Merge tag 'v3.12-rc4' into next

Merge with mainline to bring in changes to input subsystem that were
committed through other trees.

6 files changed, 410 insertions, 308 deletions

diff --git a/ipc/msg.c b/ipc/msg.c
index 9f29d9e89bac..558aa91186b6 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -70,8 +70,6 @@ struct msg_sender {
 
 #define msg_ids(ns)	((ns)->ids[IPC_MSG_IDS])
 
-#define msg_unlock(msq)		ipc_unlock(&(msq)->q_perm)
-
 static void freeque(struct ipc_namespace *, struct kern_ipc_perm *);
 static int newque(struct ipc_namespace *, struct ipc_params *);
 #ifdef CONFIG_PROC_FS
@@ -167,12 +165,21 @@ static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
 	ipc_rmid(&msg_ids(ns), &s->q_perm);
 }
 
+static void msg_rcu_free(struct rcu_head *head)
+{
+	struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
+	struct msg_queue *msq = ipc_rcu_to_struct(p);
+
+	security_msg_queue_free(msq);
+	ipc_rcu_free(head);
+}
+
 /**
  * newque - Create a new msg queue
  * @ns: namespace
  * @params: ptr to the structure that contains the key and msgflg
  *
- * Called with msg_ids.rw_mutex held (writer)
+ * Called with msg_ids.rwsem held (writer)
  */
 static int newque(struct ipc_namespace *ns, struct ipc_params *params)
 {
@@ -191,15 +198,14 @@ static int newque(struct ipc_namespace *ns, struct ipc_params *params)
 	msq->q_perm.security = NULL;
 	retval = security_msg_queue_alloc(msq);
 	if (retval) {
-		ipc_rcu_putref(msq);
+		ipc_rcu_putref(msq, ipc_rcu_free);
 		return retval;
 	}
 
 	/* ipc_addid() locks msq upon success. */
 	id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
 	if (id < 0) {
-		security_msg_queue_free(msq);
-		ipc_rcu_putref(msq);
+		ipc_rcu_putref(msq, msg_rcu_free);
 		return id;
 	}
 
@@ -259,8 +265,8 @@ static void expunge_all(struct msg_queue *msq, int res)
  * removes the message queue from message queue ID IDR, and cleans up all the
  * messages associated with this queue.
  *
- * msg_ids.rw_mutex (writer) and the spinlock for this message queue are held
- * before freeque() is called. msg_ids.rw_mutex remains locked on exit.
+ * msg_ids.rwsem (writer) and the spinlock for this message queue are held
+ * before freeque() is called. msg_ids.rwsem remains locked on exit.
  */
 static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 {
@@ -270,19 +276,19 @@ static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 	expunge_all(msq, -EIDRM);
 	ss_wakeup(&msq->q_senders, 1);
 	msg_rmid(ns, msq);
-	msg_unlock(msq);
+	ipc_unlock_object(&msq->q_perm);
+	rcu_read_unlock();
 
 	list_for_each_entry_safe(msg, t, &msq->q_messages, m_list) {
 		atomic_dec(&ns->msg_hdrs);
 		free_msg(msg);
 	}
 	atomic_sub(msq->q_cbytes, &ns->msg_bytes);
-	security_msg_queue_free(msq);
-	ipc_rcu_putref(msq);
+	ipc_rcu_putref(msq, msg_rcu_free);
 }
 
 /*
- * Called with msg_ids.rw_mutex and ipcp locked.
+ * Called with msg_ids.rwsem and ipcp locked.
  */
 static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
 {
@@ -386,9 +392,9 @@ copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
 }
 
 /*
- * This function handles some msgctl commands which require the rw_mutex
+ * This function handles some msgctl commands which require the rwsem
  * to be held in write mode.
- * NOTE: no locks must be held, the rw_mutex is taken inside this function.
+ * NOTE: no locks must be held, the rwsem is taken inside this function.
  */
 static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 		       struct msqid_ds __user *buf, int version)
@@ -403,7 +409,7 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 			return -EFAULT;
 	}
 
-	down_write(&msg_ids(ns).rw_mutex);
+	down_write(&msg_ids(ns).rwsem);
 	rcu_read_lock();
 
 	ipcp = ipcctl_pre_down_nolock(ns, &msg_ids(ns), msqid, cmd,
@@ -459,7 +465,7 @@ out_unlock0:
 out_unlock1:
 	rcu_read_unlock();
 out_up:
-	up_write(&msg_ids(ns).rw_mutex);
+	up_write(&msg_ids(ns).rwsem);
 	return err;
 }
 
@@ -494,7 +500,7 @@ static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
 		msginfo.msgmnb = ns->msg_ctlmnb;
 		msginfo.msgssz = MSGSSZ;
 		msginfo.msgseg = MSGSEG;
-		down_read(&msg_ids(ns).rw_mutex);
+		down_read(&msg_ids(ns).rwsem);
 		if (cmd == MSG_INFO) {
 			msginfo.msgpool = msg_ids(ns).in_use;
 			msginfo.msgmap = atomic_read(&ns->msg_hdrs);
@@ -505,7 +511,7 @@ static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
 			msginfo.msgtql = MSGTQL;
 		}
 		max_id = ipc_get_maxid(&msg_ids(ns));
-		up_read(&msg_ids(ns).rw_mutex);
+		up_read(&msg_ids(ns).rwsem);
 		if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
 			return -EFAULT;
 		return (max_id < 0) ? 0 : max_id;
@@ -680,16 +686,24 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
 		goto out_unlock1;
 	}
 
+	ipc_lock_object(&msq->q_perm);
+
 	for (;;) {
 		struct msg_sender s;
 
 		err = -EACCES;
 		if (ipcperms(ns, &msq->q_perm, S_IWUGO))
-			goto out_unlock1;
+			goto out_unlock0;
+
+		/* raced with RMID? */
+		if (msq->q_perm.deleted) {
+			err = -EIDRM;
+			goto out_unlock0;
+		}
 
 		err = security_msg_queue_msgsnd(msq, msg, msgflg);
 		if (err)
-			goto out_unlock1;
+			goto out_unlock0;
 
 		if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
 				1 + msq->q_qnum <= msq->q_qbytes) {
@@ -699,10 +713,9 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
 		/* queue full, wait: */
 		if (msgflg & IPC_NOWAIT) {
 			err = -EAGAIN;
-			goto out_unlock1;
+			goto out_unlock0;
 		}
 
-		ipc_lock_object(&msq->q_perm);
 		ss_add(msq, &s);
 
 		if (!ipc_rcu_getref(msq)) {
@@ -717,7 +730,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
 		rcu_read_lock();
 		ipc_lock_object(&msq->q_perm);
 
-		ipc_rcu_putref(msq);
+		ipc_rcu_putref(msq, ipc_rcu_free);
 		if (msq->q_perm.deleted) {
 			err = -EIDRM;
 			goto out_unlock0;
@@ -730,10 +743,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
 			goto out_unlock0;
 		}
 
-		ipc_unlock_object(&msq->q_perm);
 	}
-
-	ipc_lock_object(&msq->q_perm);
 	msq->q_lspid = task_tgid_vnr(current);
 	msq->q_stime = get_seconds();
 
