[PATCH 0/3] futex: compiler warning and cleanups

[PATCH 0/3] futex: compiler warning and cleanups

[Darren Hart]

The following patches include a compiler warning fix and a couple futex cleanups
that I have been sitting on for too long.

Darren Hart (3):
      futex: fix compiler warnings in exit_robust_list
      futex: replace fshared and clockrt with combined flags
      futex: add futex_q static initializer

 kernel/futex.c |  226 ++++++++++++++++++++++++++------------------------------
 1 files changed, 106 insertions(+), 120 deletions(-)

[PATCH 1/3] futex: fix compiler warnings in exit_robust_list

[Darren Hart]

The following commit introduced a compiler warning:

Commit 1dcc41bb037533839753df983d31778b30b67d93
futex: Change 3rd arg of fetch_robust_entry() to unsigned int*

The following archs/compiler versions all report:
kernel/futex.c: In function ‘exit_robust_list’:
kernel/futex.c:2492: warning: ‘next_pi’ may be used uninitialized in this function

x86_64
gcc (Ubuntu 4.4.3-4ubuntu5) 4.4.3
gcc (GCC) 4.4.4 20100630 (Red Hat 4.4.4-10)
gcc (Ubuntu/Linaro 4.4.4-14ubuntu5) 4.4.5

sh
sh-linux-gnu-gcc (Sourcery G++ Lite 4.3-143) 4.3.3

The code path really can't result in next_pi pi being unitialized (or should
not), but let's keep the build clean. Assign next_pi = 0 to avoid the warnings.

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Tested-by: Matt Fleming <matt@console-pimps.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: John Kacur <jkacur@redhat.com>
---
 kernel/futex.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index a118bf1..78715cb 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2489,7 +2489,7 @@ void exit_robust_list(struct task_struct *curr)
 {
 	struct robust_list_head __user *head = curr->robust_list;
 	struct robust_list __user *entry, *next_entry, *pending;
-	unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
+	unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi = 0, pip;
 	unsigned long futex_offset;
 	int rc;
 
-- 
1.7.1

[PATCH 2/3] futex: replace fshared and clockrt with combined flags

[Darren Hart]

In the early days we passed the mmap sem around. That became the
"int fshared" with the fast gup improvements. Then we added
"int clockrt" in places. This patch unifies these options as "flags" and
cleans up various calls which had fshared in their signature but no
longer used it.

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: John Kacur <jkacur@redhat.com>
---
 kernel/futex.c |  199 +++++++++++++++++++++++++++-----------------------------
 1 files changed, 95 insertions(+), 104 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 78715cb..8502498 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -69,6 +69,14 @@ int __read_mostly futex_cmpxchg_enabled;
 #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
 
 /*
+ * Futex flags used to encode options to functions and preserve them across
+ * restarts.
+ */
+#define FLAGS_SHARED		0x01
+#define FLAGS_CLOCKRT		0x02
+#define FLAGS_HAS_TIMEOUT	0x04
+
+/*
  * Priority Inheritance state:
  */
 struct futex_pi_state {
@@ -284,7 +292,7 @@ again:
 }
 
 static inline
-void put_futex_key(int fshared, union futex_key *key)
+void put_futex_key(union futex_key *key)
 {
 	drop_futex_key_refs(key);
 }
@@ -870,7 +878,7 @@ double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
 /*
  * Wake up waiters matching bitset queued on this futex (uaddr).
  */
-static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
+static int futex_wake(u32 __user *uaddr, int flags, int nr_wake, u32 bitset)
 {
 	struct futex_hash_bucket *hb;
 	struct futex_q *this, *next;
@@ -881,7 +889,7 @@ static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
 	if (!bitset)
 		return -EINVAL;
 
-	ret = get_futex_key(uaddr, fshared, &key);
+	ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key);
 	if (unlikely(ret != 0))
 		goto out;
 
@@ -907,7 +915,7 @@ static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
 	}
 
 	spin_unlock(&hb->lock);
-	put_futex_key(fshared, &key);
+	put_futex_key(&key);
 out:
 	return ret;
 }
@@ -917,7 +925,7 @@ out:
  * to this virtual address:
  */
 static int
-futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
+futex_wake_op(u32 __user *uaddr1, int flags, u32 __user *uaddr2,
 	      int nr_wake, int nr_wake2, int op)
 {
 	union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
@@ -927,10 +935,10 @@ futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
 	int ret, op_ret;
 
 retry:
-	ret = get_futex_key(uaddr1, fshared, &key1);
+	ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1);
 	if (unlikely(ret != 0))
 		goto out;
-	ret = get_futex_key(uaddr2, fshared, &key2);
+	ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
 	if (unlikely(ret != 0))
 		goto out_put_key1;
 
@@ -962,11 +970,11 @@ retry_private:
 		if (ret)
 			goto out_put_keys;
 
-		if (!fshared)
+		if (!(flags & FLAGS_SHARED))
 			goto retry_private;
 
-		put_futex_key(fshared, &key2);
-		put_futex_key(fshared, &key1);
+		put_futex_key(&key2);
+		put_futex_key(&key1);
 		goto retry;
 	}
 
@@ -996,9 +1004,9 @@ retry_private:
 
 	double_unlock_hb(hb1, hb2);
 out_put_keys:
-	put_futex_key(fshared, &key2);
+	put_futex_key(&key2);
 out_put_key1:
-	put_futex_key(fshared, &key1);
+	put_futex_key(&key1);
 out:
 	return ret;
 }
@@ -1148,7 +1156,7 @@ static int futex_proxy_trylock_atomic(u32 __user *pifutex,
  * >=0 - on success, the number of tasks requeued or woken
  *  <0 - on error
  */
-static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
+static int futex_requeue(u32 __user *uaddr1, int flags, u32 __user *uaddr2,
 			 int nr_wake, int nr_requeue, u32 *cmpval,
 			 int requeue_pi)
 {
@@ -1191,10 +1199,10 @@ retry:
 		pi_state = NULL;
 	}
 
-	ret = get_futex_key(uaddr1, fshared, &key1);
+	ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1);
 	if (unlikely(ret != 0))
 		goto out;
-	ret = get_futex_key(uaddr2, fshared, &key2);
+	ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
 	if (unlikely(ret != 0))
 		goto out_put_key1;
 
@@ -1216,11 +1224,11 @@ retry_private:
 			if (ret)
 				goto out_put_keys;
 
-			if (!fshared)
+			if (!(flags & FLAGS_SHARED))
 				goto retry_private;
 
-			put_futex_key(fshared, &key2);
-			put_futex_key(fshared, &key1);
+			put_futex_key(&key2);
+			put_futex_key(&key1);
 			goto retry;
 		}
 		if (curval != *cmpval) {
@@ -1260,8 +1268,8 @@ retry_private:
 			break;
 		case -EFAULT:
 			double_unlock_hb(hb1, hb2);
-			put_futex_key(fshared, &key2);
-			put_futex_key(fshared, &key1);
+			put_futex_key(&key2);
+			put_futex_key(&key1);
 			ret = fault_in_user_writeable(uaddr2);
 			if (!ret)
 				goto retry;
@@ -1269,8 +1277,8 @@ retry_private:
 		case -EAGAIN:
 			/* The owner was exiting, try again. */
 			double_unlock_hb(hb1, hb2);
-			put_futex_key(fshared, &key2);
-			put_futex_key(fshared, &key1);
+			put_futex_key(&key2);
+			put_futex_key(&key1);
 			cond_resched();
 			goto retry;
 		default:
@@ -1352,9 +1360,9 @@ out_unlock:
 		drop_futex_key_refs(&key1);
 
 out_put_keys:
-	put_futex_key(fshared, &key2);
+	put_futex_key(&key2);
 out_put_key1:
-	put_futex_key(fshared, &key1);
+	put_futex_key(&key1);
 out:
 	if (pi_state != NULL)
 		free_pi_state(pi_state);
@@ -1494,7 +1502,7 @@ static void unqueue_me_pi(struct futex_q *q)
  * private futexes.
  */
 static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
-				struct task_struct *newowner, int fshared)
+				struct task_struct *newowner)
 {
 	u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
 	struct futex_pi_state *pi_state = q->pi_state;
@@ -1587,20 +1595,11 @@ handle_fault:
 	goto retry;
 }
 
