6.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Juri Lelli juri.lelli@redhat.com
[ Upstream commit 9f239df55546ee1d28f0976130136ffd1cad0fd7 ]
dl-servers are currently initialized too early at boot when CPUs are not fully up (only boot CPU is). This results in miscalculation of per runqueue DEADLINE variables like extra_bw (which needs a stable CPU count).
Move initialization of dl-servers later on after SMP has been initialized and CPUs are all online, so that CPU count is stable and DEADLINE variables can be computed correctly.
Fixes: d741f297bceaf ("sched/fair: Fair server interface") Reported-by: Marcel Ziswiler marcel.ziswiler@codethink.co.uk Signed-off-by: Juri Lelli juri.lelli@redhat.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Waiman Long longman@redhat.com Tested-by: Marcel Ziswiler marcel.ziswiler@codethink.co.uk # nuc & rock5b Link: https://lore.kernel.org/r/20250627115118.438797-2-juri.lelli@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/core.c | 2 ++ kernel/sched/deadline.c | 48 +++++++++++++++++++++++++---------------- kernel/sched/sched.h | 1 + 3 files changed, 33 insertions(+), 18 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 7d5f51e2f761..333743f143aa 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8501,6 +8501,8 @@ void __init sched_init_smp(void) init_sched_rt_class(); init_sched_dl_class();
+ sched_init_dl_servers(); + sched_smp_initialized = true; }
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 094134c9b135..ef5b5c045769 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -824,6 +824,8 @@ static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se) struct dl_rq *dl_rq = dl_rq_of_se(dl_se); struct rq *rq = rq_of_dl_rq(dl_rq);
+ update_rq_clock(rq); + WARN_ON(is_dl_boosted(dl_se)); WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
@@ -1652,23 +1654,7 @@ void dl_server_start(struct sched_dl_entity *dl_se) { struct rq *rq = dl_se->rq;
- /* - * XXX: the apply do not work fine at the init phase for the - * fair server because things are not yet set. We need to improve - * this before getting generic. - */ - if (!dl_server(dl_se)) { - u64 runtime = 50 * NSEC_PER_MSEC; - u64 period = 1000 * NSEC_PER_MSEC; - - dl_server_apply_params(dl_se, runtime, period, 1); - - dl_se->dl_server = 1; - dl_se->dl_defer = 1; - setup_new_dl_entity(dl_se); - } - - if (!dl_se->dl_runtime || dl_se->dl_server_active) + if (!dl_server(dl_se) || dl_se->dl_server_active) return;
dl_se->dl_server_active = 1; @@ -1679,7 +1665,7 @@ void dl_server_start(struct sched_dl_entity *dl_se)
void dl_server_stop(struct sched_dl_entity *dl_se) { - if (!dl_se->dl_runtime) + if (!dl_server(dl_se) || !dl_server_active(dl_se)) return;
dequeue_dl_entity(dl_se, DEQUEUE_SLEEP); @@ -1712,6 +1698,32 @@ void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq, dl_se->server_pick_task = pick_task; }
+void sched_init_dl_servers(void) +{ + int cpu; + struct rq *rq; + struct sched_dl_entity *dl_se; + + for_each_online_cpu(cpu) { + u64 runtime = 50 * NSEC_PER_MSEC; + u64 period = 1000 * NSEC_PER_MSEC; + + rq = cpu_rq(cpu); + + guard(rq_lock_irq)(rq); + + dl_se = &rq->fair_server; + + WARN_ON(dl_server(dl_se)); + + dl_server_apply_params(dl_se, runtime, period, 1); + + dl_se->dl_server = 1; + dl_se->dl_defer = 1; + setup_new_dl_entity(dl_se); + } +} + void __dl_server_attach_root(struct sched_dl_entity *dl_se, struct rq *rq) { u64 new_bw = dl_se->dl_bw; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index d6f82833f652..063f29a228ad 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -384,6 +384,7 @@ extern void dl_server_stop(struct sched_dl_entity *dl_se); extern void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq, dl_server_has_tasks_f has_tasks, dl_server_pick_f pick_task); +extern void sched_init_dl_servers(void);
extern void dl_server_update_idle_time(struct rq *rq, struct task_struct *p);