On Fri, Sep 08, 2023 at 10:30:57PM -0700, Ankur Arora wrote: > > 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. Yes, this.
