Chromium roll (https://codereview.chromium.org/976353002)

base/threading/sequenced_worker_pool_unittest.cc

 // Copyright (c) 2012 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/threading/sequenced_worker_pool.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
@@ skipping 49 matching lines @@
     cond_var_.Signal();
   }
 
  private:
   base::Lock lock_;
   base::ConditionVariable cond_var_;
 
   size_t unblock_counter_;
 };
 
+class DestructionDeadlockChecker
+    : public base::RefCountedThreadSafe<DestructionDeadlockChecker> {
+ public:
+  DestructionDeadlockChecker(const scoped_refptr<SequencedWorkerPool>& pool)
+      : pool_(pool) {}
+
+ protected:
+  virtual ~DestructionDeadlockChecker() {
+    // This method should not deadlock.
+    pool_->RunsTasksOnCurrentThread();
+  }
+
+ private:
+  scoped_refptr<SequencedWorkerPool> pool_;
+  friend class base::RefCountedThreadSafe<DestructionDeadlockChecker>;
+};
+
 class TestTracker : public base::RefCountedThreadSafe<TestTracker> {
  public:
   TestTracker()
       : lock_(),
         cond_var_(&lock_),
         started_events_(0) {
   }
 
   // Each of these tasks appends the argument to the complete sequence vector
   // so calling code can see what order they finished in.
@@ skipping 30 matching lines @@
     EXPECT_EQ(expected_return_value,
               pool->PostWorkerTaskWithShutdownBehavior(
                   FROM_HERE, fast_task,
                   SequencedWorkerPool::SKIP_ON_SHUTDOWN));
     pool->PostWorkerTaskWithShutdownBehavior(
         FROM_HERE, fast_task,
         SequencedWorkerPool::BLOCK_SHUTDOWN);
     SignalWorkerDone(id);
   }
 
+  // This task posts itself back onto the SequencedWorkerPool before it
+  // finishes running. Each instance of the task maintains a strong reference
+  // to a DestructionDeadlockChecker. The DestructionDeadlockChecker is only
+  // destroyed when the task is destroyed without being run, which only happens
+  // during destruction of the SequencedWorkerPool.
+  void PostRepostingTask(
+      const scoped_refptr<SequencedWorkerPool>& pool,
+      const scoped_refptr<DestructionDeadlockChecker>& checker) {
+    Closure reposting_task =
+        base::Bind(&TestTracker::PostRepostingTask, this, pool, checker);
+    pool->PostWorkerTaskWithShutdownBehavior(
+        FROM_HERE, reposting_task, SequencedWorkerPool::SKIP_ON_SHUTDOWN);
+  }
+
   // Waits until the given number of tasks have started executing.
   void WaitUntilTasksBlocked(size_t count) {
     {
       base::AutoLock lock(lock_);
       while (started_events_ < count)
         cond_var_.Wait();
     }
     cond_var_.Signal();
   }
 
@@ skipping 612 matching lines @@
       base::Bind(&IsRunningOnCurrentThreadTask,
                  token2, unsequenced_token, pool(), unused_pool));
   pool()->PostWorkerTask(
       FROM_HERE,
       base::Bind(&IsRunningOnCurrentThreadTask,
                  unsequenced_token, token1, pool(), unused_pool));
   pool()->Shutdown();
   unused_pool->Shutdown();
 }
 
+// Checks that tasks are destroyed in the right context during shutdown. If a
+// task is destroyed while SequencedWorkerPool's global lock is held,
+// SequencedWorkerPool might deadlock.
+TEST_F(SequencedWorkerPoolTest, AvoidsDeadlockOnShutdown) {
+  for (int i = 0; i < 4; ++i) {
+    scoped_refptr<DestructionDeadlockChecker> checker(
+        new DestructionDeadlockChecker(pool()));
+    tracker()->PostRepostingTask(pool(), checker);
+  }
+
+  // Shutting down the pool should destroy the DestructionDeadlockCheckers,
+  // which in turn should not deadlock in their destructors.
+  pool()->Shutdown();
+}
+
 // Verify that FlushForTesting works as intended.
 TEST_F(SequencedWorkerPoolTest, FlushForTesting) {
   // Should be fine to call on a new instance.
   pool()->FlushForTesting();
 
   // Queue up a bunch of work, including  a long delayed task and
   // a task that produces additional tasks as an artifact.
   pool()->PostDelayedWorkerTask(
       FROM_HERE,
       base::Bind(&TestTracker::FastTask, tracker(), 0),
@@ skipping 147 matching lines @@
     SequencedWorkerPoolSequencedTaskRunner, TaskRunnerTest,
     SequencedWorkerPoolSequencedTaskRunnerTestDelegate);
 
 INSTANTIATE_TYPED_TEST_CASE_P(
     SequencedWorkerPoolSequencedTaskRunner, SequencedTaskRunnerTest,
     SequencedWorkerPoolSequencedTaskRunnerTestDelegate);
 
 }  // namespace
 
 }  // namespace base