column_family_test: fix a data race related to sleeping task (#7150)

Summary:
TSAN reports warning in one column_family_test:

WARNING: ThreadSanitizer: data race (pid=16352)
  Write of size 8 at 0x7ffcdf042158 by main thread:
    #0 pthread_cond_destroy <null> (column_family_test+0x471f65)
    https://github.com/facebook/rocksdb/issues/1 rocksdb::port::CondVar::~CondVar() /home/circleci/project/port/port_posix.cc:101:49 (column_family_test+0x8a627a)
    https://github.com/facebook/rocksdb/issues/2 rocksdb::test::SleepingBackgroundTask::~SleepingBackgroundTask() /home/circleci/project/./test_util/testutil.h:397:7 (column_family_test+0x54b6e2)
    https://github.com/facebook/rocksdb/issues/3 rocksdb::ColumnFamilyTest_FlushCloseWALFiles_Test::TestBody() /home/circleci/project/db/column_family_test.cc:3008:1 (column_family_test+0x54b6e2)
......
  Previous read of size 8 at 0x7ffcdf042158 by thread T2 (mutexes: write M0):
    #0 pthread_cond_broadcast <null> (column_family_test+0x471dd2)
    https://github.com/facebook/rocksdb/issues/1 rocksdb::port::CondVar::SignalAll() /home/circleci/project/port/port_posix.cc:139:28 (column_family_test+0x8a651a)
    https://github.com/facebook/rocksdb/issues/2 rocksdb::test::SleepingBackgroundTask::DoSleep() /home/circleci/project/./test_util/testutil.h:412:12 (column_family_test+0x58574b)
......

Likely, SleepingBackgroundTask::DoSleep() started to execute after the main thread has finished everything, cancelled and waited for sleeping tasks to finish. At this time, although DoSlee() will not sleep, but it also accesses the mutex, creating a data race with destructor of the test. Fix this bug by waiting for the sleeping task to start sleeping after it is scheduled.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7150

Test Plan: Run these modified tests and make sure it doesn't break.

Reviewed By: riversand963

Differential Revision: D22630716

fbshipit-source-id: cc5781cf69083685de406490438898238bdfc2d3

db/column_family_test.cc

@@ -2424,6 +2424,9 @@ TEST_P(ColumnFamilyTest, FlushAndDropRaceCondition) {
 
   env_->Schedule(&test::SleepingBackgroundTask::DoSleepTask, &sleeping_task,
                  Env::Priority::HIGH);
+  // Make sure the task is sleeping. Otherwise, it might start to execute
+  // after sleeping_task.WaitUntilDone() and cause TSAN warning.
+  sleeping_task.WaitUntilSleeping();
   
   // 1MB should create ~10 files for each CF
   int kKeysNum = 10000;
@@ -2438,6 +2441,9 @@ TEST_P(ColumnFamilyTest, FlushAndDropRaceCondition) {
   // now we sleep again. this is just so we're certain that flush job finished
   env_->Schedule(&test::SleepingBackgroundTask::DoSleepTask, &sleeping_task,
                  Env::Priority::HIGH);
+  // Make sure the task is sleeping. Otherwise, it might start to execute
+  // after sleeping_task.WaitUntilDone() and cause TSAN warning.
+  sleeping_task.WaitUntilSleeping();
   sleeping_task.WakeUp();
   sleeping_task.WaitUntilDone();
 
@@ -2987,6 +2993,9 @@ TEST_P(ColumnFamilyTest, FlushCloseWALFiles) {
   test::SleepingBackgroundTask sleeping_task;
   env_->Schedule(&test::SleepingBackgroundTask::DoSleepTask, &sleeping_task,
                  Env::Priority::HIGH);
+  // Make sure the task is sleeping. Otherwise, it might start to execute
+  // after sleeping_task.WaitUntilDone() and cause TSAN warning.
+  sleeping_task.WaitUntilSleeping();
 
   WriteOptions wo;
   wo.sync = true;
@@ -3032,6 +3041,9 @@ TEST_P(ColumnFamilyTest, IteratorCloseWALFile1) {
   test::SleepingBackgroundTask sleeping_task;
   env_->Schedule(&test::SleepingBackgroundTask::DoSleepTask, &sleeping_task,
                  Env::Priority::HIGH);
+  // Make sure the task is sleeping. Otherwise, it might start to execute
+  // after sleeping_task.WaitUntilDone() and cause TSAN warning.
+  sleeping_task.WaitUntilSleeping();
 
   WriteOptions wo;
   wo.sync = true;