Make the event-handler handle backpreasure.

runtime/bin/eventhandler_macos.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_MACOS)
 
 #include "bin/eventhandler.h"
 
 #include <errno.h>  // NOLINT
@@ skipping 29 matching lines @@
 
 bool SocketData::HasWriteEvent() {
   return (mask_ & (1 << kOutEvent)) != 0;
 }
 
 
 // Unregister the file descriptor for a SocketData structure with kqueue.
 static void RemoveFromKqueue(intptr_t kqueue_fd_, SocketData* sd) {
   if (!sd->tracked_by_kqueue()) return;
   static const intptr_t kMaxChanges = 2;
-  intptr_t changes = 0;
   struct kevent events[kMaxChanges];
-  if (sd->HasReadEvent()) {
-    EV_SET(events + changes, sd->fd(), EVFILT_READ, EV_DELETE, 0, 0, NULL);
-    ++changes;
-  }
-  if (sd->HasWriteEvent()) {
-    EV_SET(events + changes, sd->fd(), EVFILT_WRITE, EV_DELETE, 0, 0, NULL);
-    ++changes;
-  }
-  ASSERT(changes > 0);
-  ASSERT(changes <= kMaxChanges);
-  int status =
-    TEMP_FAILURE_RETRY(kevent(kqueue_fd_, events, changes, NULL, 0, NULL));
-  if (status == -1) {
-    const int kBufferSize = 1024;
-    char error_message[kBufferSize];
-    strerror_r(errno, error_message, kBufferSize);
-    FATAL1("Failed deleting events from kqueue: %s\n", error_message);
-  }
+  EV_SET(events, sd->fd(), EVFILT_READ, EV_DELETE, 0, 0, NULL);
+  VOID_TEMP_FAILURE_RETRY(kevent(kqueue_fd_, events, 1, NULL, 0, NULL));
+  EV_SET(events, sd->fd(), EVFILT_WRITE, EV_DELETE, 0, 0, NULL);
+  VOID_TEMP_FAILURE_RETRY(kevent(kqueue_fd_, events, 1, NULL, 0, NULL));
   sd->set_tracked_by_kqueue(false);
 }
 
 
 // Update the kqueue registration for SocketData structure to reflect
 // the events currently of interest.
 static void AddToKqueue(intptr_t kqueue_fd_, SocketData* sd) {
+  ASSERT(!sd->tracked_by_kqueue());
   static const intptr_t kMaxChanges = 2;
   intptr_t changes = 0;
   struct kevent events[kMaxChanges];
   // Register or unregister READ filter if needed.
   if (sd->HasReadEvent()) {
     EV_SET(events + changes,
            sd->fd(),
            EVFILT_READ,
            EV_ADD | EV_CLEAR,
            0,
            0,
            sd);
     ++changes;
   }
   // Register or unregister WRITE filter if needed.
   if (sd->HasWriteEvent()) {
     EV_SET(events + changes,
            sd->fd(),
            EVFILT_WRITE,
            EV_ADD | EV_CLEAR,
            0,
            0,
            sd);
     ++changes;
   }
   ASSERT(changes > 0);
   ASSERT(changes <= kMaxChanges);
   int status =
-    TEMP_FAILURE_RETRY(kevent(kqueue_fd_, events, changes, NULL, 0, NULL));
+      TEMP_FAILURE_RETRY(kevent(kqueue_fd_, events, changes, NULL, 0, NULL));
   if (status == -1) {
     // kQueue does not accept the file descriptor. It could be due to
     // already closed file descriptor, or unuspported devices, such
     // as /dev/null. In such case, mark the file descriptor as closed,
     // so dart will handle it accordingly.
     DartUtils::PostInt32(sd->port(), 1 << kCloseEvent);
   } else {
     sd->set_tracked_by_kqueue(true);
   }
 }
@@ skipping 29 matching lines @@
 }
 
 
 EventHandlerImplementation::~EventHandlerImplementation() {
   VOID_TEMP_FAILURE_RETRY(close(kqueue_fd_));
   VOID_TEMP_FAILURE_RETRY(close(interrupt_fds_[0]));
   VOID_TEMP_FAILURE_RETRY(close(interrupt_fds_[1]));
 }
 
 
-SocketData* EventHandlerImplementation::GetSocketData(intptr_t fd,
-                                                      bool* is_new) {
+SocketData* EventHandlerImplementation::GetSocketData(intptr_t fd) {
   ASSERT(fd >= 0);
   HashMap::Entry* entry = socket_map_.Lookup(
       GetHashmapKeyFromFd(fd), GetHashmapHashFromFd(fd), true);
   ASSERT(entry != NULL);
   SocketData* sd = reinterpret_cast<SocketData*>(entry->value);
   if (sd == NULL) {
     // If there is no data in the hash map for this file descriptor a
     // new SocketData for the file descriptor is inserted.
     sd = new SocketData(fd);
     entry->value = sd;
-    *is_new = true;
   }
   ASSERT(fd == sd->fd());
   return sd;
 }
 
