Re: [PATCH] Revert "exec: make de_thread() freezable (was: Re: Linux 4.20-rc4)

[Linus Torvalds]

On Tue, Dec 4, 2018 at 1:58 AM Michal Hocko <mhocko@xxxxxxxxxx> wrote:
>
> AFAIU both suspend and hibernation require the system to enter quiescent
> state with no task potentially interfering with suspended devices. And
> in this particular case those de-thread-ed threads will certainly not
> interfere so silencing the lockdep sounds like a reasonable workaround.

I still think it would be better to simply not freeze killed user processes.

We already  have things like

        if (test_tsk_thread_flag(p, TIF_MEMDIE))
                return false;

exactly because we do not want to freeze processes that are about to
die due to being killed. Very similar situation: we don't want to
freeze those processes, because doing so would halt them from freeing
the resources that may be needed for suspend or hibernate.

How about something like we set PF_NOFREEZE when we set PF_EXITING? At
that point we've pretty much turned into a kernel thread, no?

                Linus