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sched: Don't run cpu-online with balance_push() enabled

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We don't need to push away tasks when we come online, mark the push
complete right before the CPU dies.

XXX hotplug state machine has trouble with rollback here.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210121103506.415606087@infradead.org
This commit is contained in:
Peter Zijlstra 2021-01-15 18:17:45 +01:00
parent 547a77d02f
commit 22f667c97a
1 changed files with 14 additions and 2 deletions
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16
kernel/sched/core.c
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@ -7320,10 +7320,12 @@ static void balance_push_set(int cpu, bool on)
struct rq_flags rf; struct rq_flags rf;
rq_lock_irqsave(rq, &rf); rq_lock_irqsave(rq, &rf);
if (on) if (on) {
WARN_ON_ONCE(rq->balance_callback);
rq->balance_callback = &balance_push_callback; rq->balance_callback = &balance_push_callback;
else } else if (rq->balance_callback == &balance_push_callback) {
rq->balance_callback = NULL; rq->balance_callback = NULL;
}
rq_unlock_irqrestore(rq, &rf); rq_unlock_irqrestore(rq, &rf);
} }
@ -7441,6 +7443,10 @@ int sched_cpu_activate(unsigned int cpu)
struct rq *rq = cpu_rq(cpu); struct rq *rq = cpu_rq(cpu);
struct rq_flags rf; struct rq_flags rf;
/*
* Make sure that when the hotplug state machine does a roll-back
* we clear balance_push. Ideally that would happen earlier...
*/
balance_push_set(cpu, false); balance_push_set(cpu, false);
#ifdef CONFIG_SCHED_SMT #ifdef CONFIG_SCHED_SMT
@ -7608,6 +7614,12 @@ int sched_cpu_dying(unsigned int cpu)
} }
rq_unlock_irqrestore(rq, &rf); rq_unlock_irqrestore(rq, &rf);
/*
* Now that the CPU is offline, make sure we're welcome
* to new tasks once we come back up.
*/
balance_push_set(cpu, false);
calc_load_migrate(rq); calc_load_migrate(rq);
update_max_interval(); update_max_interval();
nohz_balance_exit_idle(rq); nohz_balance_exit_idle(rq);