Re: [PATCH] PM / hibernate: Introduce snapshot test mode for hibernation

[Chen Yu]

On 2016å07æ13æ 18:21, Pavel Machek wrote:
> Hi!
>
> > On 2016???07???13??? 17:50, Pavel Machek wrote:
> > > On Thu 2016-07-07 14:40:58, Chen Yu wrote:
> > > > This mode is to verify if the snapshot data written to
> > > > swap device can be successfully restored to memory. It
> > > > is useful to ease the debugging process on hibernation,
> > > > since this mode can not only bypass the BIOSen/bootloader,
> > > > but also the system re-initialization.
> > > >
> > > > For example:
> > > > $ sudo echo snapshot > /sys/power/disk
> > > > $ sudo echo disk > /sys/power/state
> > > >
> > > > /* manual resume.*/
> > > > $ sudo echo 8:3 > /sys/power/resume
> > > Your examples will not work, will they?
> > It works on my platform, although I did not tested it for too many
> > rounds.
> Please check again:
>
> sudo echo disk > /sys/power/state
> -bash: /sys/power/state: Permission denied
>
> ...because bash does the open, not echo.
Sorry, my bad, I logined as root:P
I'll rewrite the commit log.
> > > This is also quite tricky/dangerous. If you do this with filesystems
> > > mounted R/W, it is "good bye, filesystems".
> > Ah, yes, this is quite tricky, maybe we can use this option as a
> > debug method,
> > for example, boot with rootfs = initrd, without mounting any disks,
> > and then swapon the swap device, and do a testing. This should be safer?
> Yeah, that's the way. Read-only root is other option.
>
> > > I guess updating documentation would be welcome from my side,
> > > otherwise it should be ok.
> > OK, I'll  update the documents.
> Just add fat warning into the documentation.
OK.
> Thanks,
> 									Pavel