session: Make sr_session_stop thread-safe

[libsigrok.git] / session.c

diff --git a/session.c b/session.c
index ac5981ad050b6993478ca04f0838345c704e2eb8..acf1158b4e3ad0e75061c4aa9ab831f5c5aadbd1 100644 (file)
--- a/session.c
+++ b/session.c
@@ -79,6 +79,8 @@ SR_API struct sr_session *sr_session_new(void)
        }
 
        session->source_timeout = -1;
+       session->abort_session = FALSE;
+       g_mutex_init(&session->stop_mutex);
 
        return session;
 }
@@ -101,6 +103,8 @@ SR_API int sr_session_destroy(void)
 
        /* TODO: Error checks needed? */
 
+       g_mutex_clear(&session->stop_mutex);
+
        g_free(session);
        session = NULL;
 
@@ -283,6 +287,16 @@ static int sr_session_run_poll(void)
                                                session->sources[i].cb_data))
                                        sr_session_source_remove(session->sources[i].poll_object);
                        }
+                       /*
+                        * We want to take as little time as possible to stop
+                        * the session if we have been told to do so. Therefore,
+                        * we check the flag after processing every source, not
+                        * just once per main event loop.
+                        */
+                       g_mutex_lock(&session->stop_mutex);
+                       if (session->abort_session)
+                               sr_session_stop_sync();
+                       g_mutex_unlock(&session->stop_mutex);
                }
        }
 
@@ -372,9 +386,12 @@ SR_API int sr_session_run(void)
  * The current session is stopped immediately, with all acquisition sessions
  * being stopped and hardware drivers cleaned up.
  *
+ * This must be called from within the session thread, to prevent freeing
+ * resources that the session thread will try to use.
+ *
  * @return SR_OK upon success, SR_ERR_BUG if no session exists.
  */
-SR_API int sr_session_stop(void)
+SR_PRIV int sr_session_stop_sync(void)
 {
        struct sr_dev_inst *sdi;
        GSList *l;
@@ -406,6 +423,33 @@ SR_API int sr_session_stop(void)
        return SR_OK;
 }
 
+/**
+ * Stop the current session.
+ *
+ * The current session is stopped immediately, with all acquisition sessions
+ * being stopped and hardware drivers cleaned up.
+ *
+ * If the session is run in a separate thread, this function will not block
+ * until the session is finished executing. It is the caller's responsibility
+ * to wait for the session thread to return before assuming that the session is
+ * completely decommissioned.
+ *
+ * @return SR_OK upon success, SR_ERR_BUG if no session exists.
+ */
+SR_API int sr_session_stop(void)
+{
+       if (!session) {
+               sr_err("%s: session was NULL", __func__);
+               return SR_ERR_BUG;
+       }
+
+       g_mutex_lock(&session->stop_mutex);
+       session->abort_session = TRUE;
+       g_mutex_unlock(&session->stop_mutex);
+
+       return SR_OK;
+}
+
 /**
  * Debug helper.
  *