Hi! > * Michal Hocko <mho...@kernel.org> wrote: > > > > Do we actually have reports of this happening for people outside > > > Android? > > > > Not that I am aware of. > > I'd say outside of Android 99% of the use of hibernation is the fail-safe > that distributions offer on laptops with very low battery levels: the > emergency hibernation when there's almost no power left anymore.
Android does not use hibernation AFAICT. Just s2ram.
> Do these hibernation failure messages typically make it to persistent
> logs before the system uses power?
I'd say so. If you have enough energy left for hibernation, you also
have enough energy left to write the logs and sync.
> In practice if that is buggy the kernel won't hibernate and the laptop
> will run out of power and the user will conclude "ugh, I shouldn't have
> left my laptop turned on" - without looking into the logs and reporting,
> as they'll perceive it as a user failure not a system failure.
>
> I certainly saw random Linux laptops fail to hibernate over the years and
> didn't report it, so if the distribution doesn't do the reporting
> automatically then chances are we'll never see it.
There are many reasons while hibernation can fail. Buggy drivers,
tasks in D state... And there are some when hibernation can fail "by
design". If you swap does not have enough space to store the data, for
example.
Hibernation was designed to be non-intrusive, and reliable as in "if
it hibernates it will also resume ok", but not reliable as in "it will
always hibernate".
I see that is problematic for "hibernate on battery low".
Pavel
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