linux-kernel - Re: [PATCH for 3.12] mutex: Avoid gcc version dependent__builtin_constant

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Date:	Fri, 18 Oct 2013 17:51:18 +0200
From:	Maarten Lankhorst <maarten.lankhorst@...onical.com>
To:	Ingo Molnar <mingo@...nel.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
CC:	peterz@...radead.org, imirkin@...m.mit.edu,
	linux-kernel@...r.kernel.org, daniel.vetter@...ll.ch,
	robdclark@...il.com
Subject: Re: [PATCH for 3.12] mutex: Avoid gcc version dependent__builtin_constant_p()
 usage.

op 18-10-13 15:13, Ingo Molnar schreef:
> * Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp> wrote:
>
>> Peter Zijlstra wrote:
>>> On Thu, Oct 17, 2013 at 12:54:21PM +0200, Maarten Lankhorst wrote:
>>>> op 17-10-13 12:52, Peter Zijlstra schreef:
>>>>> On Thu, Oct 17, 2013 at 07:45:29PM +0900, Tetsuo Handa wrote:
>>>>>> Commit 040a0a37 "mutex: Add support for wound/wait style locks" used
>>>>>> "!__builtin_constant_p(p == NULL)" but gcc 3.x cannot handle such expression
>>>>>> correctly, leading to boot failure when built with CONFIG_DEBUG_MUTEXES=y.
>>>>> So I completely forgot all about this, but wouldn't something like:
>>>>>
>>>>>  !(__builtin_constant_p(p) && p == NULL)
>>>>>
>>>>> Not also work and generate the same code?
>>>>>
>>>> See earlier discussion. It was already answered why that was undesirable. ;)
>>> OK; I forgot if we covered that particular option.. I so hate this
>>> patch; but I'm afraid we'll have to take it :-/
>>>
>> I see. Ingo, would you send this patch via your tree?
>> Then, I'll post a patch for 3.11-stable which differs white spaces.
> If it has Maarten's and PeterZ's Acked-by then sure.
>
> Thanks,
>
> 	Ingo
>
Acked. ;-)
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