Messages in this thread | | | Date | Wed, 31 May 2017 01:02:51 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH v3] genirq: Check irq disabled & masked states in irq_shutdown |
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On Mon, 29 May 2017, jeffy.chen wrote: > i think if we want to make all irq enable/disable balance, maybe we can: > > 1/ only call irq_enable/disable from enable/disable_irq(change other > irq_enable/disable to enable/disable_irq), so they would be protected by the > refcnt(deph)
You cannot call enable/disable_irq() from places which call irq_enable/disable() due to locking reasons.
__disable_irq()/__enable_irq() can/must be called with desc->lock held, but __enable_irq() does more than just calling irq_enable().
So no, it's not that simple.
> 2/ disable lazy stuff in irq_shoutdown(we already did this in free_irq)
No, irq_shutdown() is called from other places as well.
> 3/ in irq_shutdown, set depth to 0 if it's not disabled and masked(for lazy stuff) > before calling disable_irq,
Uurgh, no. That's a unholy hack.
So what should be done to fix this is to make consequent use of the state bits.
irq_disable() if (irqd_irq_disabled()) return; irqd_set_irq_disabled(); ....
This should be done for both mask/unmask disable/enable. You get the idea.
We probably want a third state bit for STARTED_UP and do the same dance in startup/shutdown as well. Which brings me to a different issue, which is outside the scope of your problem, but looking at the code made me find it.
If a interrupt is marked IRQ_NOAUTOEN then request_irq() will not invoke irq_startup(). The interrupt is just completely set up, but stays disabled. It is enabled later via enable_irq(). That works so far with no complaints, but there is an interesting twist:
In that NOAUTOEN case nothing ever calls irq_startup() on that irq, which means that in case the irq_chip has a irq_startup() callback nothing will invoke it and also irq_domain_activate_irq() will never be invoked on such an irq.
Looks like all implementations which use IRQ_NOAUTOEN are not sensitive to that. It's been broken forever.
Fixing this needs the extra state bit IRQD_ STARTED_UP as we cannot reuse the IRQD_ACTIVATED bit because some of the interrupts are actually activated before they are requested.
Too tired to fix that now, but I'll have a look tomorrow. Once this is fixed, you can add the extra bits to prevent this disable/enable calls which cause the imbalance deeper down.
Thanks,
tglx
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