linux-kernel - Re: [PATCH] generic: Add the exception case checking routine for ppi interrupt

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Date:   Tue, 30 Aug 2016 12:07:36 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     "majun (F)" <majun258@...wei.com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, tglx@...utronix.de,
        dingtianhong@...wei.com, guohanjun@...wei.com
Cc:     Mark Rutland <Mark.Rutland@....com>
Subject: Re: [PATCH] generic: Add the exception case checking routine for ppi
 interrupt

+Mark

On 30/08/16 11:35, majun (F) wrote:
> 
> 
> 在 2016/8/30 16:50, Marc Zyngier 写道:
>> On 30/08/16 05:17, MaJun wrote:
>>> From: Ma Jun <majun258@...wei.com>
>>>
>>> During system booting, if the interrupt which has no action registered
>>> is triggered, it would cause system panic when try to access the
>>> action member.
>>
>> And why would that interrupt be enabled? If you enable a PPI before
>> registering a handler, you're doing something wrong.
>>
> 
> Actually,the problem described above happened during the capture
> kernel booting.
> 
> In my system, sometimes there is a pending physical timer
> interrupt(30) when the first kernel panic and the status is kept
> until the capture kernel booting.

And that's perfectly fine. The interrupt can be pending forever, as it
shouldn't get enabled.

> So, this interrupt will be handled during capture kernel booting.

Why? Who enables it?

> 
> Becasue we use virt timer interrupt but not physical timer interrupt
> in capture kernel, the interrupt 30 has no action handler.

Again: who enables this interrupt? Whichever driver enables it should be
fixed.

> Besides, I think we need to do exception check in this function just
> like "handle_fasteoi_irq" does.

I respectfully disagree. This will only hide a whole class of silly
bugs, and I'd rather squash them instead of papering over them.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...