linux-kernel - Re: [(RT RFC) PATCH v2 5/9] adaptive real-time lock support

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Message-Id: <47C40DBD.BA47.005A.0@novell.com>
Date:	Tue, 26 Feb 2008 11:01:49 -0700
From:	"Gregory Haskins" <ghaskins@...ell.com>
To:	"Pavel Machek" <pavel@....cz>
Cc:	<a.p.zijlstra@...llo.nl>, <mingo@...e.hu>, <bill.huey@...il.com>,
	<rostedt@...dmis.org>, <kevin@...man.org>, <tglx@...utronix.de>,
	<cminyard@...sta.com>, <dsingleton@...sta.com>,
	<dwalker@...sta.com>, "Moiz Kohari" <MKohari@...ell.com>,
	"Peter Morreale" <PMorreale@...ell.com>,
	"Sven Dietrich" <SDietrich@...ell.com>, <dsaxena@...xity.net>,
	<acme@...hat.com>, <ak@...e.de>, <gregkh@...e.de>,
	<npiggin@...e.de>, <linux-kernel@...r.kernel.org>,
	<linux-rt-users@...r.kernel.org>
Subject: Re: [(RT RFC) PATCH v2 5/9] adaptive real-time lock support

>>> On Tue, Feb 26, 2008 at  1:06 PM, in message
<20080226180643.GA6030@....ucw.cz>, Pavel Machek <pavel@....cz> wrote: 
> On Tue 2008-02-26 08:03:43, Gregory Haskins wrote:
>> >>> On Mon, Feb 25, 2008 at  5:03 PM, in message
>> <20080225220313.GG2659@....ucw.cz>, Pavel Machek <pavel@....cz> wrote: 
>> 
>> >> +static inline void
>> >> +prepare_adaptive_wait(struct rt_mutex *lock, struct adaptive_waiter 
>> > *adaptive)
>> > ...
>> >> +#define prepare_adaptive_wait(lock, busy) {}
>> > 
>> > This is evil. Use empty inline function instead (same for the other
>> > function, there you can maybe get away with it).
>> > 
>> 
>> I went to implement your suggested change and I remembered why I did it this 
> way:  I wanted a macro so that the "struct adaptive_waiter" local variable 
> will fall away without an #ifdef in the main body of code.  So I have left 
> this logic alone for now.
> 
> Hmm, but inline function will allow dead code elimination,  too, no?

I was getting compile errors.  Might be operator-error ;)

> 
> Anyway non-evil way to do it with macro is 
> 
> #define prepare_adaptive_wait(lock, busy) do {} while (0)
> 
> ...that behaves properly in complex statements.

Ah, I was wondering why people use that.  Will do.  Thanks!

-Greg

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