Re: rw_lock_held

[Ryota Ozaki <ozaki-r%netbsd.org@localhost>]

On Wed, Feb 7, 2018 at 2:21 PM, Taylor R Campbell
<campbell+netbsd-tech-kern%mumble.net@localhost> wrote:
>> Date: Wed, 7 Feb 2018 14:14:35 +0900
>> From: Ryota Ozaki <ozaki-r%netbsd.org@localhost>
>>
>> On Wed, Feb 7, 2018 at 2:55 AM, Taylor R Campbell
>> <campbell+netbsd-tech-kern%mumble.net@localhost> wrote:
>> >> Date: Tue, 6 Feb 2018 19:06:33 +0900
>> >> From: Ryota Ozaki <ozaki-r%netbsd.org@localhost>
>> >>
>> >> So I think we should do either:
>> >> (1) fix rw_lock_held, or
>> >>     - probably it would be rw_read_held() || rw_write_held()
>> >> (2) fix users of rw_lock_held.
>> >>     - it also would replace rw_lock_held with
>> >>       rw_read_held() || rw_write_held()
>> >>
>> >> I prefer (1) because I think there is no user of the current
>> >> behavior that is difficult to use for users (it may be useful
>> >> as an internal utility function though).
>> >
>> > I like (1) too, but check for Solaris compatibility?  It is hard to
>> > imagine that there are correct uses of the current semantics that are
>> > not also correct uses of (1).
>>
>> https://docs.oracle.com/cd/E36784_01/html/E36886/rwlock-9f.html
>>
>> They seem to have only rw_read_locked that is compatible to our
>> rw_read_held.
>
> Looks to me like rw_read_locked is actually more like:
>
>         KASSERT(rw_read_held(l) || rw_write_held(l));
>         return rw_read_held(l);
>
> or
>
>         KASSERT(rw_read_held(l) || rw_write_held(l));
>         return !rw_write_held(l);

Oops. Yes, I misunderstood rw_read_held.

  ozaki-r