The purpose of the acpi_pad driver is to implement the "processor power
aggregator" device as described in the ACPI 4.0 spec section 8.5. It
takes requests from the BIOS (via ACPI) to put a specified number of
CPUs into idle, in order to save power, until further notice.

It does this by creating high-priority threads that try to keep the CPUs
in a high C-state (using the monitor/mwait CPU instructions). The
mwait() call is in a loop that checks periodically if the thread should
end and a few other things.

It was discovered through testing that the power_saving threads were
causing the system to consume more power than the system was consuming
before the threads were created. A counter in the main loop of
power_saving_thread() revealed that it was spinning. The mwait()
instruction was not keeping the CPU in a high C state very much if at
all.

Here is a simplification of the loop in function power_saving_thread() in
drivers/acpi/acpi_pad.c

    while (!kthread_should_stop()) {
         :
        try_to_freeze()
         :
        while (!need_resched()) {
             :
            if (!need_resched())
                __mwait(power_saving_mwait_eax, 1);
             :
            if (jiffies > expire_time) {
                do_sleep = 1;
                break;
            }
        }
    }

If need_resched() returns true, then mwait() is not called. It was
returning true because of things like timer interrupts, as in the
following sequence.

hrtimer_interrupt->__run_hrtimer->tick_sched_timer-> update_process_times->
rcu_check_callbacks->rcu_pending->__rcu_pending->set_need_resched

Kernels 3.5.0-rc2+ do not exhibit this problem, because a patch to
try_to_freeze() in include/linux/freezer.h introduces a call to
might_sleep(), which ultimately calls schedule() to clear the reschedule
flag and allows the the loop to execute the call to mwait().

However, the changes to try_to_freeze are unrelated to acpi_pad, and it
does not seem like a good idea to rely on an unrelated patch in a
function that could later be changed and reintroduce this bug.

Therefore, it seems better to make an explicit call to schedule() in the
outer loop when the need_resched flag is set.
Reported-and-tested-by: NStuart Hayes <stuart_hayes@dell.com>
Signed-off-by: NTony Camuso <tcamuso@redhat.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Use public function acpi_evaluate_ost() to replace open-coded
version of evaluating ACPI _OST method.
Signed-off-by: NJiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

People seem to delight in writing wrong and broken mwait idle routines;
collapse the lot.

This leaves mwait_play_dead() the sole remaining user of __mwait() and
new __mwait() users are probably doing it wrong.

Also remove __sti_mwait() as its unused.

Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Jacob Jun Pan <jacob.jun.pan@linux.intel.com>
Cc: Mike Galbraith <bitbucket@online.de>
Cc: Len Brown <lenb@kernel.org>
Cc: Rui Zhang <rui.zhang@intel.com>
Acked-by: NRafael Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131212141654.616820819@infradead.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

Replace direct inclusions of <acpi/acpi.h>, <acpi/acpi_bus.h> and
<acpi/acpi_drivers.h>, which are incorrect, with <linux/acpi.h>
inclusions and remove some inclusions of those files that aren't
necessary.

First of all, <acpi/acpi.h>, <acpi/acpi_bus.h> and <acpi/acpi_drivers.h>
should not be included directly from any files that are built for
CONFIG_ACPI unset, because that generally leads to build warnings about
undefined symbols in !CONFIG_ACPI builds.  For CONFIG_ACPI set,
<linux/acpi.h> includes those files and for CONFIG_ACPI unset it
provides stub ACPI symbols to be used in that case.

Second, there are ordering dependencies between those files that always
have to be met.  Namely, it is required that <acpi/acpi_bus.h> be included
prior to <acpi/acpi_drivers.h> so that the acpi_pci_root declarations the
latter depends on are always there.  And <acpi/acpi.h> which provides
basic ACPICA type declarations should always be included prior to any other
ACPI headers in CONFIG_ACPI builds.  That also is taken care of including
<linux/acpi.h> as appropriate.
Signed-off-by: NLv Zheng <lv.zheng@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com> (drivers/pci stuff)
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> (Xen stuff)
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

It is quite some time that this one has been deprecated.
Get rid of it.

Should some really important user be overseen, it may be reverted and
the userspace program worked on first, but it is time to do something
to get rid of this old stuff...
Signed-off-by: NThomas Renninger <trenn@suse.de>
Acked-by: NMatthew Garrett <matthew.garrett@nebula.com>
Acked-by: NHenrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

This functions is really weird.  It sets rc to -ENOMEM, then overrides
it.  It was converted to PTR_RET in a1458187 when it should have
simply been rewritten.

This version makes it more explicit, with a single IS_ERR() test.

