Re: nptl/tst-stack4 failure

[Siddhesh Poyarekar <siddhesh at gotplt dot org>]

On Wednesday 16 November 2016 09:09 PM, Florian Weimer wrote:
> The nptl/tst-stack4 test fails reliably on several architectures for me
> (ppc, ppc64, aarch64).  I'm trying to figure out what's going on.

I saw this yesterday and bisected it to this commit:

=================
commit 17af5da98cd2c9ec958421ae2108f877e0945451
Author: Alexandre Oliva <aoliva@redhat.com>
Date: Wed Sep 21 22:01:16 2016 -0300

[PR19826] fix non-LE TLS in static programs

An earlier fix for TLS dropped early initialization of DTV entries for
modules using static TLS, leaving it for __tls_get_addr to set them
up. That worked on platforms that require the GD access model to be
relaxed to LE in the main executable, but it caused a regression on
platforms that allow GD in the main executable, particularly in
statically-linked programs: they use a custom __tls_get_addr that does
not update the DTV, which fails when the DTV early initialization is
not performed.

In static programs, __libc_setup_tls performs the DTV initialization
for the main thread, but the DTV of other threads is set up in
_dl_allocate_tls_init, so that's the fix that matters.

Restoring the initialization in the remaining functions modified by
this patch was just for uniformity. It's not clear that it is ever
needed: even on platforms that allow GD in the main executable, the
dynamically-linked version of __tls_get_addr would set up the DTV
entries, even for static TLS modules, while updating the DTV counter.
=================

I had planned to look at it later in the week but if you have the time
then please feel free to pick it up.

Siddhesh