The cpufreq governor owner refcount usage is broken.  We should only
increment that refcount when a CPUFREQ_GOV_POLICY_INIT event has come
and it should only be decremented if CPUFREQ_GOV_POLICY_EXIT has come.

Currently, there can be situations where the governor is in use, but
we have allowed it to be unloaded which may result in undefined
behavior.  Let's fix it.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

To iterate over all policies we currently iterate over all CPUs and
then get the policy for each of them.  Let's use the newly created
cpufreq_policy_list for this purpose.

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

Policies available in the cpufreq framework are now linked together.
They are accessible via cpufreq_policy_list defined in the cpufreq
core.

[rjw: Fix from Yinghai Lu folded in]
Signed-off-by: NLukasz Majewski <l.majewski@samsung.com>
Signed-off-by: NMyungjoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Chapter 14 of Documentation/CodingStyle says:

The preferred form for passing a size of a struct is the following:

	p = kmalloc(sizeof(*p), ...);

The alternative form where struct name is spelled out hurts
readability and introduces an opportunity for a bug when the pointer
variable type is changed but the corresponding sizeof that is passed
to a memory allocator is not.

This wasn't followed consistently in drivers/cpufreq, let's make it
more consistent by always following this rule.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

They are called policy, cur_policy, new_policy, data, etc.  Just call
them policy wherever possible.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch addresses the following issues in the header files in the
cpufreq core:
 - Include headers in ascending order, so that we don't add same
   many times by mistake.
 - <asm/> must be included after <linux/>, so that they override
   whatever they need to.
 - Remove unnecessary includes.
 - Don't include files already included by cpufreq.h or
   cpufreq_governor.h.

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

The caller of cpufreq_add_policy_cpu() already has a pointer to the
policy structure and there is no need to look it up again in
cpufreq_add_policy_cpu().  Let's pass it directly.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The only case triggering a jump to the err_out_unregister label in
__cpufreq_add_dev() is when cpufreq_add_dev_interface() fails.
However, if cpufreq_add_dev_interface() fails, it calls kobject_put()
for the policy kobject in its error code path and since that causes
the kobject's refcount to become 0, the additional kobject_put() for
the same kobject under err_out_unregister and the
wait_for_completion() following it are pointless, so drop them.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>

The cpufreq core is a little inconsistent in the way it uses the
driver module refcount.

Namely, if __cpufreq_add_dev() is called for a CPU that doesn't
share the policy object with any other CPUs, the driver module
refcount it grabs to start with will be dropped by it before
returning and will be equal to whatever it had been before that
function was invoked.

However, if the given CPU does share the policy object with other
CPUs, either cpufreq_add_policy_cpu() is called to link the new CPU
to the existing policy, or cpufreq_add_dev_symlink() is used to link
the other CPUs sharing the policy with it to the just created policy
object.  In that case, because both cpufreq_add_policy_cpu() and
cpufreq_add_dev_symlink() call cpufreq_cpu_get() for the given
policy (the latter possibly many times) without the balancing
cpufreq_cpu_put() (unless there is an error), the driver module
refcount will be left by __cpufreq_add_dev() with a nonzero value
(different from the initial one).

To remove that inconsistency make cpufreq_add_policy_cpu() execute
cpufreq_cpu_put() for the given policy before returning, which
decrements the driver module refcount so that it will be equal to its
initial value after __cpufreq_add_dev() returns.  Also remove the
cpufreq_cpu_get() call from cpufreq_add_dev_symlink(), since both the
policy refcount and the driver module refcount are nonzero when it is
called and they don't need to be bumped up by it.

Accordingly, drop the cpufreq_cpu_put() from __cpufreq_remove_dev(),
since it is only necessary to balance the cpufreq_cpu_get() called
by cpufreq_add_policy_cpu() or cpufreq_add_dev_symlink().
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>

Pointer to struct cpufreq_policy is already passed to these routines
and we don't need to send policy->cpu to them as well.  So, get rid
of this extra argument and use policy->cpu everywhere.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

We call cpufreq_cpu_get() in cpufreq_add_dev_symlink() to increase usage
refcount of policy, but not to get a policy for the given CPU.  So, we
don't really need to capture the return value of this routine.  We can
simply use policy passed as an argument to cpufreq_add_dev_symlink().

