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Date: Tue, 11 Mar 2008 12:11:07 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Joe Perches <joe@perches.com>
Cc: akinobu.mita@gmail.com, nickpiggin@yahoo.com.au,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/5] lib: introduce call_once()
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On Tue, 11 Mar 2008 11:56:55 -0700
Joe Perches <joe@perches.com> wrote:

> On Tue, 2008-03-11 at 10:35 -0700, Andrew Morton wrote:
> > #define ONCE()                                              \
> >     ({                                              \
> >             static long flag;                       \
> >                                                     \
> >             return !test_and_set_bit(0, flag);      \
> >     })
> 
> test_and_set_bit takes an address

duh.

> Perhaps:
> 
> #define DO_ONCE(x) \
> 	({ static long flag; if (test_and_set_bit(0, &flag)) x; 1; })
> 
> DO_ONCE(foo);

No, that's completely unnecessary and would produce nasty-looking code. 
Take a look at some of the wait_event monstrosities we have.


I'm not sure that we need any of this once() stuff really.