fix(el): Unlock EventLoop mutex before wait condition

If UA_Server_addPubSubConnection was called in a (real-time) linux system from a task with lower priority than the task that called UA_Server_run, a deadlock occured.
jpfr · Oct 7, 2023 · 25af928 · 25af928
1 parent 9ea4629
commit 25af928
Show file tree

Hide file tree

Showing 2 changed files with 7 additions and 2 deletions.
diff --git a/arch/eventloop_posix_epoll.c b/arch/eventloop_posix_epoll.c
@@ -70,7 +70,9 @@ UA_EventLoopPOSIX_pollFDs(UA_EventLoopPOSIX *el, UA_DateTime listenTimeout) {
 
     /* Poll the registered sockets */
     struct epoll_event epoll_events[64];
-    int events = epoll_wait(el->epollfd, epoll_events, 64,
+    int epollfd = el->epollfd;
+    UA_UNLOCK(&el->elMutex);
+    int events = epoll_wait(epollfd, epoll_events, 64,
                             (int)(listenTimeout / UA_DATETIME_MSEC));
     /* TODO: Replace with pwait2 for higher-precision timeouts once this is
      * available in the standard library.
@@ -79,8 +81,9 @@ UA_EventLoopPOSIX_pollFDs(UA_EventLoopPOSIX *el, UA_DateTime listenTimeout) {
      *  (long)(listenTimeout / UA_DATETIME_SEC),
      *   (long)((listenTimeout % UA_DATETIME_SEC) * 100)
      * };
-     * int events = epoll_pwait2(el->epollfd, epoll_events, 64,
+     * int events = epoll_pwait2(epollfd, epoll_events, 64,
      *                        precisionTimeout, NULL); */
+    UA_LOCK(&el->elMutex);
 
     /* Handle error conditions */
     if(events == -1) {

diff --git a/arch/eventloop_posix_select.c b/arch/eventloop_posix_select.c
@@ -123,7 +123,9 @@ UA_EventLoopPOSIX_pollFDs(UA_EventLoopPOSIX *el, UA_DateTime listenTimeout) {
 #endif
     };
 
+    UA_UNLOCK(&el->elMutex);
     int selectStatus = UA_select(highestfd+1, &readset, &writeset, &errset, &tmptv);
+    UA_LOCK(&el->elMutex);
     if(selectStatus < 0) {
         /* We will retry, only log the error */
         UA_LOG_SOCKET_ERRNO_WRAP(