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SubjectRe: [PATCH] epoll: use wrapper functions
On Thu, 6 May 2010, Changli Gao wrote:

> use wrapper functions.
>
> epoll should not touch flags in wait_queue_t. This patch introduces a new
> function add_wait_queue_head_exclusive_locked(), for the users, who use
> wait queue as a LIFO queue.

Since we already have __add_wait_queue(), __add_wait_queue_tail() and
__remove_wait_queue() (which all means "locked"), and while I agree in
having the exclusive-add wrapped into a function, I much better prefer a:

static inline void __add_wait_queue_excl(wait_queue_head_t *head,
wait_queue_t *new)
{
new->flags |= WQ_FLAG_EXCLUSIVE;
__add_wait_queue(head, new);
}
The patch you posted introduces a different naming, which leaves all the
other __*() untouched, and wraps the already one-liner __remove_wait_queue()
with yet another one-liner.





> Signed-off-by: Changli Gao <xiaosuo@gmail.com>
> ----
> fs/eventpoll.c | 5 ++---
> include/linux/wait.h | 15 +++++++++++++--
> 2 files changed, 15 insertions(+), 5 deletions(-)
> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> index bd056a5..8137f6e 100644
> --- a/fs/eventpoll.c
> +++ b/fs/eventpoll.c
> @@ -1140,8 +1140,7 @@ retry:
> * ep_poll_callback() when events will become available.
> */
> init_waitqueue_entry(&wait, current);
> - wait.flags |= WQ_FLAG_EXCLUSIVE;
> - __add_wait_queue(&ep->wq, &wait);
> + add_wait_queue_head_exclusive_locked(&ep->wq, &wait);
>
> for (;;) {
> /*
> @@ -1161,7 +1160,7 @@ retry:
> jtimeout = schedule_timeout(jtimeout);
> spin_lock_irqsave(&ep->lock, flags);
> }
> - __remove_wait_queue(&ep->wq, &wait);
> + remove_wait_queue_locked(&ep->wq, &wait);
>
> set_current_state(TASK_RUNNING);
> }
> diff --git a/include/linux/wait.h b/include/linux/wait.h
> index a48e16b..de2566d 100644
> --- a/include/linux/wait.h
> +++ b/include/linux/wait.h
> @@ -407,17 +407,28 @@ do { \
> * Must be called with the spinlock in the wait_queue_head_t held.
> */
> static inline void add_wait_queue_exclusive_locked(wait_queue_head_t *q,
> - wait_queue_t * wait)
> + wait_queue_t *wait)
> {
> wait->flags |= WQ_FLAG_EXCLUSIVE;
> __add_wait_queue_tail(q, wait);
> }
>
> /*
> + * Must be called with the spinlock in the wait_queue_head_t held, and
> + * q must be for exclusive wait only.
> + */
> +static inline void add_wait_queue_head_exclusive_locked(wait_queue_head_t *q,
> + wait_queue_t *wait)
> +{
> + wait->flags |= WQ_FLAG_EXCLUSIVE;
> + __add_wait_queue(q, wait);
> +}
> +
> +/*
> * Must be called with the spinlock in the wait_queue_head_t held.
> */
> static inline void remove_wait_queue_locked(wait_queue_head_t *q,
> - wait_queue_t * wait)
> + wait_queue_t *wait)
> {
> __remove_wait_queue(q, wait);
> }
> --
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- Davide




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