-/*
- * In case we must use restart_block to restart a futex_wait,
- * we encode in the 'flags' shared capability
- */
-#define FLAGS_SHARED		0x01
-#define FLAGS_CLOCKRT		0x02
-#define FLAGS_HAS_TIMEOUT	0x04
-
 static long futex_wait_restart(struct restart_block *restart);
 
 /**
  * fixup_owner() - Post lock pi_state and corner case management
  * @uaddr:	user address of the futex
- * @fshared:	whether the futex is shared (1) or not (0)
  * @q:		futex_q (contains pi_state and access to the rt_mutex)
  * @locked:	if the attempt to take the rt_mutex succeeded (1) or not (0)
  *
@@ -1613,8 +1612,7 @@ static long futex_wait_restart(struct restart_block *restart);
  *  0 - success, lock not taken
  * <0 - on error (-EFAULT)
  */
-static int fixup_owner(u32 __user *uaddr, int fshared, struct futex_q *q,
-		       int locked)
+static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked)
 {
 	struct task_struct *owner;
 	int ret = 0;
@@ -1625,7 +1623,7 @@ static int fixup_owner(u32 __user *uaddr, int fshared, struct futex_q *q,
 		 * did a lock-steal - fix up the PI-state in that case:
 		 */
 		if (q->pi_state->owner != current)
-			ret = fixup_pi_state_owner(uaddr, q, current, fshared);
+			ret = fixup_pi_state_owner(uaddr, q, current);
 		goto out;
 	}
 
@@ -1652,7 +1650,7 @@ static int fixup_owner(u32 __user *uaddr, int fshared, struct futex_q *q,
 		 * lock. Fix the state up.
 		 */
 		owner = rt_mutex_owner(&q->pi_state->pi_mutex);
-		ret = fixup_pi_state_owner(uaddr, q, owner, fshared);
+		ret = fixup_pi_state_owner(uaddr, q, owner);
 		goto out;
 	}
 
@@ -1715,7 +1713,7 @@ static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
  * futex_wait_setup() - Prepare to wait on a futex
  * @uaddr:	the futex userspace address
  * @val:	the expected value
- * @fshared:	whether the futex is shared (1) or not (0)
+ * @flags:	futex flags (FLAGS_SHARED, etc.)
  * @q:		the associated futex_q
  * @hb:		storage for hash_bucket pointer to be returned to caller
  *
@@ -1728,7 +1726,7 @@ static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
  *  0 - uaddr contains val and hb has been locked
  * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlcoked
  */
-static int futex_wait_setup(u32 __user *uaddr, u32 val, int fshared,
+static int futex_wait_setup(u32 __user *uaddr, u32 val, int flags,
 			   struct futex_q *q, struct futex_hash_bucket **hb)
 {
 	u32 uval;
@@ -1753,7 +1751,7 @@ static int futex_wait_setup(u32 __user *uaddr, u32 val, int fshared,
 	 */
 retry:
 	q->key = FUTEX_KEY_INIT;
-	ret = get_futex_key(uaddr, fshared, &q->key);
+	ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key);
 	if (unlikely(ret != 0))
 		return ret;
 
@@ -1769,10 +1767,10 @@ retry_private:
 		if (ret)
 			goto out;
 
-		if (!fshared)
+		if (!(flags & FLAGS_SHARED))
 			goto retry_private;
 
-		put_futex_key(fshared, &q->key);
+		put_futex_key(&q->key);
 		goto retry;
 	}
 
@@ -1783,12 +1781,12 @@ retry_private:
 
 out:
 	if (ret)
-		put_futex_key(fshared, &q->key);
+		put_futex_key(&q->key);
 	return ret;
 }
 
-static int futex_wait(u32 __user *uaddr, int fshared,
-		      u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
+static int futex_wait(u32 __user *uaddr, int flags, u32 val, ktime_t *abs_time,
+		      u32 bitset)
 {
 	struct hrtimer_sleeper timeout, *to = NULL;
 	struct restart_block *restart;
@@ -1807,8 +1805,9 @@ static int futex_wait(u32 __user *uaddr, int fshared,
 	if (abs_time) {
 		to = &timeout;
 
-		hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME :
-				      CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+		hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ?
+				      CLOCK_REALTIME : CLOCK_MONOTONIC,
+				      HRTIMER_MODE_ABS);
 		hrtimer_init_sleeper(to, current);
 		hrtimer_set_expires_range_ns(&to->timer, *abs_time,
 					     current->timer_slack_ns);
@@ -1819,7 +1818,7 @@ retry:
 	 * Prepare to wait on uaddr. On success, holds hb lock and increments
 	 * q.key refs.
 	 */
-	ret = futex_wait_setup(uaddr, val, fshared, &q, &hb);
+	ret = futex_wait_setup(uaddr, val, flags, &q, &hb);
 	if (ret)
 		goto out;
 
@@ -1852,12 +1851,7 @@ retry:
 	restart->futex.val = val;
 	restart->futex.time = abs_time->tv64;
 	restart->futex.bitset = bitset;
-	restart->futex.flags = FLAGS_HAS_TIMEOUT;
-
-	if (fshared)
-		restart->futex.flags |= FLAGS_SHARED;
-	if (clockrt)
-		restart->futex.flags |= FLAGS_CLOCKRT;
+	restart->futex.flags = flags;
 
 	ret = -ERESTART_RESTARTBLOCK;
 
@@ -1873,7 +1867,6 @@ out:
 static long futex_wait_restart(struct restart_block *restart)
 {
 	u32 __user *uaddr = restart->futex.uaddr;
-	int fshared = 0;
 	ktime_t t, *tp = NULL;
 
 	if (restart->futex.flags & FLAGS_HAS_TIMEOUT) {
@@ -1881,11 +1874,9 @@ static long futex_wait_restart(struct restart_block *restart)
 		tp = &t;
 	}
 	restart->fn = do_no_restart_syscall;
-	if (restart->futex.flags & FLAGS_SHARED)
-		fshared = 1;
-	return (long)futex_wait(uaddr, fshared, restart->futex.val, tp,
-				restart->futex.bitset,
-				restart->futex.flags & FLAGS_CLOCKRT);
+
+	return (long)futex_wait(uaddr, restart->futex.flags,
+				restart->futex.val, tp, restart->futex.bitset);
 }
 
 
@@ -1895,8 +1886,8 @@ static long futex_wait_restart(struct restart_block *restart)
  * if there are waiters then it will block, it does PI, etc. (Due to
  * races the kernel might see a 0 value of the futex too.)
  */
-static int futex_lock_pi(u32 __user *uaddr, int fshared,
-			 int detect, ktime_t *time, int trylock)
+static int futex_lock_pi(u32 __user *uaddr, int flags, int detect,
+			 ktime_t *time, int trylock)
 {
 	struct hrtimer_sleeper timeout, *to = NULL;
 	struct futex_hash_bucket *hb;
@@ -1919,7 +1910,7 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared,
 	q.requeue_pi_key = NULL;
 retry:
 	q.key = FUTEX_KEY_INIT;
-	ret = get_futex_key(uaddr, fshared, &q.key);
+	ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key);
 	if (unlikely(ret != 0))
 		goto out;
 
@@ -1941,7 +1932,7 @@ retry_private:
 			 * exit to complete.
 			 */
 			queue_unlock(&q, hb);
-			put_futex_key(fshared, &q.key);
+			put_futex_key(&q.key);
 			cond_resched();
 			goto retry;
 		default:
@@ -1971,7 +1962,7 @@ retry_private:
 	 * Fixup the pi_state owner and possibly acquire the lock if we
 	 * haven't already.
 	 */
-	res = fixup_owner(uaddr, fshared, &q, !ret);
+	res = fixup_owner(uaddr, &q, !ret);
 	/*
 	 * If fixup_owner() returned an error, proprogate that.  If it acquired
 	 * the lock, clear our -ETIMEDOUT or -EINTR.
@@ -1995,7 +1986,7 @@ out_unlock_put_key:
 	queue_unlock(&q, hb);
 
 out_put_key:
-	put_futex_key(fshared, &q.key);
+	put_futex_key(&q.key);
 out:
 	if (to)
 		destroy_hrtimer_on_stack(&to->timer);
@@ -2008,10 +1999,10 @@ uaddr_faulted:
 	if (ret)
 		goto out_put_key;
 