@@ -897,6 +907,13 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgfl
 			goto out_unlock1;
 
 		ipc_lock_object(&msq->q_perm);
+
+		/* raced with RMID? */
+		if (msq->q_perm.deleted) {
+			msg = ERR_PTR(-EIDRM);
+			goto out_unlock0;
+		}
+
 		msg = find_msg(msq, &msgtyp, mode);
 		if (!IS_ERR(msg)) {
 			/*
diff --git a/ipc/namespace.c b/ipc/namespace.c
index 7ee61bf44933..59451c1e214d 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -81,7 +81,7 @@ void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
 	int next_id;
 	int total, in_use;
 
-	down_write(&ids->rw_mutex);
+	down_write(&ids->rwsem);
 
 	in_use = ids->in_use;
 
@@ -89,11 +89,12 @@ void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
 		perm = idr_find(&ids->ipcs_idr, next_id);
 		if (perm == NULL)
 			continue;
-		ipc_lock_by_ptr(perm);
+		rcu_read_lock();
+		ipc_lock_object(perm);
 		free(ns, perm);
 		total++;
 	}
-	up_write(&ids->rw_mutex);
+	up_write(&ids->rwsem);
 }
 
 static void free_ipc_ns(struct ipc_namespace *ns)
@@ -171,7 +172,7 @@ static int ipcns_install(struct nsproxy *nsproxy, void *new)
 {
 	struct ipc_namespace *ns = new;
 	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
-	    !nsown_capable(CAP_SYS_ADMIN))
+	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 		return -EPERM;
 
 	/* Ditch state from the old ipc namespace */
diff --git a/ipc/sem.c b/ipc/sem.c
index 41088899783d..8c4f59b0204a 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -243,71 +243,122 @@ static void merge_queues(struct sem_array *sma)
 	}
 }
 
+static void sem_rcu_free(struct rcu_head *head)
+{
+	struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
+	struct sem_array *sma = ipc_rcu_to_struct(p);
+
+	security_sem_free(sma);
+	ipc_rcu_free(head);
+}
+
+/*
+ * Wait until all currently ongoing simple ops have completed.
+ * Caller must own sem_perm.lock.
+ * New simple ops cannot start, because simple ops first check
+ * that sem_perm.lock is free.
+ * that a) sem_perm.lock is free and b) complex_count is 0.
+ */
+static void sem_wait_array(struct sem_array *sma)
+{
+	int i;
+	struct sem *sem;
+
+	if (sma->complex_count)  {
+		/* The thread that increased sma->complex_count waited on
+		 * all sem->lock locks. Thus we don't need to wait again.
+		 */
+		return;
+	}
+
+	for (i = 0; i < sma->sem_nsems; i++) {
+		sem = sma->sem_base + i;
+		spin_unlock_wait(&sem->lock);
+	}
+}
+
 /*
  * If the request contains only one semaphore operation, and there are
  * no complex transactions pending, lock only the semaphore involved.
  * Otherwise, lock the entire semaphore array, since we either have
  * multiple semaphores in our own semops, or we need to look at
  * semaphores from other pending complex operations.
- *
- * Carefully guard against sma->complex_count changing between zero
- * and non-zero while we are spinning for the lock. The value of
- * sma->complex_count cannot change while we are holding the lock,
- * so sem_unlock should be fine.
- *
- * The global lock path checks that all the local locks have been released,
- * checking each local lock once. This means that the local lock paths
- * cannot start their critical sections while the global lock is held.
  */
 static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
 			      int nsops)
 {
-	int locknum;
- again:
-	if (nsops == 1 && !sma->complex_count) {
-		struct sem *sem = sma->sem_base + sops->sem_num;
+	struct sem *sem;
 
-		/* Lock just the semaphore we are interested in. */
-		spin_lock(&sem->lock);
+	if (nsops != 1) {
+		/* Complex operation - acquire a full lock */
+		ipc_lock_object(&sma->sem_perm);
 
-		/*
-		 * If sma->complex_count was set while we were spinning,
-		 * we may need to look at things we did not lock here.
+		/* And wait until all simple ops that are processed
+		 * right now have dropped their locks.
 		 */
-		if (unlikely(sma->complex_count)) {
-			spin_unlock(&sem->lock);
-			goto lock_array;
-		}
+		sem_wait_array(sma);
+		return -1;
+	}
+
+	/*
+	 * Only one semaphore affected - try to optimize locking.
+	 * The rules are:
+	 * - optimized locking is possible if no complex operation
+	 *   is either enqueued or processed right now.
+	 * - The test for enqueued complex ops is simple:
+	 *      sma->complex_count != 0
+	 * - Testing for complex ops that are processed right now is
+	 *   a bit more difficult. Complex ops acquire the full lock
+	 *   and first wait that the running simple ops have completed.
+	 *   (see above)
+	 *   Thus: If we own a simple lock and the global lock is free
+	 *	and complex_count is now 0, then it will stay 0 and
+	 *	thus just locking sem->lock is sufficient.
+	 */
+	sem = sma->sem_base + sops->sem_num;
 
+	if (sma->complex_count == 0) {
 		/*
-		 * Another process is holding the global lock on the
-		 * sem_array; we cannot enter our critical section,
-		 * but have to wait for the global lock to be released.
+		 * It appears that no complex operation is around.
+		 * Acquire the per-semaphore lock.
 		 */
-		if (unlikely(spin_is_locked(&sma->sem_perm.lock))) {
-			spin_unlock(&sem->lock);
-			spin_unlock_wait(&sma->sem_perm.lock);
-			goto again;
+		spin_lock(&sem->lock);
+
+		/* Then check that the global lock is free */
+		if (!spin_is_locked(&sma->sem_perm.lock)) {
+			/* spin_is_locked() is not a memory barrier */
+			smp_mb();
+
+			/* Now repeat the test of complex_count:
+			 * It can't change anymore until we drop sem->lock.
+			 * Thus: if is now 0, then it will stay 0.
+			 */
+			if (sma->complex_count == 0) {
+				/* fast path successful! */
+				return sops->sem_num;
+			}
 		}
+		spin_unlock(&sem->lock);
+	}
 
-		locknum = sops->sem_num;
+	/* slow path: acquire the full lock */
+	ipc_lock_object(&sma->sem_perm);
+
+	if (sma->complex_count == 0) {
+		/* False alarm:
+		 * There is no complex operation, thus we can switch
+		 * back to the fast path.
+		 */
+		spin_lock(&sem->lock);
+		ipc_unlock_object(&sma->sem_perm);
+		return sops->sem_num;
 	} else {
-		int i;
-		/*
-		 * Lock the semaphore array, and wait for all of the
-		 * individual semaphore locks to go away.  The code
-		 * above ensures no new single-lock holders will enter
-		 * their critical section while the array lock is held.
+		/* Not a false alarm, thus complete the sequence for a
+		 * full lock.
 		 */
- lock_array:
-		ipc_lock_object(&sma->sem_perm);
-		for (i = 0; i < sma->sem_nsems; i++) {
-			struct sem *sem = sma->sem_base + i;
-			spin_unlock_wait(&sem->lock);
-		}
-		locknum = -1;
+		sem_wait_array(sma);
+		return -1;
 	}
-	return locknum;
 }
 
 static inline void sem_unlock(struct sem_array *sma, int locknum)
@@ -322,7 +373,7 @@ static inline void sem_unlock(struct sem_array *sma, int locknum)
 }
 
