Re: [musl] Simple question regarding read-write locks precedence

[Rich Felker <dalias@libc.org>]

On Tue, Mar 31, 2020 at 07:21:20PM +0200, Markus Wichmann wrote:
> On Tue, Mar 31, 2020 at 11:26:46AM -0400, Rich Felker wrote:
> > Thanks. While I specifically did not implement (or define a macro for)
> > PTHREAD_RWLOCK_PREFER_WRITER_NP because it's misleading to advertise
> > support for it when it fundamentally can't work,
> > PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP seems like a viable
> > extension to support. Anyone else see potential problems supporting it
> > that I might be missing?
> >
> > Rich
> 
> I do see one problem: The manpage (the only spec available) contradicts
> itself. In the Description section, it says (of the new option):
> 
> |Setting the lock kind to this avoids writer starvation as long as any
> |read locking is not done in a recursive fashion.
> 
> OK, but in the Bugs section:
> 
> |Setting the lock kind to PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP
> |allows writers to run, but, as the name implies a writer may not lock
> |recursively.
> 
> Well, which is it? Are writers or readers not supposed to recurse? I
> thought writers aren't supposed to recurse, anyway. Or is it possible we
> need to file a bug report to Michael Kerrisk? Maybe it was supposed to
> say "reader" here, then it would make sense. As it stands, though, the
> spec is unclear.

I think that's pretty clearly just a mistake in the man page that
should be reported. CC'ing.

Rich