Re: [PATCH 6.0.y / 6.1.y] x86/split_lock: Add sysctl to control the misery mode

[stsp]

Hi Sean, thanks for a head-up!

29.03.2023 22:14, Sean Christopherson пишет:
> Resurrecting this thread with a concrete use case.
> dosemu2, which uses KVM to accelerate DOS emulation (stating the obvious), ran
> into a problem where the hardcoded (prior to this patch) behavior will effectively
> hang userspace if the 10ms sleep is interrupted, e.g. by a periodic SIGALRM[*].

Yes, and we also created a ready-to-use
host test-case with no dosemu2 involved.

> Alternatively, we could try to figure out a way to ensure forward progress without
> letting userpace run an end-around on the enforced misery, but backporting this
> patch to stable kernels seems easier.
>
> Stas, do you happen to know what the oldest stable kernel your users use, i.e.
> how far back this backport would need to go?
It seems, the "broken" code was added by
the patch b041b525dab95 which is "described"
as v5.18-rc4-1-gb041b525dab9.
So I guess the answer would be "down to 5.18".

Of course I don't believe the patch you
mention, is a real solution. Its good for
-stable, but something else needs to be
developed in the future.