From a0e813f26ebcb25c0b5e504498fbd796cca1a4ba Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 8 Nov 2019 14:16:00 +0100 Subject: sched/core: Further clarify sched_class::set_next_task() It turns out there really is something special to the first set_next_task() invocation. In specific the 'change' pattern really should not cause balance callbacks. Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: bsegall@google.com Cc: dietmar.eggemann@arm.com Cc: juri.lelli@redhat.com Cc: ktkhai@virtuozzo.com Cc: mgorman@suse.de Cc: qais.yousef@arm.com Cc: qperret@google.com Cc: rostedt@goodmis.org Cc: valentin.schneider@arm.com Cc: vincent.guittot@linaro.org Fixes: f95d4eaee6d0 ("sched/{rt,deadline}: Fix set_next_task vs pick_next_task") Link: https://lkml.kernel.org/r/20191108131909.775434698@infradead.org Signed-off-by: Ingo Molnar --- kernel/sched/deadline.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'kernel/sched/deadline.c') diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index f7fbb4427959..43323f875cb9 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1743,13 +1743,16 @@ static void start_hrtick_dl(struct rq *rq, struct task_struct *p) } #endif -static void set_next_task_dl(struct rq *rq, struct task_struct *p) +static void set_next_task_dl(struct rq *rq, struct task_struct *p, bool first) { p->se.exec_start = rq_clock_task(rq); /* You can't push away the running task */ dequeue_pushable_dl_task(rq, p); + if (!first) + return; + if (hrtick_enabled(rq)) start_hrtick_dl(rq, p); @@ -1782,7 +1785,7 @@ static struct task_struct *pick_next_task_dl(struct rq *rq) dl_se = pick_next_dl_entity(rq, dl_rq); BUG_ON(!dl_se); p = dl_task_of(dl_se); - set_next_task_dl(rq, p); + set_next_task_dl(rq, p, true); return p; } -- cgit