 /*
- * sem_lock_(check_) routines are called in the paths where the rw_mutex
+ * sem_lock_(check_) routines are called in the paths where the rwsem
  * is not held.
  *
  * The caller holds the RCU read lock.
@@ -374,12 +425,7 @@ static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns
 static inline void sem_lock_and_putref(struct sem_array *sma)
 {
 	sem_lock(sma, NULL, -1);
-	ipc_rcu_putref(sma);
-}
-
-static inline void sem_putref(struct sem_array *sma)
-{
-	ipc_rcu_putref(sma);
+	ipc_rcu_putref(sma, ipc_rcu_free);
 }
 
 static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
@@ -426,7 +472,7 @@ static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
  * @ns: namespace
  * @params: ptr to the structure that contains key, semflg and nsems
  *
- * Called with sem_ids.rw_mutex held (as a writer)
+ * Called with sem_ids.rwsem held (as a writer)
  */
 
 static int newary(struct ipc_namespace *ns, struct ipc_params *params)
@@ -458,14 +504,13 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
 	sma->sem_perm.security = NULL;
 	retval = security_sem_alloc(sma);
 	if (retval) {
-		ipc_rcu_putref(sma);
+		ipc_rcu_putref(sma, ipc_rcu_free);
 		return retval;
 	}
 
 	id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
 	if (id < 0) {
-		security_sem_free(sma);
-		ipc_rcu_putref(sma);
+		ipc_rcu_putref(sma, sem_rcu_free);
 		return id;
 	}
 	ns->used_sems += nsems;
@@ -492,7 +537,7 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
 
 
 /*
- * Called with sem_ids.rw_mutex and ipcp locked.
+ * Called with sem_ids.rwsem and ipcp locked.
  */
 static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
 {
@@ -503,7 +548,7 @@ static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
 }
 
 /*
- * Called with sem_ids.rw_mutex and ipcp locked.
+ * Called with sem_ids.rwsem and ipcp locked.
  */
 static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
 				struct ipc_params *params)
@@ -873,6 +918,24 @@ again:
 }
 
 /**
+ * set_semotime(sma, sops) - set sem_otime
+ * @sma: semaphore array
+ * @sops: operations that modified the array, may be NULL
+ *
+ * sem_otime is replicated to avoid cache line trashing.
+ * This function sets one instance to the current time.
+ */
+static void set_semotime(struct sem_array *sma, struct sembuf *sops)
+{
+	if (sops == NULL) {
+		sma->sem_base[0].sem_otime = get_seconds();
+	} else {
+		sma->sem_base[sops[0].sem_num].sem_otime =
+							get_seconds();
+	}
+}
+
+/**
  * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
  * @sma: semaphore array
  * @sops: operations that were performed
@@ -922,17 +985,10 @@ static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsop
 			}
 		}
 	}
-	if (otime) {
-		if (sops == NULL) {
-			sma->sem_base[0].sem_otime = get_seconds();
-		} else {
-			sma->sem_base[sops[0].sem_num].sem_otime =
-								get_seconds();
-		}
-	}
+	if (otime)
+		set_semotime(sma, sops);
 }
 
-
 /* The following counts are associated to each semaphore:
  *   semncnt        number of tasks waiting on semval being nonzero
  *   semzcnt        number of tasks waiting on semval being zero
@@ -994,8 +1050,8 @@ static int count_semzcnt (struct sem_array * sma, ushort semnum)
 	return semzcnt;
 }
 
-/* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
- * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
+/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
+ * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
  * remains locked on exit.
  */
 static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
@@ -1047,8 +1103,7 @@ static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 
 	wake_up_sem_queue_do(&tasks);
 	ns->used_sems -= sma->sem_nsems;
-	security_sem_free(sma);
-	ipc_rcu_putref(sma);
+	ipc_rcu_putref(sma, sem_rcu_free);
 }
 
 static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
@@ -1116,7 +1171,7 @@ static int semctl_nolock(struct ipc_namespace *ns, int semid,
 		seminfo.semmnu = SEMMNU;
 		seminfo.semmap = SEMMAP;
 		seminfo.semume = SEMUME;
-		down_read(&sem_ids(ns).rw_mutex);
+		down_read(&sem_ids(ns).rwsem);
 		if (cmd == SEM_INFO) {
 			seminfo.semusz = sem_ids(ns).in_use;
 			seminfo.semaem = ns->used_sems;
@@ -1125,7 +1180,7 @@ static int semctl_nolock(struct ipc_namespace *ns, int semid,
 			seminfo.semaem = SEMAEM;
 		}
 		max_id = ipc_get_maxid(&sem_ids(ns));
-		up_read(&sem_ids(ns).rw_mutex);
+		up_read(&sem_ids(ns).rwsem);
 		if (copy_to_user(p, &seminfo, sizeof(struct seminfo))) 
 			return -EFAULT;
 		return (max_id < 0) ? 0: max_id;
@@ -1292,7 +1347,7 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
 			rcu_read_unlock();
 			sem_io = ipc_alloc(sizeof(ushort)*nsems);
 			if(sem_io == NULL) {
-				sem_putref(sma);
+				ipc_rcu_putref(sma, ipc_rcu_free);
 				return -ENOMEM;
 			}
 
@@ -1328,20 +1383,20 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
 		if(nsems > SEMMSL_FAST) {
 			sem_io = ipc_alloc(sizeof(ushort)*nsems);
 			if(sem_io == NULL) {
-				sem_putref(sma);
+				ipc_rcu_putref(sma, ipc_rcu_free);
 				return -ENOMEM;
 			}
 		}
 
 		if (copy_from_user (sem_io, p, nsems*sizeof(ushort))) {
-			sem_putref(sma);
+			ipc_rcu_putref(sma, ipc_rcu_free);
 			err = -EFAULT;
 			goto out_free;
 		}
 
 		for (i = 0; i < nsems; i++) {
 			if (sem_io[i] > SEMVMX) {
-				sem_putref(sma);
+				ipc_rcu_putref(sma, ipc_rcu_free);
 				err = -ERANGE;
 				goto out_free;
 			}
@@ -1431,9 +1486,9 @@ copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
 }
 
 /*
- * This function handles some semctl commands which require the rw_mutex
+ * This function handles some semctl commands which require the rwsem
  * to be held in write mode.
- * NOTE: no locks must be held, the rw_mutex is taken inside this function.
+ * NOTE: no locks must be held, the rwsem is taken inside this function.
  */
 static int semctl_down(struct ipc_namespace *ns, int semid,
 		       int cmd, int version, void __user *p)
@@ -1448,7 +1503,7 @@ static int semctl_down(struct ipc_namespace *ns, int semid,
 			return -EFAULT;
 	}
 
-	down_write(&sem_ids(ns).rw_mutex);
+	down_write(&sem_ids(ns).rwsem);
 	rcu_read_lock();
 
 	ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
@@ -1487,7 +1542,7 @@ out_unlock0:
 out_unlock1:
 	rcu_read_unlock();
 out_up:
-	up_write(&sem_ids(ns).rw_mutex);
+	up_write(&sem_ids(ns).rwsem);
 	return err;
 }
 
