3 files changed, 24 insertions, 9 deletions
diff --git a/sys/kern/uipc_sockbuf.c b/sys/kern/uipc_sockbuf.c
index e1fc34106819..be4c0a250793 100644
--- a/sys/kern/uipc_sockbuf.c
+++ b/sys/kern/uipc_sockbuf.c
@@ -137,8 +137,12 @@ int
 sblock(struct sockbuf *sb, int flags)
 {
 
-	if (flags == M_WAITOK) {
-		if (sb->sb_flags & SB_NOINTR) {
+	KASSERT((flags & SBL_VALID) == flags,
+	    ("sblock: flags invalid (0x%x)", flags));
+
+	if (flags & SBL_WAIT) {
+		if ((sb->sb_flags & SB_NOINTR) ||
+		    (flags & SBL_NOINTR)) {
 			sx_xlock(&sb->sb_sx);
 			return (0);
 		}
diff --git a/sys/kern/uipc_socket.c b/sys/kern/uipc_socket.c
index e2cf09b00457..9c83b04a1565 100644
--- a/sys/kern/uipc_socket.c
+++ b/sys/kern/uipc_socket.c
@@ -916,7 +916,7 @@ out:
 }
 #endif /*ZERO_COPY_SOCKETS*/
 
-#define	SBLOCKWAIT(f)	(((f) & MSG_DONTWAIT) ? M_NOWAIT : M_WAITOK)
+#define	SBLOCKWAIT(f)	(((f) & MSG_DONTWAIT) ? 0 : SBL_WAIT)
 
 int
 sosend_dgram(struct socket *so, struct sockaddr *addr, struct uio *uio,
@@ -1884,10 +1884,16 @@ sorflush(struct socket *so)
 	 * however, we have to initialize and destroy the mutex in the copy
 	 * so that dom_dispose() and sbrelease() can lock t as needed.
 	 */
-	(void) sblock(sb, M_WAITOK);
-	SOCKBUF_LOCK(sb);
-	sb->sb_flags |= SB_NOINTR;
-	socantrcvmore_locked(so);
+
+	/*
+	 * Dislodge threads currently blocked in receive and wait to acquire
+	 * a lock against other simultaneous readers before clearing the
+	 * socket buffer.  Don't let our acquire be interrupted by a signal
+	 * despite any existing socket disposition on interruptable waiting.
+	 */
+	socantrcvmore(so);
+	(void) sblock(sb, SBL_WAIT | SBL_NOINTR);
+
 	/*
 	 * Invalidate/clear most of the sockbuf structure, but leave selinfo
 	 * and mutex data unchanged.
diff --git a/sys/kern/uipc_syscalls.c b/sys/kern/uipc_syscalls.c
index 2821a5ea07c5..6ffcda2feb72 100644
--- a/sys/kern/uipc_syscalls.c
+++ b/sys/kern/uipc_syscalls.c
@@ -1881,8 +1881,13 @@ kern_sendfile(struct thread *td, struct sendfile_args *uap,
 		}
 	}
 
-	/* Protect against multiple writers to the socket. */
-	(void) sblock(&so->so_snd, M_WAITOK);
+	/*
+	 * Protect against multiple writers to the socket.
+	 *
+	 * XXXRW: Historically this has assumed non-interruptibility, so now
+	 * we implement that, but possibly shouldn't.
+	 */
+	(void)sblock(&so->so_snd, SBL_WAIT | SBL_NOINTR);
 
 	/*
 	 * Loop through the pages of the file, starting with the requested