270 lines
12 KiB
ReStructuredText
270 lines
12 KiB
ReStructuredText
=================================
|
|
Debugging hibernation and suspend
|
|
=================================
|
|
|
|
(C) 2007 Rafael J. Wysocki <rjw@sisk.pl>, GPL
|
|
|
|
1. Testing hibernation (aka suspend to disk or STD)
|
|
===================================================
|
|
|
|
To check if hibernation works, you can try to hibernate in the "reboot" mode::
|
|
|
|
# echo reboot > /sys/power/disk
|
|
# echo disk > /sys/power/state
|
|
|
|
and the system should create a hibernation image, reboot, resume and get back to
|
|
the command prompt where you have started the transition. If that happens,
|
|
hibernation is most likely to work correctly. Still, you need to repeat the
|
|
test at least a couple of times in a row for confidence. [This is necessary,
|
|
because some problems only show up on a second attempt at suspending and
|
|
resuming the system.] Moreover, hibernating in the "reboot" and "shutdown"
|
|
modes causes the PM core to skip some platform-related callbacks which on ACPI
|
|
systems might be necessary to make hibernation work. Thus, if your machine
|
|
fails to hibernate or resume in the "reboot" mode, you should try the
|
|
"platform" mode::
|
|
|
|
# echo platform > /sys/power/disk
|
|
# echo disk > /sys/power/state
|
|
|
|
which is the default and recommended mode of hibernation.
|
|
|
|
Unfortunately, the "platform" mode of hibernation does not work on some systems
|
|
with broken BIOSes. In such cases the "shutdown" mode of hibernation might
|
|
work::
|
|
|
|
# echo shutdown > /sys/power/disk
|
|
# echo disk > /sys/power/state
|
|
|
|
(it is similar to the "reboot" mode, but it requires you to press the power
|
|
button to make the system resume).
|
|
|
|
If neither "platform" nor "shutdown" hibernation mode works, you will need to
|
|
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:
|
|
|
|
freezer
|
|
- test the freezing of processes
|
|
|
|
devices
|
|
- test the freezing of processes and suspending of devices
|
|
|
|
platform
|
|
- test the freezing of processes, suspending of devices and platform
|
|
global control methods [1]_
|
|
|
|
processors
|
|
- test the freezing of processes, suspending of devices, platform
|
|
global control methods [1]_ and the disabling of nonboot CPUs
|
|
|
|
core
|
|
- test the freezing of processes, suspending of devices, platform global
|
|
control methods\ [1]_, the disabling of nonboot CPUs and suspending
|
|
of platform/system devices
|
|
|
|
.. [1]
|
|
|
|
the platform global control methods are only available on ACPI systems
|
|
and are only tested if the hibernation mode is set to "platform"
|
|
|
|
To use one of them it is necessary to write the corresponding string to
|
|
/sys/power/pm_test (eg. "devices" to test the freezing of processes and
|
|
suspending devices) and issue the standard hibernation commands. For example,
|
|
to use the "devices" test mode along with the "platform" mode of hibernation,
|
|
you should do the following::
|
|
|
|
# echo devices > /sys/power/pm_test
|
|
# echo platform > /sys/power/disk
|
|
# echo disk > /sys/power/state
|
|
|
|
Then, the kernel will try to freeze processes, suspend devices, wait a few
|
|
seconds (5 by default, but configurable by the suspend.pm_test_delay module
|
|
parameter), resume devices and thaw processes. If "platform" is written to
|
|
/sys/power/pm_test , then after suspending devices the kernel will additionally
|
|
invoke the global control methods (eg. ACPI global control methods) used to
|
|
prepare the platform firmware for hibernation. Next, it will wait a
|
|
configurable number of seconds and invoke the platform (eg. ACPI) global
|
|
methods used to cancel hibernation etc.
|
|
|
|
Writing "none" to /sys/power/pm_test causes the kernel to switch to the normal
|
|
hibernation/suspend operations. Also, when open for reading, /sys/power/pm_test
|
|
contains a space-separated list of all available tests (including "none" that
|
|
represents the normal functionality) in which the current test level is
|
|
indicated by square brackets.
