Re: Postmaster self-deadlock due to PLT linkage resolution

On Wed, Aug 31, 2022 at 1:34 AM Thomas Munro <thomas.munro@gmail.com> wrote:
> On Wed, Aug 31, 2022 at 12:26 AM Robert Haas <robertmhaas@gmail.com> wrote:
> > On Tue, Aug 30, 2022 at 8:17 AM Thomas Munro <thomas.munro@gmail.com> wrote:
> > > FWIW I suspect FreeBSD can't break like this in a program linked with
> > > libthr, because it has a scheme for deferring signals while the
> > > runtime linker holds locks.  _rtld_bind calls _thr_rtld_rlock_acquire,
> > > which uses the THR_CRITICAL_ENTER mechanism to cause thr_sighandler to
> > > defer until release.  For a non-thread program, I'm not entirely sure,
> > > but I don't think the fork() problem exists there.  (Could be wrong,
> > > based on a quick look.)
> >
> > Well that seems a bit ironic, considering that Tom has worried in the
> > past that linking with threading libraries would break stuff.
>
> Hah.  To clarify, non-thread builds don't have that exact fork()
> problem, but it turns out they do have a related state clobbering
> problem elsewhere, which I've reported.

For the record, reporting that resulted in a change for non-libthr rtld:

https://cgit.freebsd.org/src/commit/?id=a687683b997c5805ecd6d8278798b7ef00d9908f