From 120455c514f7321981c907a01c543b05aff3f254 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 25 Sep 2020 16:42:31 +0200 Subject: [PATCH] sched: Fix hotplug vs CPU bandwidth control Since we now migrate tasks away before DYING, we should also move bandwidth unthrottle, otherwise we can gain tasks from unthrottle after we expect all tasks to be gone already. Also; it looks like the RT balancers don't respect cpu_active() and instead rely on rq->online in part, complete this. This too requires we do set_rq_offline() earlier to match the cpu_active() semantics. (The bigger patch is to convert RT to cpu_active() entirely) Since set_rq_online() is called from sched_cpu_activate(), place set_rq_offline() in sched_cpu_deactivate(). Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Valentin Schneider Reviewed-by: Daniel Bristot de Oliveira Link: https://lkml.kernel.org/r/20201023102346.639538965@infradead.org --- kernel/sched/core.c | 14 ++++++++++---- kernel/sched/deadline.c | 2 +- kernel/sched/rt.c | 2 +- 3 files changed, 12 insertions(+), 6 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 6c89806c834b..dcb88a06ef14 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6977,6 +6977,8 @@ int sched_cpu_activate(unsigned int cpu) int sched_cpu_deactivate(unsigned int cpu) { + struct rq *rq = cpu_rq(cpu); + struct rq_flags rf; int ret; set_cpu_active(cpu, false); @@ -6991,6 +6993,14 @@ int sched_cpu_deactivate(unsigned int cpu) balance_push_set(cpu, true); + rq_lock_irqsave(rq, &rf); + if (rq->rd) { + update_rq_clock(rq); + BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span)); + set_rq_offline(rq); + } + rq_unlock_irqrestore(rq, &rf); + #ifdef CONFIG_SCHED_SMT /* * When going down, decrement the number of cores with SMT present. @@ -7072,10 +7082,6 @@ int sched_cpu_dying(unsigned int cpu) sched_tick_stop(cpu); rq_lock_irqsave(rq, &rf); - if (rq->rd) { - BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span)); - set_rq_offline(rq); - } BUG_ON(rq->nr_running != 1); rq_unlock_irqrestore(rq, &rf); diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index f232305dcefe..77880fea569f 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -543,7 +543,7 @@ static int push_dl_task(struct rq *rq); static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev) { - return dl_task(prev); + return rq->online && dl_task(prev); } static DEFINE_PER_CPU(struct callback_head, dl_push_head); diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 49ec096a8aa1..40a46639f78a 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -265,7 +265,7 @@ static void pull_rt_task(struct rq *this_rq); static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev) { /* Try to pull RT tasks here if we lower this rq's prio */ - return rq->rt.highest_prio.curr > prev->prio; + return rq->online && rq->rt.highest_prio.curr > prev->prio; } static inline int rt_overloaded(struct rq *rq)