4.19 dwarf unwinding broken

[Josh Hunt]

The following commit is breaking dwarf unwinding on 4.19 kernels:

commit e5adfc3e7e774ba86f7bb725c6eef5f32df8630e
Author: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Date:   Tue Aug 7 12:09:01 2018 +0300

    perf map: Synthesize maps only for thread group leader

It looks like this was fixed later by:

commit e8ba2906f6b9054102ad035ac9cafad9d4168589
Author: John Keeping <john@xxxxxxxxxxxx>
Date:   Thu Aug 15 11:01:45 2019 +0100

    perf unwind: Fix libunwind when tid != pid

but was not selected as a backport to 4.19. Are there plans to backport 
the fix? If not, could we have the breaking commit reverted in 4.19 LTS?

Thanks
Josh