Re: [3/4] eliminate bh waitqueue hashtable

[Andrew Morton <akpm@osdl.org>]

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(...);
}