|
|
|
|
Generally, as you can see, each test level is more "invasive" than the previous
|
|
one and the "core" level tests the hardware and drivers as deeply as possible
|
|
without creating a hibernation image. Obviously, if the "devices" test fails,
|
|
the "platform" test will fail as well and so on. Thus, as a rule of thumb, you
|
|
should try the test modes starting from "freezer", through "devices", "platform"
|
|
and "processors" up to "core" (repeat the test on each level a couple of times
|
|
to make sure that any random factors are avoided).
|
|
|
|
If the "freezer" test fails, there is a task that cannot be frozen (in that case
|
|
it usually is possible to identify the offending task by analysing the output of
|
|
dmesg obtained after the failing test). Failure at this level usually means
|
|
that there is a problem with the tasks freezer subsystem that should be
|
|
reported.
|
|
|
|
If the "devices" test fails, most likely there is a driver that cannot suspend
|
|
or resume its device (in the latter case the system may hang or become unstable
|
|
after the test, so please take that into consideration). To find this driver,
|
|
you can carry out a binary search according to the rules:
|
|
|
|
- if the test fails, unload a half of the drivers currently loaded and repeat
|
|
(that would probably involve rebooting the system, so always note what drivers
|
|
have been loaded before the test),
|
|
- if the test succeeds, load a half of the drivers you have unloaded most
|
|
recently and repeat.
|
|
|
|
Once you have found the failing driver (there can be more than just one of
|
|
them), you have to unload it every time before hibernation. In that case please
|
|
make sure to report the problem with the driver.
|
|
|
|
It is also possible that the "devices" test will still fail after you have
|
|
unloaded all modules. In that case, you may want to look in your kernel
|
|
configuration for the drivers that can be compiled as modules (and test again
|
|
with these drivers compiled as modules). You may also try to use some special
|
|
kernel command line options such as "noapic", "noacpi" or even "acpi=off".
|
|
|
|
If the "platform" test fails, there is a problem with the handling of the
|
|
platform (eg. ACPI) firmware on your system. In that case the "platform" mode
|
|
of hibernation is not likely to work. You can try the "shutdown" mode, but that
|
|
is rather a poor man's workaround.
|
|
|
|
If the "processors" test fails, the disabling/enabling of nonboot CPUs does not
|
|
work (of course, this only may be an issue on SMP systems) and the problem
|
|
should be reported. In that case you can also try to switch the nonboot CPUs
|
|
off and on using the /sys/devices/system/cpu/cpu*/online sysfs attributes and
|
|
see if that works.
|
|
|
|
If the "core" test fails, which means that suspending of the system/platform
|
|
devices has failed (these devices are suspended on one CPU with interrupts off),
|
|
the problem is most probably hardware-related and serious, so it should be
|
|
reported.
|
|
|
|
A failure of any of the "platform", "processors" or "core" tests may cause your
|
|
system to hang or become unstable, so please beware. Such a failure usually
|
|
indicates a serious problem that very well may be related to the hardware, but
|
|
please report it anyway.
|
|
|
|
b) Testing minimal configuration
|
|
--------------------------------
|
|
|
|
If all of the hibernation test modes work, you can boot the system with the
|
|
"init=/bin/bash" command line parameter and attempt to hibernate in the
|
|
"reboot", "shutdown" and "platform" modes. If that does not work, there
|
|
probably is a problem with a driver statically compiled into the kernel and you
|
|
can try to compile more drivers as modules, so that they can be tested
|
|
individually. Otherwise, there is a problem with a modular driver and you can
|
|
find it by loading a half of the modules you normally use and binary searching
|
|
in accordance with the algorithm:
|
|
- if there are n modules loaded and the attempt to suspend and resume fails,
|
|
unload n/2 of the modules and try again (that would probably involve rebooting
|
|
the system),
|
|
- if there are n modules loaded and the attempt to suspend and resume succeeds,
|
|
load n/2 modules more and try again.
|
|
|
|
Again, if you find the offending module(s), it(they) must be unloaded every time
|
|
before hibernation, and please report the problem with it(them).
