lib: add ability to log from external pthread

External libraries can re-enter the FRR code through a hook function. A
crash occurs when logging from this hook function if the library has
initiated a new pthread, as the FRR RCU context is not initialized for
this thread.

Add frr_pthread_non_controlled_startup() function to initialize a valid
RCU context within a FRR pthread context, originating from an external
pthread.

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/lib/frr_pthread.c b/lib/frr_pthread.c
index 761969266a..f7e57136d6 100644
--- a/lib/frr_pthread.c
+++ b/lib/frr_pthread.c
@@ -220,6 +220,37 @@ void frr_pthread_stop_all(void)
 	}
 }
 
+static void *frr_pthread_attr_non_controlled_start(void *arg)
+{
+	struct frr_pthread *fpt = arg;
+
+	fpt->running = true;
+
+	return NULL;
+}
+
+/* Create a FRR pthread context from a non FRR pthread initialized from an
+ * external library in order to allow logging */
+int frr_pthread_non_controlled_startup(pthread_t thread, const char *name,
+				       const char *os_name)
+{
+	struct frr_pthread_attr attr = {
+		.start = frr_pthread_attr_non_controlled_start,
+		.stop = frr_pthread_attr_default.stop,
+	};
+	struct frr_pthread *fpt;
+
+	fpt = frr_pthread_new(&attr, name, os_name);
+	if (!fpt)
+		return -1;
+
+	fpt->thread = thread;
+	fpt->rcu_thread = rcu_thread_new(NULL);
+	frr_pthread_inner(fpt);
+
+	return 0;
+}
+
 /*
  * ----------------------------------------------------------------------------
  * Default Event Loop