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

From: Chen Yu
Date: Wed Jul 13 2016 - 06:33:10 EST

On 2016å07æ13æ 18:21, Pavel Machek wrote:

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
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.