Moreover debug print is rewritten to make it more clear.

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

Now that we have the infrastructure to perform a light-weight init/tear-down,
use that in the cpufreq CPU hotplug notifier when invoked from the
suspend/resume path.

This also ensures that the file permissions of the cpufreq sysfs files are
preserved across suspend/resume, something which commit a66b2e (cpufreq:
Preserve sysfs files across suspend/resume) originally intended to do, but
had to be reverted due to other problems.
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

To perform light-weight cpu-init and teardown in the cpufreq subsystem
during suspend/resume, we need to separate out the 2 main functionalities
of the cpufreq CPU hotplug callbacks, as outlined below:

1. Init/tear-down of core cpufreq and CPU-specific components, which are
   critical to the correct functioning of the cpufreq subsystem.

2. Init/tear-down of cpufreq sysfs files during suspend/resume.

The first part requires accurate updates to the policy structure such as
its ->cpus and ->related_cpus masks, whereas the second part requires that
the policy->kobj structure is not released or re-initialized during
suspend/resume.

To handle both these requirements, we need to allow updates to the policy
structure throughout suspend/resume, but prevent the structure from getting
freed up. Also, we must have a mechanism by which the cpu-up callbacks can
restore the policy structure, without allocating things afresh. (That also
helps avoid memory leaks).

To achieve this, we use 2 schemes:
a. Use a fallback per-cpu storage area for preserving the policy structures
   during suspend, so that they can be restored during resume appropriately.

b. Use the 'frozen' flag to determine when to free or allocate the policy
   structure vs when to restore the policy from the saved fallback storage.
   Thus we can successfully preserve the structure across suspend/resume.

Effectively, this helps us complete the separation of the 'light-weight'
and the 'full' init/tear-down sequences in the cpufreq subsystem, so that
this can be made use of in the suspend/resume scenario.
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

During suspend/resume we would like to do a light-weight init/teardown of
CPUs in the cpufreq subsystem and preserve certain things such as sysfs files
etc across suspend/resume transitions. Add a flag called 'frozen' to help
distinguish the full init/teardown sequence from the light-weight one.
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

During cpu offline, when the policy->cpu is going down, some other CPU
present in the policy->cpus mask is nominated as the new policy->cpu.
Extract this functionality from __cpufreq_remove_dev() and implement
it in a helper function. This helps in upcoming code reorganization.
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq_add_dev_interface() includes the work of exposing the interface
to the device, as well as a lot of unrelated stuff. Move the latter to
cpufreq_add_dev(), where it is more appropriate.
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Separate out the allocation of the cpufreq policy structure (along with
its error handling) to a helper function. This makes the code easier to
read and also helps with some upcoming code reorganization.
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The call to cpufreq_update_policy() is placed in the CPU hotplug callback
of cpufreq_stats, which has a higher priority than the CPU hotplug callback
of cpufreq-core. As a result, during CPU_ONLINE/CPU_ONLINE_FROZEN, we end up
calling cpufreq_update_policy() *before* calling cpufreq_add_dev() !
And for uninitialized CPUs, it just returns silently, not doing anything.

To add to that, cpufreq_stats is not even the right place to call
cpufreq_update_policy() to begin with. The cpufreq core ought to handle
this in its own callback, from an elegance/relevance perspective.

So move the invocation of cpufreq_update_policy() to cpufreq_cpu_callback,
and place it *after* cpufreq_add_dev().
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Since cpufreq_cpu_put() called by __cpufreq_remove_dev() drops the
driver module refcount, __cpufreq_remove_dev() causes that refcount
to become negative for the cpufreq driver after a suspend/resume
cycle.

This is not the only bad thing that happens there, however, because
kobject_put() should only be called for the policy kobject at this
point if the CPU is not the last one for that policy.

Namely, if the given CPU is the last one for that policy, the
policy kobject's refcount should be 1 at this point, as set by
cpufreq_add_dev_interface(), and only needs to be dropped once for
the kobject to go away.  This actually happens under the cpu == 1
check, so it need not be done before by cpufreq_cpu_put().

On the other hand, if the given CPU is not the last one for that
policy, this means that cpufreq_add_policy_cpu() has been called
at least once for that policy and cpufreq_cpu_get() has been
called for it too.  To balance that cpufreq_cpu_get(), we need to
call cpufreq_cpu_put() in that case.

