From: Juri Lelli Date: Mon, 21 Jul 2025 13:01:42 +0000 (+0200) Subject: sched/deadline: Always stop dl-server before changing parameters X-Git-Tag: v6.17-rc4~2^2~2 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=bb4700adc3abec34c0a38b64f66258e4e233fc16;p=users%2Fgriffoul%2Flinux.git sched/deadline: Always stop dl-server before changing parameters Commit cccb45d7c4295 ("sched/deadline: Less agressive dl_server handling") reduced dl-server overhead by delaying disabling servers only after there are no fair task around for a whole period, which means that deadline entities are not dequeued right away on a server stop event. However, the delay opens up a window in which a request for changing server parameters can break per-runqueue running_bw tracking, as reported by Yuri. Close the problematic window by unconditionally calling dl_server_stop() before applying the new parameters (ensuring deadline entities go through an actual dequeue). Fixes: cccb45d7c4295 ("sched/deadline: Less agressive dl_server handling") Reported-by: Yuri Andriaccio Signed-off-by: Juri Lelli Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Valentin Schneider Link: https://lore.kernel.org/r/20250721-upstream-fix-dlserver-lessaggressive-b4-v1-1-4ebc10c87e40@redhat.com --- diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 3f06ab84d53f..02e16b70a790 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -376,10 +376,8 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu return -EINVAL; } - if (rq->cfs.h_nr_queued) { - update_rq_clock(rq); - dl_server_stop(&rq->fair_server); - } + update_rq_clock(rq); + dl_server_stop(&rq->fair_server); retval = dl_server_apply_params(&rq->fair_server, runtime, period, 0); if (retval)