this is late I know… On 2017-09-27 18:40:26 [+0200], Peter Zijlstra wrote: > - removed superfluous local_bh_disable(), since local_irq_disable() > already implies much the same.
it is not superfluous. > Please consider... > > @@ -1768,7 +1786,6 @@ int hrtimers_dead_cpu(unsigned int scpu) > BUG_ON(cpu_online(scpu)); > tick_cancel_sched_timer(scpu); > > - local_bh_disable(); > local_irq_disable(); > old_base = &per_cpu(hrtimer_bases, scpu); > new_base = this_cpu_ptr(&hrtimer_bases); > @@ -1796,7 +1813,6 @@ int hrtimers_dead_cpu(unsigned int scpu) > /* Check, if we got expired work to do */ > __hrtimer_peek_ahead_timers(); > local_irq_enable(); > - local_bh_enable(); > return 0; > } we need in there. That local_bh_disable() is required in order to let raise_softirq_irqoff() not do anything stupid in particular we need !in_interrupt() defer wakeup_softirqd() until local_bh_enable(). Otherwise wakeup_softirqd() might actually try to wakeup the process and go after the pi_lock which can't happen while holding cpu_base->lock. Sebastian