|
|
|
|
c) Using the "test_resume" hibernation option
|
|
---------------------------------------------
|
|
|
|
/sys/power/disk generally tells the kernel what to do after creating a
|
|
hibernation image. One of the available options is "test_resume" which
|
|
causes the just created image to be used for immediate restoration. Namely,
|
|
after doing::
|
|
|
|
# echo test_resume > /sys/power/disk
|
|
# echo disk > /sys/power/state
|
|
|
|
a hibernation image will be created and a resume from it will be triggered
|
|
immediately without involving the platform firmware in any way.
|
|
|
|
That test can be used to check if failures to resume from hibernation are
|
|
related to bad interactions with the platform firmware. That is, if the above
|
|
works every time, but resume from actual hibernation does not work or is
|
|
unreliable, the platform firmware may be responsible for the failures.
|
|
|
|
On architectures and platforms that support using different kernels to restore
|
|
hibernation images (that is, the kernel used to read the image from storage and
|
|
load it into memory is different from the one included in the image) or support
|
|
kernel address space randomization, it also can be used to check if failures
|
|
to resume may be related to the differences between the restore and image
|
|
kernels.
|
|
|
|
d) Advanced debugging
|
|
---------------------
|
|
|
|
In case that hibernation does not work on your system even in the minimal
|
|
configuration and compiling more drivers as modules is not practical or some
|
|
modules cannot be unloaded, you can use one of the more advanced debugging
|
|
techniques to find the problem. First, if there is a serial port in your box,
|
|
you can boot the kernel with the 'no_console_suspend' parameter and try to log
|
|
kernel messages using the serial console. This may provide you with some
|
|
information about the reasons of the suspend (resume) failure. Alternatively,
|
|
it may be possible to use a FireWire port for debugging with firescope
|
|
(http://v3.sk/~lkundrak/firescope/). On x86 it is also possible to
|
|
use the PM_TRACE mechanism documented in Documentation/power/s2ram.rst .
|
|
|
|
2. Testing suspend to RAM (STR)
|
|
===============================
|
|
|
|
To verify that the STR works, it is generally more convenient to use the s2ram
|
|
tool available from http://suspend.sf.net and documented at
|
|
http://en.opensuse.org/SDB:Suspend_to_RAM (S2RAM_LINK).
|
|
|
|
Namely, after writing "freezer", "devices", "platform", "processors", or "core"
|
|
into /sys/power/pm_test (available if the kernel is compiled with
|
|
CONFIG_PM_DEBUG set) the suspend code will work in the test mode corresponding
|
|
to given string. The STR test modes are defined in the same way as for
|
|
hibernation, so please refer to Section 1 for more information about them. In
|
|
particular, the "core" test allows you to test everything except for the actual
|
|
invocation of the platform firmware in order to put the system into the sleep
|
|
state.
|
|
|
|
Among other things, the testing with the help of /sys/power/pm_test may allow
|
|
you to identify drivers that fail to suspend or resume their devices. They
|
|
should be unloaded every time before an STR transition.
|
|
|
|
Next, you can follow the instructions at S2RAM_LINK to test the system, but if
|
|
it does not work "out of the box", you may need to boot it with
|
|
"init=/bin/bash" and test s2ram in the minimal configuration. In that case,
|
|
you may be able to search for failing drivers by following the procedure
|
|
analogous to the one described in section 1. If you find some failing drivers,
|
|
you will have to unload them every time before an STR transition (ie. before
|
|
you run s2ram), and please report the problems with them.
|
|
|
|
There is a debugfs entry which shows the suspend to RAM statistics. Here is an
|
|
example of its output::
|
|
|
|
# mount -t debugfs none /sys/kernel/debug
|
|
# cat /sys/kernel/debug/suspend_stats
|
|
success: 20
|
|
fail: 5
|
|
failed_freeze: 0
|
|
failed_prepare: 0
|
|
failed_suspend: 5
|
|
failed_suspend_noirq: 0
|
|
failed_resume: 0
|
|
failed_resume_noirq: 0
|
|
failures:
|
|
last_failed_dev: alarm
|
|
adc
|
|
last_failed_errno: -16
|
|
-16
|
|
last_failed_step: suspend
|
|
suspend
|
|
|
|
Field success means the success number of suspend to RAM, and field fail means
|
|
the failure number. Others are the failure number of different steps of suspend
|
|
to RAM. suspend_stats just lists the last 2 failed devices, error number and
|
|
failed step of suspend.
|