On Saturday, January 31, 2015 12:06:37 AM Rafael J. Wysocki wrote: > On Saturday, January 31, 2015 09:25:45 AM NeilBrown wrote: > > > > Nested IRQs can only fire when the parent irq fires. > > So when the parent is suspended, there is no need to suspend > > the child irq. > > > > Suspending nested irqs can cause a problem is they are suspended or > > resumed in the wrong order. > > If an interrupt fires while the parent is active but the child is > > suspended, then the interrupt will not be acknowledged properly > > and so an interrupt storm can result. > > This is particularly likely if the parent is resumed before > > the child, and the interrupt was raised during suspend. > > > > Ensuring correct ordering would be possible, but it is simpler > > to just never suspend nested interrupts. This patch does that. > > Clever. :-) > > This is fine by me. Thomas, what do you think?
It looks like I've overlooked a potential problem, though. Can a nested interrupt be a wakeup one? We won't set IRQD_WAKEUP_ARMED for it then and may not handle wakeup correctly. > > This patch allows the IRQF_EARLY_RESUME to be removed from > > twl4030_sih_setup(). That flag attempts to fix the same problem > > is a very different way, but causes > > > > [ 56.095825] WARNING: CPU: 0 PID: 3 at ../kernel/irq/manage.c:661 > > irq_nested_primary_handler+0x18/0x28() > > [ 56.095825] Primary handler called for nested irq 348 > > > > warnings on resume. > > > > Signed-off-by: NeilBrown <n...@brown.name> > > > > diff --git a/kernel/irq/pm.c b/kernel/irq/pm.c > > index 3ca532592704..40cbcfb7fc43 100644 > > --- a/kernel/irq/pm.c > > +++ b/kernel/irq/pm.c > > @@ -118,6 +118,8 @@ void suspend_device_irqs(void) > > unsigned long flags; > > bool sync; > > > > + if (irq_settings_is_nested_thread(desc)) > > + continue; > > raw_spin_lock_irqsave(&desc->lock, flags); > > sync = suspend_device_irq(desc, irq); > > raw_spin_unlock_irqrestore(&desc->lock, flags); > > @@ -158,6 +160,8 @@ static void resume_irqs(bool want_early) > > > > if (!is_early && want_early) > > continue; > > + if (irq_settings_is_nested_thread(desc)) > > + continue; > > > > raw_spin_lock_irqsave(&desc->lock, flags); > > resume_irq(desc, irq); > > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.
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