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Date: Sat, 28 Aug 2004 02:43:19 -0700
From: Andrew Morton <akpm@osdl.org>
To: William Lee Irwin III <wli@holomorphy.com>
Cc: oleg@tv-sign.ru, linux-kernel@vger.kernel.org
Subject: Re: [3/4] eliminate bh waitqueue hashtable
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William Lee Irwin III <wli@holomorphy.com> wrote:
>
> +static inline int wait_on_bit(void *word, int bit,
>  +				int (*wait)(void *), unsigned mode)
>  +{
>  +	DEFINE_WAIT_BIT(q, word, bit);
>  +	wait_queue_head_t *wqh = bit_waitqueue(word, bit);
>  +
>  +	return __wait_on_bit(wqh, &q, word, bit, wait, mode);
>  +}

It worries me a bit (sic) that we're calling the relatively expensive
bit_waitqueue() even if the bit is not set.

Maybe it should be

static inline int wait_on_bit(...)
{
	if (test_bit(...))
		out_of_line_wait_on_bit(...);
}