Re: small cleanup for s_lock.h

Nathan Bossart <nathandbossart(at)gmail(dot)com> writes:
> I noticed that s_lock.h points to a default implementation of tas() in
> tas.s or s_lock.c, but AFAICT there hasn't been a tas() implementation in
> s_lock.c since commit 718aa43a4e, and commit 25f36066dd seems to have
> removed the last remaining tas.s files. So, I think this is dead code.

It is, but I think the 0001 patch should be more like

#if !defined(TAS)
-extern int tas(volatile slock_t *lock); /* in port/.../tas.s, or
- * s_lock.c */
-
-#define TAS(lock) tas(lock)
+#error "must provide a spinlock implementation"
#endif /* TAS */

Perhaps this could be merged with the earlier bit about erroring
if not HAS_TEST_AND_SET.

> I also noticed that HAS_TEST_AND_SET just means that TAS is defined, so I
> wrote a 0002 that removes it in favor of checking TAS directly.

I'm pretty much -1 on that; HAS_TEST_AND_SET is clearer than TAS, and
removing it seems quite likely to break someone's code. We could
perhaps collect all the separate instances into this end location:

#if defined(TAS)
#define HAS_TEST_AND_SET
#else
#error "must provide a spinlock implementation"
#endif /* TAS */

> I'd like
> to rewrite the comment at the top of the file, too, but haven't gotten to
> that yet. I find it a little misleading, especially because we #error if
> TAS isn't defined.

No objection in principle to improving that comment, but what did you
have in mind exactly?

regards, tom lane