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From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Jesper Juhl <juhl-lkml@dif.dk>
Cc: Ingo Molnar <mingo@elte.hu>, Robert Love <rml@tech9.net>,
	Linus Torvalds <torvalds@osdl.org>,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] sched: fix never executed code due to expression always false
Date: Fri, 15 Apr 2005 10:13:41 +1000	[thread overview]
Message-ID: <425F0735.6010407@yahoo.com.au> (raw)
In-Reply-To: <Pine.LNX.4.62.0504150213240.3466@dragon.hyggekrogen.localhost>

Jesper Juhl wrote:
> On Fri, 15 Apr 2005, Nick Piggin wrote:
> 
> 
>>Jesper Juhl wrote:
>>
>>>There are two expressions in kernel/sched.c that are always false since they
>>>test for <0 but the result of the expression is unsigned so they will never
>>>be less than zero. This patch implement the logic that I believe is intended
>>>without the signedness issue and without the nasty casts.
>>><disclaimer>patch is compile tested only</disclaimer>
>>>
>>This is not *quite* the intended behaviour. It is OK for prev->timestamp
>>to be '0 - a bit' and now to be '0 + a bit' in the case of wrapping.
>>
>>Although considering they're 64-bit values, I'm not sure how much we care.
>>
> 
> How do you propose to fix this then?  As the code is now the expressionsa 
> are always false - should we just remove the them?  Or do you have a 
> sensible definition of "a bit" ?  or ome other suggestion alltogether?
> 

Make it a signed comparison?

-- 
SUSE Labs, Novell Inc.


  reply	other threads:[~2005-04-15  0:14 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-04-14 23:49 [PATCH] sched: fix never executed code due to expression always false Jesper Juhl
2005-04-15  0:09 ` Nick Piggin
2005-04-15  0:14   ` Jesper Juhl
2005-04-15  0:13     ` Nick Piggin [this message]
2005-04-15  0:23       ` Jesper Juhl
2005-04-15  0:23         ` Nick Piggin
2005-04-15  2:32           ` Matt Mackall
2005-04-15  2:59         ` Herbert Xu
2005-04-15  3:25           ` Nick Piggin
2005-04-15  7:58         ` Ingo Molnar
2005-04-16 13:54           ` Jesper Juhl

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