sched: Minimise repeated sched_proxy_exec() checking

Peter noted: Compilers are really bad (as in they utterly refuse)
optimizing (even when marked with __pure) the static branch
things, and will happily emit multiple identical in a row.

So pull out the one obvious sched_proxy_exec() branch in
__schedule() and remove some of the 'implicit' ones in that
path.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://patch.msgid.link/20260324191337.1841376-3-jstultz@google.com

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 29741685762d5ee7d23c1c1c688021287aa59137..f3306d3f2aa1d94e74d67d2452de668e297fc057 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6597,11 +6597,7 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf)
        struct mutex *mutex;
 
        /* Follow blocked_on chain. */
-       for (p = donor; task_is_blocked(p); p = owner) {
-               mutex = p->blocked_on;
-               /* Something changed in the chain, so pick again */
-               if (!mutex)
-                       return NULL;
+       for (p = donor; (mutex = p->blocked_on); p = owner) {
                /*
                 * By taking mutex->wait_lock we hold off concurrent mutex_unlock()
                 * and ensure @owner sticks around.
@@ -6832,12 +6828,14 @@ pick_again:
        next = pick_next_task(rq, rq->donor, &rf);
        rq_set_donor(rq, next);
        rq->next_class = next->sched_class;
-       if (unlikely(task_is_blocked(next))) {
-               next = find_proxy_task(rq, next, &rf);
-               if (!next)
-                       goto pick_again;
-               if (next == rq->idle)
-                       goto keep_resched;
+       if (sched_proxy_exec()) {
+               if (unlikely(next->blocked_on)) {
+                       next = find_proxy_task(rq, next, &rf);
+                       if (!next)
+                               goto pick_again;
+                       if (next == rq->idle)
+                               goto keep_resched;
+               }
        }
 picked:
        clear_tsk_need_resched(prev);