futex: Add futex_q static initializer

The futex_q struct has grown considerably over the last couple years. I
believe it now merits a static initializer to avoid uninitialized data
errors (having spent more time than I care to admit debugging an uninitialized
q.bitset in an experimental new op code).

With the key initializer built in, several of the FUTEX_KEY_INIT calls can
be removed.

V2: use a static variable instead of an init macro.
    use a C99 initializer and don't rely on variable ordering in the struct.
V3: make futex_q_init const

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <1289252428-18383-1-git-send-email-dvhart@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/futex.c b/kernel/futex.c
index 87ad287..3019b92 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -131,6 +131,12 @@ struct futex_q {
        u32 bitset;
 };
 
+static const struct futex_q futex_q_init = {
+       /* list gets initialized in queue_me()*/
+       .key = FUTEX_KEY_INIT,
+       .bitset = FUTEX_BITSET_MATCH_ANY
+};
+
 /*
  * Hash buckets are shared by all the futex_keys that hash to the same
  * location.  Each key may have multiple futex_q structures, one for each task
@@ -1750,7 +1756,6 @@ static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
         * rare, but normal.
         */
 retry:
-       q->key = FUTEX_KEY_INIT;
        ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key);
        if (unlikely(ret != 0))
                return ret;
@@ -1791,16 +1796,12 @@ static int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
        struct hrtimer_sleeper timeout, *to = NULL;
        struct restart_block *restart;
        struct futex_hash_bucket *hb;
-       struct futex_q q;
+       struct futex_q q = futex_q_init;
        int ret;
 
        if (!bitset)
                return -EINVAL;
-
-       q.pi_state = NULL;
        q.bitset = bitset;
-       q.rt_waiter = NULL;
-       q.requeue_pi_key = NULL;
 
        if (abs_time) {
                to = &timeout;
@@ -1891,7 +1892,7 @@ static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect,
 {
        struct hrtimer_sleeper timeout, *to = NULL;
        struct futex_hash_bucket *hb;
-       struct futex_q q;
+       struct futex_q q = futex_q_init;
        int res, ret;
 
        if (refill_pi_state_cache())
@@ -1905,11 +1906,7 @@ static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect,
                hrtimer_set_expires(&to->timer, *time);
        }
 
-       q.pi_state = NULL;
-       q.rt_waiter = NULL;
-       q.requeue_pi_key = NULL;
 retry:
-       q.key = FUTEX_KEY_INIT;
        ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key);
        if (unlikely(ret != 0))
                goto out;
@@ -2197,8 +2194,8 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
        struct rt_mutex_waiter rt_waiter;
        struct rt_mutex *pi_mutex = NULL;
        struct futex_hash_bucket *hb;
-       union futex_key key2;
-       struct futex_q q;
+       union futex_key key2 = FUTEX_KEY_INIT;
+       struct futex_q q = futex_q_init;
        int res, ret;
 
        if (!bitset)
@@ -2221,12 +2218,10 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
        debug_rt_mutex_init_waiter(&rt_waiter);
        rt_waiter.task = NULL;
 
-       key2 = FUTEX_KEY_INIT;
        ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
        if (unlikely(ret != 0))
                goto out;
 
-       q.pi_state = NULL;
        q.bitset = bitset;
        q.rt_waiter = &rt_waiter;
        q.requeue_pi_key = &key2;