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 zltj/3oB 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I think something like the below will cause sufficient >> warnings to avoid growing patterns like that. > > Hmm. I don't think that warning is valid. > > Disabling preemption is actually fine if it's done in an interrupt, > iow if we have > > allow_resched(); > -> irq happens > spin_lock(); // Ok and should *not* complain > ... > spin_unlock(); > <- irq return (and preemption) > > which actually makes me worry about the nested irq case, because this > would *not* be ok: > > allow_resched(); > -> irq happens > -> *nested* irq happens > <- nested irq return (andapreemption) > > ie the allow_resched() needs to still honor the irq count, and a > nested irq return obviously must not cause any preemption. IIUC, this should be equivalent to: 01 allow_resched(); 02 -> irq happens 03 preempt_count_add(HARDIRQ_OFFSET); 04 -> nested irq happens 05 preempt_count_add(HARDIRQ_OFFSET); 06 07 preempt_count_sub(HARDIRQ_OFFSET); 08 <- nested irq return 09 preempt_count_sub(HARDIRQ_OFFSET); So, even if there were nested interrrupts, then the !preempt_count() check in raw_irqentry_exit_cond_resched() should ensure that no preemption happens until after line 09. > I've lost sight of the original patch series, and I assume / hope that > the above isn't actually an issue, but exactly because I've lost sight > of the original patches and only have this one in my mailbox I wanted > to check. Yeah, sorry about that. The irqentry_exit_allow_resched() is pretty much this: +void irqentry_exit_allow_resched(void) +{ + if (resched_allowed()) + raw_irqentry_exit_cond_resched(); +} So, as long as raw_irqentry_exit_cond_resched() won't allow early preemption, having allow_resched() set, shouldn't either. -- ankur