@@ -1629,7 +1684,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
 	/* step 2: allocate new undo structure */
 	new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
 	if (!new) {
-		sem_putref(sma);
+		ipc_rcu_putref(sma, ipc_rcu_free);
 		return ERR_PTR(-ENOMEM);
 	}
 
@@ -1795,12 +1850,17 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
 
 	error = perform_atomic_semop(sma, sops, nsops, un,
 					task_tgid_vnr(current));
-	if (error <= 0) {
-		if (alter && error == 0)
+	if (error == 0) {
+		/* If the operation was successful, then do
+		 * the required updates.
+		 */
+		if (alter)
 			do_smart_update(sma, sops, nsops, 1, &tasks);
-
-		goto out_unlock_free;
+		else
+			set_semotime(sma, sops);
 	}
+	if (error <= 0)
+		goto out_unlock_free;
 
 	/* We need to sleep on this operation, so we put the current
 	 * task into the pending queue and go to sleep.
@@ -2059,6 +2119,14 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
 	struct sem_array *sma = it;
 	time_t sem_otime;
 
+	/*
+	 * The proc interface isn't aware of sem_lock(), it calls
+	 * ipc_lock_object() directly (in sysvipc_find_ipc).
+	 * In order to stay compatible with sem_lock(), we must wait until
+	 * all simple semop() calls have left their critical regions.
+	 */
+	sem_wait_array(sma);
+
 	sem_otime = get_semotime(sma);
 
 	return seq_printf(s,
diff --git a/ipc/shm.c b/ipc/shm.c
index c6b4ad5ce3b7..d69739610fd4 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -19,6 +19,9 @@
  * namespaces support
  * OpenVZ, SWsoft Inc.
  * Pavel Emelianov <xemul@openvz.org>
+ *
+ * Better ipc lock (kern_ipc_perm.lock) handling
+ * Davidlohr Bueso <davidlohr.bueso@hp.com>, June 2013.
  */
 
 #include <linux/slab.h>
@@ -80,8 +83,8 @@ void shm_init_ns(struct ipc_namespace *ns)
 }
 
 /*
- * Called with shm_ids.rw_mutex (writer) and the shp structure locked.
- * Only shm_ids.rw_mutex remains locked on exit.
+ * Called with shm_ids.rwsem (writer) and the shp structure locked.
+ * Only shm_ids.rwsem remains locked on exit.
  */
 static void do_shm_rmid(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 {
@@ -124,8 +127,28 @@ void __init shm_init (void)
 				IPC_SHM_IDS, sysvipc_shm_proc_show);
 }
 
+static inline struct shmid_kernel *shm_obtain_object(struct ipc_namespace *ns, int id)
+{
+	struct kern_ipc_perm *ipcp = ipc_obtain_object(&shm_ids(ns), id);
+
+	if (IS_ERR(ipcp))
+		return ERR_CAST(ipcp);
+
+	return container_of(ipcp, struct shmid_kernel, shm_perm);
+}
+
+static inline struct shmid_kernel *shm_obtain_object_check(struct ipc_namespace *ns, int id)
+{
+	struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&shm_ids(ns), id);
+
+	if (IS_ERR(ipcp))
+		return ERR_CAST(ipcp);
+
+	return container_of(ipcp, struct shmid_kernel, shm_perm);
+}
+
 /*
- * shm_lock_(check_) routines are called in the paths where the rw_mutex
+ * shm_lock_(check_) routines are called in the paths where the rwsem
  * is not necessarily held.
  */
 static inline struct shmid_kernel *shm_lock(struct ipc_namespace *ns, int id)
@@ -144,15 +167,13 @@ static inline void shm_lock_by_ptr(struct shmid_kernel *ipcp)
 	ipc_lock_object(&ipcp->shm_perm);
 }
 
-static inline struct shmid_kernel *shm_lock_check(struct ipc_namespace *ns,
-						int id)
+static void shm_rcu_free(struct rcu_head *head)
 {
-	struct kern_ipc_perm *ipcp = ipc_lock_check(&shm_ids(ns), id);
-
-	if (IS_ERR(ipcp))
-		return (struct shmid_kernel *)ipcp;
+	struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
+	struct shmid_kernel *shp = ipc_rcu_to_struct(p);
 
-	return container_of(ipcp, struct shmid_kernel, shm_perm);
+	security_shm_free(shp);
+	ipc_rcu_free(head);
 }
 
 static inline void shm_rmid(struct ipc_namespace *ns, struct shmid_kernel *s)
@@ -182,7 +203,7 @@ static void shm_open(struct vm_area_struct *vma)
  * @ns: namespace
  * @shp: struct to free
  *
- * It has to be called with shp and shm_ids.rw_mutex (writer) locked,
+ * It has to be called with shp and shm_ids.rwsem (writer) locked,
  * but returns with shp unlocked and freed.
  */
 static void shm_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp)
@@ -196,8 +217,7 @@ static void shm_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp)
 		user_shm_unlock(file_inode(shp->shm_file)->i_size,
 						shp->mlock_user);
 	fput (shp->shm_file);
-	security_shm_free(shp);
-	ipc_rcu_putref(shp);
+	ipc_rcu_putref(shp, shm_rcu_free);
 }
 
 /*
@@ -230,7 +250,7 @@ static void shm_close(struct vm_area_struct *vma)
 	struct shmid_kernel *shp;
 	struct ipc_namespace *ns = sfd->ns;
 
-	down_write(&shm_ids(ns).rw_mutex);
+	down_write(&shm_ids(ns).rwsem);
 	/* remove from the list of attaches of the shm segment */
 	shp = shm_lock(ns, sfd->id);
 	BUG_ON(IS_ERR(shp));
@@ -241,10 +261,10 @@ static void shm_close(struct vm_area_struct *vma)
 		shm_destroy(ns, shp);
 	else
 		shm_unlock(shp);
-	up_write(&shm_ids(ns).rw_mutex);
+	up_write(&shm_ids(ns).rwsem);
 }
 
-/* Called with ns->shm_ids(ns).rw_mutex locked */
+/* Called with ns->shm_ids(ns).rwsem locked */
 static int shm_try_destroy_current(int id, void *p, void *data)
 {
 	struct ipc_namespace *ns = data;
@@ -275,7 +295,7 @@ static int shm_try_destroy_current(int id, void *p, void *data)
 	return 0;
 }
 
-/* Called with ns->shm_ids(ns).rw_mutex locked */
+/* Called with ns->shm_ids(ns).rwsem locked */
 static int shm_try_destroy_orphaned(int id, void *p, void *data)
 {
 	struct ipc_namespace *ns = data;
@@ -286,7 +306,7 @@ static int shm_try_destroy_orphaned(int id, void *p, void *data)
 	 * We want to destroy segments without users and with already
 	 * exit'ed originating process.
 	 *
-	 * As shp->* are changed under rw_mutex, it's safe to skip shp locking.
+	 * As shp->* are changed under rwsem, it's safe to skip shp locking.
 	 */
 	if (shp->shm_creator != NULL)
 		return 0;
@@ -300,10 +320,10 @@ static int shm_try_destroy_orphaned(int id, void *p, void *data)
 
 void shm_destroy_orphaned(struct ipc_namespace *ns)
 {
-	down_write(&shm_ids(ns).rw_mutex);
+	down_write(&shm_ids(ns).rwsem);
 	if (shm_ids(ns).in_use)
 		idr_for_each(&shm_ids(ns).ipcs_idr, &shm_try_destroy_orphaned, ns);
-	up_write(&shm_ids(ns).rw_mutex);
+	up_write(&shm_ids(ns).rwsem);
 }
 
