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

[Ingo Molnar <mingo@kernel.org>]

* Michal Hocko <mhocko@kernel.org> wrote:

> I dunno. I do not use hibernation. I am a heavy user of the suspend 
> though. I s2ram all the time. And I have certainly experienced cases 
> where suspend has failed and I onlyi found out later when I've picked 
> up my laptop from my heat up bag. Nothing fatal has resulted from that 
> but this is certainly annoying.

Hm, so I (mistakenly) thought freezing was mostly limited to hibernation 
and to a few weird cases when in flight DMA must not be suspended - but 
I'm wrong and in practice we always freeze tasks during s2ram, right?

And indeed:

 config SUSPEND_FREEZER
        bool "Enable freezer for suspend to RAM/standby" \
                if ARCH_WANTS_FREEZER_CONTROL || BROKEN
        depends on SUSPEND
        default y

which is essentially always enabled on x86.

TIL ...

s2ram is obviously a huge deal.

Just a newbie question: any chance to not do any freezing at all on 
modern laptops when doing s2ram, or at least only warn if it fails and 
try to suspend?

Because in practice losing power due to failed freezing *will* result in 
data loss, in about 90% of the time ...

So I don't even know what we are trying to protect against by refusing to 
freeze - avoiding a 0.001% data loss risk against a 90% data loss risk?

Thanks,

	Ingo