Messages in this thread |  | | Date | Tue, 19 Dec 2017 09:58:44 +0100 | From | Sebastian Andrzej Siewior <> | Subject | Re: [PATCH 17/25] hrtimer: Implementation of softirq hrtimer handling |
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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
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