Rework socket upcalls to close some races with setup/teardown of upcalls.

- Each socket upcall is now invoked with the appropriate socket buffer
  locked.  It is not permissible to call soisconnected() with this lock
  held; however, so socket upcalls now return an integer value.  The two
  possible values are SU_OK and SU_ISCONNECTED.  If an upcall returns
  SU_ISCONNECTED, then the soisconnected() will be invoked on the
  socket after the socket buffer lock is dropped.
- A new API is provided for setting and clearing socket upcalls.  The
  API consists of soupcall_set() and soupcall_clear().
- To simplify locking, each socket buffer now has a separate upcall.
- When a socket upcall returns SU_ISCONNECTED, the upcall is cleared from
  the receive socket buffer automatically.  Note that a SO_SND upcall
  should never return SU_ISCONNECTED.
- All this means that accept filters should now return SU_ISCONNECTED
  instead of calling soisconnected() directly.  They also no longer need
  to explicitly clear the upcall on the new socket.
- The HTTP accept filter still uses soupcall_set() to manage its internal
  state machine, but other accept filters no longer have any explicit
  knowlege of socket upcall internals aside from their return value.
- The various RPC client upcalls currently drop the socket buffer lock
  while invoking soreceive() as a temporary band-aid.  The plan for
  the future is to add a new flag to allow soreceive() to be called with
  the socket buffer locked.
- The AIO callback for socket I/O is now also invoked with the socket
  buffer locked.  Previously sowakeup() would drop the socket buffer
  lock only to call aio_swake() which immediately re-acquired the socket
  buffer lock for the duration of the function call.

Discussed with:	rwatson, rmacklem

1 files changed, 4 insertions, 5 deletions

diff --git a/sys/netsmb/smb_trantcp.c b/sys/netsmb/smb_trantcp.c
index 167b74be0191..1a74e728b6ff 100644
--- a/sys/netsmb/smb_trantcp.c
+++ b/sys/netsmb/smb_trantcp.c
@@ -100,14 +100,15 @@ nb_intr(struct nbpcb *nbp, struct proc *p)
 	return 0;
 }
 
-static void
+static int
 nb_upcall(struct socket *so, void *arg, int waitflag)
 {
 	struct nbpcb *nbp = arg;
 
 	if (arg == NULL || nbp->nbp_selectid == NULL)
-		return;
+		return (SU_OK);
 	wakeup(nbp->nbp_selectid);
+	return (SU_OK);
 }
 
 static int
@@ -152,10 +153,8 @@ nb_connect_in(struct nbpcb *nbp, struct sockaddr_in *to, struct thread *td)
 	if (error)
 		return error;
 	nbp->nbp_tso = so;
-	so->so_upcallarg = (caddr_t)nbp;
-	so->so_upcall = nb_upcall;
 	SOCKBUF_LOCK(&so->so_rcv);
-	so->so_rcv.sb_flags |= SB_UPCALL;
+	soupcall_set(so, SO_RCV, nb_upcall, nbp);
 	SOCKBUF_UNLOCK(&so->so_rcv);
 	so->so_rcv.sb_timeo = (5 * hz);
 	so->so_snd.sb_timeo = (5 * hz);