Pull scheduler fixes from Thomas Gleixner:
 "Two small fixes for the schedulre core:

   - Use the proper switch_mm() variant in idle_task_exit() because that
     code is not called with interrupts disabled.

   - Fix a confusing typo in a printk"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/core: Idle_task_exit() shouldn't use switch_mm_irqs_off()
  sched/fair: Fix typo in printk message

* pm-cpufreq:
  cpufreq: conservative: Allow down_threshold to take values from 1 to 10
  Revert "cpufreq: schedutil: Reduce frequencies slower"

* pm-cpuidle:
  cpuidle: dt: Add missing 'of_node_put()'

* pm-devfreq:
  PM / devfreq: exynos-ppmu: Staticize event list
  PM / devfreq: exynos-ppmu: Handle return value of clk_prepare_enable
  PM / devfreq: exynos-nocp: Handle return value of clk_prepare_enable

Revert commit 39b64aa1c007 (cpufreq: schedutil: Reduce frequencies
slower) that introduced unintentional changes in behavior leading
to adverse effects on some systems.

Reported-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

idle_task_exit() can be called with IRQs on x86 on and therefore
should use switch_mm(), not switch_mm_irqs_off().

This doesn't seem to cause any problems right now, but it will
confuse my upcoming TLB flush changes.  Nonetheless, I think it
should be backported because it's trivial.  There won't be any
meaningful performance impact because idle_task_exit() is only
used when offlining a CPU.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: f98db6013c55 ("sched/core: Add switch_mm_irqs_off() and use it in the scheduler")
Link: http://lkml.kernel.org/r/ca3d1a9fa93a0b49f5a8ff729eda3640fb6abdf9.1497034141.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

'schedstats' kernel parameter should be set to enable/disable, so
correct the printk hint saying that it should be set to 'enable'
rather than 'enabled' to enable scheduler tracepoints.

Signed-off-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1496995229-31245-1-git-send-email-marcin.nowakowski@imgtec.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

* intel_pstate:
  cpufreq: intel_pstate: Document the current behavior and user interface

* pm-cpufreq:
  cpufreq: dbx500: add a Kconfig symbol

* pm-cpufreq-sched:
  cpufreq: schedutil: use now as reference when aggregating shared policy requests

I finally got around to creating trampolines for dynamically allocated
ftrace_ops with using synchronize_rcu_tasks(). For users of the ftrace
function hook callbacks, like perf, that allocate the ftrace_ops
descriptor via kmalloc() and friends, ftrace was not able to optimize
the functions being traced to use a trampoline because they would also
need to be allocated dynamically. The problem is that they cannot be
freed when CONFIG_PREEMPT is set, as there's no way to tell if a task
was preempted on the trampoline. That was before Paul McKenney
implemented synchronize_rcu_tasks() that would make sure all tasks
(except idle) have scheduled out or have entered user space.

While testing this, I triggered this bug:

 BUG: unable to handle kernel paging request at ffffffffa0230077
 ...
 RIP: 0010:0xffffffffa0230077
 ...
 Call Trace:
  schedule+0x5/0xe0
  schedule_preempt_disabled+0x18/0x30
  do_idle+0x172/0x220

What happened was that the idle task was preempted on the trampoline.
As synchronize_rcu_tasks() ignores the idle thread, there's nothing
that lets ftrace know that the idle task was preempted on a trampoline.

The idle task shouldn't need to ever enable preemption. The idle task
is simply a loop that calls schedule or places the cpu into idle mode.
In fact, having preemption enabled is inefficient, because it can
happen when idle is just about to call schedule anyway, which would
cause schedule to be called twice. Once for when the interrupt came in
and was returning back to normal context, and then again in the normal
path that the idle loop is running in, which would be pointless, as it
had already scheduled.

The only reason schedule_preempt_disable() enables preemption is to be
able to call sched_submit_work(), which requires preemption enabled. As
this is a nop when the task is in the RUNNING state, and idle is always
in the running state, there's no reason that idle needs to enable
preemption. But that means it cannot use schedule_preempt_disable() as
other callers of that function require calling sched_submit_work().

