sched, wait: Use wrapper functions

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

__add_wait_queue_tail_exclusive() is introduced too instead of
add_wait_queue_exclusive_locked(). remove_wait_queue_locked() is removed, as
it is a duplicate of __remove_wait_queue(), disliked by users, and with less
users.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: <containers@lists.linux-foundation.org>
LKML-Reference: <1273214006-2979-1-git-send-email-xiaosuo@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

4 files changed, 18 insertions, 25 deletions

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index bd056a5b4efc..3817149919cb 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_exclusive(&ep->wq, &wait);
 
                 for (;;) {
                         /*
diff --git a/include/linux/wait.h b/include/linux/wait.h
index a48e16b77d5e..76d96d035ea0 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -127,12 +127,26 @@ static inline void __add_wait_queue(wait_queue_head_t *head, wait_queue_t *new)
 /*
  * Used for wake-one threads:
  */
+static inline void __add_wait_queue_exclusive(wait_queue_head_t *q,
+                                              wait_queue_t *wait)
+{
+        wait->flags |= WQ_FLAG_EXCLUSIVE;
+        __add_wait_queue(q, wait);
+}
+
 static inline void __add_wait_queue_tail(wait_queue_head_t *head,
-                                                wait_queue_t *new)
+                                         wait_queue_t *new)
 {
         list_add_tail(&new->task_list, &head->task_list);
 }
 
+static inline void __add_wait_queue_tail_exclusive(wait_queue_head_t *q,
+                                              wait_queue_t *wait)
+{
+        wait->flags |= WQ_FLAG_EXCLUSIVE;
+        __add_wait_queue_tail(q, wait);
+}
+
 static inline void __remove_wait_queue(wait_queue_head_t *head,
                                                         wait_queue_t *old)
 {
@@ -404,25 +418,6 @@ 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->flags |= WQ_FLAG_EXCLUSIVE;
-        __add_wait_queue_tail(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)
-{
-        __remove_wait_queue(q,  wait);
-}
-
-/*
  * These are the old interfaces to sleep waiting for an event.
  * They are racy.  DO NOT use them, use the wait_event* interfaces above.
  * We plan to remove these interfaces.
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index e2769e13980c..4a07d057a265 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3010,7 +3010,7 @@ static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
         unsigned long flags = (unsigned long)key;
 
         if (flags & POLLHUP) {
-                remove_wait_queue_locked(event->wqh, &event->wait);
+                __remove_wait_queue(event->wqh, &event->wait);
                 spin_lock(&cgrp->event_list_lock);
                 list_del(&event->list);
                 spin_unlock(&cgrp->event_list_lock);
diff --git a/kernel/sched.c b/kernel/sched.c
index 39aa9c7e22c0..b531d7934083 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3983,8 +3983,7 @@ do_wait_for_common(struct completion *x, long timeout, int state)
         if (!x->done) {
                 DECLARE_WAITQUEUE(wait, current);
 
-                wait.flags |= WQ_FLAG_EXCLUSIVE;
-                __add_wait_queue_tail(&x->wait, &wait);
+                __add_wait_queue_tail_exclusive(&x->wait, &wait);
                 do {
                         if (signal_pending_state(state, current)) {
                                 timeout = -ERESTARTSYS;