-	if (!fshared)
+	if (!(flags & FLAGS_SHARED))
 		goto retry_private;
 
-	put_futex_key(fshared, &q.key);
+	put_futex_key(&q.key);
 	goto retry;
 }
 
@@ -2020,7 +2011,7 @@ uaddr_faulted:
  * This is the in-kernel slowpath: we look up the PI state (if any),
  * and do the rt-mutex unlock.
  */
-static int futex_unlock_pi(u32 __user *uaddr, int fshared)
+static int futex_unlock_pi(u32 __user *uaddr, int flags)
 {
 	struct futex_hash_bucket *hb;
 	struct futex_q *this, *next;
@@ -2038,7 +2029,7 @@ retry:
 	if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current))
 		return -EPERM;
 
-	ret = get_futex_key(uaddr, fshared, &key);
+	ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key);
 	if (unlikely(ret != 0))
 		goto out;
 
@@ -2093,14 +2084,14 @@ retry:
 
 out_unlock:
 	spin_unlock(&hb->lock);
-	put_futex_key(fshared, &key);
+	put_futex_key(&key);
 
 out:
 	return ret;
 
 pi_faulted:
 	spin_unlock(&hb->lock);
-	put_futex_key(fshared, &key);
+	put_futex_key(&key);
 
 	ret = fault_in_user_writeable(uaddr);
 	if (!ret)
@@ -2160,7 +2151,7 @@ int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb,
 /**
  * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2
  * @uaddr:	the futex we initially wait on (non-pi)
- * @fshared:	whether the futexes are shared (1) or not (0).  They must be
+ * @flags:	futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be
  * 		the same type, no requeueing from private to shared, etc.
  * @val:	the expected value of uaddr
  * @abs_time:	absolute timeout
@@ -2198,9 +2189,9 @@ int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb,
  *  0 - On success
  * <0 - On error
  */
-static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
+static int futex_wait_requeue_pi(u32 __user *uaddr, int flags,
 				 u32 val, ktime_t *abs_time, u32 bitset,
-				 int clockrt, u32 __user *uaddr2)
+				 u32 __user *uaddr2)
 {
 	struct hrtimer_sleeper timeout, *to = NULL;
 	struct rt_mutex_waiter rt_waiter;
@@ -2215,8 +2206,9 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
 
 	if (abs_time) {
 		to = &timeout;
-		hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME :
-				      CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+		hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ?
+				      CLOCK_REALTIME : CLOCK_MONOTONIC,
+				      HRTIMER_MODE_ABS);
 		hrtimer_init_sleeper(to, current);
 		hrtimer_set_expires_range_ns(&to->timer, *abs_time,
 					     current->timer_slack_ns);
@@ -2230,7 +2222,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
 	rt_waiter.task = NULL;
 
 	key2 = FUTEX_KEY_INIT;
-	ret = get_futex_key(uaddr2, fshared, &key2);
+	ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
 	if (unlikely(ret != 0))
 		goto out;
 
@@ -2243,7 +2235,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
 	 * Prepare to wait on uaddr. On success, increments q.key (key1) ref
 	 * count.
 	 */
-	ret = futex_wait_setup(uaddr, val, fshared, &q, &hb);
+	ret = futex_wait_setup(uaddr, val, flags, &q, &hb);
 	if (ret)
 		goto out_key2;
 
@@ -2273,8 +2265,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
 		 */
 		if (q.pi_state && (q.pi_state->owner != current)) {
 			spin_lock(q.lock_ptr);
-			ret = fixup_pi_state_owner(uaddr2, &q, current,
-						   fshared);
+			ret = fixup_pi_state_owner(uaddr2, &q, current);
 			spin_unlock(q.lock_ptr);
 		}
 	} else {
@@ -2293,7 +2284,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
 		 * Fixup the pi_state owner and possibly acquire the lock if we
 		 * haven't already.
 		 */
-		res = fixup_owner(uaddr2, fshared, &q, !ret);
+		res = fixup_owner(uaddr2, &q, !ret);
 		/*
 		 * If fixup_owner() returned an error, proprogate that.  If it
 		 * acquired the lock, clear -ETIMEDOUT or -EINTR.
@@ -2324,9 +2315,9 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
 	}
 
 out_put_keys:
-	put_futex_key(fshared, &q.key);
+	put_futex_key(&q.key);
 out_key2:
-	put_futex_key(fshared, &key2);
+	put_futex_key(&key2);
 
 out:
 	if (to) {
@@ -2550,58 +2541,58 @@ void exit_robust_list(struct task_struct *curr)
 long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
 		u32 __user *uaddr2, u32 val2, u32 val3)
 {
-	int clockrt, ret = -ENOSYS;
+	int ret = -ENOSYS;
 	int cmd = op & FUTEX_CMD_MASK;
-	int fshared = 0;
+	int flags = 0;
 
 	if (!(op & FUTEX_PRIVATE_FLAG))
-		fshared = 1;
+		flags |= FLAGS_SHARED;
 
-	clockrt = op & FUTEX_CLOCK_REALTIME;
-	if (clockrt && cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI)
-		return -ENOSYS;
+	if (op & FUTEX_CLOCK_REALTIME) {
+		flags |= FLAGS_CLOCKRT;
+		if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI)
+			return -ENOSYS;
+	}
 
 	switch (cmd) {
 	case FUTEX_WAIT:
 		val3 = FUTEX_BITSET_MATCH_ANY;
 	case FUTEX_WAIT_BITSET:
-		ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt);
+		ret = futex_wait(uaddr, flags, val, timeout, val3);
 		break;
 	case FUTEX_WAKE:
 		val3 = FUTEX_BITSET_MATCH_ANY;
 	case FUTEX_WAKE_BITSET:
-		ret = futex_wake(uaddr, fshared, val, val3);
+		ret = futex_wake(uaddr, flags, val, val3);
 		break;
 	case FUTEX_REQUEUE:
-		ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL, 0);
+		ret = futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0);
 		break;
 	case FUTEX_CMP_REQUEUE:
-		ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3,
-				    0);
+		ret = futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0);
 		break;
 	case FUTEX_WAKE_OP:
-		ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3);
+		ret = futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
 		break;
 	case FUTEX_LOCK_PI:
 		if (futex_cmpxchg_enabled)
-			ret = futex_lock_pi(uaddr, fshared, val, timeout, 0);
+			ret = futex_lock_pi(uaddr, flags, val, timeout, 0);
 		break;
 	case FUTEX_UNLOCK_PI:
 		if (futex_cmpxchg_enabled)
-			ret = futex_unlock_pi(uaddr, fshared);
+			ret = futex_unlock_pi(uaddr, flags);
 		break;
 	case FUTEX_TRYLOCK_PI:
 		if (futex_cmpxchg_enabled)
-			ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1);
+			ret = futex_lock_pi(uaddr, flags, 0, timeout, 1);
 		break;
 	case FUTEX_WAIT_REQUEUE_PI:
 		val3 = FUTEX_BITSET_MATCH_ANY;
-		ret = futex_wait_requeue_pi(uaddr, fshared, val, timeout, val3,
-					    clockrt, uaddr2);
+		ret = futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,
+					    uaddr2);
 		break;
 	case FUTEX_CMP_REQUEUE_PI:
-		ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3,
-				    1);
+		ret = futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1);
 		break;
 	default:
 		ret = -ENOSYS;
-- 
1.7.1

[PATCH 3/3] futex: add futex_q static initializer

[Darren Hart]

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.

