Add survey test (and fix survey pattern).

As part of this, we've added a way to unblock callers in a message
queue with an error, even without a signal channel.  This was necessary
to interrupt blockers upon survey timeout.  They will get NNG_ETIMEDOUT,
but afterwards callers get NNG_ESTATE.

1 files changed, 18 insertions, 0 deletions

diff --git a/src/core/msgqueue.h b/src/core/msgqueue.h
index 09d7fa0c..450c55a4 100644
--- a/src/core/msgqueue.h
+++ b/src/core/msgqueue.h
@@ -87,6 +87,24 @@ extern int nni_msgq_get_sig(nni_msgq *, nni_msg **, nni_signal *);
 // It modifies the turnstile's value under the lock to a non-zero value.
 extern void nni_msgq_signal(nni_msgq *, nni_signal *);
 
+// nni_msgq_set_error sets an error condition on the message queue,
+// which causes all current and future readers/writes to return the
+// given error condition (if non-zero).  Threads waiting to put or get
+// are woken as well, if non-zero.  If zero, then any present error
+// condition is cleared, and waiters are not woken (there shouldn't be
+// any waiters unless it was already zero.)
+extern void nni_msgq_set_error(nni_msgq *, int);
+
+// nni_msgq_set_put_error sets an error condition on the put side of the
+// message queue, and for that side behaves like nni_msgq_set_error.
+// Readers (nni_msgq_get*) are unaffected.
+extern void nni_msgq_set_put_error(nni_msgq *, int);
+
+// nni_msgq_set_get_error sets an error condition on the get side of the
+// message queue, and for that side behaves like nni_msgq_set_error.
+// Readers (nni_msgq_put*) are unaffected.
+extern void nni_msgq_set_get_error(nni_msgq *, int);
+
 // nni_msgq_close closes the queue.  After this all operates on the
 // message queue will return NNG_ECLOSED.  Messages inside the queue
 // are freed.  Unlike closing a go channel, this operation is idempotent.