Fix race causing crash in net::FileNetLogObserver shutdown

net/log/file_net_log_observer_unittest.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/log/file_net_log_observer.h"
 
 #include <math.h>
 
 #include <memory>
 #include <string>
@@ skipping 774 matching lines @@
   ASSERT_TRUE(std::all_of(std::begin(events_written), std::end(events_written),
                           [](bool j) { return j; }));
 
   // Check that there are events written to all files.
   for (int i = 0; i < kTotalNumFiles; i++) {
     ASSERT_GE(GetFileSize(GetEventFilePath(i)),
               static_cast<int64_t>(kEventSize));
   }
 }
 
+void AddEntriesViaNetLog(NetLog* net_log, int num_entries) {
+  for (int i = 0; i < num_entries; i++) {
+    net_log->AddGlobalEntry(NetLogEventType::PAC_JAVASCRIPT_ERROR);
+  }
+}
+
+TEST_P(FileNetLogObserverTest, AddEventsFromMultipleThreadsWithStopObserving) {
+  const size_t kNumThreads = 10;
+  std::vector<std::unique_ptr<base::Thread>> threads(kNumThreads);
+  // Start all the threads. Waiting for them to start is to hopefuly improve
+  // the odds of hitting interesting races once events start being added.
+  for (size_t i = 0; i < threads.size(); ++i) {
+    threads[i] = base::MakeUnique<base::Thread>(
+        base::StringPrintf("WorkerThread%i", static_cast<int>(i)));
+    threads[i]->Start();
+    threads[i]->WaitUntilThreadStarted();
+  }
+
+  CreateAndStartObserving(nullptr);
+
+  const size_t kNumEventsAddedPerThread = 200;
+
+  // Add events in parallel from all the threads.
+  for (size_t i = 0; i < kNumThreads; ++i) {
+    threads[i]->task_runner()->PostTask(
+        FROM_HERE, base::Bind(&AddEntriesViaNetLog, base::Unretained(&net_log_),
+                              kNumEventsAddedPerThread));
+  }
+
+  // Stop observing.
+  TestClosure closure;
+  logger_->StopObserving(nullptr, closure.closure());
+  closure.WaitForResult();
+
+  // Join all the threads.
+  threads.clear();
+}
+
+TEST_P(FileNetLogObserverTest,
+       AddEventsFromMultipleThreadsWithoutStopObserving) {
+  const size_t kNumThreads = 10;
+  std::vector<std::unique_ptr<base::Thread>> threads(kNumThreads);
+  // Start all the threads. Waiting for them to start is to hopefuly improve
+  // the odds of hitting interesting races once events start being added.
+  for (size_t i = 0; i < threads.size(); ++i) {
+    threads[i] = base::MakeUnique<base::Thread>(
+        base::StringPrintf("WorkerThread%i", static_cast<int>(i)));
+    threads[i]->Start();
+    threads[i]->WaitUntilThreadStarted();
+  }
+
+  CreateAndStartObserving(nullptr);
+
+  const size_t kNumEventsAddedPerThread = 200;
+
+  // Add events in parallel from all the threads.
+  for (size_t i = 0; i < kNumThreads; ++i) {
+    threads[i]->task_runner()->PostTask(
+        FROM_HERE, base::Bind(&AddEntriesViaNetLog, base::Unretained(&net_log_),
+                              kNumEventsAddedPerThread));
+  }
+
+  // Destroy logger.
+  logger_.reset();
+
+  // Join all the threads.
+  threads.clear();
+}
+
 }  // namespace
 
 }  // namespace net