} else {

if (!is_migration_disabled(p)) {