wait: kill is_sync_wait()

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>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 12 deletions

diff --git a/kernel/wait.c b/kernel/wait.c
index c275c56cf2d3..cd87131f2fc2 100644
--- a/kernel/wait.c
+++ b/kernel/wait.c
@@ -72,12 +72,7 @@ prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state)
         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_head_t *q, wait_queue_t *wait, int state)
         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);