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From: Andrew Morton <akpm@linux-foundation.org>
To: Akinobu Mita <akinobu.mita@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/5] lib: introduce call_once()
Date: Mon, 10 Mar 2008 20:48:53 -0700	[thread overview]
Message-ID: <20080310204853.3108d21c.akpm@linux-foundation.org> (raw)
In-Reply-To: <20080310145704.GA6396@APFDCB5C>

On Mon, 10 Mar 2008 23:57:05 +0900 Akinobu Mita <akinobu.mita@gmail.com> wrote:

> call_once() is an utility function which has similar functionality of
> pthread_once().
> 
> +/*
> + * call_once - call the initialization function only once
> + *
> + * @once_control: guarantee that the init_routine will be called only once
> + * @init_routine: initialization function
> + *
> + * The first call to call_once(), with a given once_control, shall call the
> + * init_routine with no arguments and return the value init_routine returned.
> + * If the init_routine returns zero which indicates the initialization
> + * succeeded, subsequent calls of call_once() with the same once_control shall
> + * not call the init_routine and return zero.
> + */
> +
> +static inline int call_once(struct once_control *once_control,
> +			    int (*init_rouine)(void))
> +{
> +	return likely(once_control->done) ? 0
> +			: call_once_slow(once_control, init_rouine);
> +}

I don't believe that this shold be described in terms of an "init_routine". 
This mechanism can be used for things other than initialisation routines.

It is spelled "routine", not "rouine".


Would it not be simpler and more general to do:

#define ONCE()						\
	({						\
		static long flag;			\
							\
		return !test_and_set_bit(0, flag);	\
	})

and then callers can do

	if (ONCE())
		do_something();

?

  parent reply	other threads:[~2008-03-11  3:49 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-10 14:57 Akinobu Mita
2008-03-10 15:00 ` [PATCH 2/5] idr: use call_once() Akinobu Mita
2008-03-10 15:01   ` [PATCH 3/5] hugetlbfs: " Akinobu Mita
2008-03-10 15:03     ` [PATCH 4/5] shmem: " Akinobu Mita
2008-03-10 15:05       ` [PATCH 5/5] tiny-shmem: " Akinobu Mita
2008-03-10 22:15       ` [PATCH 4/5] shmem: " Hugh Dickins
2008-03-11 12:29         ` Akinobu Mita
2008-03-11 13:41           ` Hugh Dickins
2008-03-10 15:29 ` [PATCH 1/5] lib: introduce call_once() Joe Perches
2008-03-11 12:17   ` Akinobu Mita
2008-03-11  3:48 ` Andrew Morton [this message]
2008-03-11  4:10   ` Nick Piggin
2008-03-11  4:21     ` Andrew Morton
2008-03-11 12:27       ` Akinobu Mita
2008-03-11 17:35         ` Andrew Morton
2008-03-11 18:56           ` Joe Perches
2008-03-11 19:11             ` Andrew Morton
2008-03-15  4:01           ` Akinobu Mita
2008-03-11 12:41 ` Nick Piggin

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