Thus, to fix the described problem and keep the reference
counters balanced in both cases, move the cpufreq_cpu_get() call
in __cpufreq_remove_dev() to the code path executed only for
CPUs that share the policy with other CPUs.
Reported-and-tested-by: NToralf Förster <toralf.foerster@gmx.de>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: 3.10+ <stable@vger.kernel.org>

The target frequency calculation method in the ondemand governor has
changed and it is now independent of the measured average frequency.
Consequently, the __cpufreq_driver_getavg() function and getavg
member of struct cpufreq_driver are not used any more, so drop them.

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

The __cpuinit type of throwaway sections might have made sense
some time ago when RAM was more constrained, but now the savings
do not offset the cost and complications.  For example, the fix in
commit 5e427ec2 ("x86: Fix bit corruption at CPU resume time")
is a good example of the nasty type of bugs that can be created
with improper use of the various __init prefixes.

After a discussion on LKML[1] it was decided that cpuinit should go
the way of devinit and be phased out.  Once all the users are gone,
we can then finally remove the macros themselves from linux/init.h.

This removes all the drivers/cpufreq uses of the __cpuinit macros
from all C files.

[1] https://lkml.org/lkml/2013/5/20/589

[v2: leave 2nd lines of args misaligned as requested by Viresh]
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
Acked-by: NDirk Brandewie <dirk.j.brandewie@intel.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>

commit a66b2e (cpufreq: Preserve sysfs files across suspend/resume)
has unfortunately caused several things in the cpufreq subsystem to
break subtly after a suspend/resume cycle.

The intention of that patch was to retain the file permissions of the
cpufreq related sysfs files across suspend/resume.  To achieve that,
the commit completely removed the calls to cpufreq_add_dev() and
__cpufreq_remove_dev() during suspend/resume transitions.  But the
problem is that those functions do 2 kinds of things:
  1. Low-level initialization/tear-down that are critical to the
     correct functioning of cpufreq-core.
  2. Kobject and sysfs related initialization/teardown.

Ideally we should have reorganized the code to cleanly separate these
two responsibilities, and skipped only the sysfs related parts during
suspend/resume.  Since we skipped the entire callbacks instead (which
also included some CPU and cpufreq-specific critical components),
cpufreq subsystem started behaving erratically after suspend/resume.

So revert the commit to fix the regression.  We'll revisit and address
the original goal of that commit separately, since it involves quite a
bit of careful code reorganization and appears to be non-trivial.

(While reverting the commit, note that another commit f51e1eb6
 (cpufreq: Fix cpufreq regression after suspend/resume) already
 reverted part of the original set of changes.  So revert only the
 remaining ones).
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Tested-by: NPaul Bolle <pebolle@tiscali.nl>
Cc: 3.10+ <stable@vger.kernel.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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>

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>

__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>

struct cpufreq_policy is already passed as argument to some routines
like: __cpufreq_driver_getavg() and so we don't really need to do
cpufreq_cpu_get() before and cpufreq_cpu_put() in them to get a
policy structure.

Remove them.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

When we don't have any file in cpu/cpufreq directory we shouldn't
create it. Specially with the introduction of per-policy governor
instance patchset, even governors are moved to
cpu/cpu*/cpufreq/governor-name directory and so this directory is
just not required.

Lets have it only when required.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Governors other than ondemand and conservative can also use
get_cpu_idle_time() and they aren't required to compile
cpufreq_governor.c. So, move these independent routines to
cpufreq.c instead.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

get_governor_parent_kobj() can be used by any governor, generic
cpufreq governors or platform specific ones and so must be present in
cpufreq.c instead of cpufreq_governor.c.

This patch moves it to cpufreq.c. This also adds
EXPORT_SYMBOL_GPL(get_governor_parent_kobj) so that modules can use
this function too.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This patch adds: EXPORT_SYMBOL_GPL(have_governor_per_policy), so that
this routine can be used by modules too.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

With the rwsem lock around
__cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT), we
get circular dependency when we call sysfs_remove_group().

