futex: Use futex_top_waiter() in lookup_pi_state()

No point in open coding the same function again.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Darren Hart <darren@dvhart.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Kees Cook <kees@outflux.net>
Cc: wad@chromium.org
Link: http://lkml.kernel.org/r/20140611204237.092947239@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 61 insertions, 63 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 346d5c280545..fff1ed9b1c43 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -796,87 +796,85 @@ static int
 lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
                 union futex_key *key, struct futex_pi_state **ps)
 {
+        struct futex_q *match = futex_top_waiter(hb, key);
         struct futex_pi_state *pi_state = NULL;
-        struct futex_q *this, *next;
         struct task_struct *p;
         pid_t pid = uval & FUTEX_TID_MASK;
 
-        plist_for_each_entry_safe(this, next, &hb->chain, list) {
-                if (match_futex(&this->key, key)) {
-                        /*
-                         * Sanity check the waiter before increasing
-                         * the refcount and attaching to it.
-                         */
-                        pi_state = this->pi_state;
-                        /*
-                         * Userspace might have messed up non-PI and
-                         * PI futexes [3]
-                         */
-                        if (unlikely(!pi_state))
-                                return -EINVAL;
+        if (match) {
+                /*
+                 * Sanity check the waiter before increasing the
+                 * refcount and attaching to it.
+                 */
+                pi_state = match->pi_state;
+                /*
+                 * Userspace might have messed up non-PI and PI
+                 * futexes [3]
+                 */
+                if (unlikely(!pi_state))
+                        return -EINVAL;
 
-                        WARN_ON(!atomic_read(&pi_state->refcount));
+                WARN_ON(!atomic_read(&pi_state->refcount));
 
+                /*
+                 * Handle the owner died case:
+                 */
+                if (uval & FUTEX_OWNER_DIED) {
                         /*
-                         * Handle the owner died case:
+                         * exit_pi_state_list sets owner to NULL and
+                         * wakes the topmost waiter. The task which
+                         * acquires the pi_state->rt_mutex will fixup
+                         * owner.
                          */
-                        if (uval & FUTEX_OWNER_DIED) {
+                        if (!pi_state->owner) {
                                 /*
-                                 * exit_pi_state_list sets owner to NULL and
-                                 * wakes the topmost waiter. The task which
-                                 * acquires the pi_state->rt_mutex will fixup
-                                 * owner.
+                                 * No pi state owner, but the user
+                                 * space TID is not 0. Inconsistent
+                                 * state. [5]
                                  */
-                                if (!pi_state->owner) {
-                                        /*
-                                         * No pi state owner, but the user
-                                         * space TID is not 0. Inconsistent
-                                         * state. [5]
-                                         */
-                                        if (pid)
-                                                return -EINVAL;
-                                        /*
-                                         * Take a ref on the state and
-                                         * return. [4]
-                                         */
-                                        goto out_state;
-                                }
-
-                                /*
-                                 * If TID is 0, then either the dying owner
-                                 * has not yet executed exit_pi_state_list()
-                                 * or some waiter acquired the rtmutex in the
-                                 * pi state, but did not yet fixup the TID in
-                                 * user space.
-                                 *
-                                 * Take a ref on the state and return. [6]
-                                 */
-                                if (!pid)
-                                        goto out_state;
-                        } else {
+                                if (pid)
+                                        return -EINVAL;
                                 /*
-                                 * If the owner died bit is not set,
-                                 * then the pi_state must have an
-                                 * owner. [7]
+                                 * Take a ref on the state and
+                                 * return. [4]
                                  */
-                                if (!pi_state->owner)
-                                        return -EINVAL;
+                                goto out_state;
                         }
 
                         /*
-                         * Bail out if user space manipulated the
-                         * futex value. If pi state exists then the
-                         * owner TID must be the same as the user
-                         * space TID. [9/10]
+                         * If TID is 0, then either the dying owner
+                         * has not yet executed exit_pi_state_list()
+                         * or some waiter acquired the rtmutex in the
+                         * pi state, but did not yet fixup the TID in
+                         * user space.
+                         *
+                         * Take a ref on the state and return. [6]
+                         */
+                        if (!pid)
+                                goto out_state;
+                } else {
+                        /*
+                         * If the owner died bit is not set,
+                         * then the pi_state must have an
+                         * owner. [7]
                          */
-                        if (pid != task_pid_vnr(pi_state->owner))
+                        if (!pi_state->owner)
                                 return -EINVAL;
-
-                out_state:
-                        atomic_inc(&pi_state->refcount);
-                        *ps = pi_state;
-                        return 0;
                 }
+
+                /*
+                 * Bail out if user space manipulated the
+                 * futex value. If pi state exists then the
+                 * owner TID must be the same as the user
+                 * space TID. [9/10]
+                 */
+                if (pid != task_pid_vnr(pi_state->owner))
+                        return -EINVAL;
+
+        out_state:
+                atomic_inc(&pi_state->refcount);
+                *ps = pi_state;
+                return 0;
         }
 
         /*