tracing: fix edge case when dumping while trace being disabled

base/trace_event/memory_dump_manager_unittest.cc

 // Copyright 2015 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 "base/trace_event/memory_dump_manager.h"
 
 #include <stdint.h>
 
 #include <vector>
 
@@ skipping 72 matching lines @@
   }
 
   MOCK_METHOD2(RequestGlobalMemoryDump,
                void(const MemoryDumpRequestArgs& args,
                     const MemoryDumpCallback& callback));
 
   uint64_t GetTracingProcessId() const override {
     NOTREACHED();
     return MemoryDumpManager::kInvalidTracingProcessId;
   }
+
+  // Promote the CreateProcessDump to public so it can be used by test fixtures.
+  using MemoryDumpManagerDelegate::CreateProcessDump;
 };
 
 class MockMemoryDumpProvider : public MemoryDumpProvider {
  public:
   MOCK_METHOD0(Destructor, void());
   MOCK_METHOD2(OnMemoryDump,
                bool(const MemoryDumpArgs& args, ProcessMemoryDump* pmd));
 
   MockMemoryDumpProvider() : enable_mock_destructor(false) {}
   ~MockMemoryDumpProvider() override {
@@ skipping 721 matching lines @@
                           MemoryDumpLevelOfDetail::DETAILED, callback);
   DisableTracing();
   tracing_disabled_event.Signal();
   run_loop.Run();
 
   // RequestGlobalMemoryDump() should still suceed even if some threads were
   // torn down during the dump.
   EXPECT_TRUE(last_callback_success_);
 }
 
+// Tests against race conditions that can happen if tracing is disabled before
+// the CreateProcessDump() call. Real-world regression: crbug.com/580295 .
+TEST_F(MemoryDumpManagerTest, DisableTracingRightBeforeStartOfDump) {
+  base::WaitableEvent tracing_disabled_event(false, false);
+  InitializeMemoryDumpManager(false /* is_coordinator */);
+
+  MockMemoryDumpProvider mdp;
+  RegisterDumpProvider(&mdp);
+  EnableTracingWithLegacyCategories(MemoryDumpManager::kTraceCategory);
+
+  EXPECT_CALL(*delegate_, RequestGlobalMemoryDump(_, _))
+      .WillOnce(Invoke([this](const MemoryDumpRequestArgs& args,
+                              const MemoryDumpCallback& callback) {
+        DisableTracing();
+        delegate_->CreateProcessDump(args, callback);
+      }));
+
+  last_callback_success_ = true;
+  RequestGlobalDumpAndWait(MemoryDumpType::EXPLICITLY_TRIGGERED,
+                           MemoryDumpLevelOfDetail::DETAILED);
+  EXPECT_FALSE(last_callback_success_);
+}
+
 TEST_F(MemoryDumpManagerTest, DumpOnBehalfOfOtherProcess) {
   using trace_analyzer::Query;
 
   InitializeMemoryDumpManager(false /* is_coordinator */);
 
   // Standard provider with default options (create dump for current process).
   MemoryDumpProvider::Options options;
   MockMemoryDumpProvider mdp1;
   RegisterDumpProvider(&mdp1, nullptr, options);
 
@@ skipping 105 matching lines @@
   EXPECT_CALL(*delegate_, RequestGlobalMemoryDump(_, _)).Times(2);
   for (int i = 0; i < 2; ++i) {
     RequestGlobalDumpAndWait(MemoryDumpType::EXPLICITLY_TRIGGERED,
                              MemoryDumpLevelOfDetail::DETAILED);
   }
   DisableTracing();
 }
 
 }  // namespace trace_event
 }  // namespace base