 
@@ -315,10 +335,10 @@ void exit_shm(struct task_struct *task)
 		return;
 
 	/* Destroy all already created segments, but not mapped yet */
-	down_write(&shm_ids(ns).rw_mutex);
+	down_write(&shm_ids(ns).rwsem);
 	if (shm_ids(ns).in_use)
 		idr_for_each(&shm_ids(ns).ipcs_idr, &shm_try_destroy_current, ns);
-	up_write(&shm_ids(ns).rw_mutex);
+	up_write(&shm_ids(ns).rwsem);
 }
 
 static int shm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
@@ -452,7 +472,7 @@ static const struct vm_operations_struct shm_vm_ops = {
  * @ns: namespace
  * @params: ptr to the structure that contains key, size and shmflg
  *
- * Called with shm_ids.rw_mutex held as a writer.
+ * Called with shm_ids.rwsem held as a writer.
  */
 
 static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
@@ -485,7 +505,7 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
 	shp->shm_perm.security = NULL;
 	error = security_shm_alloc(shp);
 	if (error) {
-		ipc_rcu_putref(shp);
+		ipc_rcu_putref(shp, ipc_rcu_free);
 		return error;
 	}
 
@@ -554,13 +574,12 @@ no_id:
 		user_shm_unlock(size, shp->mlock_user);
 	fput(file);
 no_file:
-	security_shm_free(shp);
-	ipc_rcu_putref(shp);
+	ipc_rcu_putref(shp, shm_rcu_free);
 	return error;
 }
 
 /*
- * Called with shm_ids.rw_mutex and ipcp locked.
+ * Called with shm_ids.rwsem and ipcp locked.
  */
 static inline int shm_security(struct kern_ipc_perm *ipcp, int shmflg)
 {
@@ -571,7 +590,7 @@ static inline int shm_security(struct kern_ipc_perm *ipcp, int shmflg)
 }
 
 /*
- * Called with shm_ids.rw_mutex and ipcp locked.
+ * Called with shm_ids.rwsem and ipcp locked.
  */
 static inline int shm_more_checks(struct kern_ipc_perm *ipcp,
 				struct ipc_params *params)
@@ -684,7 +703,7 @@ static inline unsigned long copy_shminfo_to_user(void __user *buf, struct shminf
 
 /*
  * Calculate and add used RSS and swap pages of a shm.
- * Called with shm_ids.rw_mutex held as a reader
+ * Called with shm_ids.rwsem held as a reader
  */
 static void shm_add_rss_swap(struct shmid_kernel *shp,
 	unsigned long *rss_add, unsigned long *swp_add)
@@ -711,7 +730,7 @@ static void shm_add_rss_swap(struct shmid_kernel *shp,
 }
 
 /*
- * Called with shm_ids.rw_mutex held as a reader
+ * Called with shm_ids.rwsem held as a reader
  */
 static void shm_get_stat(struct ipc_namespace *ns, unsigned long *rss,
 		unsigned long *swp)
@@ -740,9 +759,9 @@ static void shm_get_stat(struct ipc_namespace *ns, unsigned long *rss,
 }
 
 /*
- * This function handles some shmctl commands which require the rw_mutex
+ * This function handles some shmctl commands which require the rwsem
  * to be held in write mode.
- * NOTE: no locks must be held, the rw_mutex is taken inside this function.
+ * NOTE: no locks must be held, the rwsem is taken inside this function.
  */
 static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd,
 		       struct shmid_ds __user *buf, int version)
@@ -757,14 +776,13 @@ static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd,
 			return -EFAULT;
 	}
 
-	down_write(&shm_ids(ns).rw_mutex);
+	down_write(&shm_ids(ns).rwsem);
 	rcu_read_lock();
 
-	ipcp = ipcctl_pre_down(ns, &shm_ids(ns), shmid, cmd,
-			       &shmid64.shm_perm, 0);
+	ipcp = ipcctl_pre_down_nolock(ns, &shm_ids(ns), shmid, cmd,
+				      &shmid64.shm_perm, 0);
 	if (IS_ERR(ipcp)) {
 		err = PTR_ERR(ipcp);
-		/* the ipc lock is not held upon failure */
 		goto out_unlock1;
 	}
 
@@ -772,14 +790,16 @@ static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd,
 
 	err = security_shm_shmctl(shp, cmd);
 	if (err)
-		goto out_unlock0;
+		goto out_unlock1;
 
 	switch (cmd) {
 	case IPC_RMID:
+		ipc_lock_object(&shp->shm_perm);
 		/* do_shm_rmid unlocks the ipc object and rcu */
 		do_shm_rmid(ns, ipcp);
 		goto out_up;
 	case IPC_SET:
+		ipc_lock_object(&shp->shm_perm);
 		err = ipc_update_perm(&shmid64.shm_perm, ipcp);
 		if (err)
 			goto out_unlock0;
@@ -787,6 +807,7 @@ static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd,
 		break;
 	default:
 		err = -EINVAL;
+		goto out_unlock1;
 	}
 
 out_unlock0:
@@ -794,33 +815,28 @@ out_unlock0:
 out_unlock1:
 	rcu_read_unlock();
 out_up:
-	up_write(&shm_ids(ns).rw_mutex);
+	up_write(&shm_ids(ns).rwsem);
 	return err;
 }
 
-SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
+static int shmctl_nolock(struct ipc_namespace *ns, int shmid,
+			 int cmd, int version, void __user *buf)
 {
+	int err;
 	struct shmid_kernel *shp;
-	int err, version;
-	struct ipc_namespace *ns;
 
-	if (cmd < 0 || shmid < 0) {
-		err = -EINVAL;
-		goto out;
+	/* preliminary security checks for *_INFO */
+	if (cmd == IPC_INFO || cmd == SHM_INFO) {
+		err = security_shm_shmctl(NULL, cmd);
+		if (err)
+			return err;
 	}
 
-	version = ipc_parse_version(&cmd);
-	ns = current->nsproxy->ipc_ns;
-
-	switch (cmd) { /* replace with proc interface ? */
+	switch (cmd) {
 	case IPC_INFO:
 	{
 		struct shminfo64 shminfo;
 
-		err = security_shm_shmctl(NULL, cmd);
-		if (err)
-			return err;
-
 		memset(&shminfo, 0, sizeof(shminfo));
 		shminfo.shmmni = shminfo.shmseg = ns->shm_ctlmni;
 		shminfo.shmmax = ns->shm_ctlmax;
@@ -830,9 +846,9 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
 		if(copy_shminfo_to_user (buf, &shminfo, version))
 			return -EFAULT;
 
-		down_read(&shm_ids(ns).rw_mutex);
+		down_read(&shm_ids(ns).rwsem);
 		err = ipc_get_maxid(&shm_ids(ns));
-		up_read(&shm_ids(ns).rw_mutex);
+		up_read(&shm_ids(ns).rwsem);
 
 		if(err<0)
 			err = 0;
@@ -842,19 +858,15 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
 	{
 		struct shm_info shm_info;
 
