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From: Maarten Lankhorst <maarten.lankhorst@canonical.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: mingo@kernel.org, imirkin@alum.mit.edu,
	linux-kernel@vger.kernel.org, daniel.vetter@ffwll.ch,
	robdclark@gmail.com
Subject: Re: [PATCH for 3.12] mutex: Avoid gcc version dependent __builtin_constant_p() usage.
Date: Thu, 17 Oct 2013 12:54:21 +0200	[thread overview]
Message-ID: <525FC1DD.4030205@canonical.com> (raw)
In-Reply-To: <20131017105243.GM2675@laptop.programming.kicks-ass.net>

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. ;)

~Maarten

  reply	other threads:[~2013-10-17 10:54 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-10-17 10:45 [PATCH for 3.12] mutex: Avoid gcc version dependent __builtin_constant_p() usage Tetsuo Handa
2013-10-17 10:52 ` Peter Zijlstra
2013-10-17 10:54   ` Maarten Lankhorst [this message]
2013-10-17 11:02     ` Peter Zijlstra
2013-10-18 12:51       ` [PATCH for 3.12] mutex: Avoid gcc version dependent__builtin_constant_p() usage Tetsuo Handa
2013-10-18 13:13         ` Ingo Molnar
2013-10-18 15:51           ` Maarten Lankhorst
2013-10-30 13:14             ` [PATCH 3.11-stable] mutex: Avoid gcc version dependent __builtin_constant_p() usage Tetsuo Handa
2013-10-20 19:31 ` [tip:core/urgent] " tip-bot for Tetsuo Handa

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