Mojo EDK: Add tests to exercise races in handle transit

mojo/edk/system/multiprocess_message_pipe_unittest.cc

Index: mojo/edk/system/multiprocess_message_pipe_unittest.cc
diff --git a/mojo/edk/system/multiprocess_message_pipe_unittest.cc b/mojo/edk/system/multiprocess_message_pipe_unittest.cc
index 124daec9a8b0c6703bf712c037bd304d4a472f7d..03f89987295c2eb747cf15f91904d18fe83aa3d8 100644
--- a/mojo/edk/system/multiprocess_message_pipe_unittest.cc
+++ b/mojo/edk/system/multiprocess_message_pipe_unittest.cc
@@ -18,6 +18,8 @@
 #include "base/files/scoped_file.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/logging.h"
+#include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
 #include "base/strings/string_split.h"
 #include "build/build_config.h"
 #include "mojo/edk/embedder/platform_channel_pair.h"
@@ -29,6 +31,7 @@
 #include "mojo/public/c/system/buffer.h"
 #include "mojo/public/c/system/functions.h"
 #include "mojo/public/c/system/types.h"
+#include "mojo/public/cpp/system/watcher.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 
@@ -1294,6 +1297,75 @@ TEST_F(MultiprocessMessagePipeTest, BootstrapMessagePipeAsync) {
   END_CHILD()
 }
 
+DEFINE_TEST_CLIENT_TEST_WITH_PIPE(MessagePipeStatusChangeInTransitClient,
+                                  MultiprocessMessagePipeTest, parent) {
+  // This test verifies that peer closure is detectable through various
+  // mechanisms when it races with handle transfer.
+  MojoHandle handles[4];
+  EXPECT_EQ("o_O", ReadMessageWithHandles(parent, handles, 4));
+  MojoHandle b = handles[0];

[yzshen1, 2016/08/19 22:20:05]

optional, nit: it seems a little easier to read if we directly use an array to
refer to the handles here, and at line 1351.

[Ken Rockot(use gerrit already), 2016/08/19 22:28:00]

Done

+  MojoHandle d = handles[1];
+  MojoHandle f = handles[2];
+  MojoHandle h = handles[3];
+
+  // Wait on handle |b| using MojoWait.
+  EXPECT_EQ(MOJO_RESULT_OK, MojoWait(b, MOJO_HANDLE_SIGNAL_PEER_CLOSED,
+                                     MOJO_DEADLINE_INDEFINITE, nullptr));
+
+  base::MessageLoop message_loop;
+
+  // Wait on handle |d| using a Watcher.
+  {
+    base::RunLoop run_loop;
+    Watcher watcher;
+    watcher.Start(Handle(d), MOJO_HANDLE_SIGNAL_PEER_CLOSED,
+                  base::Bind([] (base::RunLoop* loop, MojoResult result) {
+                    EXPECT_EQ(MOJO_RESULT_OK, result);
+                    loop->Quit();
+                  }, &run_loop));
+    run_loop.Run();
+  }
+
+  // Wait on handle |f| by polling with MojoReadMessage.
+  MojoResult result;
+  do {
+    result = MojoReadMessage(f, nullptr, nullptr, nullptr, nullptr,
+                             MOJO_READ_MESSAGE_FLAG_NONE);
+  } while (result == MOJO_RESULT_SHOULD_WAIT);
+  EXPECT_EQ(MOJO_RESULT_FAILED_PRECONDITION, result);
+
+  // Wait on handle |h| by polling with MojoWriteMessage.
+  do {
+    result = MojoWriteMessage(h, nullptr, 0, nullptr, 0,
+                              MOJO_WRITE_MESSAGE_FLAG_NONE);
+  } while (result == MOJO_RESULT_OK);
+  EXPECT_EQ(MOJO_RESULT_FAILED_PRECONDITION, result);
+
+  CloseHandle(b);
+  CloseHandle(d);
+  CloseHandle(f);
+  CloseHandle(h);
+}
+
+TEST_F(MultiprocessMessagePipeTest, MessagePipeStatusChangeInTransit) {
+  MojoHandle a, b, c, d, e, f, g, h;
+  CreateMessagePipe(&a, &b);
+  CreateMessagePipe(&c, &d);
+  CreateMessagePipe(&e, &f);
+  CreateMessagePipe(&g, &h);
+
+  RUN_CHILD_ON_PIPE(MessagePipeStatusChangeInTransitClient, child)
+    MojoHandle handles[] = { b, d, f, h };
+
+    // Send 4 handles and let their transfer race with their peers' closure.
+    WriteMessageWithHandles(child, "o_O", handles, 4);
+    CloseHandle(a);
+    CloseHandle(c);
+    CloseHandle(e);
+    CloseHandle(g);
+  END_CHILD()
+}
+
 DEFINE_TEST_CLIENT_TEST_WITH_PIPE(BadMessageClient, MultiprocessMessagePipeTest,
                                   parent) {
   MojoHandle pipe;