diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index f431acf3dcea..fe7f5ae1c513 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -304,10 +304,11 @@ struct sctp_sock {
 	__u32 autoclose;
 	__u8 nodelay;
 	__u8 disable_fragments;
-	__u8 pd_mode;
 	__u8 v4mapped;
+	__u8 frag_interleave;
 	__u32 adaptation_ind;
 
+	atomic_t pd_mode;
 	/* Receive to here while partial delivery is in effect. */
 	struct sk_buff_head pd_lobby;
 };
diff --git a/include/net/sctp/ulpqueue.h b/include/net/sctp/ulpqueue.h
index ab26ab3adae1..39ea3f442b47 100644
--- a/include/net/sctp/ulpqueue.h
+++ b/include/net/sctp/ulpqueue.h
@@ -78,7 +78,7 @@ void sctp_ulpq_partial_delivery(struct sctp_ulpq *, struct sctp_chunk *, gfp_t);
 void sctp_ulpq_abort_pd(struct sctp_ulpq *, gfp_t);
 
 /* Clear the partial data delivery condition on this socket. */
-int sctp_clear_pd(struct sock *sk);
+int sctp_clear_pd(struct sock *sk, struct sctp_association *asoc);
 
 /* Skip over an SSN. */
 void sctp_ulpq_skip(struct sctp_ulpq *ulpq, __u16 sid, __u16 ssn);
diff --git a/include/net/sctp/user.h b/include/net/sctp/user.h
index 67a30eb2b3a4..e77316088dc7 100644
--- a/include/net/sctp/user.h
+++ b/include/net/sctp/user.h
@@ -97,6 +97,8 @@ enum sctp_optname {
 #define SCTP_DELAYED_ACK_TIME SCTP_DELAYED_ACK_TIME
 	SCTP_CONTEXT,	/* Receive Context */
 #define SCTP_CONTEXT SCTP_CONTEXT
+	SCTP_FRAGMENT_INTERLEAVE,
+#define SCTP_FRAGMENT_INTERLEAVE SCTP_FRAGMENT_INTERLEAVE
 
 	/* Internal Socket Options. Some of the sctp library functions are 
 	 * implemented using these socket options.
@@ -530,7 +532,7 @@ struct sctp_paddrparams {
 	__u32			spp_flags;
 } __attribute__((packed, aligned(4)));
 
-/* 7.1.24. Delayed Ack Timer (SCTP_DELAYED_ACK_TIME)
+/* 7.1.23. Delayed Ack Timer (SCTP_DELAYED_ACK_TIME)
  *
  *   This options will get or set the delayed ack timer.  The time is set
  *   in milliseconds.  If the assoc_id is 0, then this sets or gets the
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index a1d026f12b0e..b4be473c68b0 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -2255,7 +2255,7 @@ static int sctp_setsockopt_peer_addr_params(struct sock *sk,
 	return 0;
 }
 
-/* 7.1.24. Delayed Ack Timer (SCTP_DELAYED_ACK_TIME)
+/* 7.1.23. Delayed Ack Timer (SCTP_DELAYED_ACK_TIME)
  *
  *   This options will get or set the delayed ack timer.  The time is set
  *   in milliseconds.  If the assoc_id is 0, then this sets or gets the
@@ -2792,6 +2792,46 @@ static int sctp_setsockopt_context(struct sock *sk, char __user *optval,
 	return 0;
 }
 
