Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 269 insertions, 0 deletions

diff --git a/Documentation/power/basic-pm-debugging.rst b/Documentation/power/basic-pm-debugging.rst
new file mode 100644
index 000000000..69862e759
--- /dev/null
+++ b/Documentation/power/basic-pm-debugging.rst
@@ -0,0 +1,269 @@
+=================================
+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.