-		err = security_shm_shmctl(NULL, cmd);
-		if (err)
-			return err;
-
 		memset(&shm_info, 0, sizeof(shm_info));
-		down_read(&shm_ids(ns).rw_mutex);
+		down_read(&shm_ids(ns).rwsem);
 		shm_info.used_ids = shm_ids(ns).in_use;
 		shm_get_stat (ns, &shm_info.shm_rss, &shm_info.shm_swp);
 		shm_info.shm_tot = ns->shm_tot;
 		shm_info.swap_attempts = 0;
 		shm_info.swap_successes = 0;
 		err = ipc_get_maxid(&shm_ids(ns));
-		up_read(&shm_ids(ns).rw_mutex);
+		up_read(&shm_ids(ns).rwsem);
 		if (copy_to_user(buf, &shm_info, sizeof(shm_info))) {
 			err = -EFAULT;
 			goto out;
@@ -869,27 +881,31 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
 		struct shmid64_ds tbuf;
 		int result;
 
+		rcu_read_lock();
 		if (cmd == SHM_STAT) {
-			shp = shm_lock(ns, shmid);
+			shp = shm_obtain_object(ns, shmid);
 			if (IS_ERR(shp)) {
 				err = PTR_ERR(shp);
-				goto out;
+				goto out_unlock;
 			}
 			result = shp->shm_perm.id;
 		} else {
-			shp = shm_lock_check(ns, shmid);
+			shp = shm_obtain_object_check(ns, shmid);
 			if (IS_ERR(shp)) {
 				err = PTR_ERR(shp);
-				goto out;
+				goto out_unlock;
 			}
 			result = 0;
 		}
+
 		err = -EACCES;
 		if (ipcperms(ns, &shp->shm_perm, S_IRUGO))
 			goto out_unlock;
+
 		err = security_shm_shmctl(shp, cmd);
 		if (err)
 			goto out_unlock;
+
 		memset(&tbuf, 0, sizeof(tbuf));
 		kernel_to_ipc64_perm(&shp->shm_perm, &tbuf.shm_perm);
 		tbuf.shm_segsz	= shp->shm_segsz;
@@ -899,43 +915,76 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
 		tbuf.shm_cpid	= shp->shm_cprid;
 		tbuf.shm_lpid	= shp->shm_lprid;
 		tbuf.shm_nattch	= shp->shm_nattch;
-		shm_unlock(shp);
-		if(copy_shmid_to_user (buf, &tbuf, version))
+		rcu_read_unlock();
+
+		if (copy_shmid_to_user(buf, &tbuf, version))
 			err = -EFAULT;
 		else
 			err = result;
 		goto out;
 	}
+	default:
+		return -EINVAL;
+	}
+
+out_unlock:
+	rcu_read_unlock();
+out:
+	return err;
+}
+
+SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
+{
+	struct shmid_kernel *shp;
+	int err, version;
+	struct ipc_namespace *ns;
+
+	if (cmd < 0 || shmid < 0)
+		return -EINVAL;
+
+	version = ipc_parse_version(&cmd);
+	ns = current->nsproxy->ipc_ns;
+
+	switch (cmd) {
+	case IPC_INFO:
+	case SHM_INFO:
+	case SHM_STAT:
+	case IPC_STAT:
+		return shmctl_nolock(ns, shmid, cmd, version, buf);
+	case IPC_RMID:
+	case IPC_SET:
+		return shmctl_down(ns, shmid, cmd, buf, version);
 	case SHM_LOCK:
 	case SHM_UNLOCK:
 	{
 		struct file *shm_file;
 
-		shp = shm_lock_check(ns, shmid);
+		rcu_read_lock();
+		shp = shm_obtain_object_check(ns, shmid);
 		if (IS_ERR(shp)) {
 			err = PTR_ERR(shp);
-			goto out;
+			goto out_unlock1;
 		}
 
 		audit_ipc_obj(&(shp->shm_perm));
+		err = security_shm_shmctl(shp, cmd);
+		if (err)
+			goto out_unlock1;
 
+		ipc_lock_object(&shp->shm_perm);
 		if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) {
 			kuid_t euid = current_euid();
 			err = -EPERM;
 			if (!uid_eq(euid, shp->shm_perm.uid) &&
 			    !uid_eq(euid, shp->shm_perm.cuid))
-				goto out_unlock;
+				goto out_unlock0;
 			if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK))
-				goto out_unlock;
+				goto out_unlock0;
 		}
 
-		err = security_shm_shmctl(shp, cmd);
-		if (err)
-			goto out_unlock;
-
 		shm_file = shp->shm_file;
 		if (is_file_hugepages(shm_file))
-			goto out_unlock;
+			goto out_unlock0;
 
 		if (cmd == SHM_LOCK) {
 			struct user_struct *user = current_user();
@@ -944,32 +993,31 @@ SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
 				shp->shm_perm.mode |= SHM_LOCKED;
 				shp->mlock_user = user;
 			}
-			goto out_unlock;
+			goto out_unlock0;
 		}
 
 		/* SHM_UNLOCK */
 		if (!(shp->shm_perm.mode & SHM_LOCKED))
-			goto out_unlock;
+			goto out_unlock0;
 		shmem_lock(shm_file, 0, shp->mlock_user);
 		shp->shm_perm.mode &= ~SHM_LOCKED;
 		shp->mlock_user = NULL;
 		get_file(shm_file);
-		shm_unlock(shp);
+		ipc_unlock_object(&shp->shm_perm);
+		rcu_read_unlock();
 		shmem_unlock_mapping(shm_file->f_mapping);
+
 		fput(shm_file);
-		goto out;
-	}
-	case IPC_RMID:
-	case IPC_SET:
-		err = shmctl_down(ns, shmid, cmd, buf, version);
 		return err;
+	}
 	default:
 		return -EINVAL;
 	}
 
-out_unlock:
-	shm_unlock(shp);
-out:
+out_unlock0:
+	ipc_unlock_object(&shp->shm_perm);
+out_unlock1:
+	rcu_read_unlock();
 	return err;
 }
 
@@ -1037,10 +1085,11 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
 	 * additional creator id...
 	 */
 	ns = current->nsproxy->ipc_ns;
-	shp = shm_lock_check(ns, shmid);
+	rcu_read_lock();
+	shp = shm_obtain_object_check(ns, shmid);
 	if (IS_ERR(shp)) {
 		err = PTR_ERR(shp);
-		goto out;
+		goto out_unlock;
 	}
 
 	err = -EACCES;
@@ -1051,24 +1100,31 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
 	if (err)
 		goto out_unlock;
 
