debuggerd_client: properly wait for completion.

Use an intermediate pipe to detect and report when a requested dump has
completed.

Bug: http://b/35241370
Bug: http://b/35813071
Test: debuggerd_test
Test: manually triggered a background ANR
Change-Id: If14aedf6071288360f1a7853d5a2ee79db121759

1 files changed, 91 insertions, 0 deletions

diff --git a/debuggerd/client/debuggerd_client_test.cpp b/debuggerd/client/debuggerd_client_test.cpp
new file mode 100644
index 000000000..86d03149b
--- /dev/null
+++ b/debuggerd/client/debuggerd_client_test.cpp
@@ -0,0 +1,91 @@
+/*
+ * Copyright 2017, The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <debuggerd/client.h>
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include <chrono>
+#include <thread>
+#include <vector>
+
+#include <gtest/gtest.h>
+
+#include <android-base/file.h>
+#include <android-base/stringprintf.h>
+#include <android-base/strings.h>
+#include <android-base/unique_fd.h>
+
+#include <debuggerd/util.h>
+
+using namespace std::chrono_literals;
+using android::base::unique_fd;
+
+TEST(debuggerd_client, race) {
+  static constexpr int THREAD_COUNT = 1024;
+  pid_t forkpid = fork();
+
+  ASSERT_NE(-1, forkpid);
+
+  if (forkpid == 0) {
+    // Spawn a bunch of threads, to make crash_dump take longer.
+    std::vector<std::thread> threads;
+    for (int i = 0; i < THREAD_COUNT; ++i) {
+      threads.emplace_back([]() {
+        while (true) {
+          std::this_thread::sleep_for(60s);
+        }
+      });
+    }
+
+    std::this_thread::sleep_for(60s);
+    exit(0);
+  }
+
+  unique_fd pipe_read, pipe_write;
+  ASSERT_TRUE(Pipe(&pipe_read, &pipe_write));
+
+  // 64 kB should be enough for everyone.
+  constexpr int PIPE_SIZE = 64 * 1024 * 1024;
+  ASSERT_EQ(PIPE_SIZE, fcntl(pipe_read.get(), F_SETPIPE_SZ, PIPE_SIZE));
+
+  // Wait for a bit to let the child spawn all of its threads.
+  std::this_thread::sleep_for(250ms);
+
+  ASSERT_TRUE(debuggerd_trigger_dump(forkpid, std::move(pipe_write), kDebuggerdBacktrace, 10000));
+  // Immediately kill the forked child, to make sure that the dump didn't return early.
+  ASSERT_EQ(0, kill(forkpid, SIGKILL)) << strerror(errno);
+
+  // Check the output.
+  std::string result;
+  ASSERT_TRUE(android::base::ReadFdToString(pipe_read.get(), &result));
+
+  // Look for "----- end <PID> -----"
+  int found_end = 0;
+
+  std::string expected_end = android::base::StringPrintf("----- end %d -----", forkpid);
+
+  std::vector<std::string> lines = android::base::Split(result, "\n");
+  for (const std::string& line : lines) {
+    if (line == expected_end) {
+      ++found_end;
+    }
+  }
+
+  EXPECT_EQ(1, found_end) << "\nOutput: \n" << result;
+}