Re-signal when caught

Summary:
This makes it so systemd properly determines that the process died due
to a signal and avoids unclean exits.

Reviewed By: brianc118

Differential Revision: D51814324

fbshipit-source-id: 9c136a9d1b31e384ebddff4589f936886a06ec9a

src/oomd/Oomd.cpp

@@ -135,8 +135,11 @@ int Oomd::run(const sigset_t* mask) {
       perror("sigtimedwait");
       exit(EXIT_FAILURE);
     } else if (rc != -1) {
-      OLOG << "Received signal " << rc << ". Exiting!";
-      return 128 + rc;
+      // Synchronously log to stderr so there's no buffering
+      std::cerr << "Received signal " << rc << ". Exiting!";
+      pthread_sigmask(SIG_UNBLOCK, mask, nullptr);
+      pthread_kill(pthread_self(), rc);
+      return -1;
     }
 
     if (fs_drop_in_service_) {