I need to use the lock in the Inline::C parts and the regular perl parts. If the implementation uses pthreads that's great, but I still need to identify the actual mutexes used by the interpreter.

The function you need to call is Perl_sharedsv_locksv(pTHX_ SV *sv) found in threads::shared.xs.

But good luck in working out how to link to it.

Another mystery that has long defeated me is quite where the perl-level lock() function (keyword or operator) lives and how it gets translated into a call to the above.

The way I understand, you use threads::shared; and then SvLOCK and SvUNLOCK will call threads::shared::lock, but if threads::shared isn't loaded, it falls back to sv_nolocking and sv_nounlocking

Yes, thanks. But that doesn't get you very far.

c:\test\perl-5.14.0-RC1>findstr SvLOCK *.?
pp.c:    SvLOCK(sv);
sv.h:=for apidoc Am|void|SvLOCK|SV* sv
sv.h:#define SvLOCK(sv) PL_lockhook(aTHX_ sv)

c:\test\perl-5.14.0-RC1>findstr PL_lockhook *.?
embedvar.h:#define PL_lockhook          (vTHX->Ilockhook)
embedvar.h:#define PL_Ilockhook         PL_lockhook
sv.c:    PL_lockhook            = proto_perl->Ilockhook;
sv.h:#define SvLOCK(sv) PL_lockhook(aTHX_ sv)

c:\test\perl-5.14.0-RC1>findstr Ilockhook *.?
embedvar.h:#define PL_lockhook          (vTHX->Ilockhook)
embedvar.h:#define PL_Ilockhook         PL_lockhook
intrpvar.h:PERLVARI(Ilockhook,  share_proc_t,   Perl_sv_nosharing)
sv.c:    PL_lockhook            = proto_perl->Ilockhook;
[download]

The whole 'lock locks the variable if threading is enable but is a silent noop otherwise', is the single most pointless piece of logic ever. (After the over-elaborate feature mechanism that is.)

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

OP is talking about threads::shared#lock VARIABLE