[Bug nptl/25847] pthread_cond_signal failed to wake up pthread_cond_wait due to a bug in undoing stealing

[carlos at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=25847

--- Comment #75 from Carlos O'Donell <carlos at redhat dot com> ---
(In reply to Florian Weimer from comment #74)
> (In reply to yangyanchao6@huawei.com from comment #73)
> > Is there any plan to incorporate this fix into earlier versions?
> 
> I'm concerned about immediate breakage of applications that use
> process-shared condition variables in mapped files. In the past, condition
> variable changes have broken RPM due to its use of Berkeley DB. That's why
> I'm leaning towards distributions making an assessment whether they can
> incorporate this change.
> 
> Any backport should drop
> 
> commit c36fc50781995e6758cae2b6927839d0157f213c
> Author: Malte Skarupke <malteskarupke@fastmail.fm>
> Date:   Wed Dec 4 07:56:38 2024 -0500
> 
>     nptl: Remove g_refs from condition variables
>     
>     This variable used to be needed to wait in group switching until all
> sleepers
>     have confirmed that they have woken. This is no longer needed. Nothing
> waits
>     on this variable so there is no need to track how many threads are
> currently
>     asleep in each group.
>     
>     Signed-off-by: Malte Skarupke <malteskarupke@fastmail.fm>
>     Reviewed-by: Carlos O'Donell <carlos@redhat.com>
> 
> so that
> 
> commit dbc5a50d12eff4cb3f782129029d04b8a76f58e7
> Author: Florian Weimer <fweimer@redhat.com>
> Date:   Thu Mar 13 06:07:07 2025 +0100
> 
>     nptl: PTHREAD_COND_INITIALIZER compatibility with pre-2.41 versions (bug
> 32786)
>     
>     The new initializer and struct layout does not initialize the
>     __g_signals field in the old struct layout before the change in
>     commit c36fc50781995e6758cae2b6927839d0157f213c ("nptl: Remove
>     g_refs from condition variables").  Bring back fields at the end
>     of struct __pthread_cond_s, so that they are again zero-initialized.
>     
>     Reviewed-by: Sam James <sam@gentoo.org>
> 
> isn't needed (and use of condition variables does not tricker ABI change
> warnings in external code).

My plan is to backport exactly what we did in the main development branch, so
I'd include both of these patches instead of dropping a patch (which isn't
always clear why we did so).

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