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) <[email protected]> --- kernel/sched/core.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7320,10 +7320,12 @@ static void balance_push_set(int cpu, bo struct rq_flags rf; rq_lock_irqsave(rq, &rf); - if (on) + if (on) { + WARN_ON_ONCE(rq->balance_callback); rq->balance_callback = &balance_push_callback; - else + } else if (rq->balance_callback == &balance_push_callback) { rq->balance_callback = NULL; + } rq_unlock_irqrestore(rq, &rf); } @@ -7441,6 +7443,10 @@ int sched_cpu_activate(unsigned int cpu) struct rq *rq = cpu_rq(cpu); 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); #ifdef CONFIG_SCHED_SMT @@ -7608,6 +7614,12 @@ int sched_cpu_dying(unsigned int cpu) } rq_unlock_irqrestore(rq, &rf); + /* + * Should really be after we clear cpu_online(), but we're in + * stop_machine(), so it all works. + */ + balance_push_set(cpu, false); + calc_load_migrate(rq); update_max_interval(); nohz_balance_exit_idle(rq);
