linux-kernel - Re: Crash on reading the whole PCI config of PIIX4 SMBus

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Date:	Wed, 23 Sep 2009 18:30:29 +0200
From:	Jean Delvare <khali@...ux-fr.org>
To:	Henrik Kretzschmar <henne@...htwindheim.de>
Cc:	Wolfram Sang <w.sang@...gutronix.de>, linux-pci@...r.kernel.org,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Crash on reading the whole PCI config of PIIX4 SMBus

On Wed, 23 Sep 2009 17:49:22 +0200, Henrik Kretzschmar wrote:
> Jean Delvare schrieb:
> 
> > That's right, but it doesn't explain why i2c-piix4 crashes in the first
> > place, not why merely loading it causes further lspci -xxx to crash
> > when they did not beforehand. I admit I am totally clueless.
> >   
> Sorry, I expressed myself a bit unclear.
> 
> With _worked_ I meant the system crashed (thats what killer commands are for).
> 
> lspci -xxx (and co) bring this system down in every case, module loaded or not.
> Obvious this crash occuress when reading the config space in short periods.

Ah, OK, thanks for the clarification.

> lspci (or better proc-fs and sys-fs) do that, and i2c-piix4 does it sometimes.
> 
> Looking at read() of drivers/pci/proc.c i had the idea of stalking the critical area with:
> 
> #!/bin/sh
> for i in `seq 100`; do
>  dd if=/proc/bus/pci/00/07.3 of=/dev/null bs=1 count=n 2>/dev/null;
> done
> 
> 
> I got no crashes with n == 192, but with n == 193 theres no reaction from the system.
> 
> Maybe it's interesting, that (all the time after crashes) the screen
> (in my case the console with a blinking cursor) can still be seen.
> But no reaction on keyboard hits.

I think it is typical of IRQ routing gone out to lunch.

> Also strange is, that the device works well IF those two read accesses have not done the crash.
> I'll test tomorrow without the second read access, just to know if it works.

-- 
Jean Delvare
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