linux.git/include/linux/sched, branch v5.0

oom, oom_reaper: do not enqueue same task twice

2019-02-01T23:46:23+00:00

Arkadiusz reported that enabling memcg's group oom killing causes
strange memcg statistics where there is no task in a memcg despite the
number of tasks in that memcg is not 0.  It turned out that there is a
bug in wake_oom_reaper() which allows enqueuing same task twice which
makes impossible to decrease the number of tasks in that memcg due to a
refcount leak.

This bug existed since the OOM reaper became invokable from
task_will_free_mem(current) path in out_of_memory() in Linux 4.7,

  T1@P1     |T2@P1     |T3@P1     |OOM reaper
  ----------+----------+----------+------------
                                   # Processing an OOM victim in a different memcg domain.
                        try_charge()
                          mem_cgroup_out_of_memory()
                            mutex_lock(&oom_lock)
             try_charge()
               mem_cgroup_out_of_memory()
                 mutex_lock(&oom_lock)
  try_charge()
    mem_cgroup_out_of_memory()
      mutex_lock(&oom_lock)
                            out_of_memory()
                              oom_kill_process(P1)
                                do_send_sig_info(SIGKILL, @P1)
                                mark_oom_victim(T1@P1)
                                wake_oom_reaper(T1@P1) # T1@P1 is enqueued.
                            mutex_unlock(&oom_lock)
                 out_of_memory()
                   mark_oom_victim(T2@P1)
                   wake_oom_reaper(T2@P1) # T2@P1 is enqueued.
                 mutex_unlock(&oom_lock)
      out_of_memory()
        mark_oom_victim(T1@P1)
        wake_oom_reaper(T1@P1) # T1@P1 is enqueued again due to oom_reaper_list == T2@P1 && T1@P1->oom_reaper_list == NULL.
      mutex_unlock(&oom_lock)
                                   # Completed processing an OOM victim in a different memcg domain.
                                   spin_lock(&oom_reaper_lock)
                                   # T1P1 is dequeued.
                                   spin_unlock(&oom_reaper_lock)

but memcg's group oom killing made it easier to trigger this bug by
calling wake_oom_reaper() on the same task from one out_of_memory()
request.

Fix this bug using an approach used by commit 855b018325737f76 ("oom,
oom_reaper: disable oom_reaper for oom_kill_allocating_task").  As a
side effect of this patch, this patch also avoids enqueuing multiple
threads sharing memory via task_will_free_mem(current) path.

Link: http://lkml.kernel.org/r/e865a044-2c10-9858-f4ef-254bc71d6cc2@i-love.sakura.ne.jp
Link: http://lkml.kernel.org/r/5ee34fc6-1485-34f8-8790-903ddabaa809@i-love.sakura.ne.jp
Fixes: af8e15cc85a25315 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head")
Signed-off-by: Tetsuo Handa 
Reported-by: Arkadiusz Miskiewicz 
Tested-by: Arkadiusz Miskiewicz 
Acked-by: Michal Hocko 
Acked-by: Roman Gushchin 
Cc: Tejun Heo 
Cc: Aleksa Sarai 
Cc: Jay Kamat 
Cc: Johannes Weiner 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sched/wake_q: Document wake_q_add()

2019-01-21T10:15:36+00:00

The only guarantee provided by wake_q_add() is that a wakeup will
happen after it, it does _NOT_ guarantee the wakeup will be delayed
until the matching wake_up_q().

If wake_q_add() fails the cmpxchg() a concurrent wakeup is pending and
that can happen at any time after the cmpxchg(). This means we should
not rely on the wakeup happening at wake_q_up(), but should be ready
for wake_q_add() to issue the wakeup.

The delay; if provided (most likely); should only result in more efficient
behaviour.

Reported-by: Yongji Xie 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Davidlohr Bueso 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Waiman Long 
Cc: Will Deacon 
Signed-off-by: Ingo Molnar

fork: fix some -Wmissing-prototypes warnings

2019-01-04T21:13:47+00:00

We get a warning when building kernel with W=1:

  kernel/fork.c:167:13: warning: no previous prototype for `arch_release_thread_stack' [-Wmissing-prototypes]
  kernel/fork.c:779:13: warning: no previous prototype for `fork_init' [-Wmissing-prototypes]

Add the missing declaration in head file to fix this.

Also, remove arch_release_thread_stack() completely because no arch
seems to implement it since bb9d81264 (arch: remove tile port).

Link: http://lkml.kernel.org/r/1542170087-23645-1-git-send-email-wang.yi59@zte.com.cn
Signed-off-by: Yi Wang 
Acked-by: Michal Hocko 
Acked-by: Mike Rapoport 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sched/cpufreq: Prepare schedutil for Energy Aware Scheduling

2018-12-11T14:16:58+00:00

Schedutil requests frequency by aggregating utilization signals from
the scheduler (CFS, RT, DL, IRQ) and applying a 25% margin on top of
them. Since Energy Aware Scheduling (EAS) needs to be able to predict
the frequency requests, it needs to forecast the decisions made by the
governor.

In order to prepare the introduction of EAS, introduce
schedutil_freq_util() to centralize the aforementioned signal
aggregation and make it available to both schedutil and EAS. Since
frequency selection and energy estimation still need to deal with RT and
DL signals slightly differently, schedutil_freq_util() is called with a
different 'type' parameter in those two contexts, and returns an
aggregated utilization signal accordingly. While at it, introduce the
map_util_freq() function which is designed to make schedutil's 25%
margin usable easily for both sugov and EAS.

As EAS will be able to predict schedutil's frequency requests more
accurately than any other governor by design, it'd be sensible to make
sure EAS cannot be used without schedutil. This will be done later, once
EAS has actually been introduced.

