init/epoll: Make Epoll::Wait() easier to use

Invoke the callback functions from inside Epoll::Wait() instead of
returning a vector with pointers to callback functions. Remove handlers
after handler invocation finished to prevent that self-removal triggers
a use-after-free.

The CL that made Epoll::Wait() return a vector is available at
https://android-review.googlesource.com/c/platform/system/core/+/1112042.

Bug: 213617178
Change-Id: I52c6ade5746a911510746f83802684f2d9cfb429
Signed-off-by: Bart Van Assche <bvanassche@google.com>
diff --git a/init/init.cpp b/init/init.cpp
index f9e7c6e..837d955 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -1177,14 +1177,10 @@
             if (am.HasMoreCommands()) epoll_timeout = 0ms;
         }
 
-        auto pending_functions = epoll.Wait(epoll_timeout);
-        if (!pending_functions.ok()) {
-            LOG(ERROR) << pending_functions.error();
-        } else if (!pending_functions->empty()) {
-            for (const auto& function : *pending_functions) {
-                (*function)();
-            }
-        } else if (Service::is_exec_service_running()) {
+        auto epoll_result = epoll.Wait(epoll_timeout);
+        if (!epoll_result.ok()) {
+            LOG(ERROR) << epoll_result.error();
+        } else if (*epoll_result <= 0 && Service::is_exec_service_running()) {
             static bool dumped_diagnostics = false;
             std::chrono::duration<double> waited =
                     std::chrono::steady_clock::now() - Service::exec_service_started();