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, 1 insertions, 2 deletions

diff --git a/sys/kern/vfs_aio.c b/sys/kern/vfs_aio.c
index 7cd077b..f22dea7 100644
--- a/sys/kern/vfs_aio.c
+++ b/sys/kern/vfs_aio.c
@@ -1313,12 +1313,12 @@ aio_swake_cb(struct socket *so, struct sockbuf *sb)
 	struct aiocblist *cb, *cbn;
 	int opcode;
 
+	SOCKBUF_LOCK_ASSERT(sb);
 	if (sb == &so->so_snd)
 		opcode = LIO_WRITE;
 	else
 		opcode = LIO_READ;
 
-	SOCKBUF_LOCK(sb);
 	sb->sb_flags &= ~SB_AIO;
 	mtx_lock(&aio_job_mtx);
 	TAILQ_FOREACH_SAFE(cb, &so->so_aiojobq, list, cbn) {
@@ -1336,7 +1336,6 @@ aio_swake_cb(struct socket *so, struct sockbuf *sb)
 		}
 	}
 	mtx_unlock(&aio_job_mtx);
-	SOCKBUF_UNLOCK(sb);
 }
 
 static int