From f40a0a8d12aee873e5bfbde048ecf9261f43e5ad Mon Sep 17 00:00:00 2001
From: Rodrigo Arias <rodrigo.arias@bsc.es>
Date: Wed, 11 Jan 2023 12:42:18 +0100
Subject: [PATCH] Prevent propagation loops

---
 src/emu/bay.c |  9 ++++++---
 src/emu/bay.h |  1 +
 src/emu/mux.c | 17 +++++++++++++++--
 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/src/emu/bay.c b/src/emu/bay.c
index a8f968b..c112f29 100644
--- a/src/emu/bay.c
+++ b/src/emu/bay.c
@@ -14,7 +14,11 @@ cb_chan_is_dirty(struct chan *chan, void *arg)
 	struct bay_chan *bchan = arg;
 	struct bay *bay = bchan->bay;
 
-	/* TODO: check duplicate? */
+	if (bchan->is_dirty) {
+		err("channel %s already on dirty list\n", chan->name);
+		return -1;
+	}
+
 	DL_APPEND(bay->dirty, bchan);
 	return 0;
 }
@@ -94,8 +98,6 @@ bay_add_cb(struct bay *bay, struct chan *chan, bay_cb_func_t func, void *arg)
 	return 0;
 }
 
-
-
 void
 bay_init(struct bay *bay)
 {
@@ -142,6 +144,7 @@ bay_propagate(struct bay *bay)
 			err("bay_propagate: chan_flush failed\n");
 			return -1;
 		}
+		cur->is_dirty = 0;
 	}
 
 	bay->dirty = NULL;
diff --git a/src/emu/bay.h b/src/emu/bay.h
index 94114cf..2cada96 100644
--- a/src/emu/bay.h
+++ b/src/emu/bay.h
@@ -28,6 +28,7 @@ struct bay_chan {
 	int ncallbacks;
 	struct bay_cb *cb;
 	struct bay *bay;
+	int is_dirty;
 
 	/* Global hash table with all channels in bay */
 	UT_hash_handle hh;
diff --git a/src/emu/mux.c b/src/emu/mux.c
index 43f1492..b37b1b4 100644
--- a/src/emu/mux.c
+++ b/src/emu/mux.c
@@ -88,8 +88,6 @@ cb_input(struct chan *in_chan, void *ptr)
 {
 	struct mux *mux = ptr;
 
-	/* TODO: We may need to cache the last read value from select to avoid
-	 * problems reading the select channel too soon */
 	struct value sel_value;
 	if (chan_read(mux->select, &sel_value) != 0) {
 		err("cb_input: chan_read(select) failed\n");
@@ -139,6 +137,11 @@ mux_init(struct mux *mux,
 		return -1;
 	}
 
+	if (select == output) {
+		err("mux_init: cannot use same channel as select and output\n");
+		return -1;
+	}
+
 	/* The output channel must accept multiple writes in the same
 	 * propagation phase while the channel is dirty, as we may write to the
 	 * input and select channel at the same time. */
@@ -178,6 +181,16 @@ mux_find_input(struct mux *mux, struct value value)
 int
 mux_add_input(struct mux *mux, struct value key, struct chan *chan)
 {
+	if (chan == mux->output) {
+		err("mux_init: cannot use same input channel as output\n");
+		return -1;
+	}
+
+	if (chan == mux->select) {
+		err("mux_init: cannot use same input channel as select\n");
+		return -1;
+	}
+
 	if (mux_find_input(mux, key) != NULL) {
 		char buf[128];
 		err("mux_add_input: input key %s already in mux\n",