fixes #568 Want a single reader/write lock on socket child objects

fixes #170 Make more use of reaper

This is a complete restructure/rethink of how child objects interact
with the socket.  (This also backs out #576 as it turns out not to be
needed.)  While 568 says reader/writer lock, for now we have settled
for a single writer lock. Its likely that this is sufficient.

Essentially we use the single socket lock to guard lists of the socket
children.  We also use deferred deletion in the idhash to facilitate
teardown, which means endpoint closes are no longer synchronous.

We use the reaper to clean up objects when the reference count drops
to zero.  We make a special exception for pipes, since they really
are not reference counted by their parents, and they are leaf objects
anyway.

We believe this addresses the main outstanding race conditions in
a much more correct and holistic way.

Note that endpoint shutdown is a little tricky, as it makes use of
atomic flags to guard against double entry, and against recursive
lock entry. This is something that would be nice to make a bit more
obvious, but what we have is safe, and the complexity is at least
confined to one place.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/protocol/reqrep0/req.c b/src/protocol/reqrep0/req.c
index 43751d14..018dd0e8 100644
--- a/src/protocol/reqrep0/req.c
+++ b/src/protocol/reqrep0/req.c
@@ -305,7 +305,7 @@ req0_send_cb(void *arg)
 		// We failed to send... clean up and deal with it.
 		nni_msg_free(nni_aio_get_msg(p->aio_send));
 		nni_aio_set_msg(p->aio_send, NULL);
-		nni_pipe_stop(p->pipe);
+		nni_pipe_close(p->pipe);
 		return;
 	}
 
@@ -345,7 +345,7 @@ req0_recv_cb(void *arg)
 	uint32_t   id;
 
 	if (nni_aio_result(p->aio_recv) != 0) {
-		nni_pipe_stop(p->pipe);
+		nni_pipe_close(p->pipe);
 		return;
 	}
 
@@ -409,7 +409,7 @@ req0_recv_cb(void *arg)
 
 malformed:
 	nni_msg_free(msg);
-	nni_pipe_stop(p->pipe);
+	nni_pipe_close(p->pipe);
 }
 
 static void