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: John Kacur <jkacur@redhat.com>
---
 kernel/futex.c |   25 ++++++++++---------------
 1 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 8502498..4a10d44 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -131,6 +131,12 @@ struct futex_q {
 	u32 bitset;
 };
 
+#define FUTEX_Q_INIT \
+	{ /* list gets initialized in queue_me()*/ \
+	  .task = NULL, NULL, FUTEX_KEY_INIT \
+	, NULL, NULL, NULL, 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, 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, int flags, u32 val, ktime_t *abs_time,
 	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, 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, 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, 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, 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;
-- 
1.7.1

Re: [1/3] futex: fix compiler warnings in exit_robust_list

[Uwe Kleine-König]

Hey Darren,

On Wed, Oct 27, 2010 at 09:54:24PM -0000, Darren Hart wrote:
> The following commit introduced a compiler warning:
> 
> Commit 1dcc41bb037533839753df983d31778b30b67d93
> futex: Change 3rd arg of fetch_robust_entry() to unsigned int*
> 
> The following archs/compiler versions all report:
> kernel/futex.c: In function ‘exit_robust_list’:
> kernel/futex.c:2492: warning: ‘next_pi’ may be used uninitialized in this function
> 
> x86_64
> gcc (Ubuntu 4.4.3-4ubuntu5) 4.4.3
> gcc (GCC) 4.4.4 20100630 (Red Hat 4.4.4-10)
> gcc (Ubuntu/Linaro 4.4.4-14ubuntu5) 4.4.5
> 
> sh
> sh-linux-gnu-gcc (Sourcery G++ Lite 4.3-143) 4.3.3
You can add

arm
arm-1136jfs-linux-gnueabi-gcc (OSELAS.Toolchain-1.99.3) 4.3.2

if you want.

> 
> The code path really can't result in next_pi pi being unitialized (or should
> not), but let's keep the build clean. Assign next_pi = 0 to avoid the warnings.
> 
> Signed-off-by: Darren Hart <dvhart@linux.intel.com>
> Tested-by: Matt Fleming <matt@console-pimps.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@elte.hu>
> CC: Eric Dumazet <eric.dumazet@gmail.com>
> CC: John Kacur <jkacur@redhat.com>
> 
> ---
> kernel/futex.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/futex.c b/kernel/futex.c
> index a118bf1..78715cb 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -2489,7 +2489,7 @@ void exit_robust_list(struct task_struct *curr)
>  {
>  	struct robust_list_head __user *head = curr->robust_list;
>  	struct robust_list __user *entry, *next_entry, *pending;
> -	unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
> +	unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi = 0, pip;
I'd prefer

+	unsigned int limit = ROBUST_LIST_LIMIT, pi, uninitialized_var(next_pi), pip;

(modulo line length).  This makes your change more explicit.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

[PATCH V2] futex: fix compiler warnings in exit_robust_list

[Darren Hart]

The following commit introduced a compiler warning:

Commit 1dcc41bb037533839753df983d31778b30b67d93
futex: Change 3rd arg of fetch_robust_entry() to unsigned int*

The following archs/compiler versions all report:
kernel/futex.c: In function ‘exit_robust_list’:
kernel/futex.c:2492: warning: ‘next_pi’ may be used uninitialized in this function

x86_64
gcc (Ubuntu 4.4.3-4ubuntu5) 4.4.3
gcc (GCC) 4.4.4 20100630 (Red Hat 4.4.4-10)
gcc (Ubuntu/Linaro 4.4.4-14ubuntu5) 4.4.5

sh
sh-linux-gnu-gcc (Sourcery G++ Lite 4.3-143) 4.3.3

arm
arm-1136jfs-linux-gnueabi-gcc (OSELAS.Toolchain-1.99.3) 4.3.2

The code path really can't result in next_pi being unitialized (or should
not), but let's keep the build clean. Annotate next_pi as an uninitialized_var.

V2: Implement Uwe's suggestion to use uninitialized_var()

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Tested-by: Matt Fleming <matt@console-pimps.org>
Tested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: John Kacur <jkacur@redhat.com>
---
 kernel/futex.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 6c683b3..40a8777 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2489,7 +2489,8 @@ void exit_robust_list(struct task_struct *curr)
 {
 	struct robust_list_head __user *head = curr->robust_list;
 	struct robust_list __user *entry, *next_entry, *pending;
-	unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
+	unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
+	unsigned int uninitialized_var(next_pi);
 	unsigned long futex_offset;
 	int rc;
 
-- 
1.7.1

Re: [PATCH 3/3] futex: add futex_q static initializer

[Thomas Gleixner]

On Wed, 27 Oct 2010, Darren Hart wrote:

> 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.
> 
> Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@elte.hu>
> CC: Eric Dumazet <eric.dumazet@gmail.com>
> CC: John Kacur <jkacur@redhat.com>
> ---
>  kernel/futex.c |   25 ++++++++++---------------
>  1 files changed, 10 insertions(+), 15 deletions(-)
> 
> diff --git a/kernel/futex.c b/kernel/futex.c
> index 8502498..4a10d44 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -131,6 +131,12 @@ struct futex_q {
>  	u32 bitset;
>  };
>  
> +#define FUTEX_Q_INIT \
> +	{ /* list gets initialized in queue_me()*/ \
> +	  .task = NULL, NULL, FUTEX_KEY_INIT \
> +	, NULL, NULL, NULL, FUTEX_BITSET_MATCH_ANY }
> +

That should be a static readonly variable with a proper C99
initializer. 

Thanks,

	tglx

Re: [PATCH 2/3] futex: replace fshared and clockrt with combined flags

[Thomas Gleixner]

On Wed, 27 Oct 2010, Darren Hart wrote:
> -static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
> +static int futex_wake(u32 __user *uaddr, int flags, int nr_wake, u32 bitset)

Can we make the flags unsigned please ?

Aside of that it'd be nice to split out the patches which cleanup the
functions which do not use fshared anymore.

Thanks,

	tglx

Re: [PATCH 3/3] futex: add futex_q static initializer

[Peter Zijlstra]

On Mon, 2010-11-08 at 17:42 +0100, Thomas Gleixner wrote:
> > +#define FUTEX_Q_INIT \
> > +     { /* list gets initialized in queue_me()*/ \
> > +       .task = NULL, NULL, FUTEX_KEY_INIT \
> > +     , NULL, NULL, NULL, FUTEX_BITSET_MATCH_ANY }
> > +
> 
> That should be a static readonly variable with a proper C99
> initializer. 

Well, it doesn't need to actually be an existing variable, but yeah it
should definately use C99 initializers.

Re: [PATCH 3/3] futex: add futex_q static initializer

[Thomas Gleixner]

On Mon, 8 Nov 2010, Peter Zijlstra wrote:

> On Mon, 2010-11-08 at 17:42 +0100, Thomas Gleixner wrote:
> > > +#define FUTEX_Q_INIT \
> > > +     { /* list gets initialized in queue_me()*/ \
> > > +       .task = NULL, NULL, FUTEX_KEY_INIT \
> > > +     , NULL, NULL, NULL, FUTEX_BITSET_MATCH_ANY }
> > > +
> > 
> > That should be a static readonly variable with a proper C99
> > initializer. 
> 
> Well, it doesn't need to actually be an existing variable, but yeah it
> should definately use C99 initializers.

If you have multiple instances of q = q_init; the static variable is
more efficient vs. code/data size 

Thanks,

	tglx

[PATCH V2] futex: replace fshared and clockrt with combined flags

[Darren Hart]

In the early days we passed the mmap sem around. That became the
"int fshared" with the fast gup improvements. Then we added
"int clockrt" in places. This patch unifies these options as "flags" and
cleans up various calls which had fshared in their signature but no
longer used it.

V2: use unsigned int for the flags.

Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: John Kacur <jkacur@redhat.com>
---
 kernel/futex.c |  204 +++++++++++++++++++++++++++-----------------------------
 1 files changed, 98 insertions(+), 106 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 40a8777..fd3fbe1 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -69,6 +69,14 @@ int __read_mostly futex_cmpxchg_enabled;
 #define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
 
 /*
+ * Futex flags used to encode options to functions and preserve them across
+ * restarts.
+ */
+#define FLAGS_SHARED		0x01
+#define FLAGS_CLOCKRT		0x02
+#define FLAGS_HAS_TIMEOUT	0x04
+
+/*
  * Priority Inheritance state:
  */
 struct futex_pi_state {
@@ -284,7 +292,7 @@ again:
 }
 
 static inline
-void put_futex_key(int fshared, union futex_key *key)
+void put_futex_key(union futex_key *key)
 {
 	drop_futex_key_refs(key);
 }
@@ -870,7 +878,8 @@ double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
 /*
  * Wake up waiters matching bitset queued on this futex (uaddr).
  */
-static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
+static int futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake,
+		      u32 bitset)
 {
 	struct futex_hash_bucket *hb;
 	struct futex_q *this, *next;
@@ -881,7 +890,7 @@ static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
 	if (!bitset)
 		return -EINVAL;
 
