On Fri, Dec 22, 2017 at 02:11:04PM +1100, NeilBrown wrote:
> The new TASK_IDLE state (TASK_UNINTERRUPTIBLE | __TASK_NOLOAD)
> is not much used. One way to make it easier to use is to
> add wait_event*() family functions that make use of it.
> This patch adds:
> wait_event_idle()
> wait_event_idle_timeout()
> wait_event_idle_exclusive()
>
> This set were chosen because lustre needs them before
> it can discard its own l_wait_event() macro.
Seems sane enough; please take through the tree that introduces the
first users of this.
Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org>
> Signed-off-by: NeilBrown <ne...@suse.com>
> ---
> include/linux/wait.h | 77
> ++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 77 insertions(+)
>
> diff --git a/include/linux/wait.h b/include/linux/wait.h
> index 158715445ffb..3aea0780c9d0 100644
> --- a/include/linux/wait.h
> +++ b/include/linux/wait.h
> @@ -597,6 +597,83 @@ do {
> \
> __ret;
> \
> })
>
> +/**
> + * wait_event_idle - wait for a condition with contributing to system load
> + * @wq_head: the waitqueue to wait on
> + * @condition: a C expression for the event to wait for
> + *
> + * The process is put to sleep (TASK_IDLE) until the
> + * @condition evaluates to true.
> + * The @condition is checked each time the waitqueue @wq_head is woken up.
> + *
> + * wake_up() has to be called after changing any variable that could
> + * change the result of the wait condition.
> + *
> + */
> +#define wait_event_idle(wq_head, condition)
> \
> +do {
> \
> + might_sleep();
> \
> + if (!(condition))
> \
> + ___wait_event(wq_head, condition, TASK_IDLE, 0, 0, schedule());
> \
> +} while (0)
> +
> +/**
> + * wait_event_idle_exclusive - wait for a condition with contributing to
> system load
> + * @wq_head: the waitqueue to wait on
> + * @condition: a C expression for the event to wait for
> + *
> + * The process is put to sleep (TASK_IDLE) until the
> + * @condition evaluates to true.
> + * The @condition is checked each time the waitqueue @wq_head is woken up.
> + *
> + * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag
> + * set thus when other process waits process on the list if this
> + * process is awaken further processes are not considered.
> + *
> + * wake_up() has to be called after changing any variable that could
> + * change the result of the wait condition.
> + *
> + */
> +#define wait_event_idle_exclusive(wq_head, condition)
> \
> +do {
> \
> + might_sleep();
> \
> + if (!(condition))
> \
> + ___wait_event(wq_head, condition, TASK_IDLE, 1, 0, schedule());
> \
> +} while (0)
> +
> +#define __wait_event_idle_timeout(wq_head, condition, timeout)
> \
> + ___wait_event(wq_head, ___wait_cond_timeout(condition),
> \
> + TASK_IDLE, 0, timeout,
> \
> + __ret = schedule_timeout(__ret))
> +
> +/**
> + * wait_event_idle_timeout - sleep without load until a condition gets true
> or a timeout elapses
> + * @wq_head: the waitqueue to wait on
> + * @condition: a C expression for the event to wait for
> + * @timeout: timeout, in jiffies
> + *
> + * The process is put to sleep (TASK_IDLE) until the
> + * @condition evaluates to true. The @condition is checked each time
> + * the waitqueue @wq_head is woken up.
> + *
> + * wake_up() has to be called after changing any variable that could
> + * change the result of the wait condition.
> + *
> + * Returns:
> + * 0 if the @condition evaluated to %false after the @timeout elapsed,
> + * 1 if the @condition evaluated to %true after the @timeout elapsed,
> + * or the remaining jiffies (at least 1) if the @condition evaluated
> + * to %true before the @timeout elapsed.
> + */
> +#define wait_event_idle_timeout(wq_head, condition, timeout)
> \
> +({
> \
> + long __ret = timeout;
> \
> + might_sleep();
> \
> + if (!___wait_cond_timeout(condition))
> \
> + __ret = __wait_event_timeout(wq_head, condition, timeout);
> \
> + __ret;
> \
> +})
> +
> extern int do_wait_intr(wait_queue_head_t *, wait_queue_entry_t *);
> extern int do_wait_intr_irq(wait_queue_head_t *, wait_queue_entry_t *);
>
>
>
