linux-kernel - Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops callsites to make them patchable

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Message-ID: <Pine.LNX.4.64.0703200947501.6730@woody.linux-foundation.org>
Date:	Tue, 20 Mar 2007 09:52:42 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andi Kleen <ak@...e.de>
cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	David Miller <davem@...emloft.net>,
	virtualization@...ts.linux-foundation.org, jbeulich@...ell.com,
	jeremy@...p.org, xen-devel@...ts.xensource.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	chrisw@...s-sol.org, virtualization@...ts.osdl.org,
	anthony@...emonkey.ws, akpm@...ux-foundation.org, mingo@...e.hu
Subject: Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops
 callsites to make them patchable

On Tue, 20 Mar 2007, Andi Kleen wrote:
> 
> No, me and Jan fixed all reported bugs as far as I know.

No you did not. You didn't fix the ones I reported. Which is why it got 
removed, and will not get added back until there is another maintainer.

The ones I reported were all about trusting the stack contents implicitly, 
and assuming that the unwind info was there and valid. Using things like 
"__get_user()" didn't fix it, because if a WARN_ON() happened while we 
held the mm semaphore and the unwind info was bogus, it would take a 
page-fault and deadlock.

Those kinds of things are not acceptable for debugging output. If I cannot 
use WARN_ON() because I hold the MM lock and I'm afraid there might be 
kernel corruption, then something is *wrong*!

And I told you guys this. Over *months*. And you ignored me. You told me 
everything was fine. Each time, somebody else ended up reporting a hang 
where the unwinder was at fault. And since I couldn't trust the 
maintainers to fix it, removing the broken feature that only caused more 
problems than it fixed was the only option.

And you clearly *still* haven't accepted the fact that the code was buggy. 

Does anybody wonder why I wouldn't merge it back?

		Linus
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