 ======================================================
 [ INFO: possible circular locking dependency detected ]
 3.9.0-rc7+ #15 Not tainted
 -------------------------------------------------------
 cat/2387 is trying to acquire lock:
  (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [<c02f6179>] lock_policy_rwsem_read+0x25/0x34

 but task is already holding lock:
  (s_active#41){++++.+}, at: [<c00f9bf7>] sysfs_read_file+0x4f/0xcc

 which lock already depends on the new lock.

 the existing dependency chain (in reverse order) is:

-> #1 (s_active#41){++++.+}:
        [<c0055a79>] lock_acquire+0x61/0xbc
        [<c00fabf1>] sysfs_addrm_finish+0xc1/0x128
        [<c00f9819>] sysfs_hash_and_remove+0x35/0x64
        [<c00fbe6f>] remove_files.isra.0+0x1b/0x24
        [<c00fbea5>] sysfs_remove_group+0x2d/0xa8
        [<c02f9a0b>] cpufreq_governor_interactive+0x13b/0x35c
        [<c02f61df>] __cpufreq_governor+0x2b/0x8c
        [<c02f6579>] __cpufreq_set_policy+0xa9/0xf8
        [<c02f6b75>] store_scaling_governor+0x61/0x100
        [<c02f6f4d>] store+0x39/0x60
        [<c00f9b81>] sysfs_write_file+0xed/0x114
        [<c00b3fd1>] vfs_write+0x65/0xd8
        [<c00b424b>] sys_write+0x2f/0x50
        [<c000cdc1>] ret_fast_syscall+0x1/0x52

-> #0 (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}:
        [<c0055253>] __lock_acquire+0xef3/0x13dc
        [<c0055a79>] lock_acquire+0x61/0xbc
        [<c03ee1f5>] down_read+0x25/0x30
        [<c02f6179>] lock_policy_rwsem_read+0x25/0x34
        [<c02f6edd>] show+0x21/0x58
        [<c00f9c0f>] sysfs_read_file+0x67/0xcc
        [<c00b40a7>] vfs_read+0x63/0xd8
        [<c00b41fb>] sys_read+0x2f/0x50
        [<c000cdc1>] ret_fast_syscall+0x1/0x52

 other info that might help us debug this:

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(s_active#41);
                                lock(&per_cpu(cpu_policy_rwsem, cpu));
                                lock(s_active#41);
   lock(&per_cpu(cpu_policy_rwsem, cpu));

  *** DEADLOCK ***

 2 locks held by cat/2387:
  #0:  (&buffer->mutex){+.+.+.}, at: [<c00f9bcd>] sysfs_read_file+0x25/0xcc
  #1:  (s_active#41){++++.+}, at: [<c00f9bf7>] sysfs_read_file+0x4f/0xcc

 stack backtrace:
 [<c0011d55>] (unwind_backtrace+0x1/0x9c) from [<c03e9a09>] (print_circular_bug+0x19d/0x1e8)
 [<c03e9a09>] (print_circular_bug+0x19d/0x1e8) from [<c0055253>] (__lock_acquire+0xef3/0x13dc)
 [<c0055253>] (__lock_acquire+0xef3/0x13dc) from [<c0055a79>] (lock_acquire+0x61/0xbc)
 [<c0055a79>] (lock_acquire+0x61/0xbc) from [<c03ee1f5>] (down_read+0x25/0x30)
 [<c03ee1f5>] (down_read+0x25/0x30) from [<c02f6179>] (lock_policy_rwsem_read+0x25/0x34)
 [<c02f6179>] (lock_policy_rwsem_read+0x25/0x34) from [<c02f6edd>] (show+0x21/0x58)
 [<c02f6edd>] (show+0x21/0x58) from [<c00f9c0f>] (sysfs_read_file+0x67/0xcc)
 [<c00f9c0f>] (sysfs_read_file+0x67/0xcc) from [<c00b40a7>] (vfs_read+0x63/0xd8)
 [<c00b40a7>] (vfs_read+0x63/0xd8) from [<c00b41fb>] (sys_read+0x2f/0x50)
 [<c00b41fb>] (sys_read+0x2f/0x50) from [<c000cdc1>] (ret_fast_syscall+0x1/0x52)

This lock isn't required while calling __cpufreq_governor(policy,
CPUFREQ_GOV_POLICY_EXIT). Remove it.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The file permissions of cpufreq per-cpu sysfs files are not preserved
across suspend/resume because we internally go through the CPU
Hotplug path which reinitializes the file permissions on CPU online.

