sm: Support attributes

Signed-off-by: Cole Miller <[email protected]>

src/lib/sm.c

@@ -32,6 +32,17 @@ void sm_relate(const struct sm *from, const struct sm *to)
 		from->name, to->name, from->pid, to->pid, from->id, to->id);
 }
 
+void sm_attr(const struct sm *m, const char *k, const char *fmt, ...)
+{
+	char v[SM_MAX_ATTR_LENGTH];
+	va_list ap;
+	va_start(ap, fmt);
+	vsnprintf(v, sizeof(v), fmt, ap);
+	va_end(ap);
+	tracef("%s-attr pid: %d sm_id: %" PRIu64 " %s %s |",
+	       m->name, m->pid, m->id, k, v);
+}
+
 void sm_init(struct sm *m,
 	     bool (*invariant)(const struct sm *, int),
 	     bool (*is_locked)(const struct sm *),

src/lib/sm.h

@@ -10,6 +10,7 @@
 #define CHECK(cond) sm_check((cond), __FILE__, __LINE__, #cond)
 
 #define SM_MAX_NAME_LENGTH 50
+#define SM_MAX_ATTR_LENGTH 100
 
 enum {
 	SM_PREV_NONE = -1,
@@ -54,5 +55,9 @@ int sm_state(const struct sm *m);
 bool sm_check(bool b, const char *f, int n, const char *s);
 /* Relates one state machine to another for observability. */
 void sm_relate(const struct sm *from, const struct sm *to);
+/**
+ * Records an attribute of a state machine for observability.
+ */
+void sm_attr(const struct sm *m, const char *k, const char *fmt, ...);
 
 #endif /* __LIB_SM__ */