Workaround attempt for timeout flakiness: Avoid running atexit() handlers in fork()ed process on li…

runtime/bin/process_linux.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #if !defined(DART_IO_DISABLED)
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_LINUX)
 
 #include "bin/process.h"
@@ skipping 145 matching lines @@
     MonitorLocker locker(monitor_);
 
     if (!running_) {
       return;
     }
 
     // Set terminate_done_ to false, so we can use it as a guard for our
     // monitor.
     running_ = false;
 
-    // Fork to wake up waitpid.
+    // Wake up the [ExitCodeHandler] thread which is blocked on `wait()` (see
+    // [ExitCodeHandlerEntry]).
     if (TEMP_FAILURE_RETRY(fork()) == 0) {
-      exit(0);
+      // We avoid running through registered atexit() handlers because that is
+      // unnecessary work.
+      _exit(0);
     }
 
     monitor_->Notify();
 
     while (!terminate_done_) {
       monitor_->Wait(Monitor::kNoTimeout);
     }
   }
 
  private:
@@ skipping 808 matching lines @@
     sigaction(signal, &act, NULL);
   }
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)
 
 #endif  // !defined(DART_IO_DISABLED)