Mark select channel as dirty on mux_init()

Ensures that the select callback will be called on the propagation
phase, immediately setting the right output. Otherwise the mux won't be
updated until the select channel sets a new value.

src/emu/mux.c

@@ -192,6 +192,13 @@ mux_init(struct mux *mux,
 		return -1;
 	}
 
+	/* Mark the select channel as dirty, so it runs the select
+	 * callback even if it doesn't have a new value */
+	if (chan_dirty(select) != 0) {
+		err("chan_dirty failed");
+		return -1;
+	}
+
 	return 0;
 }
 

test/emu/nanos6/CMakeLists.txt

@@ -8,3 +8,4 @@ ovni_test(task-types.c MP)
 ovni_test(blocking.c MP)
 ovni_test(ss-mismatch.c SHOULD_FAIL
   REGEX "thread [0-9]\\+ ended with 1 stacked nanos6 subsystems")
+ovni_test(delayed-connect-ss.c)

test/emu/nanos6/delayed-connect-ss.c

@@ -0,0 +1,28 @@
+/* Copyright (c) 2023 Barcelona Supercomputing Center (BSC)
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include "instr_nanos6.h"
+
+int
+main(void)
+{
+	instr_start(0, 1);
+
+	/* Until here, the nanos6 model has not been connected to the
+	 * patchbay yet. The next event will cause the subsystem mux to
+	 * be connected to the patchbay. We need to ensure that at that
+	 * moment the select channel is evaluated, otherwise the mux
+	 * will remain selecting a null input until the thread state
+	 * changes. */
+
+	/* FIXME: We should be able to test that after emitting the
+	 * nanos6 event the emulator follows some properties. */
+
+	instr_nanos6_worker_loop_enter();
+
+	instr_nanos6_worker_loop_exit();
+
+	instr_end();
+
+	return 0;
+}