Add sockbuf_pushsync(), an inline function that, following a change to

the head of the mbuf chains in a socket buffer, re-synchronizes the
cache pointers used to optimize socket buffer appends.  This will be
used by soreceive() before dropping socket buffer mutexes to make sure
a consistent version of the socket buffer is visible to other threads.

While here, update copyright to account for substantial rewrite of much
socket code required for fine-grained locking.

1 files changed, 38 insertions, 0 deletions

diff --git a/sys/kern/uipc_socket.c b/sys/kern/uipc_socket.c
index 160c89e..065dd11 100644
--- a/sys/kern/uipc_socket.c
+++ b/sys/kern/uipc_socket.c
@@ -1,4 +1,6 @@
 /*
+ * Copyright (c) 2004 The FreeBSD Foundation
+ * Copyright (c) 2004 Robert Watson
  * Copyright (c) 1982, 1986, 1988, 1990, 1993
  *	The Regents of the University of California.  All rights reserved.
  *
@@ -892,6 +894,42 @@ bad:
 }
 
 /*
+ * Following replacement or removal of the first mbuf on the first mbuf chain
+ * of a socket buffer, push necessary state changes back into the socket
+ * buffer so that other consumers see the values consistently.  'nextrecord'
+ * is the callers locally stored value of the original value of
+ * sb->sb_mb->m_nextpkt which must be restored when the lead mbuf changes.
+ * NOTE: 'nextrecord' may be NULL.
+ */
+static __inline void
+sockbuf_pushsync(struct sockbuf *sb, struct mbuf *nextrecord)
+{
+
+	SOCKBUF_LOCK_ASSERT(sb);
+	/*
+	 * First, update for the new value of nextrecord.  If necessary, make
+	 * it the first record.
+	 */
+	if (sb->sb_mb != NULL)
+		sb->sb_mb->m_nextpkt = nextrecord;
+	else
+		sb->sb_mb = nextrecord;
+
+        /*
+         * Now update any dependent socket buffer fields to reflect the new
+         * state.  This is an expanded inline of SB_EMPTY_FIXUP(), with the
+	 * addition of a second clause that takes care of the case where
+	 * sb_mb has been updated, but remains the last record.
+         */
+        if (sb->sb_mb == NULL) {
+                sb->sb_mbtail = NULL;
+                sb->sb_lastrecord = NULL;
+        } else if (sb->sb_mb->m_nextpkt == NULL)
+                sb->sb_lastrecord = sb->sb_mb;
+}
+
+
+/*
  * Implement receive operations on a socket.
  * We depend on the way that records are added to the sockbuf
  * by sbappend*.  In particular, each record (mbufs linked through m_next)