Cc: Alexandru Gheorghiu <gheorghiuandru@gmail.com>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Acked-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Use PTR_RET instead of explicit checking with IS_ERR.
Signed-off-by: NAlexandru Gheorghiu <gheorghiuandru@gmail.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The second argument of ACPI driver .remove() operation is only used
by the ACPI processor driver and the value passed to that driver
through it is always available from the given struct acpi_device
object's removal_type field.  For this reason, the second ACPI driver
.remove() argument is in fact useless, so drop it.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: NJiang Liu <jiang.liu@huawei.com>
Acked-by: NToshi Kani <toshi.kani@hp.com>
Acked-by: NYinghai Lu <yinghai@kernel.org>

Replace a few calls to strict_strtoul() in acpi_pad.c with kstrtoul()
and use pr_warn() instead of printk() in the same file.

[rjw: Modified the subject and changelog.]
Signed-off-by: NJosh Taylor <joshua.taylor0@gmail.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

In an effort to be fair to bound processes,
acpi_pad periodically moves its forced-idle threads.

The default interval for moving the threads is 10 seconds.
Measurements show that reducing this to 1 second has no
power or performance impact, so reduce default to 1 second.
Signed-off-by: NLen Brown <len.brown@intel.com>

The acpi_pad driver can get stuck in destroy_power_saving_task()
waiting for kthread_stop() to stop a power_saving thread.  The problem
is that the isolated_cpus_lock mutex is owned when
destroy_power_saving_task() calls kthread_stop(), which waits for a
power_saving thread to end, and the power_saving thread tries to
acquire the isolated_cpus_lock when it calls round_robin_cpu().  This
patch fixes the issue by making round_robin_cpu() use its own mutex.

https://bugzilla.kernel.org/show_bug.cgi?id=42981

Cc: stable@vger.kernel.org
Signed-off-by: NStuart Hayes <Stuart_Hayes@Dell.com>
Signed-off-by: NLen Brown <len.brown@intel.com>

"acpi_pad/%d" is a better thread name than
generic "power_saving/%d" because users who see
these threads will know the name of the driver
that caused them.
Signed-off-by: NLen Brown <len.brown@intel.com>

Minor format change.
Signed-off-by: NNaga Chumbalkar <nagananda.chumbalkar@hp.com>
Signed-off-by: NLen Brown <len.brown@intel.com>

Make /sys output from acpi_pad more readable.

Before the fix:
# cat idlecpus idlepct rrtime
00000000510

After the fix:
# cat idlecpus idlepct rrtime
00000000
5
10
Signed-off-by: NNaga Chumbalkar <nagananda.chumbalkar@hp.com>
Signed-off-by: NLen Brown <len.brown@intel.com>

acpi_pad.c:432: warning: ‘num_cpus’ may be used uninitialized in this function

gcc 4.4.4 was unable to notice that num_cpus is always set.
Re-arrange the code to un-confuse gcc, and also make
it easier for humans to read....
Signed-off-by: NLen Brown <len.browns@intel.com>

We have MWAIT constants spread across three different .c files, for no
good reason.  Move them all into a common header file.
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>
Reviewed-by: NArjan van de Ven <arjan@linux.intel.com>
Cc: Len Brown <lenb@kernel.org>
LKML-Reference: <tip-*@git.kernel.org>

Now that all arches have been converted over to use generic time via
clocksources or arch_gettimeoffset(), we can remove the GENERIC_TIME
config option and simplify the generic code.
Signed-off-by: NJohn Stultz <johnstul@us.ibm.com>
LKML-Reference: <1279068988-21864-4-git-send-email-johnstul@us.ibm.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

As suggested in Venki's suggestion in the commit 0dc698b9,
add LAPIC unstable detection in the acpi_pad drvier too.
Signed-off-by: NChen Gong <gong.chen@linux.intel.com>
Signed-off-by: NLen Brown <len.brown@intel.com>

acpi pad driver kind of aggressively marks TSC as unstable at init
time, on mwait capable and non X86_FEATURE_NONSTOP_TSC systems. This is
irrespective of whether pad driver is ever going to be used on the
system or deep C-states are supported/used. This will affect every user
who just happens to compile in (or get a kernel version which
compiles in) acpi pad driver.

Move mark_tsc_unstable() out of init to the actual idle invocation path
of the pad driver.

There is also another bug/missing_feature in the code that it does not
support 'always running apic timer' and switches to broadcast mode
unconditionally. Shaohua, can you take a look at that please.
Signed-off-by: NVenkatesh Pallipadi <venki@google.com>
Signed-off-by: NLen Brown <len.brown@intel.com>

api_pad exclusively uses MONITOR/MWAIT to sleep in idle,
so it does not need the wakeup IPI during idle sleep
that is provoked by clearing TS_POLLING.
Signed-off-by: NLen Brown <len.brown@intel.com>
Cc: Shaohua Li <shaohua.li@intel.com>

cpi_device_class can only be 19 characters and a NULL terminator.

With the current name we get a buffer overflow in acpi_pad_add()
	strcpy(acpi_device_class(device), ACPI_PROCESSOR_AGGREGATOR_CLASS);

[akpm@linux-foundation.org: call it acpi_pad, per Shaohua Li]
Signed-off-by: NDan Carpenter <error27@gmail.com>
Cc: walter harms <wharms@bfs.de>
Acked-by: NShaohua Li <shaohua.li@intel.com>
Cc: Len Brown <lenb@kernel.org>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLen Brown <len.brown@intel.com>

include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h

percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files.  percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.

percpu.h -> slab.h dependency is about to be removed.  Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability.  As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.

  http://userweb.kernel.org/~tj/misc/slabh-sweep.py

The script does the followings.

