linux-kernel - Re: [PATCH] Fix x86_64 TIF_SYSCALL

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Date:	Sun, 28 Oct 2007 22:21:50 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix x86_64 TIF_SYSCALL_TRACE race in entry.S

> Setting the thread flag being an atomic operation, I would expect
> setting/clearing it asynchronously from another thread to be a valid

It could be a very short stop. Also do you start kernel tracing that often?

> Here is a modified version where I add my test only in the path where we
> know that we have work to do, therefore removing the supplementary test
> from the performance critical path. Would it be more acceptable ?

It's better, but stopping would be even better. I wouldn't
be surprised if there are other problems with async thread flags changing.
 
Also I object to you calling this a bug. It's a new feature.

-Andi
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