Re: [PATCH v2] PM/Hibernation: Fix the early termination of test modes

[Rafael J. Wysocki]

On Friday, November 18, 2011, Srivatsa S. Bhat wrote:
> On 11/18/2011 02:50 PM, Rafael J. Wysocki wrote:
> > On Friday, November 18, 2011, Srivatsa S. Bhat wrote:
> >> Commit 2aede851ddf08666f68ffc17be446420e9d2a056
> >> (PM / Hibernate: Freeze kernel threads after preallocating memory)
> >> postponed the freezing of kernel threads to after preallocating memory
> >> for hibernation. But while doing that, the hibernation test TEST_FREEZER
> >> and the test mode HIBERNATION_TESTPROC were not moved accordingly.
> >>
> >> As a result, when using these test modes, it only goes upto the freezing of
> >> userspace and exits, when in fact it should go till the complete end of task
> >> freezing stage, namely the freezing of kernel threads as well.
> >>
> >> So, move these points of exit to appropriate places so that freezing of
> >> kernel threads is also tested while using these test harnesses. And while at
> >> it, add some documentation about these test modes.
> >>
> >> v2: Changed 'freezer_test_done' flag from int to bool.
> >>
> >> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
> > 
> > On a second thought I'm not sure about the documentation changes.
> > In fact, the "test" and "testproc" modes are deprecated and I was going to
> > remove them some time this year.  That's why they weren't documented
> > (i.e. intentionally) and it's better to keep it that way IMO.
> > 
> 
> I was actually wondering about the same thing (why are test and testproc
> both still there, when pm_test is also there)..
> 
> So I'll drop the documentation changes in this patch, and maybe send a
> separate patch that will remove the 2? Will that be good?

Yes, please.

> >> ---
> >>
> >>  Documentation/power/basic-pm-debugging.txt |   16 ++++++++++++----
> >>  kernel/power/hibernate.c                   |   28 ++++++++++++++++++++++------
> >>  2 files changed, 34 insertions(+), 10 deletions(-)
> >>
> >> diff --git a/Documentation/power/basic-pm-debugging.txt b/Documentation/power/basic-pm-debugging.txt
> >> index 40a4c65..ba6c879 100644
> >> --- a/Documentation/power/basic-pm-debugging.txt
> >> +++ b/Documentation/power/basic-pm-debugging.txt
> >> @@ -38,10 +38,18 @@ identify what goes wrong.
> >>  
> >>  a) Test modes of hibernation
> >>  
> >> -To find out why hibernation fails on your system, you can use a special testing
> >> -facility available if the kernel is compiled with CONFIG_PM_DEBUG set.  Then,
> >> -there is the file /sys/power/pm_test that can be used to make the hibernation
> >> -core run in a test mode.  There are 5 test modes available:
> >> +To find out why hibernation fails on your system, you can use some special
> >> +testing facilities available if the kernel is compiled with CONFIG_PM_DEBUG set.
> >> +Hibernation will then have 2 more modes that can be used, namely "testproc" and
> >> +"test". When the "testproc" mode is used, it executes everything upto the task
> >> +freezing phase and reverts back. When the "test" mode is used, it goes much
> >> +deeper down, stopping just short of actually hibernating the machine, and then
> >> +reverts back to normal state.
> >> +
> >> +However, there is an even more fine-grained debugging tool, also enabled by
> >> +setting CONFIG_PM_DEBUG: there appears a file /sys/power/pm_test that can be
> >> +used to make the hibernation core run in a test mode.
> >> +There are 5 test modes available:
> >>  
> >>  freezer
> >>  - test the freezing of processes
> >> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> >> index b4511b6..257e8e7 100644
> >> --- a/kernel/power/hibernate.c
> >> +++ b/kernel/power/hibernate.c
> >> @@ -55,6 +55,8 @@ enum {
> >>  
> >>  static int hibernation_mode = HIBERNATION_SHUTDOWN;
> >>  
> >> +static bool freezer_test_done;
> >> +
> >>  static const struct platform_hibernation_ops *hibernation_ops;
> >>  
> >>  /**
> >> @@ -347,6 +349,17 @@ int hibernation_snapshot(int platform_mode)
> >>  	if (error)
> >>  		goto Close;
> >>  
> >> +	if (hibernation_test(TEST_FREEZER) ||
> >> +		hibernation_testmode(HIBERNATION_TESTPROC)) {
> >> +
> >> +		/*
> >> +		 * Indicate to the caller that we are returning due to a
> >> +		 * successful freezer test.
> >> +		 */
> >> +		freezer_test_done = true;
> >> +		goto Close;
> >> +	}
> >> +
> >>  	error = dpm_prepare(PMSG_FREEZE);
> >>  	if (error)
> >>  		goto Complete_devices;
> >> @@ -641,15 +654,13 @@ int hibernate(void)
> >>  	if (error)
> >>  		goto Finish;
> >>  
> >> -	if (hibernation_test(TEST_FREEZER))
> >> -		goto Thaw;
> >> -
> >> -	if (hibernation_testmode(HIBERNATION_TESTPROC))
> >> -		goto Thaw;
> >> -
> >>  	error = hibernation_snapshot(hibernation_mode == HIBERNATION_PLATFORM);
> >>  	if (error)
> >>  		goto Thaw;
> >> +	if (freezer_test_done) {
> >> +		freezer_test_done = false;
> >> +		goto Thaw;
> >> +	}
> > 
> > What happens if hibernation_snapshot() and freezer_test_done is 'true'?
> > Won't that leek freezer_test_done to the next hibernation cycle?
> > 
> 
> Oh yes, thanks for catching that! I'll fix that and send an updated patch.

OK

Thanks,
Rafael
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