Commit 7c30ed ("cpufreq: make sure frequency transitions are serialized")
interacts poorly with systems that have a single core freqency for all
cores.  On such systems we have a single policy for all cores with
several CPUs.  When we do a frequency transition the governor calls the
pre and post change notifiers which causes cpufreq_notify_transition()
per CPU.  Since the policy is the same for all of them all CPUs after
the first and the warnings added are generated by checking a per-policy
flag the warnings will be triggered for all cores after the first.

Fix this by allowing notifier to be called for n times. Where n is the number of
cpus in policy->cpus.
Reported-and-tested-by: NMark Brown <broonie@linaro.org>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Toralf Förster reported that the cpufreq ondemand governor behaves erratically
(doesn't scale well) after a suspend/resume cycle. The problem was that the
cpufreq subsystem's idea of the cpu frequencies differed from the actual
frequencies set in the hardware after a suspend/resume cycle. Toralf bisected
the problem to commit a66b2e50 (cpufreq: Preserve sysfs files across
suspend/resume).

Among other (harmless) things, that commit skipped the call to
cpufreq_update_policy() in the resume path. But cpufreq_update_policy() plays
an important role during resume, because it is responsible for checking if
the BIOS changed the cpu frequencies behind our back and resynchronize the
cpufreq subsystem's knowledge of the cpu frequencies, and update them
accordingly.

So, restore the call to cpufreq_update_policy() in the resume path to fix
the cpufreq regression.
Reported-and-tested-by: NToralf Förster <toralf.foerster@gmx.de>
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: 3.10+ <stable@vger.kernel.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Clear ->cur_policy when stopping a governor, or the ->cur_policy
pointer may be stale on systems with have_governor_per_policy when a
new policy is allocated due to CPU hotplug offline/online.

[rjw: Changelog]
Suggested-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NJacob Shin <jacob.shin@amd.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Commits fcf80582 (cpufreq: Simplify cpufreq_add_dev()) and aa77a527
(cpufreq: acpi-cpufreq: Don't set policy->related_cpus from .init())
changed the contents of the "related_cpus" sysfs attribute on systems
where acpi-cpufreq is used and user space can't get the list of CPUs
which are in the same hardware coordination CPU domain (provided by
the ACPI AML method _PSD) via "related_cpus" any more.

To make up for that loss add a new sysfs attribute "freqdomian_cpus"
for the acpi-cpufreq driver which exposes the list of CPUs in the
same domain regardless of whether it is coordinated by hardware or
software.

[rjw: Changelog, documentation]
References: https://bugzilla.kernel.org/show_bug.cgi?id=58761Reported-by: NJean-Philippe Halimi <jean-philippe.halimi@exascale-computing.eu>
Signed-off-by: NLan Tianyu <tianyu.lan@intel.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Whenever we are changing frequency of a cpu, we are calling PRECHANGE and
POSTCHANGE notifiers. They must be serialized. i.e. PRECHANGE or POSTCHANGE
shouldn't be called twice contiguously.

This can happen due to bugs in users of __cpufreq_driver_target() or actual
cpufreq drivers who are sending these notifiers.

This patch adds some protection against this. Now, we keep track of the last
transaction and see if something went wrong.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

When initializing the default powersave_bias value, we need to first
make sure that this policy is running the ondemand governor.
Reported-and-tested-by: NTim Gardner <tim.gardner@canonical.com>
Signed-off-by: NJacob Shin <jacob.shin@amd.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

PRECHANGE and POSTCHANGE notifiers must be called in groups, i.e either both
should be called or both shouldn't be.

In case we have started PRECHANGE notifier and found an error, we must call
POSTCHANGE notifier with freqs.new = freqs.old to guarantee that sequence of
calling notifiers is complete.

This patch fixes it.
Acked-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

PRECHANGE and POSTCHANGE notifiers must be called in groups, i.e either both
should be called or both shouldn't be.

In case we have started PRECHANGE notifier and found an error, we must call
POSTCHANGE notifier with freqs.new = freqs.old to guarantee that sequence of
calling notifiers is complete.

This patch fixes it.

