On Wed, 13 Oct 2021 10:04:52 +0800 王贇 <yun.wang@xxxxxxxxxxxxxxxxx> wrote: > I see, while the user can still check smp_processor_id() after trylock > return bit 0... But preemption would have already been disabled. That's because a bit 0 means that a recursion check has already been made by a previous caller and this one is nested, thus preemption is already disabled. If bit is 0, then preemption had better be disabled as well. -- Steve
