linux-kernel - Re: preemption counter havoc on kgdb-taken faults

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Message-ID: <468E95AF.4070600@web.de>
Date:	Fri, 06 Jul 2007 21:19:11 +0200
From:	Jan Kiszka <jan.kiszka@....de>
To:	Jason Wessel <jason.wessel@...driver.com>
CC:	kgdb-bugreport@...ts.sourceforge.net,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: preemption counter havoc on kgdb-taken faults

Jason Wessel wrote:
> Jan Kiszka wrote:
>>
>> At this chance... Reminds me that this old issue still seems to be
>> unsolved in current kgdb:
>>
>> http://www.mail-archive.com/kgdb-bugreport@lists.sourceforge.net/msg00442.html
>>
>>
>> I'm only looking at that spot in kgdb right now and /may/ oversee new
>> border conditions elsewhere. But my feeling is there are none.
>>
>> Jan (looking forward to see kgdb merged)
>>
>>   
> 
> 
> Hi Jan,
> 
> This issue was fixed in a generic way in the patch set that is in the
> -mm tree.  Had you tried your test case in the current -mm tree?

Nope, I have unfortunately no adequate test setup at hand right now.

> 
> The problem you mentioned was fixed by saving and restoring the preempt
> count as a part of the fault handling from the kgdb core and not in the
> arch specific portion.

Ah, OK, that was the piece I missed.

Then /me is just curious to finally learn why that hack I once proposed
(which unfortunately never received some feedback) is not the right way
to go. In other words, what is the reason for this special
fault_setjmp/fault_longjmp?

Jan


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