+/*
+ * 7.1.24.  Get or set fragmented interleave (SCTP_FRAGMENT_INTERLEAVE)
+ *
+ * This options will at a minimum specify if the implementation is doing
+ * fragmented interleave.  Fragmented interleave, for a one to many
+ * socket, is when subsequent calls to receive a message may return
+ * parts of messages from different associations.  Some implementations
+ * may allow you to turn this value on or off.  If so, when turned off,
+ * no fragment interleave will occur (which will cause a head of line
+ * blocking amongst multiple associations sharing the same one to many
+ * socket).  When this option is turned on, then each receive call may
+ * come from a different association (thus the user must receive data
+ * with the extended calls (e.g. sctp_recvmsg) to keep track of which
+ * association each receive belongs to.
+ *
+ * This option takes a boolean value.  A non-zero value indicates that
+ * fragmented interleave is on.  A value of zero indicates that
+ * fragmented interleave is off.
+ *
+ * Note that it is important that an implementation that allows this
+ * option to be turned on, have it off by default.  Otherwise an unaware
+ * application using the one to many model may become confused and act
+ * incorrectly.
+ */
+static int sctp_setsockopt_fragment_interleave(struct sock *sk,
+					       char __user *optval,
+					       int optlen)
+{
+	int val;
+
+	if (optlen != sizeof(int))
+		return -EINVAL;
+	if (get_user(val, (int __user *)optval))
+		return -EFAULT;
+
+	sctp_sk(sk)->frag_interleave = (val == 0) ? 0 : 1;
+
+	return 0;
+}
+
 /* API 6.2 setsockopt(), getsockopt()
  *
  * Applications use setsockopt() and getsockopt() to set or retrieve
@@ -2906,7 +2946,9 @@ SCTP_STATIC int sctp_setsockopt(struct sock *sk, int level, int optname,
 	case SCTP_CONTEXT:
 		retval = sctp_setsockopt_context(sk, optval, optlen);
 		break;
-
+	case SCTP_FRAGMENT_INTERLEAVE:
+		retval = sctp_setsockopt_fragment_interleave(sk, optval, optlen);
+		break;
 	default:
 		retval = -ENOPROTOOPT;
 		break;
@@ -3134,8 +3176,9 @@ SCTP_STATIC int sctp_init_sock(struct sock *sk)
 	sp->pf = sctp_get_pf_specific(sk->sk_family);
 
 	/* Control variables for partial data delivery. */
-	sp->pd_mode           = 0;
+	atomic_set(&sp->pd_mode, 0);
 	skb_queue_head_init(&sp->pd_lobby);
+	sp->frag_interleave = 0;
 
 	/* Create a per socket endpoint structure.  Even if we
 	 * change the data structure relationships, this may still
@@ -3642,7 +3685,7 @@ static int sctp_getsockopt_peer_addr_params(struct sock *sk, int len,
 	return 0;
 }
 
-/* 7.1.24. Delayed Ack Timer (SCTP_DELAYED_ACK_TIME)
+/* 7.1.23. Delayed Ack Timer (SCTP_DELAYED_ACK_TIME)
  *
  *   This options will get or set the delayed ack timer.  The time is set
  *   in milliseconds.  If the assoc_id is 0, then this sets or gets the
@@ -4536,6 +4579,29 @@ static int sctp_getsockopt_maxseg(struct sock *sk, int len,
 	return 0;
 }
 
+/*
+ * 7.1.24.  Get or set fragmented interleave (SCTP_FRAGMENT_INTERLEAVE)
+ * (chapter and verse is quoted at sctp_setsockopt_fragment_interleave())
+ */
+static int sctp_getsockopt_fragment_interleave(struct sock *sk, int len,
+					       char __user *optval, int __user *optlen)
+{
+	int val;
+
+	if (len < sizeof(int))
+		return -EINVAL;
+
+	len = sizeof(int);
+
+	val = sctp_sk(sk)->frag_interleave;
+	if (put_user(len, optlen))
+		return -EFAULT;
+	if (copy_to_user(optval, &val, len))
+		return -EFAULT;
+
+	return 0;
+}
+
 SCTP_STATIC int sctp_getsockopt(struct sock *sk, int level, int optname,
 				char __user *optval, int __user *optlen)
 {
@@ -4648,6 +4714,10 @@ SCTP_STATIC int sctp_getsockopt(struct sock *sk, int level, int optname,
 	case SCTP_CONTEXT:
 		retval = sctp_getsockopt_context(sk, len, optval, optlen);
 		break;
+	case SCTP_FRAGMENT_INTERLEAVE:
+		retval = sctp_getsockopt_fragment_interleave(sk, len, optval,
+							     optlen);
+		break;
 	default:
 		retval = -ENOPROTOOPT;
 		break;
@@ -5742,9 +5812,9 @@ static void sctp_sock_migrate(struct sock *oldsk, struct sock *newsk,
 	 * 3) Peeling off non-partial delivery; move pd_lobby to receive_queue.
 	 */
 	skb_queue_head_init(&newsp->pd_lobby);
-	sctp_sk(newsk)->pd_mode = assoc->ulpq.pd_mode;
+	atomic_set(&sctp_sk(newsk)->pd_mode, assoc->ulpq.pd_mode);
 
