Fix end_to_end_test performance regression caused by using mutexes

net/tools/quic/test_tools/server_thread.cc

 // Copyright 2013 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/test_tools/server_thread.h"
 
 #include "net/tools/quic/test_tools/quic_server_peer.h"
 
 namespace net {
 namespace tools {
 namespace test {
 
 ServerThread::ServerThread(IPEndPoint address,
                            const QuicConfig& config,
                            const QuicVersionVector& supported_versions,
                            bool strike_register_no_startup_period)
     : SimpleThread("server_thread"),
-      listening_(true, false),
       confirmed_(true, false),
+      pause_(true, false),
+      paused_(true, false),
+      resume_(true, false),
       quit_(true, false),
       server_(config, supported_versions),
       address_(address),
-      port_(0) {
+      port_(0),
+      initialized_(false) {
   if (strike_register_no_startup_period) {
     server_.SetStrikeRegisterNoStartupPeriod();
   }
 }
 
-ServerThread::~ServerThread() {
-}
+ServerThread::~ServerThread() {}
 
-void ServerThread::Run() {
+void ServerThread::Initialize() {
+  if (initialized_) {
+    return;
+  }
+
   server_.Listen(address_);
 
   port_lock_.Acquire();
   port_ = server_.port();
   port_lock_.Release();
 
-  listening_.Signal();
+  initialized_ = true;
+}
+
+void ServerThread::Run() {
+  if (!initialized_) {
+    Initialize();
+  }
+
   while (!quit_.IsSignaled()) {
-    event_loop_mu_.Acquire();
+    if (pause_.IsSignaled() && !resume_.IsSignaled()) {
+      paused_.Signal();
+      resume_.Wait();
+    }
     server_.WaitForEvents();
     MaybeNotifyOfHandshakeConfirmation();
-    event_loop_mu_.Release();
   }
 
   server_.Shutdown();
 }
 
 int ServerThread::GetPort() {
   port_lock_.Acquire();
   int rc = port_;
   port_lock_.Release();
-    return rc;
-}
-
-void ServerThread::WaitForServerStartup() {
-  listening_.Wait();
+  return rc;
 }
 
 void ServerThread::WaitForCryptoHandshakeConfirmed() {
   confirmed_.Wait();
 }
 
 void ServerThread::Pause() {
-  event_loop_mu_.Acquire();
+  DCHECK(!pause_.IsSignaled());
+  pause_.Signal();
+  paused_.Wait();
 }
 
 void ServerThread::Resume() {
-  event_loop_mu_.AssertAcquired();  // Checks the calling thread only!
-  event_loop_mu_.Release();
+  DCHECK(!resume_.IsSignaled());
+  DCHECK(pause_.IsSignaled());
+  resume_.Signal();
 }
 
 void ServerThread::Quit() {
+  if (pause_.IsSignaled() && !resume_.IsSignaled()) {
+    resume_.Signal();
+  }
   quit_.Signal();
 }
 
 void ServerThread::MaybeNotifyOfHandshakeConfirmation() {
   if (confirmed_.IsSignaled()) {
     // Only notify once.
     return;
   }
   QuicDispatcher* dispatcher = QuicServerPeer::GetDispatcher(server());
   if (dispatcher->session_map().empty()) {
     // Wait for a session to be created.
     return;
   }
   QuicSession* session = dispatcher->session_map().begin()->second;
   if (session->IsCryptoHandshakeConfirmed()) {
     confirmed_.Signal();
   }
 }
 
 }  // namespace test
 }  // namespace tools
 }  // namespace net