fixes #419 want to nni_aio_stop without blocking (#428)

* fixes #419 want to nni_aio_stop without blocking

This actually introduces an nni_aio_close() API that causes
nni_aio_begin to return NNG_ECLOSED, while scheduling a callback
on the AIO to do an NNG_ECLOSED as well.  This should be called
in non-blocking close() contexts instead of nni_aio_stop(), and
the cases where we call nni_aio_fini() multiple times are updated
updated to add nni_aio_stop() calls on all "interlinked" aios before
finalizing them.

Furthermore, we call nni_aio_close() as soon as practical in the
close path.  This closes an annoying race condition where the
callback from a lower subsystem could wind up rescheduling an
operation that we wanted to abort.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/core/aio.h b/src/core/aio.h
index 2ed0fb5b..5462c40b 100644
--- a/src/core/aio.h
+++ b/src/core/aio.h
@@ -42,6 +42,12 @@ extern void nni_aio_fini(nni_aio *);
 // use nni_aio_cancel instead.)
 extern void nni_aio_stop(nni_aio *);
 
+// nni_aio_close closes the aio for further activity. It aborts any in-progress
+// transaction (if it can), and future calls nni_aio_begin or nni_aio_schedule
+// with both result in NNG_ECLOSED. The expectation is that protocols call this
+// for all their aios in a stop routine, before calling fini on any of them.
+extern void nni_aio_close(nni_aio *);
+
 // nni_aio_set_data sets user data.  This should only be done by the
 // consumer, initiating the I/O.  The intention is to be able to store
 // additional data for use when the operation callback is executed.