linux-kernel - Re: [PATCH 10/13] x86: Move cond resched for copy_{from,to}

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Message-ID: <20130810182309.GA5714@pd.tnic>
Date:	Sat, 10 Aug 2013 20:23:09 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Ingo Molnar <mingo@...nel.org>, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 10/13] x86: Move cond resched for copy_{from,to}_user
 into low level code 64bit

On Sat, Aug 10, 2013 at 09:27:33AM -0700, Linus Torvalds wrote:
> Now, the *debug* logic is entirely different, of course. Maybe the
> problem is that we have mixed up the two so badly, and we have
> "might_sleep()" that implies more of a debug issue than a preemption
> issue, and then people add those because they want the debug coverage
> (and then you *absolutely* want it even for a single-byte user
> mode access). And then because the concept is tied together with
> preemption, we end up doing preemption even for that single-byte
> access despite the fact that it makes no sense what-so-ever.

Sounds like the debug aspect and the preemption point addition need
to be sorf-of split into two different functions/macros and each used
separately.

Something like keep the current might_sleep and have debug_sleep or
similar which does only __might_sleep without the resched...

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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