Re: [3/10 PATCH] inline wake_up_bit

Mikulas Patocka
2008-06-25T14:37:39Z

On Wed, 25 Jun 2008, Denys Vlasenko wrote:

> On Tuesday 24 June 2008 07:57, Mikulas Patocka wrote:
>> Inline wake_up_bit. The function just pases arguments around.
>>
>> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
>>
>> int __wait_on_bit_lock(wait_queue_head_t *, struct wait_bit_queue *, int (*)(void *), unsigned);
>> -void wake_up_bit(void *, int);
>> int out_of_line_wait_on_bit(void *, int, int (*)(void *), unsigned);
>
>> +static __always_inline void wake_up_bit(void *word, int bit)
>> +{
>> + __wake_up_bit(bit_waitqueue(word, bit), word, bit);
>> +}
>
> So now every call to wake_up_bit(word, bit) now is converted to:
>
> __wake_up_bit(bit_waitqueue(word, bit), word, bit);
>
> which is in turn converted to (looking into your next patch):
>
> {
> wait_queue_head_t *wq = bit_waitqueue(word, bit);
> struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
> if (waitqueue_active(wq))
> __wake_up(wq, TASK_NORMAL, 1, &key);
> }
>
> which is in turn converted to (looking into your other patch):
>
> {
> wait_queue_head_t *wq = bit_waitqueue(word, bit);
> struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
> if (waitqueue_active(wq))
> {
> unsigned long flags;
> spin_lock_irqsave(&qw->lock, flags);
> __wake_up_common(wq, TASK_NORMAL, 1, 0, &key);
> spin_unlock_irqrestore(&wq->lock, flags);
> }
> }
>
> And you know what? This is likely not the end yet! It's possible
> spin_lock_irqXXX, __wake_up_common, waitqueue_active or bit_waitqueue
> are inlines - I didn't check.
> --
> vda

Yes, that's 0.2% code size increase (or none increase, if drop
inline-__wake_up_bit.patch and apply only the other patches). To me it
seems crazy, how this code was refactored again and again over time, up to
8 levels of functions (including passing a pointer to a method). In 2.0.x
kernel series, it was just a single call to wake up a queue.

Mikulas