WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

[Xen-devel] Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravi

To: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops callsites to make them patchable
From: Andi Kleen <ak@xxxxxxx>
Date: Tue, 20 Mar 2007 20:21:19 +0100
Cc: jeremy@xxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxx, netdev@xxxxxxxxxxxxxxx, mingo@xxxxxxx, Andi Kleen <ak@xxxxxxx>, jbeulich@xxxxxxxxxx, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, chrisw@xxxxxxxxxxxx, virtualization@xxxxxxxxxxxxxx, "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>, anthony@xxxxxxxxxxxxx, akpm@xxxxxxxxxxxxxxxxxxxx, David Miller <davem@xxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx
Delivery-date: Tue, 20 Mar 2007 11:21:30 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <Pine.LNX.4.64.0703201022040.6730@xxxxxxxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <20070319.120854.30182994.davem@xxxxxxxxxxxxx> <20070319.204712.118947830.davem@xxxxxxxxxxxxx> <m13b40wnrb.fsf@xxxxxxxxxxxxxxxxxxxxxxxxx> <200703201428.50564.ak@xxxxxxx> <m1ircvswzz.fsf@xxxxxxxxxxxxxxxxxxxxxxxxx> <20070320174159.GA4286@xxxxxxxxxxxxxx> <Pine.LNX.4.64.0703200947501.6730@xxxxxxxxxxxxxxxxxxxxxxxxxx> <20070320180359.GB4286@xxxxxxxxxxxxxx> <Pine.LNX.4.64.0703201022040.6730@xxxxxxxxxxxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
On Tue, Mar 20, 2007 at 10:27:00AM -0700, Linus Torvalds wrote:
> 
> 
> On Tue, 20 Mar 2007, Andi Kleen wrote:
> > 
> > The code never did that. In fact many of the problems we had initially
> > especially came out of that -- the fallback code that would handle
> > this case wasn't fully correct.
> 
> I don't keep my emails any more, but you *never* fixed the problems in 
> arch/*/kernel/traps.c.

I fixed that one after you dropped it (hmm, double checking: or at least
I thought I had fixed it, but don't see the code right now; will redo then) 
Basically it was just a one liner anyways - always check against all the
stacks that are there.


> Yes, the kernel/unwind.c issues generally got fixed. The infinite loops in 
> the *callers* never did.

There was later a weaker form that should have caught most loops, but admittedly
it wasn't 100% bullet-proof with exception stacks.

> 
> > Also frankly often your analysis about what went wrong was just
> > incorrect.
> 
> Still in denial, I see.
> 
> Do you still claim that "the fallback position always did the right 
> thing"

No initially it was buggy and that caused several of the crashes.

> Despite the fact that the unwinder had sometimes *corrupted* the 
> incoming information so much that the fallback position was the one that 
> oopsed? And no, you didn't fix that.

No, it oopsed because it was broken by itself.
Anyways that got fixed quickly.

> 
> And no, IT DID NOT use probe_kernel_address like you still claim.

There definitely was a patch that made it use it. You might have
not merged it though.
 
> Anyway, you work for Suse, I don't care what you do to the Suse kernel. 
> Maybe it will get stable some day. Somehow, I doubt it. 

So what is your proposed alternative to handle long backtraces? 
You didn't answer that question. Please do, I'm curious about your thoughts
in this area.

-Andi


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

<Prev in Thread] Current Thread [Next in Thread>