-	if (sctp_sk(oldsk)->pd_mode) {
+	if (atomic_read(&sctp_sk(oldsk)->pd_mode)) {
 		struct sk_buff_head *queue;
 
 		/* Decide which queue to move pd_lobby skbs to. */
@@ -5770,7 +5840,7 @@ static void sctp_sock_migrate(struct sock *oldsk, struct sock *newsk,
 		 * delivery to finish.
 		 */
 		if (assoc->ulpq.pd_mode)
-			sctp_clear_pd(oldsk);
+			sctp_clear_pd(oldsk, NULL);
 
 	}
 
diff --git a/net/sctp/ulpqueue.c b/net/sctp/ulpqueue.c
index b29e3e4b72c9..ac80c34f6c2c 100644
--- a/net/sctp/ulpqueue.c
+++ b/net/sctp/ulpqueue.c
@@ -138,18 +138,42 @@ int sctp_ulpq_tail_data(struct sctp_ulpq *ulpq, struct sctp_chunk *chunk,
 /* Clear the partial delivery mode for this socket.   Note: This
  * assumes that no association is currently in partial delivery mode.
  */
-int sctp_clear_pd(struct sock *sk)
+int sctp_clear_pd(struct sock *sk, struct sctp_association *asoc)
 {
 	struct sctp_sock *sp = sctp_sk(sk);
 
-	sp->pd_mode = 0;
-	if (!skb_queue_empty(&sp->pd_lobby)) {
-		struct list_head *list;
-		sctp_skb_list_tail(&sp->pd_lobby, &sk->sk_receive_queue);
-		list = (struct list_head *)&sctp_sk(sk)->pd_lobby;
-		INIT_LIST_HEAD(list);
-		return 1;
+	if (atomic_dec_and_test(&sp->pd_mode)) {
+		/* This means there are no other associations in PD, so
+		 * we can go ahead and clear out the lobby in one shot
+		 */
+		if (!skb_queue_empty(&sp->pd_lobby)) {
+			struct list_head *list;
+			sctp_skb_list_tail(&sp->pd_lobby, &sk->sk_receive_queue);
+			list = (struct list_head *)&sctp_sk(sk)->pd_lobby;
+			INIT_LIST_HEAD(list);
+			return 1;
+		}
+	} else {
+		/* There are other associations in PD, so we only need to
+		 * pull stuff out of the lobby that belongs to the
+		 * associations that is exiting PD (all of its notifications
+		 * are posted here).
+		 */
+		if (!skb_queue_empty(&sp->pd_lobby) && asoc) {
+			struct sk_buff *skb, *tmp;
+			struct sctp_ulpevent *event;
+
+			sctp_skb_for_each(skb, &sp->pd_lobby, tmp) {
+				event = sctp_skb2event(skb);
+				if (event->asoc == asoc) {
+					__skb_unlink(skb, &sp->pd_lobby);
+					__skb_queue_tail(&sk->sk_receive_queue,
+							 skb);
+				}
+			}
+		}
 	}
+
 	return 0;
 }
 
