RAID5 md device hangs during resync

Issue

• RAID5 md device hangs during resync:

  PID: 1076372  TASK: ffffa031c545c000  CPU: 4    COMMAND: "md0_resync"
  #0 [ffffc1f2e2f67be0] __schedule at ffffffff85c0e191
  #1 [ffffc1f2e2f67c38] schedule at ffffffff85c0e785
  #2 [ffffc1f2e2f67c50] raid5_get_active_stripe at ffffffffc06ba90e [raid456]
  #3 [ffffc1f2e2f67cd0] raid5_sync_request at ffffffffc06bf88d [raid456]
  #4 [ffffc1f2e2f67d38] md_do_sync.cold.94 at ffffffff85996b8f
  #5 [ffffc1f2e2f67eb8] md_thread at ffffffff859887d4
  #6 [ffffc1f2e2f67f10] kthread at ffffffff8531e974
  #7 [ffffc1f2e2f67f50] ret_from_fork at ffffffff85e0028f