-	ret = get_futex_key(uaddr, fshared, &key);
+	ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key);
 	if (unlikely(ret != 0))
 		goto out;
 
@@ -907,7 +916,7 @@ static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
 	}
 
 	spin_unlock(&hb->lock);
-	put_futex_key(fshared, &key);
+	put_futex_key(&key);
 out:
 	return ret;
 }
@@ -917,7 +926,7 @@ out:
  * to this virtual address:
  */
 static int
-futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
+futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2,
 	      int nr_wake, int nr_wake2, int op)
 {
 	union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
@@ -927,10 +936,10 @@ futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
 	int ret, op_ret;
 
 retry:
-	ret = get_futex_key(uaddr1, fshared, &key1);
+	ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1);
 	if (unlikely(ret != 0))
 		goto out;
-	ret = get_futex_key(uaddr2, fshared, &key2);
+	ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
 	if (unlikely(ret != 0))
 		goto out_put_key1;
 
@@ -962,11 +971,11 @@ retry_private:
 		if (ret)
 			goto out_put_keys;
 
-		if (!fshared)
+		if (!(flags & FLAGS_SHARED))
 			goto retry_private;
 
-		put_futex_key(fshared, &key2);
-		put_futex_key(fshared, &key1);
+		put_futex_key(&key2);
+		put_futex_key(&key1);
 		goto retry;
 	}
 
@@ -996,9 +1005,9 @@ retry_private:
 
 	double_unlock_hb(hb1, hb2);
 out_put_keys:
-	put_futex_key(fshared, &key2);
+	put_futex_key(&key2);
 out_put_key1:
-	put_futex_key(fshared, &key1);
+	put_futex_key(&key1);
 out:
 	return ret;
 }
@@ -1148,9 +1157,9 @@ static int futex_proxy_trylock_atomic(u32 __user *pifutex,
  * >=0 - on success, the number of tasks requeued or woken
  *  <0 - on error
  */
-static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
-			 int nr_wake, int nr_requeue, u32 *cmpval,
-			 int requeue_pi)
+static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
+			 u32 __user *uaddr2, int nr_wake, int nr_requeue,
+			 u32 *cmpval, int requeue_pi)
 {
 	union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
 	int drop_count = 0, task_count = 0, ret;
@@ -1191,10 +1200,10 @@ retry:
 		pi_state = NULL;
 	}
 
-	ret = get_futex_key(uaddr1, fshared, &key1);
+	ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1);
 	if (unlikely(ret != 0))
 		goto out;
-	ret = get_futex_key(uaddr2, fshared, &key2);
+	ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
 	if (unlikely(ret != 0))
 		goto out_put_key1;
 
@@ -1216,11 +1225,11 @@ retry_private:
 			if (ret)
 				goto out_put_keys;
 
-			if (!fshared)
+			if (!(flags & FLAGS_SHARED))
 				goto retry_private;
 
-			put_futex_key(fshared, &key2);
-			put_futex_key(fshared, &key1);
+			put_futex_key(&key2);
+			put_futex_key(&key1);
 			goto retry;
 		}
 		if (curval != *cmpval) {
@@ -1260,8 +1269,8 @@ retry_private:
 			break;
 		case -EFAULT:
 			double_unlock_hb(hb1, hb2);
-			put_futex_key(fshared, &key2);
-			put_futex_key(fshared, &key1);
+			put_futex_key(&key2);
+			put_futex_key(&key1);
 			ret = fault_in_user_writeable(uaddr2);
 			if (!ret)
 				goto retry;
@@ -1269,8 +1278,8 @@ retry_private:
 		case -EAGAIN:
 			/* The owner was exiting, try again. */
 			double_unlock_hb(hb1, hb2);
-			put_futex_key(fshared, &key2);
-			put_futex_key(fshared, &key1);
+			put_futex_key(&key2);
+			put_futex_key(&key1);
 			cond_resched();
 			goto retry;
 		default:
@@ -1352,9 +1361,9 @@ out_unlock:
 		drop_futex_key_refs(&key1);
 
 out_put_keys:
-	put_futex_key(fshared, &key2);
+	put_futex_key(&key2);
 out_put_key1:
-	put_futex_key(fshared, &key1);
+	put_futex_key(&key1);
 out:
 	if (pi_state != NULL)
 		free_pi_state(pi_state);
@@ -1494,7 +1503,7 @@ static void unqueue_me_pi(struct futex_q *q)
  * private futexes.
  */
 static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
-				struct task_struct *newowner, int fshared)
+				struct task_struct *newowner)
 {
 	u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
 	struct futex_pi_state *pi_state = q->pi_state;
@@ -1587,20 +1596,11 @@ handle_fault:
 	goto retry;
 }
 
-/*
- * In case we must use restart_block to restart a futex_wait,
- * we encode in the 'flags' shared capability
- */
-#define FLAGS_SHARED		0x01
-#define FLAGS_CLOCKRT		0x02
-#define FLAGS_HAS_TIMEOUT	0x04
-
 static long futex_wait_restart(struct restart_block *restart);
 
 /**
  * fixup_owner() - Post lock pi_state and corner case management
  * @uaddr:	user address of the futex
- * @fshared:	whether the futex is shared (1) or not (0)
  * @q:		futex_q (contains pi_state and access to the rt_mutex)
  * @locked:	if the attempt to take the rt_mutex succeeded (1) or not (0)
  *
@@ -1613,8 +1613,7 @@ static long futex_wait_restart(struct restart_block *restart);
  *  0 - success, lock not taken
  * <0 - on error (-EFAULT)
  */
-static int fixup_owner(u32 __user *uaddr, int fshared, struct futex_q *q,
-		       int locked)
+static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked)
 {
 	struct task_struct *owner;
 	int ret = 0;
@@ -1625,7 +1624,7 @@ static int fixup_owner(u32 __user *uaddr, int fshared, struct futex_q *q,
 		 * did a lock-steal - fix up the PI-state in that case:
 		 */
 		if (q->pi_state->owner != current)
-			ret = fixup_pi_state_owner(uaddr, q, current, fshared);
+			ret = fixup_pi_state_owner(uaddr, q, current);
 		goto out;
 	}
 
@@ -1652,7 +1651,7 @@ static int fixup_owner(u32 __user *uaddr, int fshared, struct futex_q *q,
 		 * lock. Fix the state up.
 		 */
 		owner = rt_mutex_owner(&q->pi_state->pi_mutex);
-		ret = fixup_pi_state_owner(uaddr, q, owner, fshared);
+		ret = fixup_pi_state_owner(uaddr, q, owner);
 		goto out;
 	}
 
@@ -1715,7 +1714,7 @@ static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
  * futex_wait_setup() - Prepare to wait on a futex
  * @uaddr:	the futex userspace address
  * @val:	the expected value
- * @fshared:	whether the futex is shared (1) or not (0)
+ * @flags:	futex flags (FLAGS_SHARED, etc.)
  * @q:		the associated futex_q
  * @hb:		storage for hash_bucket pointer to be returned to caller
  *
@@ -1728,7 +1727,7 @@ static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
  *  0 - uaddr contains val and hb has been locked
  * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlcoked
  */
-static int futex_wait_setup(u32 __user *uaddr, u32 val, int fshared,
+static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
 			   struct futex_q *q, struct futex_hash_bucket **hb)
 {
 	u32 uval;
@@ -1753,7 +1752,7 @@ static int futex_wait_setup(u32 __user *uaddr, u32 val, int fshared,
 	 */
 retry:
 	q->key = FUTEX_KEY_INIT;
-	ret = get_futex_key(uaddr, fshared, &q->key);
+	ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key);
 	if (unlikely(ret != 0))
 		return ret;
 
@@ -1769,10 +1768,10 @@ retry_private:
 		if (ret)
 			goto out;
 
-		if (!fshared)
+		if (!(flags & FLAGS_SHARED))
 			goto retry_private;
 
-		put_futex_key(fshared, &q->key);
+		put_futex_key(&q->key);
 		goto retry;
 	}
 
@@ -1783,12 +1782,12 @@ retry_private:
 
 out:
 	if (ret)
-		put_futex_key(fshared, &q->key);
+		put_futex_key(&q->key);
 	return ret;
 }
 