@@ -157,7 +181,7 @@ int sctp_clear_pd(struct sock *sk)
 static int sctp_ulpq_clear_pd(struct sctp_ulpq *ulpq)
 {
 	ulpq->pd_mode = 0;
-	return sctp_clear_pd(ulpq->asoc->base.sk);
+	return sctp_clear_pd(ulpq->asoc->base.sk, ulpq->asoc);
 }
 
 /* If the SKB of 'event' is on a list, it is the first such member
@@ -187,25 +211,35 @@ int sctp_ulpq_tail_event(struct sctp_ulpq *ulpq, struct sctp_ulpevent *event)
 	 * the association the cause of the partial delivery.
 	 */
 
-	if (!sctp_sk(sk)->pd_mode) {
+	if (atomic_read(&sctp_sk(sk)->pd_mode) == 0) {
 		queue = &sk->sk_receive_queue;
-	} else if (ulpq->pd_mode) {
-		/* If the association is in partial delivery, we
-		 * need to finish delivering the partially processed
-		 * packet before passing any other data.  This is
-		 * because we don't truly support stream interleaving.
-		 */
-		if ((event->msg_flags & MSG_NOTIFICATION) ||
-		    (SCTP_DATA_NOT_FRAG ==
-			    (event->msg_flags & SCTP_DATA_FRAG_MASK)))
-			queue = &sctp_sk(sk)->pd_lobby;
-		else {
-			clear_pd = event->msg_flags & MSG_EOR;
-			queue = &sk->sk_receive_queue;
+	} else {
+		if (ulpq->pd_mode) {
+			/* If the association is in partial delivery, we
+			 * need to finish delivering the partially processed
+			 * packet before passing any other data.  This is
+			 * because we don't truly support stream interleaving.
+			 */
+			if ((event->msg_flags & MSG_NOTIFICATION) ||
+			    (SCTP_DATA_NOT_FRAG ==
+				    (event->msg_flags & SCTP_DATA_FRAG_MASK)))
+				queue = &sctp_sk(sk)->pd_lobby;
+			else {
+				clear_pd = event->msg_flags & MSG_EOR;
+				queue = &sk->sk_receive_queue;
+			}
+		} else {
+			/*
+			 * If fragment interleave is enabled, we
+			 * can queue this to the recieve queue instead
+			 * of the lobby.
+			 */
+			if (sctp_sk(sk)->frag_interleave)
+				queue = &sk->sk_receive_queue;
+			else
+				queue = &sctp_sk(sk)->pd_lobby;
 		}
-	} else
-		queue = &sctp_sk(sk)->pd_lobby;
-
+	}
 
 	/* If we are harvesting multiple skbs they will be
 	 * collected on a list.
@@ -826,18 +860,29 @@ void sctp_ulpq_partial_delivery(struct sctp_ulpq *ulpq,
 {
 	struct sctp_ulpevent *event;
 	struct sctp_association *asoc;
+	struct sctp_sock *sp;
 
 	asoc = ulpq->asoc;
+	sp = sctp_sk(asoc->base.sk);
 
-	/* Are we already in partial delivery mode?  */
-	if (!sctp_sk(asoc->base.sk)->pd_mode) {
+	/* If the association is already in Partial Delivery mode
+	 * we have noting to do.
+	 */
+	if (ulpq->pd_mode)
+		return;
 
+	/* If the user enabled fragment interleave socket option,
+	 * multiple associations can enter partial delivery.
+	 * Otherwise, we can only enter partial delivery if the
+	 * socket is not in partial deliver mode.
+	 */
+	if (sp->frag_interleave || atomic_read(&sp->pd_mode) == 0) {
 		/* Is partial delivery possible?  */
 		event = sctp_ulpq_retrieve_first(ulpq);
 		/* Send event to the ULP.   */
 		if (event) {
 			sctp_ulpq_tail_event(ulpq, event);
-			sctp_sk(asoc->base.sk)->pd_mode = 1;
+			atomic_inc(&sp->pd_mode);
 			ulpq->pd_mode = 1;
 			return;
 		}