 
 void EventHandlerImplementation::WakeupHandler(intptr_t id,
                                                Dart_Port dart_port,
                                                int64_t data) {
   InterruptMessage msg;
@@ skipping 18 matching lines @@
   const intptr_t MAX_MESSAGES = kInterruptMessageSize;
   InterruptMessage msg[MAX_MESSAGES];
   ssize_t bytes = TEMP_FAILURE_RETRY(
       read(interrupt_fds_[0], msg, MAX_MESSAGES * kInterruptMessageSize));
   for (ssize_t i = 0; i < bytes / kInterruptMessageSize; i++) {
     if (msg[i].id == kTimerId) {
       timeout_queue_.UpdateTimeout(msg[i].dart_port, msg[i].data);
     } else if (msg[i].id == kShutdownId) {
       shutdown_ = true;
     } else {
-      bool is_new = false;
-      SocketData* sd = GetSocketData(msg[i].id, &is_new);
-      if (is_new) {
-        sd->SetPortAndMask(msg[i].dart_port, msg[i].data);
-      }
+      SocketData* sd = GetSocketData(msg[i].id);
       if ((msg[i].data & (1 << kShutdownReadCommand)) != 0) {
         ASSERT(msg[i].data == (1 << kShutdownReadCommand));
         // Close the socket for reading.
-        sd->ShutdownRead();
+        shutdown(sd->fd(), SHUT_RD);
       } else if ((msg[i].data & (1 << kShutdownWriteCommand)) != 0) {
         ASSERT(msg[i].data == (1 << kShutdownWriteCommand));
         // Close the socket for writing.
-        sd->ShutdownWrite();
+        shutdown(sd->fd(), SHUT_WR);
       } else if ((msg[i].data & (1 << kCloseCommand)) != 0) {
         ASSERT(msg[i].data == (1 << kCloseCommand));
         // Close the socket and free system resources.
         RemoveFromKqueue(kqueue_fd_, sd);
         intptr_t fd = sd->fd();
         sd->Close();
         socket_map_.Remove(GetHashmapKeyFromFd(fd), GetHashmapHashFromFd(fd));
         delete sd;
         DartUtils::PostInt32(msg[i].dart_port, 1 << kDestroyedEvent);
-      } else {
-        if (is_new) {
+      } else if ((msg[i].data & (1 << kReturnTokenCommand)) != 0) {
+        if (sd->ReturnToken()) {
           AddToKqueue(kqueue_fd_, sd);
         }
+      } else {
+        // Setup events to wait for.
+        ASSERT((msg[i].data > 0) && (msg[i].data < kIntptrMax));
+        ASSERT(sd->port() == 0);
+        sd->SetPortAndMask(msg[i].dart_port,
+                           static_cast<intptr_t>(msg[i].data));
+        AddToKqueue(kqueue_fd_, sd);
       }
     }
   }
 }
 
 #ifdef DEBUG_KQUEUE
 static void PrintEventMask(intptr_t fd, struct kevent* event) {
   Log::Print("%d ", static_cast<int>(fd));
   Log::Print("filter=0x%x:", event->filter);
   if (event->filter == EVFILT_READ) Log::Print("EVFILT_READ ");
@@ skipping 71 matching lines @@
       char error_message[kBufferSize];
       strerror_r(events[i].data, error_message, kBufferSize);
       FATAL1("kevent failed %s\n", error_message);
     }
     if (events[i].udata == NULL) {
       interrupt_seen = true;
     } else {
       SocketData* sd = reinterpret_cast<SocketData*>(events[i].udata);
       intptr_t event_mask = GetEvents(events + i, sd);
       if (event_mask != 0) {
+        if (sd->TakeToken()) {
+          // Took last token, remove from epoll.
+          RemoveFromKqueue(kqueue_fd_, sd);
+        }
         Dart_Port port = sd->port();
         ASSERT(port != 0);
         DartUtils::PostInt32(port, event_mask);
       }
     }
   }
   if (interrupt_seen) {
     // Handle after socket events, so we avoid closing a socket before we handle
     // the current events.
     HandleInterruptFd();
@@ skipping 68 matching lines @@
   int result =
       dart::Thread::Start(&EventHandlerImplementation::EventHandlerEntry,
                           reinterpret_cast<uword>(handler));
   if (result != 0) {
     FATAL1("Failed to start event handler thread %d", result);
   }
 }
 
 
 void EventHandlerImplementation::Shutdown() {
-  Notify(kShutdownId, 0, 0);
+  SendData(kShutdownId, 0, 0);
 }
 
 
-void EventHandlerImplementation::Notify(intptr_t id,
-                                        Dart_Port dart_port,
-                                        int64_t data) {
+void EventHandlerImplementation::SendData(intptr_t id,
+                                          Dart_Port dart_port,
+                                          int64_t data) {
   WakeupHandler(id, dart_port, data);
 }
 
 
 void* EventHandlerImplementation::GetHashmapKeyFromFd(intptr_t fd) {
   // The hashmap does not support keys with value 0.
   return reinterpret_cast<void*>(fd + 1);
 }
 
 
 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_MACOS)