is_sync_wait() is used to distinguish between sync and async waits.
Basically sync waits are the ones initialized with
init_waitqueue_entry() and async ones with init_waitqueue_func_entry().
The sync/async distinction is used only in prepare_to_wait[_exclusive]()
and its only function is to skip setting the current task state if the
wait is async. This has a few problems.
* No one uses it. None of func_entry users use prepare_to_wait()
functions, so the code path never gets executed.
* The distinction is bogus. Maybe back when func_entry is used only
by aio but it's now also used by epoll and in future possibly by 9p
and poll/select.
* Taking @state as argument and ignoring it silenly depending on how
@wait is initialized is just a bad error-prone API.
* It prevents func_entry waits from using wait->private for no good
reason.
This patch kills is_sync_wait() and the associated code paths from
prepare_to_wait[_exclusive](). As there was no user of these code
paths, this patch doesn't cause any behavior difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
---
include/linux/wait.h | 9 ---------
kernel/wait.c | 14 ++------------
2 files changed, 2 insertions(+), 21 deletions(-)
Index: work/kernel/wait.c
===================================================================
--- work.orig/kernel/wait.c
+++ work/kernel/wait.c
@@ -72,12 +72,7 @@ prepare_to_wait(wait_queue_head_t *q, wa
spin_lock_irqsave(&q->lock, flags);
if (list_empty(&wait->task_list))
__add_wait_queue(q, wait);
- /*
- * don't alter the task state if this is just going to
- * queue an async wait queue callback
- */
- if (is_sync_wait(wait))
- set_current_state(state);
+ set_current_state(state);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(prepare_to_wait);
@@ -91,12 +86,7 @@ prepare_to_wait_exclusive(wait_queue_hea
spin_lock_irqsave(&q->lock, flags);
if (list_empty(&wait->task_list))
__add_wait_queue_tail(q, wait);
- /*
- * don't alter the task state if this is just going to
- * queue an async wait queue callback
- */
- if (is_sync_wait(wait))
- set_current_state(state);
+ set_current_state(state);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(prepare_to_wait_exclusive);
Index: work/include/linux/wait.h
===================================================================
--- work.orig/include/linux/wait.h
+++ work/include/linux/wait.h
@@ -108,15 +108,6 @@ static inline int waitqueue_active(wait_
return !list_empty(&q->task_list);
}
-/*
- * Used to distinguish between sync and async io wait context:
- * sync i/o typically specifies a NULL wait queue entry or a wait
- * queue entry bound to a task (current task) to wake up.
- * aio specifies a wait queue entry with an async notification
- * callback routine, not associated with any task.
- */
-#define is_sync_wait(wait) (!(wait) || ((wait)->private))
-
extern void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait);
extern void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait);
extern void remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait);
--
