From 0abcf895c96d7ec5ede84841d94f635b20f1bc19 Mon Sep 17 00:00:00 2001
From: "wtc@chromium.org"
 <wtc@chromium.org@0039d316-1c4b-4281-b951-d872f2087c98>
Date: Fri, 30 Jan 2009 21:33:29 +0000
Subject: In rare cases (when running inside QEMU), the event object is not yet
 in the signaled state after a Winsock function succeeds synchronously, so it
 is necessary to wait for it to become signaled.

R=eroman
BUG=6500
Review URL: http://codereview.chromium.org/19515

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@8989 0039d316-1c4b-4281-b951-d872f2087c98
---
 net/base/tcp_client_socket.h      |  8 ++++++++
 net/base/tcp_client_socket_win.cc | 37 +++++++++++++------------------------
 2 files changed, 21 insertions(+), 24 deletions(-)

diff --git a/net/base/tcp_client_socket.h b/net/base/tcp_client_socket.h
index 5fca519..96e40e6 100644
--- a/net/base/tcp_client_socket.h
+++ b/net/base/tcp_client_socket.h
@@ -86,6 +86,14 @@ class TCPClientSocket : public ClientSocket,
   // base::ObjectWatcher::Delegate methods:
   virtual void OnObjectSignaled(HANDLE object);
 
+  // After a Winsock function succeeds synchronously, waits for the
+  // (manual-reset) event object to become signaled and resets it.
+  //
+  // Our testing shows that except in rare cases (when running inside QEMU),
+  // the event object is already signaled at this point, so we just call this
+  // method on the IO thread to avoid a context switch.
+  void WaitForAndResetEvent();
+
   OVERLAPPED overlapped_;
   WSABUF buffer_;
 
diff --git a/net/base/tcp_client_socket_win.cc b/net/base/tcp_client_socket_win.cc
index 4b42fd2..d2a1452 100644
--- a/net/base/tcp_client_socket_win.cc
+++ b/net/base/tcp_client_socket_win.cc
@@ -88,9 +88,7 @@ int TCPClientSocket::Connect(CompletionCallback* callback) {
 
   if (!connect(socket_, ai->ai_addr, static_cast<int>(ai->ai_addrlen))) {
     // Connected without waiting!
-    CHECK(WaitForSingleObject(overlapped_.hEvent, 0) == WAIT_OBJECT_0);
-    BOOL ok = WSAResetEvent(overlapped_.hEvent);
-    CHECK(ok);
+    WaitForAndResetEvent();
     TRACE_EVENT_END("socket.connect", this, "");
     return OK;
   }
@@ -170,14 +168,12 @@ int TCPClientSocket::Read(char* buf,
   buffer_.buf = buf;
 
   TRACE_EVENT_BEGIN("socket.read", this, "");
-  // TODO(wtc): Remove the CHECKs after enough testing.
+  // TODO(wtc): Remove the CHECK after enough testing.
   CHECK(WaitForSingleObject(overlapped_.hEvent, 0) == WAIT_TIMEOUT);
   DWORD num, flags = 0;
   int rv = WSARecv(socket_, &buffer_, 1, &num, &flags, &overlapped_, NULL);
   if (rv == 0) {
-    CHECK(WaitForSingleObject(overlapped_.hEvent, 0) == WAIT_OBJECT_0);
-    BOOL ok = WSAResetEvent(overlapped_.hEvent);
-    CHECK(ok);
+    WaitForAndResetEvent();
     TRACE_EVENT_END("socket.read", this, StringPrintf("%d bytes", num));
 
     // Because of how WSARecv fills memory when used asynchronously, Purify
@@ -199,15 +195,6 @@ int TCPClientSocket::Read(char* buf,
   return MapWinsockError(err);
 }
 
-// TODO(wtc): This temporary function is intended to determine the return
-// value and error code of the WaitForSingleObject call in
-// TCPClientSocket::Write if it doesn't return the expected WAIT_OBJECT_0.
-// See http://crbug.com/6500.
-static void CrashBug6500(DWORD wait_rv, DWORD wait_error) {
-  // wait_error is meaningful only if wait_rv is WAIT_FAILED.
-  CHECK(false) << wait_rv << wait_error;
-}
-
 int TCPClientSocket::Write(const char* buf,
                            int buf_len,
                            CompletionCallback* callback) {
@@ -219,18 +206,12 @@ int TCPClientSocket::Write(const char* buf,
   buffer_.buf = const_cast<char*>(buf);
 
   TRACE_EVENT_BEGIN("socket.write", this, "");
-  // TODO(wtc): Remove the CHECKs after enough testing.
+  // TODO(wtc): Remove the CHECK after enough testing.
   CHECK(WaitForSingleObject(overlapped_.hEvent, 0) == WAIT_TIMEOUT);
   DWORD num;
   int rv = WSASend(socket_, &buffer_, 1, &num, 0, &overlapped_, NULL);
   if (rv == 0) {
-    DWORD wait_rv = WaitForSingleObject(overlapped_.hEvent, 0);
-    if (wait_rv != WAIT_OBJECT_0) {
-      DWORD wait_error = GetLastError();
-      CrashBug6500(wait_rv, wait_error);
-    }
-    BOOL ok = WSAResetEvent(overlapped_.hEvent);
-    CHECK(ok);
+    WaitForAndResetEvent();
     TRACE_EVENT_END("socket.write", this, StringPrintf("%d bytes", num));
     return static_cast<int>(num);
   }
@@ -379,5 +360,13 @@ void TCPClientSocket::OnObjectSignaled(HANDLE object) {
   }
 }
 
+void TCPClientSocket::WaitForAndResetEvent() {
+  // TODO(wtc): Remove the CHECKs after enough testing.
+  DWORD wait_rv = WaitForSingleObject(overlapped_.hEvent, INFINITE);
+  CHECK(wait_rv == WAIT_OBJECT_0);
+  BOOL ok = WSAResetEvent(overlapped_.hEvent);
+  CHECK(ok);
+}
+
 }  // namespace net
 
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