-static int futex_wait(u32 __user *uaddr, int fshared,
-		      u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
+static int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
+		      ktime_t *abs_time, u32 bitset)
 {
 	struct hrtimer_sleeper timeout, *to = NULL;
 	struct restart_block *restart;
@@ -1807,8 +1806,9 @@ static int futex_wait(u32 __user *uaddr, int fshared,
 	if (abs_time) {
 		to = &timeout;
 
-		hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME :
-				      CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+		hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ?
+				      CLOCK_REALTIME : CLOCK_MONOTONIC,
+				      HRTIMER_MODE_ABS);
 		hrtimer_init_sleeper(to, current);
 		hrtimer_set_expires_range_ns(&to->timer, *abs_time,
 					     current->timer_slack_ns);
@@ -1819,7 +1819,7 @@ retry:
 	 * Prepare to wait on uaddr. On success, holds hb lock and increments
 	 * q.key refs.
 	 */
-	ret = futex_wait_setup(uaddr, val, fshared, &q, &hb);
+	ret = futex_wait_setup(uaddr, val, flags, &q, &hb);
 	if (ret)
 		goto out;
 
@@ -1852,12 +1852,7 @@ retry:
 	restart->futex.val = val;
 	restart->futex.time = abs_time->tv64;
 	restart->futex.bitset = bitset;
-	restart->futex.flags = FLAGS_HAS_TIMEOUT;
-
-	if (fshared)
-		restart->futex.flags |= FLAGS_SHARED;
-	if (clockrt)
-		restart->futex.flags |= FLAGS_CLOCKRT;
+	restart->futex.flags = flags;
 
 	ret = -ERESTART_RESTARTBLOCK;
 
@@ -1873,7 +1868,6 @@ out:
 static long futex_wait_restart(struct restart_block *restart)
 {
 	u32 __user *uaddr = restart->futex.uaddr;
-	int fshared = 0;
 	ktime_t t, *tp = NULL;
 
 	if (restart->futex.flags & FLAGS_HAS_TIMEOUT) {
@@ -1881,11 +1875,9 @@ static long futex_wait_restart(struct restart_block *restart)
 		tp = &t;
 	}
 	restart->fn = do_no_restart_syscall;
-	if (restart->futex.flags & FLAGS_SHARED)
-		fshared = 1;
-	return (long)futex_wait(uaddr, fshared, restart->futex.val, tp,
-				restart->futex.bitset,
-				restart->futex.flags & FLAGS_CLOCKRT);
+
+	return (long)futex_wait(uaddr, restart->futex.flags,
+				restart->futex.val, tp, restart->futex.bitset);
 }
 
 
@@ -1895,8 +1887,8 @@ static long futex_wait_restart(struct restart_block *restart)
  * if there are waiters then it will block, it does PI, etc. (Due to
  * races the kernel might see a 0 value of the futex too.)
  */
-static int futex_lock_pi(u32 __user *uaddr, int fshared,
-			 int detect, ktime_t *time, int trylock)
+static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect,
+			 ktime_t *time, int trylock)
 {
 	struct hrtimer_sleeper timeout, *to = NULL;
 	struct futex_hash_bucket *hb;
@@ -1919,7 +1911,7 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared,
 	q.requeue_pi_key = NULL;
 retry:
 	q.key = FUTEX_KEY_INIT;
-	ret = get_futex_key(uaddr, fshared, &q.key);
+	ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key);
 	if (unlikely(ret != 0))
 		goto out;
 
@@ -1941,7 +1933,7 @@ retry_private:
 			 * exit to complete.
 			 */
 			queue_unlock(&q, hb);
-			put_futex_key(fshared, &q.key);
+			put_futex_key(&q.key);
 			cond_resched();
 			goto retry;
 		default:
@@ -1971,7 +1963,7 @@ retry_private:
 	 * Fixup the pi_state owner and possibly acquire the lock if we
 	 * haven't already.
 	 */
-	res = fixup_owner(uaddr, fshared, &q, !ret);
+	res = fixup_owner(uaddr, &q, !ret);
 	/*
 	 * If fixup_owner() returned an error, proprogate that.  If it acquired
 	 * the lock, clear our -ETIMEDOUT or -EINTR.
@@ -1995,7 +1987,7 @@ out_unlock_put_key:
 	queue_unlock(&q, hb);
 
 out_put_key:
-	put_futex_key(fshared, &q.key);
+	put_futex_key(&q.key);
 out:
 	if (to)
 		destroy_hrtimer_on_stack(&to->timer);
@@ -2008,10 +2000,10 @@ uaddr_faulted:
 	if (ret)
 		goto out_put_key;
 
-	if (!fshared)
+	if (!(flags & FLAGS_SHARED))
 		goto retry_private;
 
-	put_futex_key(fshared, &q.key);
+	put_futex_key(&q.key);
 	goto retry;
 }
 
@@ -2020,7 +2012,7 @@ uaddr_faulted:
  * This is the in-kernel slowpath: we look up the PI state (if any),
  * and do the rt-mutex unlock.
  */
-static int futex_unlock_pi(u32 __user *uaddr, int fshared)
+static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags)
 {
 	struct futex_hash_bucket *hb;
 	struct futex_q *this, *next;
@@ -2038,7 +2030,7 @@ retry:
 	if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current))
 		return -EPERM;
 
-	ret = get_futex_key(uaddr, fshared, &key);
+	ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key);
 	if (unlikely(ret != 0))
 		goto out;
 
@@ -2093,14 +2085,14 @@ retry:
 
 out_unlock:
 	spin_unlock(&hb->lock);
-	put_futex_key(fshared, &key);
+	put_futex_key(&key);
 
 out:
 	return ret;
 
 pi_faulted:
 	spin_unlock(&hb->lock);
-	put_futex_key(fshared, &key);
+	put_futex_key(&key);
 
 	ret = fault_in_user_writeable(uaddr);
 	if (!ret)
@@ -2160,7 +2152,7 @@ int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb,
 /**
  * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2
  * @uaddr:	the futex we initially wait on (non-pi)
- * @fshared:	whether the futexes are shared (1) or not (0).  They must be
+ * @flags:	futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be
  * 		the same type, no requeueing from private to shared, etc.
  * @val:	the expected value of uaddr
  * @abs_time:	absolute timeout
@@ -2198,9 +2190,9 @@ int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb,
  *  0 - On success
  * <0 - On error
  */
-static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
+static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 				 u32 val, ktime_t *abs_time, u32 bitset,
-				 int clockrt, u32 __user *uaddr2)
+				 u32 __user *uaddr2)
 {
 	struct hrtimer_sleeper timeout, *to = NULL;
 	struct rt_mutex_waiter rt_waiter;
@@ -2215,8 +2207,9 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
 
 	if (abs_time) {
 		to = &timeout;
-		hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME :
-				      CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+		hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ?
+				      CLOCK_REALTIME : CLOCK_MONOTONIC,
+				      HRTIMER_MODE_ABS);
 		hrtimer_init_sleeper(to, current);
 		hrtimer_set_expires_range_ns(&to->timer, *abs_time,
 					     current->timer_slack_ns);
@@ -2230,7 +2223,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
 	rt_waiter.task = NULL;
 
 	key2 = FUTEX_KEY_INIT;
-	ret = get_futex_key(uaddr2, fshared, &key2);
+	ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2);
 	if (unlikely(ret != 0))
 		goto out;
 
@@ -2243,7 +2236,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
 	 * Prepare to wait on uaddr. On success, increments q.key (key1) ref
 	 * count.
 	 */
-	ret = futex_wait_setup(uaddr, val, fshared, &q, &hb);
+	ret = futex_wait_setup(uaddr, val, flags, &q, &hb);
 	if (ret)
 		goto out_key2;
 
