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Date: Thu, 31 Jul 2008 12:46:52 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Chuck Ebbert <cebbert@redhat.com>
Cc: Jan Beulich <jbeulich@novell.com>, Andi Kleen <andi@firstfloor.org>,
       tglx@linutronix.de, linux-kernel@vger.kernel.org,
       "H. Peter Anvin" <hpa@zytor.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH] i386: improve double fault handling
Message-ID: <20080731104651.GJ488@elte.hu>
References: <4880A912.76E4.0078.0@novell.com> <4881263B.7060700@zytor.com> <48846B02.76E4.0078.0@novell.com> <20080721110510.GC10782@elte.hu> <4885CEFE.76E4.0078.0@novell.com> <20080728134252.GI5515@elte.hu> <488E4166.5070304@redhat.com>
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* Chuck Ebbert <cebbert@redhat.com> wrote:

> Ingo Molnar wrote:
>>
>> All CPUs hitting a double fault simultaneously and corrupting each  
>> others' kernel stack is a theoretical possibility - but is handling it  
>> worth the complexity? It appears to me that a lock plus a short stub  
>> function that takes the lock (with no stack usage) would handle that  
>> much better.
>
> That can't happen now because the TSS gets marked busy so we will get 
> a triple fault instead. One thing we might want to do in the current 
> code is unset the busy flag after handling the fault and before we 
> start looping at the end of the handler so we can handle another fault 
> later.

that would be a nice improvement.

	Ingo