* Scan files for gfp and slab usages and update includes such that
  only the necessary includes are there.  ie. if only gfp is used,
  gfp.h, if slab is used, slab.h.

* When the script inserts a new include, it looks at the include
  blocks and try to put the new include such that its order conforms
  to its surrounding.  It's put in the include block which contains
  core kernel includes, in the same order that the rest are ordered -
  alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
  doesn't seem to be any matching order.

* If the script can't find a place to put a new include (mostly
  because the file doesn't have fitting include block), it prints out
  an error message indicating which .h file needs to be added to the
  file.

The conversion was done in the following steps.

1. The initial automatic conversion of all .c files updated slightly
   over 4000 files, deleting around 700 includes and adding ~480 gfp.h
   and ~3000 slab.h inclusions.  The script emitted errors for ~400
   files.

2. Each error was manually checked.  Some didn't need the inclusion,
   some needed manual addition while adding it to implementation .h or
   embedding .c file was more appropriate for others.  This step added
   inclusions to around 150 files.

3. The script was run again and the output was compared to the edits
   from #2 to make sure no file was left behind.

4. Several build tests were done and a couple of problems were fixed.
   e.g. lib/decompress_*.c used malloc/free() wrappers around slab
   APIs requiring slab.h to be added manually.

5. The script was run on all .h files but without automatically
   editing them as sprinkling gfp.h and slab.h inclusions around .h
   files could easily lead to inclusion dependency hell.  Most gfp.h
   inclusion directives were ignored as stuff from gfp.h was usually
   wildly available and often used in preprocessor macros.  Each
   slab.h inclusion directive was examined and added manually as
   necessary.

6. percpu.h was updated not to include slab.h.

7. Build test were done on the following configurations and failures
   were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
   distributed build env didn't work with gcov compiles) and a few
   more options had to be turned off depending on archs to make things
   build (like ipr on powerpc/64 which failed due to missing writeq).

   * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
   * powerpc and powerpc64 SMP allmodconfig
   * sparc and sparc64 SMP allmodconfig
   * ia64 SMP allmodconfig
   * s390 SMP allmodconfig
   * alpha SMP allmodconfig
   * um on x86_64 SMP allmodconfig

8. percpu.h modifications were reverted so that it could be applied as
   a separate patch and serve as bisection point.

Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.
Signed-off-by: NTejun Heo <tj@kernel.org>
Guess-its-ok-by: NChristoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>

There are some fixes listed below:
1. When met a bogus BIOS, the return value of cpu number maybe is
   a negative value so that acpi_pad_pur get an unexpected result.
2. the return value of function acpi_pad_idle_cpus is useless.
3. enhance the process of create_power_saving_task/destroy_power_saving_task
4. Add more error checks when evaluating _PUR object.
5. one typo fix
Signed-off-by: NChen Gong <gong.chen@linux.intel.com>
Acked-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NLen Brown <len.brown@intel.com>

drivers/acpi/acpi_pad.c: In function 'power_saving_thread':
drivers/acpi/acpi_pad.c:103: warning: 'preferred_cpu' may be used uninitialized in this function

Cc: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLen Brown <len.brown@intel.com>

ACPI 4.0 created the logical "processor aggregator device" as
a mechinism for platforms to ask the OS to force otherwise busy
processors to enter (power saving) idle.

The intent is to lower power consumption to ride-out
transient electrical and thermal emergencies,
rather than powering off the server.

On platforms that can save more power/performance via P-states,
the platform will first exhaust P-states before forcing idle.
However, the relative benefit of P-states vs. idle states
is platform dependent, and thus this driver need not know
or care about it.

This driver does not use the kernel's CPU hot-plug mechanism
because after the transient emergency is over, the system must
be returned to its normal state, and hotplug would permanently
break both cpusets and binding.

So to force idle, the driver creates a power saving thread.
The scheduler will migrate the thread to the preferred CPU.
The thread has max priority and has SCHED_RR policy,
so it can occupy one CPU.  To save power, the thread will
invoke the deep C-state entry instructions.

To avoid starvation, the thread will sleep 5% of the time
time for every second (current RT scheduler has threshold
to avoid starvation, but if other CPUs are idle,
the CPU can borrow CPU timer from other,
which makes the mechanism not work here)

Vaidyanathan Srinivasan has proposed scheduler enhancements
to allow injecting idle time into the system.  This driver doesn't
depend on those enhancements, but could cut over to them
when they are available.

Peter Z. does not favor upstreaming this driver until
the those scheduler enhancements are in place.  However,
we favor upstreaming this driver now because it is useful
now, and can be enhanced over time.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
NACKed-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: NLen Brown <len.brown@intel.com>