@@ -2273,8 +2266,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
 		 */
 		if (q.pi_state && (q.pi_state->owner != current)) {
 			spin_lock(q.lock_ptr);
-			ret = fixup_pi_state_owner(uaddr2, &q, current,
-						   fshared);
+			ret = fixup_pi_state_owner(uaddr2, &q, current);
 			spin_unlock(q.lock_ptr);
 		}
 	} else {
@@ -2293,7 +2285,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
 		 * Fixup the pi_state owner and possibly acquire the lock if we
 		 * haven't already.
 		 */
-		res = fixup_owner(uaddr2, fshared, &q, !ret);
+		res = fixup_owner(uaddr2, &q, !ret);
 		/*
 		 * If fixup_owner() returned an error, proprogate that.  If it
 		 * acquired the lock, clear -ETIMEDOUT or -EINTR.
@@ -2324,9 +2316,9 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
 	}
 
 out_put_keys:
-	put_futex_key(fshared, &q.key);
+	put_futex_key(&q.key);
 out_key2:
-	put_futex_key(fshared, &key2);
+	put_futex_key(&key2);
 
 out:
 	if (to) {
@@ -2551,58 +2543,58 @@ void exit_robust_list(struct task_struct *curr)
 long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
 		u32 __user *uaddr2, u32 val2, u32 val3)
 {
-	int clockrt, ret = -ENOSYS;
+	int ret = -ENOSYS;
 	int cmd = op & FUTEX_CMD_MASK;
-	int fshared = 0;
+	unsigned int flags = 0;
 
 	if (!(op & FUTEX_PRIVATE_FLAG))
-		fshared = 1;
+		flags |= FLAGS_SHARED;
 
-	clockrt = op & FUTEX_CLOCK_REALTIME;
-	if (clockrt && cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI)
-		return -ENOSYS;
+	if (op & FUTEX_CLOCK_REALTIME) {
+		flags |= FLAGS_CLOCKRT;
+		if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI)
+			return -ENOSYS;
+	}
 
 	switch (cmd) {
 	case FUTEX_WAIT:
 		val3 = FUTEX_BITSET_MATCH_ANY;
 	case FUTEX_WAIT_BITSET:
-		ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt);
+		ret = futex_wait(uaddr, flags, val, timeout, val3);
 		break;
 	case FUTEX_WAKE:
 		val3 = FUTEX_BITSET_MATCH_ANY;
 	case FUTEX_WAKE_BITSET:
-		ret = futex_wake(uaddr, fshared, val, val3);
+		ret = futex_wake(uaddr, flags, val, val3);
 		break;
 	case FUTEX_REQUEUE:
-		ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL, 0);
+		ret = futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0);
 		break;
 	case FUTEX_CMP_REQUEUE:
-		ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3,
-				    0);
+		ret = futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0);
 		break;
 	case FUTEX_WAKE_OP:
-		ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3);
+		ret = futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
 		break;
 	case FUTEX_LOCK_PI:
 		if (futex_cmpxchg_enabled)
-			ret = futex_lock_pi(uaddr, fshared, val, timeout, 0);
+			ret = futex_lock_pi(uaddr, flags, val, timeout, 0);
 		break;
 	case FUTEX_UNLOCK_PI:
 		if (futex_cmpxchg_enabled)
-			ret = futex_unlock_pi(uaddr, fshared);
+			ret = futex_unlock_pi(uaddr, flags);
 		break;
 	case FUTEX_TRYLOCK_PI:
 		if (futex_cmpxchg_enabled)
-			ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1);
+			ret = futex_lock_pi(uaddr, flags, 0, timeout, 1);
 		break;
 	case FUTEX_WAIT_REQUEUE_PI:
 		val3 = FUTEX_BITSET_MATCH_ANY;
-		ret = futex_wait_requeue_pi(uaddr, fshared, val, timeout, val3,
-					    clockrt, uaddr2);
+		ret = futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,
+					    uaddr2);
 		break;
 	case FUTEX_CMP_REQUEUE_PI:
-		ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3,
-				    1);
+		ret = futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1);
 		break;
 	default:
 		ret = -ENOSYS;
-- 
1.7.1

[PATCH V2] futex: add futex_q static initializer

[Darren Hart]

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.

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: John Kacur <jkacur@redhat.com>
---
 kernel/futex.c |   25 ++++++++++---------------
 1 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index fd3fbe1..1eea066 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -131,6 +131,12 @@ struct futex_q {
 	u32 bitset;
 };
 
+static 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
@@ -1751,7 +1757,6 @@ 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;
@@ -1792,16 +1797,12 @@ 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;
@@ -1892,7 +1893,7 @@ 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())
@@ -1906,11 +1907,7 @@ 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;
@@ -2198,8 +2195,8 @@ 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)
@@ -2222,12 +2219,10 @@ 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;
-- 
1.7.1

[PATCH V3] futex: add futex_q static initializer

[Darren Hart]

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: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: John Kacur <jkacur@redhat.com>
---
 kernel/futex.c |   25 ++++++++++---------------
 1 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index fd3fbe1..e6df2de 100644
--- 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
@@ -1751,7 +1757,6 @@ 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;
@@ -1792,16 +1797,12 @@ 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;
@@ -1892,7 +1893,7 @@ 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())
@@ -1906,11 +1907,7 @@ 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;
@@ -2198,8 +2195,8 @@ 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)
@@ -2222,12 +2219,10 @@ 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;
-- 
1.7.1

Re: [PATCH V3] futex: add futex_q static initializer

[Thomas Gleixner]

On Mon, 8 Nov 2010, Darren Hart wrote:

> 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: Thomas Gleixner <tglx@linutronix.de>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@elte.hu>
> CC: Eric Dumazet <eric.dumazet@gmail.com>
> CC: John Kacur <jkacur@redhat.com>
> ---
>  kernel/futex.c |   25 ++++++++++---------------
>  1 files changed, 10 insertions(+), 15 deletions(-)
> 
> diff --git a/kernel/futex.c b/kernel/futex.c
> index fd3fbe1..e6df2de 100644
> --- 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
> @@ -1751,7 +1757,6 @@ static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
>  	 * rare, but normal.
>  	 */
>  retry:
> -	q->key = FUTEX_KEY_INIT;

You sure about that one in the retry path ?

> @@ -1906,11 +1907,7 @@ 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;

Ditto

Thanks,

	tglx

Re: [PATCH V3] futex: add futex_q static initializer

[Darren Hart]

On 11/08/2010 01:48 PM, Thomas Gleixner wrote:
> On Mon, 8 Nov 2010, Darren Hart wrote:

>>   /*
>>    * 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
>> @@ -1751,7 +1757,6 @@ static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
>>   	 * rare, but normal.
>>   	 */
>>   retry:
>> -	q->key = FUTEX_KEY_INIT;
>
> You sure about that one in the retry path ?
>
>> @@ -1906,11 +1907,7 @@ 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;
>
> Ditto

Yes, these are fine. get_futex_key (called immediately after retry: in 
both cases) will set the mm or inode or error out. On error we return 
immediately. No need to zero both.ptr.

Thanks,

-- 
Darren Hart
Embedded Linux Kernel

Re: [PATCH V2] futex: fix compiler warnings in exit_robust_list

[Thomas Gleixner]

On Thu, 4 Nov 2010, Darren Hart wrote:

> The following commit introduced a compiler warning:
> 
> Commit 1dcc41bb037533839753df983d31778b30b67d93
> futex: Change 3rd arg of fetch_robust_entry() to unsigned int*

This makes not really sense. That commit changed "int *pi" to
"unsigned int *pi" which did not introduce the warning by any
means. It's gcc being stupid, in fact it should have warned before
that change already.

And your patch is incomplete as it forgot to fix the same problem in
futex_compat.c

/me fixes

Re: [tip:core/urgent] futex: Address compiler warnings in exit_robust_list

[Darren Hart]

On 11/10/2010 04:30 AM, tip-bot for Darren Hart wrote:
> Commit-ID:  4c115e951d80aff126468adaec7a6c7854f61ab8
> Gitweb:     http://git.kernel.org/tip/4c115e951d80aff126468adaec7a6c7854f61ab8
> Author:     Darren Hart<dvhart@linux.intel.com>
> AuthorDate: Thu, 4 Nov 2010 15:00:00 -0400
> Committer:  Thomas Gleixner<tglx@linutronix.de>
> CommitDate: Wed, 10 Nov 2010 13:27:50 +0100
>
> futex: Address compiler warnings in exit_robust_list
>
> Since commit 1dcc41bb (futex: Change 3rd arg of fetch_robust_entry()
> to unsigned int*) some gcc versions decided to emit the following
> warning:
>
> kernel/futex.c: In function ‘exit_robust_list’:
> kernel/futex.c:2492: warning: ‘next_pi’ may be used uninitialized in this function
>
> The commit did not introduce the warning as gcc should have warned
> before that commit as well. It's just gcc being silly.


