test/objectstore/TestRocksdbOptionParse.cc: Fix race hazard

Race hazard - rocksdb does not register its threads until they start
running, and only guarantees the threads have been created before
returning. We need to be prepared to wait for the scheduler to
run the threads to avoid false positives.

Fixes: https://tracker.ceph.com/issues/66575
Signed-off-by: Bill Scales <[email protected]>

Author: bill-scales

src/test/objectstore/TestRocksdbOptionParse.cc

@@ -55,11 +55,20 @@ TEST(RocksDBOption, interpret) {
   ASSERT_EQ(0, r);
   ASSERT_TRUE(db->compact_on_mount);
   //check thread pool setting
-  options.env->SleepForMicroseconds(100000);
   std::vector<rocksdb::ThreadStatus> thread_list;
-  status = options.env->GetThreadList(&thread_list);
-  ASSERT_TRUE(status.ok());
-
+  /* Race hazard - rocksdb does not register its threads until they start
+   * running, and only guarantees the threads have been created before
+   * returning. We need to be prepared to wait for the scheduler to
+   * run the threads to avoid false positives.
+   */
+  for (int attempt = 0; attempt < 50; attempt++) {
+    options.env->SleepForMicroseconds(100000);
+    status = options.env->GetThreadList(&thread_list);
+    ASSERT_TRUE(status.ok());
+    if (thread_list.size() >= 15u) {
+      break;
+    }
+  }
   int num_high_pri_threads = 0;
   int num_low_pri_threads = 0;
   for (vector<rocksdb::ThreadStatus>::iterator it = thread_list.begin();