But the user is not supposed to know that we are using CPU hotplug
internally within suspend/resume (IOW, the kernel should not silently
wreck the user-set file permissions across a suspend cycle).
Therefore, we need to preserve the file permissions as they are
across suspend/resume.

The simplest way to achieve that is to just not touch the sysfs files
at all - ie., just ignore the CPU hotplug notifications in the
suspend/resume path (_FROZEN) in the cpufreq hotplug callback.
Reported-by: NRobert Jarzmik <robert.jarzmik@intel.com>
Reported-by: NDurgadoss R <durgadoss.r@intel.com>
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

We must call __cpufreq_governor(data, CPUFREQ_GOV_POLICY_EXIT) before
calling cpufreq_cpu_put(data), so that policy kobject have valid
fields. Otherwise, removing last online cpu of policy->cpus causes
this crash for ondemand/conservative governor.

 [<c00fb076>] (sysfs_find_dirent+0xe/0xa8) from [<c00fb1bd>] (sysfs_get_dirent+0x21/0x58)
 [<c00fb1bd>] (sysfs_get_dirent+0x21/0x58) from [<c00fc259>] (sysfs_remove_group+0x85/0xbc)
 [<c00fc259>] (sysfs_remove_group+0x85/0xbc) from [<c02faad9>] (cpufreq_governor_dbs+0x369/0x4a0)
 [<c02faad9>] (cpufreq_governor_dbs+0x369/0x4a0) from [<c02f66d7>] (__cpufreq_governor+0x2b/0x8c)
 [<c02f66d7>] (__cpufreq_governor+0x2b/0x8c) from [<c02f6893>] (__cpufreq_remove_dev.isra.12+0x15b/0x250)
 [<c02f6893>] (__cpufreq_remove_dev.isra.12+0x15b/0x250) from [<c03e91c7>] (cpufreq_cpu_callback+0x2f/0x3c)
 [<c03e91c7>] (cpufreq_cpu_callback+0x2f/0x3c) from [<c0036fe1>] (notifier_call_chain+0x45/0x54)
 [<c0036fe1>] (notifier_call_chain+0x45/0x54) from [<c001e611>] (__cpu_notify+0x1d/0x34)
 [<c001e611>] (__cpu_notify+0x1d/0x34) from [<c03e5833>] (_cpu_down+0x63/0x1ac)
 [<c03e5833>] (_cpu_down+0x63/0x1ac) from [<c03e5997>] (cpu_down+0x1b/0x30)
 [<c03e5997>] (cpu_down+0x1b/0x30) from [<c03e60eb>] (store_online+0x27/0x54)
 [<c03e60eb>] (store_online+0x27/0x54) from [<c0295629>] (dev_attr_store+0x11/0x18)
 [<c0295629>] (dev_attr_store+0x11/0x18) from [<c00f9edd>] (sysfs_write_file+0xed/0x114)
 [<c00f9edd>] (sysfs_write_file+0xed/0x114) from [<c00b42a9>] (vfs_write+0x65/0xd8)
 [<c00b42a9>] (vfs_write+0x65/0xd8) from [<c00b4523>] (sys_write+0x2f/0x50)
 [<c00b4523>] (sys_write+0x2f/0x50) from [<c000cdc1>] (ret_fast_syscall+0x1/0x52)

Of course this only impacted drivers which have
have_governor_per_policy set to true. i.e. big LITTLE cpufreq driver.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Commit 5800043b (cpufreq: convert cpufreq_driver to using RCU) causes
the following call trace to be spit on boot:

 BUG: sleeping function called from invalid context at /scratch/rafael/work/linux-pm/mm/slab.c:3179
 in_atomic(): 0, irqs_disabled(): 0, pid: 292, name: systemd-udevd
 2 locks held by systemd-udevd/292:
  #0:  (subsys mutex){+.+.+.}, at: [<ffffffff8146851a>] subsys_interface_register+0x4a/0xe0
  #1:  (rcu_read_lock){.+.+.+}, at: [<ffffffff81538210>] cpufreq_add_dev_interface+0x60/0x5e0
 Pid: 292, comm: systemd-udevd Not tainted 3.9.0-rc8+ #323
 Call Trace:
  [<ffffffff81072c90>] __might_sleep+0x140/0x1f0
  [<ffffffff811581c2>] kmem_cache_alloc+0x42/0x2b0
  [<ffffffff811e7179>] sysfs_new_dirent+0x59/0x130
  [<ffffffff811e63cb>] sysfs_add_file_mode+0x6b/0x110
  [<ffffffff81538210>] ? cpufreq_add_dev_interface+0x60/0x5e0
  [<ffffffff810a3254>] ? __lock_is_held+0x54/0x80
  [<ffffffff811e647d>] sysfs_add_file+0xd/0x10
  [<ffffffff811e6541>] sysfs_create_file+0x21/0x30
  [<ffffffff81538280>] cpufreq_add_dev_interface+0xd0/0x5e0
  [<ffffffff81538210>] ? cpufreq_add_dev_interface+0x60/0x5e0
  [<ffffffffa000337f>] ? acpi_processor_get_platform_limit+0x32/0xbb [processor]
  [<ffffffffa022f540>] ? do_drv_write+0x70/0x70 [acpi_cpufreq]
  [<ffffffff810a3254>] ? __lock_is_held+0x54/0x80
  [<ffffffff8106c97e>] ? up_read+0x1e/0x40
  [<ffffffff8106e632>] ? __blocking_notifier_call_chain+0x72/0xc0
  [<ffffffff81538dbd>] cpufreq_add_dev+0x62d/0xae0
  [<ffffffff815389b8>] ? cpufreq_add_dev+0x228/0xae0
  [<ffffffff81468569>] subsys_interface_register+0x99/0xe0
  [<ffffffffa014d000>] ? 0xffffffffa014cfff
  [<ffffffff81535d5d>] cpufreq_register_driver+0x9d/0x200
  [<ffffffffa014d000>] ? 0xffffffffa014cfff
  [<ffffffffa014d0e9>] acpi_cpufreq_init+0xe9/0x1000 [acpi_cpufreq]
  [<ffffffff810002fa>] do_one_initcall+0x11a/0x170
  [<ffffffff810b4b87>] load_module+0x1cf7/0x2920
  [<ffffffff81322580>] ? ddebug_proc_open+0xb0/0xb0
  [<ffffffff816baee0>] ? retint_restore_args+0xe/0xe
  [<ffffffff810b5887>] sys_init_module+0xd7/0x120
  [<ffffffff816bb6d2>] system_call_fastpath+0x16/0x1b

which is quite obvious, because that commit put (multiple instances
of) sysfs_create_file() under rcu_read_lock()/rcu_read_unlock(),
although sysfs_create_file() may cause memory to be allocated with
GFP_KERNEL and that may sleep, which is not permitted in RCU read
critical section.

Revert the buggy commit altogether along with some changes on top
of it.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Some cpufreq drivers implement their own governor and so don't need
us to call generic governors interface via __cpufreq_governor(). Few
recent commits haven't obeyed this law well and we saw some
regressions.

This patch is an attempt to fix the above issue.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Reported-and-tested-by: NSedat Dilek <sedat.dilek@gmail.com>
Tested-by: NDirk Brandewie <dirk.brandewie@gmail.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

__cpufreq_governor() must be called with a correct policy->cpus mask.
In __cpufreq_remove_dev() we initially clear policy->cpus with
cpumask_clear_cpu() and then call
__cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT). If the governor
is doing some per-cpu stuff in EXIT callback, this can create
uncertain behavior.

Generic governors in drivers/cpufreq/ doesn't do any per-cpu stuff
in EXIT callback and so we don't face any issues currently. But its
better to keep the code clean, so we don't face any issues in future.

Now, we call cpumask_clear_cpu() only when multiple cpus are managed
by policy.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

We eventually would like to remove the rwlock cpufreq_driver_lock or
convert it back to a spinlock and protect the read sections with RCU.
The first step in that direction is to make cpufreq_driver use RCU.
I don't see an easy wasy to protect the cpufreq_cpu_data structure
with RCU, so I am leaving it with the rwlock for now since under
certain configs __cpufreq_cpu_get is a hot spot with 256+ cores.

[rjw: Subject, changelog, white space]
Signed-off-by: NNathan Zimmer <nzimmer@sgi.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>