I agree that it should not have - but I did the bisect and this is the 
patch where the warning was first observed. I agree that it is still gcc 
being silly, and I don't know why it treats uninitialized ints different 
than uninitialized unsigned ints (or why it thinks this value is every 
used uninitialized for that matter).

Thanks for catching the compat-futex.c

--
Darren

>
> The code path really can't result in next_pi being unitialized (or
> should not), but let's keep the build clean. Annotate next_pi as an
> uninitialized_var.
>
> [ tglx: Addressed the same issue in futex_compat.c and massaged the
>    	changelog ]
>
> Signed-off-by: Darren Hart<dvhart@linux.intel.com>
> Tested-by: Matt Fleming<matt@console-pimps.org>
> Tested-by: Uwe Kleine-König<u.kleine-koenig@pengutronix.de>
> 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:<1288897200-13008-1-git-send-email-dvhart@linux.intel.com>
> Signed-off-by: Thomas Gleixner<tglx@linutronix.de>
> ---
>   kernel/futex.c        |    3 ++-
>   kernel/futex_compat.c |    3 ++-
>   2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/futex.c b/kernel/futex.c
> index 6c683b3..40a8777 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -2489,7 +2489,8 @@ void exit_robust_list(struct task_struct *curr)
>   {
>   	struct robust_list_head __user *head = curr->robust_list;
>   	struct robust_list __user *entry, *next_entry, *pending;
> -	unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
> +	unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
> +	unsigned int uninitialized_var(next_pi);
>   	unsigned long futex_offset;
>   	int rc;
>
> diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c
> index 06da4df..a7934ac 100644
> --- a/kernel/futex_compat.c
> +++ b/kernel/futex_compat.c
> @@ -49,7 +49,8 @@ void compat_exit_robust_list(struct task_struct *curr)
>   {
>   	struct compat_robust_list_head __user *head = curr->compat_robust_list;
>   	struct robust_list __user *entry, *next_entry, *pending;
> -	unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
> +	unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
> +	unsigned int uninitialized_var(next_pi);
>   	compat_uptr_t uentry, next_uentry, upending;
>   	compat_long_t futex_offset;
>   	int rc;


-- 
Darren Hart
Embedded Linux Kernel

Re: [tip:core/urgent] futex: Address compiler warnings in exit_robust_list

[Uwe Kleine-König]

Hallo Thomas,

On Wed, Nov 10, 2010 at 12:30:44PM +0000, tip-bot for Darren Hart wrote:
> Commit-ID:  4c115e951d80aff126468adaec7a6c7854f61ab8
> Gitweb:     http://git.kernel.org/tip/4c115e951d80aff126468adaec7a6c7854f61ab8
> Author:     Darren Hart <dvhart@linux.intel.com>
> AuthorDate: Thu, 4 Nov 2010 15:00:00 -0400
> Committer:  Thomas Gleixner <tglx@linutronix.de>
> CommitDate: Wed, 10 Nov 2010 13:27:50 +0100
> 
> futex: Address compiler warnings in exit_robust_list
> 
> Since commit 1dcc41bb (futex: Change 3rd arg of fetch_robust_entry()
> to unsigned int*) some gcc versions decided to emit the following
> warning:
> 
> kernel/futex.c: In function ‘exit_robust_list’:
> kernel/futex.c:2492: warning: ‘next_pi’ may be used uninitialized in this function
> 
> The commit did not introduce the warning as gcc should have warned
> before that commit as well. It's just gcc being silly.
> 
> The code path really can't result in next_pi being unitialized (or
> should not), but let's keep the build clean. Annotate next_pi as an
> uninitialized_var.
> 
> [ tglx: Addressed the same issue in futex_compat.c and massaged the
>   	changelog ]
> 
> Signed-off-by: Darren Hart <dvhart@linux.intel.com>
> Tested-by: Matt Fleming <matt@console-pimps.org>
> Tested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
I don't care much (at least until someone claims this change to
introduce a regression), but I didn't test it.  I only suggested to use 
uninitialized_var instead of = 0.

Thanks
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

Re: [tip:core/urgent] futex: Address compiler warnings in exit_robust_list

[Darren Hart]

2010/11/10 Uwe Kleine-König <u.kleine-koenig@pengutronix.de>:
> Hallo Thomas,
>
> On Wed, Nov 10, 2010 at 12:30:44PM +0000, tip-bot for Darren Hart wrote:
>> Commit-ID:  4c115e951d80aff126468adaec7a6c7854f61ab8
>> Gitweb:     http://git.kernel.org/tip/4c115e951d80aff126468adaec7a6c7854f61ab8
>> Author:     Darren Hart <dvhart@linux.intel.com>
>> AuthorDate: Thu, 4 Nov 2010 15:00:00 -0400
>> Committer:  Thomas Gleixner <tglx@linutronix.de>
>> CommitDate: Wed, 10 Nov 2010 13:27:50 +0100
>>
>> futex: Address compiler warnings in exit_robust_list
>>
>> Since commit 1dcc41bb (futex: Change 3rd arg of fetch_robust_entry()
>> to unsigned int*) some gcc versions decided to emit the following
>> warning:
>>
>> kernel/futex.c: In function ‘exit_robust_list’:
>> kernel/futex.c:2492: warning: ‘next_pi’ may be used uninitialized in this function
>>
>> The commit did not introduce the warning as gcc should have warned
>> before that commit as well. It's just gcc being silly.
>>
>> The code path really can't result in next_pi being unitialized (or
>> should not), but let's keep the build clean. Annotate next_pi as an
>> uninitialized_var.
>>
>> [ tglx: Addressed the same issue in futex_compat.c and massaged the
>>       changelog ]
>>
>> Signed-off-by: Darren Hart <dvhart@linux.intel.com>
>> Tested-by: Matt Fleming <matt@console-pimps.org>
>> Tested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> I don't care much (at least until someone claims this change to
> introduce a regression), but I didn't test it.  I only suggested to use
> uninitialized_var instead of = 0.
>

Uwe, I added you after you said I could add the ARM platform and
compiler to the list. I took that to mean you had confirmed that the
patch fixed the warning on that platform. I apologize as this is
apparently not the case.

--
Darren

Re: [tip:core/urgent] futex: Address compiler warnings in exit_robust_list

[Darren Hart]

On 11/10/2010 12:16 PM, Uwe Kleine-König wrote:
> Hallo Thomas,
>
> On Wed, Nov 10, 2010 at 12:30:44PM +0000, tip-bot for Darren Hart wrote:
>> Commit-ID:  4c115e951d80aff126468adaec7a6c7854f61ab8
>> Gitweb:     http://git.kernel.org/tip/4c115e951d80aff126468adaec7a6c7854f61ab8
>> Author:     Darren Hart<dvhart@linux.intel.com>
>> AuthorDate: Thu, 4 Nov 2010 15:00:00 -0400
>> Committer:  Thomas Gleixner<tglx@linutronix.de>
>> CommitDate: Wed, 10 Nov 2010 13:27:50 +0100
>>
>> futex: Address compiler warnings in exit_robust_list
>>
>> Since commit 1dcc41bb (futex: Change 3rd arg of fetch_robust_entry()
>> to unsigned int*) some gcc versions decided to emit the following
>> warning:
>>
>> kernel/futex.c: In function ‘exit_robust_list’:
>> kernel/futex.c:2492: warning: ‘next_pi’ may be used uninitialized in this function
>>
>> The commit did not introduce the warning as gcc should have warned
>> before that commit as well. It's just gcc being silly.
>>
>> The code path really can't result in next_pi being unitialized (or
>> should not), but let's keep the build clean. Annotate next_pi as an
>> uninitialized_var.
>>
>> [ tglx: Addressed the same issue in futex_compat.c and massaged the
>>    	changelog ]
>>
>> Signed-off-by: Darren Hart<dvhart@linux.intel.com>
>> Tested-by: Matt Fleming<matt@console-pimps.org>
>> Tested-by: Uwe Kleine-König<u.kleine-koenig@pengutronix.de>
> I don't care much (at least until someone claims this change to
> introduce a regression), but I didn't test it.  I only suggested to use
> uninitialized_var instead of = 0.


Uwe,

I added you after you said I could add the ARM platform and compiler to 
the list. I took that to mean you had confirmed that the patch fixed the 
warning on that platform. I apologize as this is apparently not the case.

--
Darren