use SeqCst to make things simple in places where called not frequently (#4268)
use SeqCst to make things simple in places where called not frequently (#4268)

Signed-off-by: zhangjinpeng1987 <0be30061b56e3ccbb0c7506bec92d245aba78ed7@pingcap.com>

BusyJay/tikv,pingcap/tikv,BusyJay/tikv,c4pt0r/tikv,BusyJay/tikv,pingcap/tikv,BusyJay/tikv