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From: Alexander Motin <mav@FreeBSD.org>
Subject: git: b3fb4c60c50c - stable/13 - sched_ule(4): Fix interactive threads stealing.
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The branch stable/13 has been updated by mav:
URL: https://cgit.FreeBSD.org/src/commit/?id=b3fb4c60c50c217e64069e6fd3f1d2bb3915b43a
commit b3fb4c60c50c217e64069e6fd3f1d2bb3915b43a
Author: Alexander Motin <mav@FreeBSD.org>
AuthorDate: 2021-09-21 19:56:49 +0000
Commit: Alexander Motin <mav@FreeBSD.org>
CommitDate: 2021-10-05 02:28:33 +0000
sched_ule(4): Fix interactive threads stealing.
In scenarios when first thread in the queue can migrate to specified
CPU, but later ones can't runq_steal_from() incorrectly returned NULL.
MFC after: 2 weeks
(cherry picked from commit bd84094a51c4648a7c97ececdaccfb30bc832096)
---
sys/kern/sched_ule.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/sys/kern/sched_ule.c b/sys/kern/sched_ule.c
index 60f92a16f2e9..53d5a59a3605 100644
--- a/sys/kern/sched_ule.c
+++ b/sys/kern/sched_ule.c
@@ -1110,10 +1110,12 @@ again:
continue;
rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)];
TAILQ_FOREACH(td, rqh, td_runq) {
- if (first && THREAD_CAN_MIGRATE(td) &&
- THREAD_CAN_SCHED(td, cpu))
- return (td);
- first = td;
+ if (first) {
+ if (THREAD_CAN_MIGRATE(td) &&
+ THREAD_CAN_SCHED(td, cpu))
+ return (td);
+ } else
+ first = td;
}
}
}