Ceph

int FileStore::umount()
......
do_force_sync();

lock.Lock();
  stop = true;
  sync_cond.Signal();
  lock.Unlock();

because force_sync flag isn't protect by the same lock acquire, it will sync thread wait two times which isn't expected:

utime_t startwait = ceph_clock_now(g_ceph_context);
    if (!force_sync) {
      dout(20) << "sync_entry waiting for max_interval " << max_interval << dendl;
      sync_cond.WaitInterval(g_ceph_context, lock, max_interval);
    } else {
      dout(20) << "sync_entry not waiting, force_sync set" << dendl;
    }

if (force_sync) {
      dout(20) << "sync_entry force_sync set" << dendl;
      force_sync = false;
    } else {
      // wait for at least the min interval
      utime_t woke = ceph_clock_now(g_ceph_context);
      woke -= startwait;
      dout(20) << "sync_entry woke after " << woke << dendl;
      if (woke < min_interval) {
    utime_t t = min_interval;
    t -= woke;
    dout(20) << "sync_entry waiting for another " << t
         << " to reach min interval " << min_interval << dendl;
    sync_cond.WaitInterval(g_ceph_context, lock, t);
      }
    }

http://pulpito.ceph.com/haomai-2016-05-01_23:40:37-rados-wip-haomai-testing-distro-basic-smithi/161404/
http://pulpito.ceph.com/haomai-2016-05-01_23:40:37-rados-wip-haomai-testing-distro-basic-smithi/161419

These two jobs all stuck into this case, and WaitInterval for 10hours because of cmd line arguments!:

ceph_test_filestore_idempotent_sequence run-sequence-to 0 b.00 b.00/journal --test-seed 59 --osd-journal-size 100 --log-file b.00.clean --debug-filestore 20 --filestore-min-sync-interval 36000 --filestore-max-sync-interval 36001