+	ipc_lock_object(&shp->shm_perm);
 	path = shp->shm_file->f_path;
 	path_get(&path);
 	shp->shm_nattch++;
 	size = i_size_read(path.dentry->d_inode);
-	shm_unlock(shp);
+	ipc_unlock_object(&shp->shm_perm);
+	rcu_read_unlock();
 
 	err = -ENOMEM;
 	sfd = kzalloc(sizeof(*sfd), GFP_KERNEL);
-	if (!sfd)
-		goto out_put_dentry;
+	if (!sfd) {
+		path_put(&path);
+		goto out_nattch;
+	}
 
 	file = alloc_file(&path, f_mode,
 			  is_file_hugepages(shp->shm_file) ?
 				&shm_file_operations_huge :
 				&shm_file_operations);
 	err = PTR_ERR(file);
-	if (IS_ERR(file))
-		goto out_free;
+	if (IS_ERR(file)) {
+		kfree(sfd);
+		path_put(&path);
+		goto out_nattch;
+	}
 
 	file->private_data = sfd;
 	file->f_mapping = shp->shm_file->f_mapping;
@@ -1094,7 +1150,7 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
 		    addr > current->mm->start_stack - size - PAGE_SIZE * 5)
 			goto invalid;
 	}
-		
+
 	addr = do_mmap_pgoff(file, addr, size, prot, flags, 0, &populate);
 	*raddr = addr;
 	err = 0;
@@ -1109,7 +1165,7 @@ out_fput:
 	fput(file);
 
 out_nattch:
-	down_write(&shm_ids(ns).rw_mutex);
+	down_write(&shm_ids(ns).rwsem);
 	shp = shm_lock(ns, shmid);
 	BUG_ON(IS_ERR(shp));
 	shp->shm_nattch--;
@@ -1117,20 +1173,13 @@ out_nattch:
 		shm_destroy(ns, shp);
 	else
 		shm_unlock(shp);
-	up_write(&shm_ids(ns).rw_mutex);
-
-out:
+	up_write(&shm_ids(ns).rwsem);
 	return err;
 
 out_unlock:
-	shm_unlock(shp);
-	goto out;
-
-out_free:
-	kfree(sfd);
-out_put_dentry:
-	path_put(&path);
-	goto out_nattch;
+	rcu_read_unlock();
+out:
+	return err;
 }
 
 SYSCALL_DEFINE3(shmat, int, shmid, char __user *, shmaddr, int, shmflg)
@@ -1235,8 +1284,7 @@ SYSCALL_DEFINE1(shmdt, char __user *, shmaddr)
 #else /* CONFIG_MMU */
 	/* under NOMMU conditions, the exact address to be destroyed must be
 	 * given */
-	retval = -EINVAL;
-	if (vma->vm_start == addr && vma->vm_ops == &shm_vm_ops) {
+	if (vma && vma->vm_start == addr && vma->vm_ops == &shm_vm_ops) {
 		do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start);
 		retval = 0;
 	}
diff --git a/ipc/util.c b/ipc/util.c
index 4704223bfad4..fdb8ae740775 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -15,6 +15,14 @@
  * Jun 2006 - namespaces ssupport
  *            OpenVZ, SWsoft Inc.
  *            Pavel Emelianov <xemul@openvz.org>
+ *
+ * General sysv ipc locking scheme:
+ *  when doing ipc id lookups, take the ids->rwsem
+ *      rcu_read_lock()
+ *          obtain the ipc object (kern_ipc_perm)
+ *          perform security, capabilities, auditing and permission checks, etc.
+ *          acquire the ipc lock (kern_ipc_perm.lock) throught ipc_lock_object()
+ *             perform data updates (ie: SET, RMID, LOCK/UNLOCK commands)
  */
 
 #include <linux/mm.h>
@@ -119,7 +127,7 @@ __initcall(ipc_init);
  
 void ipc_init_ids(struct ipc_ids *ids)
 {
-	init_rwsem(&ids->rw_mutex);
+	init_rwsem(&ids->rwsem);
 
 	ids->in_use = 0;
 	ids->seq = 0;
@@ -174,7 +182,7 @@ void __init ipc_init_proc_interface(const char *path, const char *header,
  *	@ids: Identifier set
  *	@key: The key to find
  *	
- *	Requires ipc_ids.rw_mutex locked.
+ *	Requires ipc_ids.rwsem locked.
  *	Returns the LOCKED pointer to the ipc structure if found or NULL
  *	if not.
  *	If key is found ipc points to the owning ipc structure
@@ -197,7 +205,8 @@ static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
 			continue;
 		}
 
-		ipc_lock_by_ptr(ipc);
+		rcu_read_lock();
+		ipc_lock_object(ipc);
 		return ipc;
 	}
 
@@ -208,7 +217,7 @@ static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
  *	ipc_get_maxid 	-	get the last assigned id
  *	@ids: IPC identifier set
  *
- *	Called with ipc_ids.rw_mutex held.
+ *	Called with ipc_ids.rwsem held.
  */
 
 int ipc_get_maxid(struct ipc_ids *ids)
@@ -246,7 +255,7 @@ int ipc_get_maxid(struct ipc_ids *ids)
  *	is returned. The 'new' entry is returned in a locked state on success.
  *	On failure the entry is not locked and a negative err-code is returned.
  *
- *	Called with writer ipc_ids.rw_mutex held.
+ *	Called with writer ipc_ids.rwsem held.
  */
 int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 {
@@ -312,9 +321,9 @@ static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
 {
 	int err;
 
-	down_write(&ids->rw_mutex);
+	down_write(&ids->rwsem);
 	err = ops->getnew(ns, params);
-	up_write(&ids->rw_mutex);
+	up_write(&ids->rwsem);
 	return err;
 }
 
@@ -331,7 +340,7 @@ static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
  *
  *	On success, the IPC id is returned.
  *
- *	It is called with ipc_ids.rw_mutex and ipcp->lock held.
+ *	It is called with ipc_ids.rwsem and ipcp->lock held.
  */
 static int ipc_check_perms(struct ipc_namespace *ns,
 			   struct kern_ipc_perm *ipcp,
@@ -376,7 +385,7 @@ static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
 	 * Take the lock as a writer since we are potentially going to add
 	 * a new entry + read locks are not "upgradable"
 	 */
-	down_write(&ids->rw_mutex);
+	down_write(&ids->rwsem);
 	ipcp = ipc_findkey(ids, params->key);
 	if (ipcp == NULL) {
 		/* key not used */
@@ -402,7 +411,7 @@ static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
 		}
 		ipc_unlock(ipcp);
 	}
-	up_write(&ids->rw_mutex);
+	up_write(&ids->rwsem);
 
 	return err;
 }
@@ -413,7 +422,7 @@ static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
  *	@ids: IPC identifier set
  *	@ipcp: ipc perm structure containing the identifier to remove
  *
- *	ipc_ids.rw_mutex (as a writer) and the spinlock for this ID are held
+ *	ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
  *	before this function is called, and remain locked on the exit.
  */
  
@@ -465,11 +474,6 @@ void ipc_free(void* ptr, int size)
 		kfree(ptr);
 }
 
-struct ipc_rcu {
-	struct rcu_head rcu;
-	atomic_t refcount;
-} ____cacheline_aligned_in_smp;
-
 /**
  *	ipc_rcu_alloc	-	allocate ipc and rcu space 
  *	@size: size desired
@@ -496,27 +500,24 @@ int ipc_rcu_getref(void *ptr)
 	return atomic_inc_not_zero(&p->refcount);
 }
 
