Mojo EDK: Add tests to exercise races in handle transit

mojo/edk/system/data_pipe_unittest.cc

Index: mojo/edk/system/data_pipe_unittest.cc
diff --git a/mojo/edk/system/data_pipe_unittest.cc b/mojo/edk/system/data_pipe_unittest.cc
index 526444c6d58095e13cc76115380c2c9cc6b390da..6f8362e69c4a9607626dc7c942a549ebebb8e381 100644
--- a/mojo/edk/system/data_pipe_unittest.cc
+++ b/mojo/edk/system/data_pipe_unittest.cc
@@ -12,6 +12,7 @@
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
 #include "mojo/edk/embedder/embedder.h"
 #include "mojo/edk/embedder/platform_channel_pair.h"
 #include "mojo/edk/system/test_utils.h"
@@ -20,6 +21,7 @@
 #include "mojo/public/c/system/data_pipe.h"
 #include "mojo/public/c/system/functions.h"
 #include "mojo/public/c/system/message_pipe.h"
+#include "mojo/public/cpp/system/watcher.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace mojo {
@@ -1898,6 +1900,90 @@ TEST_F(DataPipeTest, CreateInChild) {
   END_CHILD()
 }
 
+DEFINE_TEST_CLIENT_TEST_WITH_PIPE(DataPipeStatusChangeInTransitClient,
+                                  DataPipeTest, parent) {
+  // This test verifies that peer closure is detectable through various
+  // mechanisms when it races with handle transfer.
+
+  MojoHandle handles[6];
+  EXPECT_EQ("o_O", ReadMessageWithHandles(parent, handles, 6));
+  MojoHandle* producers = &handles[0];
+  MojoHandle* consumers = &handles[3];
+
+  // Wait on producer 0 using MojoWait.
+  EXPECT_EQ(MOJO_RESULT_OK,
+            MojoWait(producers[0], MOJO_HANDLE_SIGNAL_PEER_CLOSED,
+                     MOJO_DEADLINE_INDEFINITE, nullptr));
+
+  // Wait on consumer 0 using MojoWait.
+  EXPECT_EQ(MOJO_RESULT_OK,
+            MojoWait(consumers[0], MOJO_HANDLE_SIGNAL_PEER_CLOSED,
+                     MOJO_DEADLINE_INDEFINITE, nullptr));
+
+  base::MessageLoop message_loop;
+
+  // Wait on producer 1 and consumer 1 using Watchers.
+  {
+    base::RunLoop run_loop;
+    int count = 0;
+    auto callback = base::Bind(
+        [] (base::RunLoop* loop, int* count, MojoResult result) {
+          EXPECT_EQ(MOJO_RESULT_OK, result);
+          if (++*count == 2)
+            loop->Quit();
+        },
+        &run_loop, &count);
+    Watcher producer_watcher, consumer_watcher;
+    producer_watcher.Start(
+        Handle(producers[1]), MOJO_HANDLE_SIGNAL_PEER_CLOSED, callback);
+    consumer_watcher.Start(
+        Handle(consumers[1]), MOJO_HANDLE_SIGNAL_PEER_CLOSED, callback);
+    run_loop.Run();
+  }
+
+  // Wait on producer 2 by polling with MojoWriteData.
+  MojoResult result;
+  do {
+    uint32_t num_bytes = 0;
+    result = MojoWriteData(
+        producers[2], nullptr, &num_bytes, MOJO_WRITE_DATA_FLAG_NONE);
+  } while (result == MOJO_RESULT_OK);
+  EXPECT_EQ(MOJO_RESULT_FAILED_PRECONDITION, result);
+
+  // Wait on consumer 2 by polling with MojoReadData.
+  do {
+    char byte;
+    uint32_t num_bytes = 1;
+    result = MojoReadData(
+        consumers[2], &byte, &num_bytes, MOJO_READ_DATA_FLAG_NONE);
+  } while (result == MOJO_RESULT_SHOULD_WAIT);
+  EXPECT_EQ(MOJO_RESULT_FAILED_PRECONDITION, result);
+
+  for (size_t i = 0; i < 6; ++i)
+    CloseHandle(handles[i]);
+}
+
+TEST_F(DataPipeTest, StatusChangeInTransit) {
+  MojoHandle producers[6];
+  MojoHandle consumers[6];
+  for (size_t i = 0; i < 6; ++i)
+    CreateDataPipe(&producers[i], &consumers[i], 1);
+
+  RUN_CHILD_ON_PIPE(DataPipeStatusChangeInTransitClient, child)
+    MojoHandle handles[] = { producers[0], producers[1], producers[2],
+                             consumers[3], consumers[4], consumers[5] };
+
+    // Send 3 producers and 3 consumers, and let their transfer race with their
+    // peers' closure.
+    WriteMessageWithHandles(child, "o_O", handles, 6);
+
+    for (size_t i = 0; i < 3; ++i)
+      CloseHandle(consumers[i]);
+    for (size_t i = 3; i < 6; ++i)
+      CloseHandle(producers[i]);
+  END_CHILD()
+}
+
 #endif  // !defined(OS_IOS)
 
 }  // namespace