Simplify the QuicDispatcher::OnCanWrite logic

net/tools/quic/quic_dispatcher.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/tools/quic/quic_dispatcher.h"
 
 #include <errno.h>
 
 #include "base/debug/stack_trace.h"
 #include "base/logging.h"
@@ skipping 278 matching lines @@
 }
 
 void QuicDispatcher::DeleteSessions() {
   STLDeleteElements(&closed_session_list_);
 }
 
 void QuicDispatcher::OnCanWrite() {
   // We got an EPOLLOUT: the socket should not be blocked.
   writer_->SetWritable();
 
-  // Give each writer one attempt to write.
-  int num_writers = write_blocked_list_.size();
-  for (int i = 0; i < num_writers; ++i) {
-    if (write_blocked_list_.empty()) {
-      return;
-    }
+  // Give all the blocked writers one chance to write, until we're blocked again
+  // or there's no work left.
+  while (!write_blocked_list_.empty() && !writer_->IsWriteBlocked()) {
     QuicBlockedWriterInterface* blocked_writer =
         write_blocked_list_.begin()->first;
     write_blocked_list_.erase(write_blocked_list_.begin());
     blocked_writer->OnCanWrite();
-    if (writer_->IsWriteBlocked()) {
-      // We were unable to write.  Wait for the next EPOLLOUT. The writer is
-      // responsible for adding itself to the blocked list via OnWriteBlocked().
-      return;
-    }
   }
 }
 
 bool QuicDispatcher::HasPendingWrites() const {
   return !write_blocked_list_.empty();
 }
 
 void QuicDispatcher::Shutdown() {
   while (!session_map_.empty()) {
     QuicSession* session = session_map_.begin()->second;
@@ skipping 21 matching lines @@
                                         << QuicUtils::ErrorToString(error);
 
   if (closed_session_list_.empty()) {
     epoll_server_->RegisterAlarmApproximateDelta(
         0, delete_sessions_alarm_.get());
   }
   closed_session_list_.push_back(it->second);
   CleanUpSession(it);
 }
 
-void QuicDispatcher::OnWriteBlocked(QuicBlockedWriterInterface* writer) {
-  DCHECK(writer_->IsWriteBlocked());
-  write_blocked_list_.insert(make_pair(writer, true));
+void QuicDispatcher::OnWriteBlocked(
+    QuicBlockedWriterInterface* blocked_writer) {
+  if (!writer_->IsWriteBlocked()) {
+    LOG(DFATAL) <<
+        "QuicDispatcher::OnWriteBlocked called when the writer is not blocked.";
+    // Return without adding the connection to the blocked list, to avoid
+    // infinite loops in OnCanWrite.
+    return;
+  }
+  write_blocked_list_.insert(make_pair(blocked_writer, true));
 }
 
 QuicPacketWriter* QuicDispatcher::CreateWriter(int fd) {
   return new QuicDefaultPacketWriter(fd);
 }
 
 QuicSession* QuicDispatcher::CreateQuicSession(
     QuicConnectionId connection_id,
     const IPEndPoint& server_address,
     const IPEndPoint& client_address) {
@@ skipping 39 matching lines @@
   framer_.set_version(time_wait_list_manager_->GetQuicVersionFromConnectionId(
       header.connection_id));
 
   // Continue parsing the packet to extract the sequence number.  Then
   // send it to the time wait manager in OnUnathenticatedHeader.
   return true;
 }
 
 }  // namespace tools
 }  // namespace net