[RFC patch 1/7] futex: Provide helpers for hash bucket add/remove

[Thomas Gleixner]

Provide helpers for adding/removing futex_q to/from a hash bucket so we don't
have more open coded places when adding support for attached futexes.

Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
 kernel/futex.c |   39 +++++++++++++++++++++++++++++++++------
 1 file changed, 33 insertions(+), 6 deletions(-)

Index: b/kernel/futex.c
===================================================================
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -373,6 +373,35 @@ static inline int hb_waiters_pending(str
 #endif
 }
 
+/**
+ * hb_insert_q - Insert futex_q into a hash bucket
+ * @q:         Pointer to the futex_q object
+ * @hb:                Pointer to the hash bucket
+ * @prio:      Priority ordering for insertion
+ *
+ * Inserts @q into the hash buckets @hb plist. Must be called with @hb->lock
+ * held.
+ */
+static inline void
+hb_insert_q(struct futex_q *q, struct futex_hash_bucket *hb, int prio)
+{
+       plist_node_init(&q->list, prio);
+       plist_add(&q->list, &hb->chain);
+}
+
+/**
+ * hb_remove_q - Remove futex_q from a hash bucket
+ * @q:         Pointer to the futex_q object
+ * @hb:                Pointer to the hash bucket
+ *
+ * Removes @q from the hash buckets @hb plist. Must be called with @hb->lock
+ * held.
+ */
+static inline void hb_remove_q(struct futex_q *q, struct futex_hash_bucket *hb)
+{
+       plist_del(&q->list, &hb->chain);
+}
+
 /*
  * We hash on the keys returned from get_futex_key (see below).
  */
@@ -1221,7 +1250,7 @@ static void __unqueue_futex(struct futex
                return;
 
        hb = container_of(q->lock_ptr, struct futex_hash_bucket, lock);
-       plist_del(&q->list, &hb->chain);
+       hb_remove_q(q, hb);
        hb_waiters_dec(hb);
 }
 
@@ -1523,7 +1552,7 @@ void requeue_futex(struct futex_q *q, st
         * requeue.
         */
        if (likely(&hb1->chain != &hb2->chain)) {
-               plist_del(&q->list, &hb1->chain);
+               hb_remove_q(q, hb1);
                hb_waiters_dec(hb1);
                plist_add(&q->list, &hb2->chain);
                hb_waiters_inc(hb2);
@@ -1985,9 +2014,7 @@ static inline void queue_me(struct futex
         * the others are woken last, in FIFO order.
         */
        prio = min(current->normal_prio, MAX_RT_PRIO);
-
-       plist_node_init(&q->list, prio);
-       plist_add(&q->list, &hb->chain);
+       hb_insert_q(q, hb, prio);
        q->task = current;
        spin_unlock(&hb->lock);
 }
@@ -2697,7 +2724,7 @@ int handle_early_requeue_pi_wakeup(struc
                 * We were woken prior to requeue by a timeout or a signal.
                 * Unqueue the futex_q and determine which it was.
                 */
-               plist_del(&q->list, &hb->chain);
+               hb_remove_q(q, hb);
                hb_waiters_dec(hb);
 
                /* Handle spurious wakeups gracefully */