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

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Date:	Wed, 13 Jul 2016 18:39:44 +0800
From:	Chen Yu <yu.c.chen@...el.com>
To:	Pavel Machek <pavel@....cz>
Cc:	linux-pm@...r.kernel.org, "Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM / hibernate: Introduce snapshot test mode for
 hibernation



On 2016年07月13日 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