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Date: Fri, 18 Nov 2011 10:20:43 +0100
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc: len.brown@...el.com, pavel@....cz, rdunlap@...otime.net,
tj@...nel.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v2] PM/Hibernation: Fix the early termination of test modes
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@...ux.vnet.ibm.com>
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.
> ---
>
> 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?
>
> if (in_suspend) {
> unsigned int flags = 0;
> @@ -864,6 +875,11 @@ static const char * const hibernation_modes[] = {
> *
> * If a platform hibernation driver is in use, 'platform' will be supported
> * and will be used by default. Otherwise, 'shutdown' will be used by default.
> + * The 2 test modes are useful only when CONFIG_PM_DEBUG is set. In that case,
> + * using the 'testproc' mode will do everything upto the freezing of tasks
> + * and exits after undoing all that it did. The 'test' mode is deeper, in that,
> + * it does everything except actually hibernating the machine and exits after
> + * restoring the machine back to its original state.
> * The selected option (i.e. the one corresponding to the current value of
> * hibernation_mode) is enclosed by a square bracket.
> *
Thanks,
Rafael
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