Merge pull request #19556 from gnossen/subprocess_gevent

Fix segfault when forking while using gevent

src/core/lib/iomgr/ev_posix.cc

@@ -206,7 +206,8 @@ void grpc_register_event_engine_factory(const char* name,
   GPR_ASSERT(false);
 }
 
-/* Call this only after calling grpc_event_engine_init() */
+/*If grpc_event_engine_init() has been called, returns the poll_strategy_name.
+ * Otherwise, returns nullptr. */
 const char* grpc_get_poll_strategy_name() { return g_poll_strategy_name; }
 
 void grpc_event_engine_init(void) {

src/core/lib/iomgr/fork_posix.cc

@@ -59,8 +59,10 @@ void grpc_prefork() {
             "environment variable GRPC_ENABLE_FORK_SUPPORT=1");
     return;
   }
-  if (strcmp(grpc_get_poll_strategy_name(), "epoll1") != 0 &&
-      strcmp(grpc_get_poll_strategy_name(), "poll") != 0) {
+  const char* poll_strategy_name = grpc_get_poll_strategy_name();
+  if (poll_strategy_name == nullptr ||
+      (strcmp(poll_strategy_name, "epoll1") != 0 &&
+       strcmp(poll_strategy_name, "poll") != 0)) {
     gpr_log(GPR_INFO,
             "Fork support is only compatible with the epoll1 and poll polling "
             "strategies");