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Date:      Fri, 19 Feb 2021 01:07:54 +0000
From:      Jessica Clarke <jrtc27@freebsd.org>
To:        Brandon Bergren <bdragon@FreeBSD.org>
Cc:        Konstantin Belousov <kostikbel@gmail.com>, John Baldwin <jhb@freebsd.org>, src-committers <src-committers@freebsd.org>, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org
Subject:   Re: git: 24fd63e0970f - main - mips: Don't set __NO_TLS to disable some uses of TLS.
Message-ID:  <012169A0-67EC-48B7-A1CB-2A9921EF63FA@freebsd.org>
In-Reply-To: <bc966f88-292e-4c2f-b1e7-6f93f890af7a@www.fastmail.com>
References:  <202102180035.11I0ZnL3070354@gitrepo.freebsd.org> <9687575c-dd7c-1496-850b-2018f4bca3da@FreeBSD.org> <YC7TcMtrg8r7eAuL@kib.kiev.ua> <DBFAB331-737A-44E0-BBAA-65AF2C870AA9@freebsd.org> <ce964b75-4a11-4b5e-b47e-43a384da047f@www.fastmail.com> <3045F222-DBAC-463C-B429-075B2CFB115A@freebsd.org> <bc966f88-292e-4c2f-b1e7-6f93f890af7a@www.fastmail.com>

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On 19 Feb 2021, at 00:03, Brandon Bergren <bdragon@FreeBSD.org> wrote:
> On Thu, Feb 18, 2021, at 6:00 PM, Jessica Clarke wrote:
>>=20
>> But TLS isn't broken for ELFv1? Otherwise jemalloc would die in a =
fire
>> and nothing would ever work. TLS should have been working for ELFv1 =
for
>> many years by this point.
>>=20
>> Jess
>=20
> It's not broken, but it's an ABI change to flip it back and forth. You =
get RuneLocale errors in the middle of installworld if you try and =
install a build with TLS enabled and have to do a double installworld to =
compensate for the crashes.
>=20
> For ABI stability reasons, it needs to stay on in 12 and below.

Ok, so the mistake was not deleting it 8 years ago and instead leaving
it around to become part of the ABI. The issue you're referring to
specifically is __getCurrentRuneLocale and _ThreadRuneLocale (the
latter doesn't exist for __NO_TLS, and the former changes between
static inline and extern)? __NO_TLS should have blocked powerpc64 (and
mips) from becoming tier 2 IMO, but we're stuck with it, so yeah, it's
a major ABI break (frustratingly tiny but breaks the core system
libraries) and thus can't be MFC'ed.

Jess




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