Only read from interrupt_fd when data is available.

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 162 matching lines @@
       FDUtils::WriteToBlocking(interrupt_fds_[1], &msg, kInterruptMessageSize);
   if (result != kInterruptMessageSize) {
     if (result == -1) {
       perror("Interrupt message failure:");
     }
     FATAL1("Interrupt message failure. Wrote %" Pd " bytes.", result);
   }
 }
 
 
-bool EventHandlerImplementation::GetInterruptMessage(InterruptMessage* msg) {
-  char* dst = reinterpret_cast<char*>(msg);
-  int total_read = 0;
-  int bytes_read =
-      TEMP_FAILURE_RETRY(read(interrupt_fds_[0], dst, kInterruptMessageSize));
-  if (bytes_read < 0) {
-    return false;
-  }
-  total_read = bytes_read;
-  while (total_read < kInterruptMessageSize) {
-    bytes_read = TEMP_FAILURE_RETRY(read(interrupt_fds_[0],
-                                         dst + total_read,
-                                         kInterruptMessageSize - total_read));
-    if (bytes_read > 0) {
-      total_read = total_read + bytes_read;
-    }
-  }
-  return (total_read == kInterruptMessageSize) ? true : false;
-}
-
-
 void EventHandlerImplementation::HandleInterruptFd() {
   InterruptMessage msg;
-  while (GetInterruptMessage(&msg)) {
+  intptr_t available = FDUtils::AvailableBytes(interrupt_fds_[0]);
+  for (int i = 0;
+       i + kInterruptMessageSize <= available;
+       i += kInterruptMessageSize) {
+    VOID_TEMP_FAILURE_RETRY(read(interrupt_fds_[0],
+                                 reinterpret_cast<char*>(&msg),
+                                 kInterruptMessageSize));
     if (msg.id == kTimerId) {
       timeout_queue_.UpdateTimeout(msg.dart_port, msg.data);
     } else if (msg.id == kShutdownId) {
       shutdown_ = true;
     } else {
       SocketData* sd = GetSocketData(msg.id);
       if ((msg.data & (1 << kShutdownReadCommand)) != 0) {
         ASSERT(msg.data == (1 << kShutdownReadCommand));
         // Close the socket for reading.
         sd->ShutdownRead();
@@ skipping 125 matching lines @@
       }
     }
   }
 
   return event_mask;
 }
 
 
 void EventHandlerImplementation::HandleEvents(struct epoll_event* events,
                                               int size) {
+  bool interrupt_seen = false;
   for (int i = 0; i < size; i++) {
-    if (events[i].data.ptr != NULL) {
+    if (events[i].data.ptr == NULL) {
+      interrupt_seen = true;
+    } else {
       SocketData* sd = reinterpret_cast<SocketData*>(events[i].data.ptr);
       intptr_t event_mask = GetPollEvents(events[i].events, sd);
       if (event_mask != 0) {
         // Unregister events for the file descriptor. Events will be
         // registered again when the current event has been handled in
         // Dart code.
         RemoveFromEpollInstance(epoll_fd_, sd);
         Dart_Port port = sd->port();
         ASSERT(port != 0);
         DartUtils::PostInt32(port, event_mask);
       }
     }
   }
-  // Handle after socket events, so we avoid closing a socket before we handle
-  // the current events.
-  HandleInterruptFd();
+  if (interrupt_seen) {
+    // Handle after socket events, so we avoid closing a socket before we handle
+    // the current events.
+    HandleInterruptFd();
+  }
 }
 
 
 int64_t EventHandlerImplementation::GetTimeout() {
   if (!timeout_queue_.HasTimeout()) {
     return kInfinityTimeout;
   }
   int64_t millis = timeout_queue_.CurrentTimeout() -
       TimerUtils::GetCurrentTimeMilliseconds();
   return (millis < 0) ? 0 : millis;
@@ skipping 70 matching lines @@
 
 uint32_t EventHandlerImplementation::GetHashmapHashFromFd(intptr_t fd) {
   // The hashmap does not support keys with value 0.
   return dart::Utils::WordHash(fd + 1);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)