-/**
- * ipc_schedule_free - free ipc + rcu space
- * @head: RCU callback structure for queued work
- */
-static void ipc_schedule_free(struct rcu_head *head)
-{
-	vfree(container_of(head, struct ipc_rcu, rcu));
-}
-
-void ipc_rcu_putref(void *ptr)
+void ipc_rcu_putref(void *ptr, void (*func)(struct rcu_head *head))
 {
 	struct ipc_rcu *p = ((struct ipc_rcu *)ptr) - 1;
 
 	if (!atomic_dec_and_test(&p->refcount))
 		return;
 
-	if (is_vmalloc_addr(ptr)) {
-		call_rcu(&p->rcu, ipc_schedule_free);
-	} else {
-		kfree_rcu(p, rcu);
-	}
+	call_rcu(&p->rcu, func);
+}
+
+void ipc_rcu_free(struct rcu_head *head)
+{
+	struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
+
+	if (is_vmalloc_addr(p))
+		vfree(p);
+	else
+		kfree(p);
 }
 
 /**
@@ -621,7 +622,7 @@ struct kern_ipc_perm *ipc_obtain_object(struct ipc_ids *ids, int id)
 }
 
 /**
- * ipc_lock - Lock an ipc structure without rw_mutex held
+ * ipc_lock - Lock an ipc structure without rwsem held
  * @ids: IPC identifier set
  * @id: ipc id to look for
  *
@@ -677,22 +678,6 @@ out:
 	return out;
 }
 
-struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id)
-{
-	struct kern_ipc_perm *out;
-
-	out = ipc_lock(ids, id);
-	if (IS_ERR(out))
-		return out;
-
-	if (ipc_checkid(out, id)) {
-		ipc_unlock(out);
-		return ERR_PTR(-EIDRM);
-	}
-
-	return out;
-}
-
 /**
  * ipcget - Common sys_*get() code
  * @ns : namsepace
@@ -733,7 +718,7 @@ int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
 }
 
 /**
- * ipcctl_pre_down - retrieve an ipc and check permissions for some IPC_XXX cmd
+ * ipcctl_pre_down_nolock - retrieve an ipc and check permissions for some IPC_XXX cmd
  * @ns:  the ipc namespace
  * @ids:  the table of ids where to look for the ipc
  * @id:   the id of the ipc to retrieve
@@ -746,29 +731,13 @@ int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
  * It must be called without any lock held and
  *  - retrieves the ipc with the given id in the given table.
  *  - performs some audit and permission check, depending on the given cmd
- *  - returns the ipc with the ipc lock held in case of success
- *    or an err-code without any lock held otherwise.
+ *  - returns a pointer to the ipc object or otherwise, the corresponding error.
  *
- * Call holding the both the rw_mutex and the rcu read lock.
+ * Call holding the both the rwsem and the rcu read lock.
  */
-struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
-				      struct ipc_ids *ids, int id, int cmd,
-				      struct ipc64_perm *perm, int extra_perm)
-{
-	struct kern_ipc_perm *ipcp;
-
-	ipcp = ipcctl_pre_down_nolock(ns, ids, id, cmd, perm, extra_perm);
-	if (IS_ERR(ipcp))
-		goto out;
-
-	spin_lock(&ipcp->lock);
-out:
-	return ipcp;
-}
-
 struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
-					     struct ipc_ids *ids, int id, int cmd,
-					     struct ipc64_perm *perm, int extra_perm)
+					struct ipc_ids *ids, int id, int cmd,
+					struct ipc64_perm *perm, int extra_perm)
 {
 	kuid_t euid;
 	int err = -EPERM;
@@ -846,7 +815,8 @@ static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
 		ipc = idr_find(&ids->ipcs_idr, pos);
 		if (ipc != NULL) {
 			*new_pos = pos + 1;
-			ipc_lock_by_ptr(ipc);
+			rcu_read_lock();
+			ipc_lock_object(ipc);
 			return ipc;
 		}
 	}
@@ -884,7 +854,7 @@ static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 	 * Take the lock - this will be released by the corresponding
 	 * call to stop().
 	 */
-	down_read(&ids->rw_mutex);
+	down_read(&ids->rwsem);
 
 	/* pos < 0 is invalid */
 	if (*pos < 0)
@@ -911,7 +881,7 @@ static void sysvipc_proc_stop(struct seq_file *s, void *it)
 
 	ids = &iter->ns->ids[iface->ids];
 	/* Release the lock we took in start() */
-	up_read(&ids->rw_mutex);
+	up_read(&ids->rwsem);
 }
 
 static int sysvipc_proc_show(struct seq_file *s, void *it)
diff --git a/ipc/util.h b/ipc/util.h
index b6a6a88f3002..f2f5036f2eed 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -47,6 +47,13 @@ static inline void msg_exit_ns(struct ipc_namespace *ns) { }
 static inline void shm_exit_ns(struct ipc_namespace *ns) { }
 #endif
 
+struct ipc_rcu {
+	struct rcu_head rcu;
+	atomic_t refcount;
+} ____cacheline_aligned_in_smp;
+
+#define ipc_rcu_to_struct(p)  ((void *)(p+1))
+
 /*
  * Structure that holds the parameters needed by the ipc operations
  * (see after)
@@ -94,10 +101,10 @@ void __init ipc_init_proc_interface(const char *path, const char *header,
 #define ipcid_to_idx(id) ((id) % SEQ_MULTIPLIER)
 #define ipcid_to_seqx(id) ((id) / SEQ_MULTIPLIER)
 
-/* must be called with ids->rw_mutex acquired for writing */
+/* must be called with ids->rwsem acquired for writing */
 int ipc_addid(struct ipc_ids *, struct kern_ipc_perm *, int);
 
-/* must be called with ids->rw_mutex acquired for reading */
+/* must be called with ids->rwsem acquired for reading */
 int ipc_get_maxid(struct ipc_ids *);
 
 /* must be called with both locks acquired. */
@@ -120,7 +127,8 @@ void ipc_free(void* ptr, int size);
  */
 void* ipc_rcu_alloc(int size);
 int ipc_rcu_getref(void *ptr);
-void ipc_rcu_putref(void *ptr);
+void ipc_rcu_putref(void *ptr, void (*func)(struct rcu_head *head));
+void ipc_rcu_free(struct rcu_head *head);
 
 struct kern_ipc_perm *ipc_lock(struct ipc_ids *, int);
 struct kern_ipc_perm *ipc_obtain_object(struct ipc_ids *ids, int id);
@@ -131,9 +139,6 @@ int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out);
 struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
 					     struct ipc_ids *ids, int id, int cmd,
 					     struct ipc64_perm *perm, int extra_perm);
-struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
-				      struct ipc_ids *ids, int id, int cmd,
-				      struct ipc64_perm *perm, int extra_perm);
 
 #ifndef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
   /* On IA-64, we always use the "64-bit version" of the IPC structures.  */ 
@@ -174,19 +179,12 @@ static inline void ipc_assert_locked_object(struct kern_ipc_perm *perm)
 	assert_spin_locked(&perm->lock);
 }
 
-static inline void ipc_lock_by_ptr(struct kern_ipc_perm *perm)
-{
-	rcu_read_lock();
-	ipc_lock_object(perm);
-}
-
 static inline void ipc_unlock(struct kern_ipc_perm *perm)
 {
 	ipc_unlock_object(perm);
 	rcu_read_unlock();
 }
 
-struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id);
 struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id);
 int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
 			struct ipc_ops *ops, struct ipc_params *params);