Cc: Mark Brown <broonie@linaro.org>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

PRECHANGE and POSTCHANGE notifiers must be called in groups, i.e either both
should be called or both shouldn't be.

In case we have started PRECHANGE notifier and found an error, we must call
POSTCHANGE notifier with freqs.new = freqs.old to guarantee that sequence of
calling notifiers is complete.

Omap driver was taking care of it well, but wasn't restoring freqs.new to
freqs.old in some cases. I wasn't required to add code for it as moving
PRECHANGE notifier down was a better option, so that we call it just before
starting frequency transition.
Acked-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

PRECHANGE and POSTCHANGE notifiers must be called in groups, i.e either both
should be called or both shouldn't be.

In case we have started PRECHANGE notifier and found an error, we must call
POSTCHANGE notifier with freqs.new = freqs.old to guarantee that sequence of
calling notifiers is complete.

This patch fixes it.

This also moves PRECHANGE notifier down so that we call it just before starting
frequency transition.
Acked-by: NShawn Guo <shawn.guo@linaro.org>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

PRECHANGE and POSTCHANGE notifiers must be called in groups, i.e either both
should be called or both shouldn't be.

In case we have started PRECHANGE notifier and found an error, we must call
POSTCHANGE notifier with freqs.new = freqs.old to guarantee that sequence of
calling notifiers is complete.

This patch fixes it.

Cc: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

PRECHANGE and POSTCHANGE notifiers must be called in groups, i.e either both
should be called or both shouldn't be.

In case we have started PRECHANGE notifier and found an error, we must call
POSTCHANGE notifier with freqs.new = freqs.old to guarantee that sequence of
calling notifiers is complete.

This patch fixes it.
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

PRECHANGE and POSTCHANGE notifiers must be called in groups, i.e either both
should be called or both shouldn't be.

In case we have started PRECHANGE notifier and found an error, we must call
POSTCHANGE notifier with freqs.new = freqs.old to guarantee that sequence of
calling notifiers is complete.

Davinci driver was taking care of it but frequency isn't restored to freqs.old.

This patch fixes it.
Acked-by: NSekhar Nori <nsekhar@ti.com>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

PRECHANGE and POSTCHANGE notifiers must be called in groups, i.e either both
should be called or both shouldn't be.

In case we have started PRECHANGE notifier and found an error, we must call
POSTCHANGE notifier with freqs.new = freqs.old to guarantee that sequence of
calling notifiers is complete.

This patch fixes it.

This also removes code setting policy->cur as this is also done by POSTCHANGE
notifier.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

PRECHANGE and POSTCHANGE notifiers must be called in groups, i.e.
either both should be called or both shouldn't be.

In case we have started PRECHANGE notifier and found an error, we
must call POSTCHANGE notifier with freqs.new = freqs.old to guarantee
that sequence of calling notifiers is complete.

This patch fixes it.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

PRECHANGE and POSTCHANGE notifiers must be called in groups, i.e
either both should be called or both shouldn't be.

In case we have started PRECHANGE notifier and found an error, we
must call POSTCHANGE notifier with freqs.new = freqs.old to guarantee
that the sequence of calling notifiers is complete.

This patch fixes it.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

In case we have started PRECHANGE notifier and found an error, we
must call POSTCHANGE notifier with freqs.new = freqs.old.

This driver does take care of it, but the POSTCHANGE is called with
freqs.new on errors too, which is incorrect, so fix it.

[rjw: Changelog]
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

PRECHANGE and POSTCHANGE notifiers must be called in groups, i.e either both
should be called or both shouldn't be.

In case we have started PRECHANGE notifier and found an error, we
must call POSTCHANGE notifier with freqs.new = freqs.old to
guarantee that the sequence of calling notifiers is complete.

This patch fixes it.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Commit 50701588 (cpufreq: rename index as driver_data in
cpufreq_frequency_table) renamed the index field to driver_data.

But it seems some uses in the s3c2416 driver were forgotten.

So convert the last index users to read driver_data.
Signed-off-by: NHeiko Stuebner <heiko@sntech.de>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

__cpufreq_notify_transition() is used only in cpufreq.c,
make it static.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

There were a few noticeable formatting issues in core cpufreq code.
This cleans them up to make code look better.  The changes include:
 - Whitespace cleanup.
 - Rearrangements of code.
 - Multiline comments fixes.
 - Formatting changes to fit 80 columns.

