Add missing mutex protection for timeout queue with mutex

runtime/bin/eventhandler_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.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_LINUX)
 
 #include "bin/eventhandler.h"
 
 #include <errno.h>  // NOLINT
@@ skipping 113 matching lines @@
   if (events & EPOLLOUT) event_mask |= (1 << kOutEvent);
   if (events & (EPOLLHUP | EPOLLRDHUP)) event_mask |= (1 << kCloseEvent);
   return event_mask;
 }
 
 
 void EventHandlerImplementation::HandleEvents(struct epoll_event* events,
                                               int size) {
   for (int i = 0; i < size; i++) {
     uint64_t data = events[i].data.u64;
+    // ILLEGAL_PORT is used to identify timer-fd.
     if (data == ILLEGAL_PORT) {
       int64_t val;
       VOID_TEMP_FAILURE_RETRY(read(timer_fd_, &val, sizeof(val)));
+      timer_mutex_.Lock();
       if (timeout_queue_.HasTimeout()) {
         DartUtils::PostNull(timeout_queue_.CurrentPort());
         timeout_queue_.RemoveCurrent();
       }
+      timer_mutex_.Unlock();
     } else {
       int32_t event_mask = GetPollEvents(events[i].events);
       if (event_mask != 0) {
         Dart_Port port = data;
         ASSERT(port != 0);
         DartUtils::PostInt32(port, event_mask);
       }
     }
   }
 }
@@ skipping 78 matching lines @@
       // Add to epoll - this is the first time we see it.
       AddToEpollInstance(epoll_fd_, id, dart_port, data);
     }
   }
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)