Adding a new function local to kernel/sched/ that allows idle to call
the scheduler without enabling preemption, fixes the
synchronize_rcu_tasks() issue, as well as removes the pointless spurious
schedule calls caused by interrupts happening in the brief window where
preemption is enabled just before it calls schedule.

Reviewed: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170414084809.3dacde2a@gandalf.local.home
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Pull RCU updates from Ingo Molnar:
 "The main changes are:

   - Debloat RCU headers

   - Parallelize SRCU callback handling (plus overlapping patches)

   - Improve the performance of Tree SRCU on a CPU-hotplug stress test

   - Documentation updates

   - Miscellaneous fixes"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (74 commits)
  rcu: Open-code the rcu_cblist_n_lazy_cbs() function
  rcu: Open-code the rcu_cblist_n_cbs() function
  rcu: Open-code the rcu_cblist_empty() function
  rcu: Separately compile large rcu_segcblist functions
  srcu: Debloat the <linux/rcu_segcblist.h> header
  srcu: Adjust default auto-expediting holdoff
  srcu: Specify auto-expedite holdoff time
  srcu: Expedite first synchronize_srcu() when idle
  srcu: Expedited grace periods with reduced memory contention
  srcu: Make rcutorture writer stalls print SRCU GP state
  srcu: Exact tracking of srcu_data structures containing callbacks
  srcu: Make SRCU be built by default
  srcu: Fix Kconfig botch when SRCU not selected
  rcu: Make non-preemptive schedule be Tasks RCU quiescent state
  srcu: Expedite srcu_schedule_cbs_snp() callback invocation
  srcu: Parallelize callback handling
  kvm: Move srcu_struct fields to end of struct kvm
  rcu: Fix typo in PER_RCU_NODE_PERIOD header comment
  rcu: Use true/false in assignment to bool
  rcu: Use bool value directly
  ...

Currently, sugov_next_freq_shared() uses last_freq_update_time as a
reference to decide when to start considering CPU contributions as
stale.

However, since last_freq_update_time is set by the last CPU that issued
a frequency transition, this might cause problems in certain cases. In
practice, the detection of stale utilization values fails whenever the
CPU with such values was the last to update the policy. For example (and
please note again that the SCHED_CPUFREQ_RT flag is not the problem
here, but only the detection of after how much time that flag has to be
considered stale), suppose a policy with 2 CPUs:

               CPU0                |               CPU1
                                   |
                                   |     RT task scheduled
                                   |     SCHED_CPUFREQ_RT is set
                                   |     CPU1->last_update = now
                                   |     freq transition to max
                                   |     last_freq_update_time = now
                                   |

                        more than TICK_NSEC nsecs

                                   |
     a small CFS wakes up          |
     CPU0->last_update = now1      |
     delta_ns(CPU0) < TICK_NSEC*   |
     CPU0's util is considered     |
     delta_ns(CPU1) =              |
      last_freq_update_time -      |
      CPU1->last_update = 0        |
      < TICK_NSEC                  |
     CPU1 is still considered      |
     CPU1->SCHED_CPUFREQ_RT is set |
     we stay at max (until CPU1    |
     exits from idle)              |

* delta_ns is actually negative as now1 > last_freq_update_time

While last_freq_update_time is a sensible reference for rate limiting,
it doesn't seem to be useful for working around stale CPU states.

Fix the problem by always considering now (time) as the reference for
deciding when CPUs have stale contributions.

Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Pull trivial tree updates from Jiri Kosina.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial:
  tty: fix comment for __tty_alloc_driver()
  init/main: properly align the multi-line comment
  init/main: Fix double "the" in comment
  Fix dead URLs to ftp.kernel.org
  drivers: Clean up duplicated email address
  treewide: Fix typo in xml/driver-api/basics.xml
  tools/testing/selftests/powerpc: remove redundant CFLAGS in Makefile: "-Wall -O2 -Wall" -> "-O2 -Wall"
  selftests/timers: Spelling s/privledges/privileges/
  HID: picoLCD: Spelling s/REPORT_WRTIE_MEMORY/REPORT_WRITE_MEMORY/
  net: phy: dp83848: Fix Typo
  UBI: Fix typos
  Documentation: ftrace.txt: Correct nice value of 120 priority
  net: fec: Fix typo in error msg and comment
  treewide: Fix typos in printk