Copyright information in cpufreq.c is also updated to include my name
for 2013.

[rjw: Changelog]
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Cpufreq governors' stop and start operations should be carried out
in sequence.  Otherwise, there will be unexpected behavior, like in
the example below.

Suppose there are 4 CPUs and policy->cpu=CPU0, CPU1/2/3 are linked
to CPU0.  The normal sequence is:

 1) Current governor is userspace.  An application tries to set the
    governor to ondemand.  It will call __cpufreq_set_policy() in
    which it will stop the userspace governor and then start the
    ondemand governor.

 2) Current governor is userspace.  The online of CPU3 runs on CPU0.
    It will call cpufreq_add_policy_cpu() in which it will first
    stop the userspace governor, and then start it again.

If the sequence of the above two cases interleaves, it becomes:

 1) Application stops userspace governor
 2)                                  Hotplug stops userspace governor

which is a problem, because the governor shouldn't be stopped twice
in a row.  What happens next is:

 3) Application starts ondemand governor
 4)                                  Hotplug starts a governor

In step 4, the hotplug is supposed to start the userspace governor,
but now the governor has been changed by the application to ondemand,
so the ondemand governor is started once again, which is incorrect.

The solution is to prevent policy governors from being stopped
multiple times in a row.  A governor should only be stopped once for
one policy.  After it has been stopped, no more governor stop
operations should be executed.

Also add a mutex to serialize governor operations.

[rjw: Changelog.  And you owe me a beverage of my choice.]
Signed-off-by: NXiaoguang Chen <chenxg@marvell.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Userspace governor has got more code than what it needs for its
functioning, so simplify it.

Portions of code removed are:
 - Extra header files which aren't required anymore (rearrange them
   as well).
 - cpu_{max|min|cur|set}_freq, as they are always the same as
   policy->{max|min|cur}.
 - userspace_cpufreq_notifier_block as we don't need to set
   cpu_cur_freq anymore.
 - cpus_using_userspace_governor as it was for the notifier code.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Correct spelling typo in printk within various drivers.
Signed-off-by: NMasanari Iida <standby24x7@gmail.com>
Acked-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

This CPUFreq driver uses APIs from freq_table.c and so must select
CPU_FREQ_TABLE.
Acked-by: NJacob Shin <jacob.shin@amd.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

currently Tegra cpufreq driver gets built based on ARCH_TEGRA, which doesn't
depend on nor select CPU_FREQ itself, so:

        select CPU_FREQ_TABLE if CPU_FREQ

... isn't guaranteed to fire.

The correct solution seems to be:

* Add CONFIG_ARM_TEGRA_CPUFREQ to drivers/cpufreq/Kconfig.arm.
* Make that Kconfig option selct CPU_FREQ_TABLE.
* Make that Kconfig option be def_bool ARCH_TEGRA.
* Modify drivers/cpufreq/Makefile to build tegra-cpufreq.c based on that.
* Remove all the cpufreq-related stuff from arch/arm/mach-tegra/Kconfig.

That way, tegra-cpufreq.c can't be built if !CPU_FREQ, and Tegra's
cpufreq works the same way as all the other cpufreq drivers.

This patch does it.
Suggested-by: NStephen Warren <swarren@nvidia.com>
Tested-by: NStephen Warren <swarren@nvidia.com>
Acked-by: NStephen Warren <swarren@nvidia.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

CPUFreq driver of this platform uses APIs from freq_table.c and so must select
CPU_FREQ_TABLE.
Acked-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NHeiko Stuebner <heiko@sntech.de>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

CPUFreq driver of this platform uses APIs from freq_table.c and so must select
CPU_FREQ_TABLE.

Cc: linuxppc-dev@lists.ozlabs.org
Acked-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

CPUFreq driver of this platform uses APIs from freq_table.c and so must select
CPU_FREQ_TABLE.
Acked-by: NShawn Guo <shawn.guo@linaro.org>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

Highbank cpufreq driver doesn't use any APIs from freq_table.c and so must not
select CPU_FREQ_TABLE.
Acked-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NMark Langsdorf <mark.langsdorf@calxeda.com>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

CPUFreq driver of this platform uses APIs from freq_table.c and so must select
CPU_FREQ_TABLE.

