[Bug dynamic-link/19329] dl-tls.c assert failure at concurrent pthread_create and dlopen

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=19329

--- Comment #32 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Szabolcs Nagy <nsz@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f4f8f4d4e0f92488431b268c8cd9555730b9afe9

commit f4f8f4d4e0f92488431b268c8cd9555730b9afe9
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Wed Dec 30 19:19:37 2020 +0000

    elf: Use relaxed atomics for racy accesses [BZ #19329]

    This is a follow up patch to the fix for bug 19329.  This adds relaxed
    MO atomics to accesses that were previously data races but are now
    race conditions, and where relaxed MO is sufficient.

    The race conditions all follow the pattern that the write is behind the
    dlopen lock, but a read can happen concurrently (e.g. during tls access)
    without holding the lock.  For slotinfo entries the read value only
    matters if it reads from a synchronized write in dlopen or dlclose,
    otherwise the related dtv entry is not valid to access so it is fine
    to leave it in an inconsistent state.  The same applies for
    GL(dl_tls_max_dtv_idx) and GL(dl_tls_generation), but there the
    algorithm relies on the fact that the read of the last synchronized
    write is an increasing value.

    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

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