Remove two simultaneous acquisitions of multiple unpcb locks from

uipc_send in cases where only a global read lock is held by breaking
them out and avoiding the unpcb lock acquire in the common case.  This
avoids deadlocks which manifested with X11, and should also marginally
further improve performance.

Reported by:	sepotvin, brooks

1 files changed, 19 insertions, 22 deletions

diff --git a/sys/kern/uipc_usrreq.c b/sys/kern/uipc_usrreq.c
index 3a30138..17a8fb5 100644
--- a/sys/kern/uipc_usrreq.c
+++ b/sys/kern/uipc_usrreq.c
@@ -774,21 +774,18 @@ uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
 
 		unp2 = unp->unp_conn;
 		if (nam != NULL) {
+			UNP_GLOBAL_WLOCK_ASSERT();
 			if (unp2 != NULL) {
 				error = EISCONN;
-				UNP_PCB_LOCK(unp);
 				break;
 			}
 			error = unp_connect(so, nam, td);
-			UNP_PCB_LOCK(unp);
 			if (error)
 				break;
 			unp2 = unp->unp_conn;
 		} else {
-			UNP_PCB_LOCK(unp);
 			if (unp2 == NULL) {
 				error = ENOTCONN;
-				UNP_PCB_LOCK(unp);
 				break;
 			}
 		}
@@ -799,19 +796,19 @@ uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
 		 * return the slightly counter-intuitive but otherwise
 		 * correct error that the socket is not connected.
 		 */
-		UNP_PCB_LOCK_ASSERT(unp);
 		if (unp2 == NULL) {
 			error = ENOTCONN;
 			break;
 		}
-		UNP_PCB_LOCK(unp2);
-		so2 = unp2->unp_socket;
+		/* Lockless read. */
+		if (unp2->unp_flags & UNP_WANTCRED)
+			control = unp_addsockcred(td, control);
+		UNP_PCB_LOCK(unp);
 		if (unp->unp_addr != NULL)
 			from = (struct sockaddr *)unp->unp_addr;
 		else
 			from = &sun_noname;
-		if (unp2->unp_flags & UNP_WANTCRED)
-			control = unp_addsockcred(td, control);
+		so2 = unp2->unp_socket;
 		SOCKBUF_LOCK(&so2->so_rcv);
 		if (sbappendaddr_locked(&so2->so_rcv, from, m, control)) {
 			sorwakeup_locked(so2);
@@ -821,9 +818,13 @@ uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
 			SOCKBUF_UNLOCK(&so2->so_rcv);
 			error = ENOBUFS;
 		}
-		if (nam != NULL)
+		if (nam != NULL) {
+			UNP_GLOBAL_WLOCK_ASSERT();
+			UNP_PCB_LOCK(unp2);
 			unp_disconnect(unp, unp2);
-		UNP_PCB_UNLOCK(unp2);
+			UNP_PCB_UNLOCK(unp2);
+		}
+		UNP_PCB_UNLOCK(unp);
 		break;
 	}
 
@@ -836,18 +837,15 @@ uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
 		 */
 		if ((so->so_state & SS_ISCONNECTED) == 0) {
 			if (nam != NULL) {
+				UNP_GLOBAL_WLOCK_ASSERT();
 				error = unp_connect(so, nam, td);
-				UNP_PCB_LOCK(unp);
 				if (error)
 					break;	/* XXX */
 			} else {
 				error = ENOTCONN;
-				UNP_PCB_LOCK(unp);
 				break;
 			}
-		} else
-			UNP_PCB_LOCK(unp);
-		UNP_PCB_LOCK_ASSERT(unp);
+		}
 
 		/* Lockless read. */
 		if (so->so_snd.sb_state & SBS_CANTSENDMORE) {
@@ -874,13 +872,12 @@ uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
 			error = ENOTCONN;
 			break;
 		}
-		UNP_PCB_LOCK(unp2);
 		so2 = unp2->unp_socket;
+		UNP_PCB_LOCK(unp2);
 		SOCKBUF_LOCK(&so2->so_rcv);
 		if (unp2->unp_flags & UNP_WANTCRED) {
 			/*
-			 * Credentials are passed only once on
-			 * SOCK_STREAM.
+			 * Credentials are passed only once on SOCK_STREAM.
 			 */
 			unp2->unp_flags &= ~UNP_WANTCRED;
 			control = unp_addsockcred(td, control);
@@ -915,14 +912,14 @@ uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
 	}
 
 	/*
-	 * SEND_EOF is equivalent to a SEND followed by
-	 * a SHUTDOWN.
+	 * SEND_EOF is equivalent to a SEND followed by a SHUTDOWN.
 	 */
 	if (flags & PRUS_EOF) {
+		UNP_PCB_LOCK(unp);
 		socantsendmore(so);
 		unp_shutdown(unp);
+		UNP_PCB_UNLOCK(unp);
 	}
-	UNP_PCB_UNLOCK(unp);
 
 	if ((nam != NULL) || (flags & PRUS_EOF))
 		UNP_GLOBAL_WUNLOCK();