linux-kernel - Re: [PATCH][RFC v5] PM / hibernate: Introduce test

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Date:	Fri, 22 Jul 2016 10:25:29 +0800
From:	Chen Yu <yu.c.chen@...el.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Pavel Machek <pavel@....cz>, Len Brown <lenb@...nel.org>,
	Linux PM <linux-pm@...r.kernel.org>,
	Linux Kernel Mail List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][RFC v5] PM / hibernate: Introduce test_resume mode for
 hibernation

On Thu, Jul 21, 2016 at 03:23:32PM +0200, Rafael J. Wysocki wrote:
> On Tuesday, July 19, 2016 08:36:44 AM Chen Yu wrote:
> > test_resume 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 BIOSes/bootloader, but also the system re-initialization.
> > 
> > For example:
> > echo test_resume > /sys/power/disk
> > echo disk > /sys/power/state
> > 
> > [  187.306470] PM: Image saving progress:  70%
> > [  187.395298] PM: Image saving progress:  80%
> > [  187.476697] PM: Image saving progress:  90%
> > [  187.554641] PM: Image saving done.
> > [  187.558896] PM: Wrote 594600 kbytes in 0.90 seconds (660.66 MB/s)
> > [  187.566000] PM: S|
> > [  187.589742] PM: Basic memory bitmaps freed
> > [  187.594694] PM: Checking hibernation image
> > [  187.599865] PM: Image signature found, resuming
> > [  187.605209] PM: Loading hibernation image.
> > [  187.665753] PM: Basic memory bitmaps created
> > [  187.691397] PM: Using 3 thread(s) for decompression.
> > [  187.691397] PM: Loading and decompressing image data (148650 pages)...
> > [  187.889719] PM: Image loading progress:   0%
> > [  188.100452] PM: Image loading progress:  10%
> > [  188.244781] PM: Image loading progress:  20%
> > [  189.057305] PM: Image loading done.
> > [  189.068793] PM: Image successfully loaded
> > 
> > Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> > ---
> > v5:
> >  - Introduce a new function to be shared with software_resume().
> > v4:
> >  - Fix some errors and modify the comment for software_resume_unthaw.
> > v3:
> >  - As Pavel mentioned, there was a potential risk in previous
> >    version that might break the filesystem. According to Rafael's suggestion,
> >    this version avoids that issue by restoring the pages with user/kernel
> >    threads kept in frozen. Also updated the patch on top of linux-next.
> > ---
> >  kernel/power/hibernate.c | 61 ++++++++++++++++++++++++++++++++----------------
> >  kernel/power/swap.c      |  6 +++++
> >  2 files changed, 47 insertions(+), 20 deletions(-)
> > 
> > diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> > index 5f3523e..73ec63c 100644
> >  		pr_debug("PM: writing image.\n");
> >  		error = swsusp_write(flags);
> >  		swsusp_free();
> > -		if (!error)
> > +		if (hibernation_mode == HIBERNATION_TEST_RESUME)
> > +			snapshot_test = true;
> > +		if (!error && !snapshot_test)
> 
> The above change isn't correct IMO.
> 
> If swsusp_write() returns an error, snapshot_test shouldn't be set (that
> basically means "no image", so nothing to test).
> 
> So this code should look like
> 
> 	if (!error) {
> 		if (hibernation_mode == HIBERNATION_TEST_RESUME)
> 			snapshot_test = true;
> 		else
> 			power_down();
>
OK, I'll send another version to fix this, thanks!

Thanks,
Yu