Enforce documented RCU preconditions with assertions

[lttng-tools.git] / src / bin / lttng-relayd / ctf-trace.cpp

diff --git a/src/bin/lttng-relayd/ctf-trace.cpp b/src/bin/lttng-relayd/ctf-trace.cpp
index 7a3cbdea0ebde00f0613ccff1cb42553d2d6d798..861bcfbb3f7a44c6d055babdc544abc584835dfc 100644 (file)
--- a/src/bin/lttng-relayd/ctf-trace.cpp
+++ b/src/bin/lttng-relayd/ctf-trace.cpp
@@ -41,6 +41,8 @@ static void ctf_trace_destroy(struct ctf_trace *trace)
         * control side.
         */
        LTTNG_ASSERT(cds_list_empty(&trace->stream_list));
+       ASSERT_RCU_READ_LOCKED();
+
        session_put(trace->session);
        trace->session = NULL;
        free(trace->path);
@@ -62,11 +64,26 @@ static void ctf_trace_release(struct urcu_ref *ref)
 }
 
 /*
- * Should be called with RCU read-side lock held.
+ * The caller must either:
+ * - hold the RCU read side lock, or
+ * - guarantee the existence of the object by already holding a reference to
+ *   the object.
  */
 bool ctf_trace_get(struct ctf_trace *trace)
 {
-       return urcu_ref_get_unless_zero(&trace->ref);
+       const bool ref = urcu_ref_get_unless_zero(&trace->ref);
+
+       if (!ref) {
+               /*
+                * The ref count is already zero. It means the object is being
+                * torn down concurently.
+                * This is only acceptable if we hold the RCU read-side lock,
+                * else it's a logic error.
+                */
+               ASSERT_RCU_READ_LOCKED();
+       }
+
+       return ref;
 }
 
 /*