Cc: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

By mistake blackfin's cpufreq driver is enabled when CONFIG_BLACKFIN was
present, whereas it should have been enabled only when CONFIG_BFIN_CPU_FREQ is
present.

Fix it.
Acked-by: NMike Frysinger <vapier@gentoo.org>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

Move cpufreq driver of powerpc platform to drivers/cpufreq.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

After commit ac212b69 (ACPI / processor: Use common hotplug
infrastructure) the acpi-cpufreq module is not loaded automatically
by udev which fails to match it against the x86cpu modalias.  Still,
it can be matched against ACPI processor device IDs, which even
makes more sense, because it depends on the ACPI processor driver
that uses those device IDs to bind to processor devices.

For this reason, add ACPI processor device IDs to acpi-cpufreq.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>

We need to select CPU_FREQ_TABLE in order to build without
this kind of errors:

drivers/built-in.o: In function `kirkwood_cpufreq_cpu_exit':
/home/zeta/linux-devel/marvell-legacy/drivers/cpufreq/kirkwood-cpufreq.c:145:
undefined reference to `cpufreq_frequency_table_put_attr'
Signed-off-by: NEzequiel Garcia <ezequiel.garcia@free-electrons.com>
Acked-by: NJason Cooper <jason@lakedaemon.net>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

Like a lot of the other cpufreq drivers, this one needs to
select CONFIG_CPU_FREQ_TABLE to avoid a build error like

built-in.o: In function `bL_cpufreq_set_target':
cpufreq/arm_big_little.c:71: undefined reference to `cpufreq_frequency_table_target'
built-in.o: In function `bL_cpufreq_verify_policy':
cpufreq/arm_big_little.c:55: undefined reference to `cpufreq_frequency_table_verify'
built-in.o: In function `bL_cpufreq_init':
cpufreq/arm_big_little.c:170: undefined reference to `cpufreq_frequency_table_cpuinfo'
cpufreq/arm_big_little.c:178: undefined reference to `cpufreq_frequency_table_get_attr'
built-in.o:(.data+0x5a80c): undefined reference to `cpufreq_freq_attr_scaling_available_freqs'
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

Like a lot of the other cpufreq drivers, this one needs to
select CONFIG_CPU_FREQ_TABLE to avoid a build error like

drivers/built-in.o: In function `spear_cpufreq_exit':
spear-cpufreq.c:198: undefined reference to `cpufreq_frequency_table_put_attr'
drivers/built-in.o: In function `spear_cpufreq_verify':
spear-cpufreq.c:35: undefined reference to `cpufreq_frequency_table_verify'
drivers/built-in.o: In function `spear_cpufreq_init':
spear-cpufreq.c:181: undefined reference to `cpufreq_frequency_table_cpuinfo'
spear-cpufreq.c:187: undefined reference to `cpufreq_frequency_table_get_attr'
drivers/built-in.o: In function `spear_cpufreq_target':
spear-cpufreq.c:120: undefined reference to `cpufreq_frequency_table_target'
drivers/built-in.o:(.data+0x5e63c): undefined reference to `cpufreq_freq_attr_scaling_available_freqs'
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: cpufreq@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>

Add cpufreq driver for Freescale e500mc, e5500 and e6500 SoCs
which are capable of changing the CPU frequency dynamically
Signed-off-by: NTang Yuantian <Yuantian.Tang@freescale.com>
Signed-off-by: NLi Yang <leoli@freescale.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

clk_set_rate() isn't supposed to accept approximate frequencies, instead
a supported frequency should be obtained from clk_round_rate() and then
used to set the clock.
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: NShawn Guo <shawn.guo@linaro.org>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Jiri Kosina <jkosina@suse.cz> and Borislav Petkov <bp@alien8.de>
reported the warning:

[   51.616759] ------------[ cut here ]------------
[   51.621460] WARNING: at arch/x86/kernel/smp.c:123 native_smp_send_reschedule+0x58/0x60()
[   51.629638] Modules linked in: ext2 vfat fat loop snd_hda_codec_hdmi usbhid snd_hda_codec_realtek coretemp kvm_intel kvm snd_hda_intel snd_hda_codec crc32_pclmul crc32c_intel ghash_clmulni_intel snd_hwdep snd_pcm aesni_intel sb_edac aes_x86_64 ehci_pci snd_page_alloc glue_helper snd_timer xhci_hcd snd iTCO_wdt iTCO_vendor_support ehci_hcd edac_core lpc_ich acpi_cpufreq lrw gf128mul ablk_helper cryptd mperf usbcore usb_common soundcore mfd_core dcdbas evdev pcspkr processor i2c_i801 button microcode
[   51.675581] CPU: 0 PID: 244 Comm: kworker/1:1 Tainted: G        W    3.10.0-rc1+ #10
[   51.683407] Hardware name: Dell Inc. Precision T3600/0PTTT9, BIOS A08 01/24/2013
[   51.690901] Workqueue: events od_dbs_timer
[   51.695069]  0000000000000009 ffff88043a2f5b68 ffffffff8161441c ffff88043a2f5ba8
[   51.702602]  ffffffff8103e540 0000000000000033 0000000000000001 ffff88043d5f8000
[   51.710136]  00000000ffff0ce1 0000000000000001 ffff88044fc4fc08 ffff88043a2f5bb8
[   51.717691] Call Trace:
[   51.720191]  [<ffffffff8161441c>] dump_stack+0x19/0x1b
[   51.725396]  [<ffffffff8103e540>] warn_slowpath_common+0x70/0xa0
[   51.731473]  [<ffffffff8103e58a>] warn_slowpath_null+0x1a/0x20
[   51.737378]  [<ffffffff81025628>] native_smp_send_reschedule+0x58/0x60
[   51.744013]  [<ffffffff81072cfd>] wake_up_nohz_cpu+0x2d/0xa0
[   51.749745]  [<ffffffff8104f6bf>] add_timer_on+0x8f/0x110
[   51.755214]  [<ffffffff8105f6fe>] __queue_delayed_work+0x16e/0x1a0
[   51.761470]  [<ffffffff8105f251>] ? try_to_grab_pending+0xd1/0x1a0
[   51.767724]  [<ffffffff8105f78a>] mod_delayed_work_on+0x5a/0xa0
[   51.773719]  [<ffffffff814f6b5d>] gov_queue_work+0x4d/0xc0
[   51.779271]  [<ffffffff814f60cb>] od_dbs_timer+0xcb/0x170
[   51.784734]  [<ffffffff8105e75d>] process_one_work+0x1fd/0x540
[   51.790634]  [<ffffffff8105e6f2>] ? process_one_work+0x192/0x540
[   51.796711]  [<ffffffff8105ef22>] worker_thread+0x122/0x380
[   51.802350]  [<ffffffff8105ee00>] ? rescuer_thread+0x320/0x320
[   51.808264]  [<ffffffff8106634a>] kthread+0xea/0xf0
[   51.813200]  [<ffffffff81066260>] ? flush_kthread_worker+0x150/0x150
[   51.819644]  [<ffffffff81623d5c>] ret_from_fork+0x7c/0xb0
[   51.918165] nouveau E[     DRM] GPU lockup - switching to software fbcon
[   51.930505]  [<ffffffff81066260>] ? flush_kthread_worker+0x150/0x150
[   51.936994] ---[ end trace f419538ada83b5c5 ]---

It was caused by the policy->cpus changed during the process of
__gov_queue_work(), in other word, cpu offline happened.

Use get/put_online_cpus() to prevent the offline from happening while
__gov_queue_work() is running.

[rjw: The problem has been present since recent commit 031299b3
(cpufreq: governors: Avoid unnecessary per cpu timer interrupts)]

References: https://lkml.org/lkml/2013/6/5/88Reported-by: NBorislav Petkov <bp@alien8.de>
Reported-and-tested-by: NJiri Kosina <jkosina@suse.cz>
Signed-off-by: NMichael Wang <wangyun@linux.vnet.ibm.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>