Fix flaky thread number DCHECK in KioskTest.

EmbeddedTestServer::StopThread might be returned before GetNumberOfThreads
gets an updated thread number. Add a busy loop to wait for it to update.

BUG=322732

Review URL: https://codereview.chromium.org/105823002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239141 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 27 insertions, 5 deletions

diff --git a/net/test/embedded_test_server/embedded_test_server.cc b/net/test/embedded_test_server/embedded_test_server.cc
index aacecd2..b60cea4 100644
--- a/net/test/embedded_test_server/embedded_test_server.cc
+++ b/net/test/embedded_test_server/embedded_test_server.cc
@@ -9,6 +9,7 @@
 #include "base/files/file_path.h"
 #include "base/message_loop/message_loop.h"
 #include "base/path_service.h"
+#include "base/process/process_metrics.h"
 #include "base/run_loop.h"
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
@@ -128,10 +129,29 @@ bool EmbeddedTestServer::InitializeAndWaitUntilReady() {
 }
 
 void EmbeddedTestServer::StopThread() {
+  DCHECK(io_thread_ && io_thread_->IsRunning());
+
+#if defined(OS_LINUX)
+  const int thread_count =
+      base::GetNumberOfThreads(base::GetCurrentProcessHandle());
+#endif
+
   io_thread_->Stop();
   io_thread_.reset();
   thread_checker_.DetachFromThread();
   listen_socket_->DetachFromThread();
+
+#if defined(OS_LINUX)
+  // Busy loop to wait for thread count to decrease. This is needed because
+  // pthread_join does not guarantee that kernel stat is updated when it
+  // returns. Thus, GetNumberOfThreads does not immediately reflect the stopped
+  // thread and hits the thread number DCHECK in render_sandbox_host_linux.cc
+  // in browser_tests.
+  while (thread_count ==
+         base::GetNumberOfThreads(base::GetCurrentProcessHandle())) {
+    base::PlatformThread::YieldCurrentThread();
+  }
+#endif
 }
 
 void EmbeddedTestServer::RestartThreadAndListen() {
diff --git a/net/test/embedded_test_server/embedded_test_server.h b/net/test/embedded_test_server/embedded_test_server.h
index 5600e0f..1232388 100644
--- a/net/test/embedded_test_server/embedded_test_server.h
+++ b/net/test/embedded_test_server/embedded_test_server.h
@@ -73,22 +73,24 @@ class HttpListenSocket : public TCPListenSocket {
 //   return http_response.Pass();
 // }
 //
-// For a test that spawns another process such as browser_tests, you
-// need to stop the server's thread so that there is no no other
+// For a test that spawns another process such as browser_tests, it is
+// suggested to call InitializeAndWaitUntilReady in SetUpOnMainThread after
+// the process is spawned. If you have to do it before the process spawns,
+// you need to stop the server's thread so that there is no no other
 // threads running while spawning the process. To do so, please follow
 // the following example:
 //
 // void SetUp() {
-//   test_server_.reset(new EmbeddedTestServer());
+//   ASSERT_TRUE(embedded_test_server()->InitializeAndWaitUntilReady());
 //   // EmbeddedTestServer spawns a thread to initialize socket.
 //   // Stop the thread in preparation for fork and exec.
-//   test_server_->StopThread();
+//   embedded_test_server()->StopThread();
 //   ...
 //   InProcessBrowserTest::SetUp();
 // }
 //
 // void SetUpOnMainThread() {
-//   test_server_->RestartThreadAndListen();
+//   embedded_test_server()->RestartThreadAndListen();
 // }
 //
 class EmbeddedTestServer : public StreamListenSocket::Delegate {