Add a mutex ng_tty_mtx to protect the global variable ngt_unit. Note

that the locking of globals here isn't complete, and there's also a
locking issue relating to calling into and out of the tty code.

1 files changed, 10 insertions, 0 deletions

diff --git a/sys/netgraph/ng_tty.c b/sys/netgraph/ng_tty.c
index 9e4ecc31b40f..bd341da51639 100644
--- a/sys/netgraph/ng_tty.c
+++ b/sys/netgraph/ng_tty.c
@@ -166,10 +166,18 @@ static struct ng_type typestruct = {
 };
 NETGRAPH_INIT(tty, &typestruct);
 
+/*
+ * XXXRW: ngt_unit is protected by ng_tty_mtx.  ngt_ldisc is constant once
+ * ng_tty is initialized.  ngt_nodeop_ok is untouched, and might want to be a
+ * sleep lock in the future?
+ */
 static int ngt_unit;
 static int ngt_nodeop_ok;	/* OK to create/remove node */
 static int ngt_ldisc;
 
+static struct mtx	ng_tty_mtx;
+MTX_SYSINIT(ng_tty, &ng_tty_mtx, "ng_tty", MTX_DEF);
+
 /******************************************************************
 		    LINE DISCIPLINE METHODS
 ******************************************************************/
@@ -214,7 +222,9 @@ ngt_open(struct cdev *dev, struct tty *tp)
 		FREE(sc, M_NETGRAPH);
 		goto done;
 	}
+	mtx_lock(&ng_tty_mtx);
 	snprintf(name, sizeof(name), "%s%d", typestruct.name, ngt_unit++);
+	mtx_unlock(&ng_tty_mtx);
 
 	/* Assign node its name */
 	if ((error = ng_name_node(sc->node, name))) {