Suggested-by: Peter Zijlstra 
Signed-off-by: Quentin Perret 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Thomas Gleixner 
Cc: adharmap@codeaurora.org
Cc: chris.redpath@arm.com
Cc: currojerez@riseup.net
Cc: dietmar.eggemann@arm.com
Cc: edubezval@gmail.com
Cc: gregkh@linuxfoundation.org
Cc: javi.merino@kernel.org
Cc: joel@joelfernandes.org
Cc: juri.lelli@redhat.com
Cc: morten.rasmussen@arm.com
Cc: patrick.bellasi@arm.com
Cc: pkondeti@codeaurora.org
Cc: rjw@rjwysocki.net
Cc: skannan@codeaurora.org
Cc: smuckle@google.com
Cc: srinivas.pandruvada@linux.intel.com
Cc: thara.gopinath@linaro.org
Cc: tkjos@google.com
Cc: valentin.schneider@arm.com
Cc: vincent.guittot@linaro.org
Cc: viresh.kumar@linaro.org
Link: https://lkml.kernel.org/r/20181203095628.11858-3-quentin.perret@arm.com
Signed-off-by: Ingo Molnar

sched/topology: Relocate arch_scale_cpu_capacity() to the internal header

2018-12-11T14:16:58+00:00

By default, arch_scale_cpu_capacity() is only visible from within the
kernel/sched folder. Relocate it to include/linux/sched/topology.h to
make it visible to other clients needing to know about the capacity of
CPUs, such as the Energy Model framework.

This also shrinks the  public header.

Signed-off-by: Quentin Perret 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: adharmap@codeaurora.org
Cc: chris.redpath@arm.com
Cc: currojerez@riseup.net
Cc: dietmar.eggemann@arm.com
Cc: edubezval@gmail.com
Cc: gregkh@linuxfoundation.org
Cc: javi.merino@kernel.org
Cc: joel@joelfernandes.org
Cc: juri.lelli@redhat.com
Cc: morten.rasmussen@arm.com
Cc: patrick.bellasi@arm.com
Cc: pkondeti@codeaurora.org
Cc: rjw@rjwysocki.net
Cc: skannan@codeaurora.org
Cc: smuckle@google.com
Cc: srinivas.pandruvada@linux.intel.com
Cc: thara.gopinath@linaro.org
Cc: tkjos@google.com
Cc: valentin.schneider@arm.com
Cc: vincent.guittot@linaro.org
Cc: viresh.kumar@linaro.org
Link: https://lkml.kernel.org/r/20181203095628.11858-2-quentin.perret@arm.com
Signed-off-by: Ingo Molnar

sched/topology: Remove the ::smt_gain field from 'struct sched_domain'

2018-12-11T14:16:57+00:00

::smt_gain is used to compute the capacity of CPUs of a SMT core with the
constraint 1 < ::smt_gain < 2 in order to be able to compute number of CPUs
per core. The field has_free_capacity of struct numa_stat, which was the
last user of this computation of number of CPUs per core, has been removed
by:

  2d4056fafa19 ("sched/numa: Remove numa_has_capacity()")

We can now remove this constraint on core capacity and use the defautl value
SCHED_CAPACITY_SCALE for SMT CPUs. With this remove, SCHED_CAPACITY_SCALE
becomes the maximum compute capacity of CPUs on every systems. This should
help to simplify some code and remove fields like rd->max_cpu_capacity

Furthermore, arch_scale_cpu_capacity() is used with a NULL sd in several other
places in the code when it wants the capacity of a CPUs to scale
some metrics like in pelt, deadline or schedutil. In case on SMT, the value
returned is not the capacity of SMT CPUs but default SCHED_CAPACITY_SCALE.

So remove it.

Signed-off-by: Vincent Guittot 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1535548752-4434-4-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar

sched: Fix various typos in comments

2018-12-03T10:55:42+00:00

Go over the scheduler source code and fix common typos
in comments - and a typo in an actual variable name.

No change in functionality intended.

Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Linus Torvalds 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

x86/speculation: Rework SMT state change

2018-11-28T10:57:07+00:00

arch_smt_update() is only called when the sysfs SMT control knob is
changed. This means that when SMT is enabled in the sysfs control knob the
system is considered to have SMT active even if all siblings are offline.

To allow finegrained control of the speculation mitigations, the actual SMT
state is more interesting than the fact that siblings could be enabled.

Rework the code, so arch_smt_update() is invoked from each individual CPU
hotplug function, and simplify the update function while at it.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Andy Lutomirski 
Cc: Linus Torvalds 
Cc: Jiri Kosina 
Cc: Tom Lendacky 
Cc: Josh Poimboeuf 
Cc: Andrea Arcangeli 
Cc: David Woodhouse 
Cc: Tim Chen 
Cc: Andi Kleen 
Cc: Dave Hansen 
Cc: Casey Schaufler 
Cc: Asit Mallick 
Cc: Arjan van de Ven 
Cc: Jon Masters 
Cc: Waiman Long 
Cc: Greg KH 
Cc: Dave Stewart 
Cc: Kees Cook 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181125185004.521974984@linutronix.de

sched/smt: Expose sched_smt_present static key

2018-11-28T10:57:07+00:00

Make the scheduler's 'sched_smt_present' static key globaly available, so
it can be used in the x86 speculation control code.

Provide a query function and a stub for the CONFIG_SMP=n case.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Andy Lutomirski 
Cc: Linus Torvalds 
Cc: Jiri Kosina 
Cc: Tom Lendacky 
Cc: Josh Poimboeuf 
Cc: Andrea Arcangeli 
Cc: David Woodhouse 
Cc: Tim Chen 
Cc: Andi Kleen 
Cc: Dave Hansen 
Cc: Casey Schaufler 
Cc: Asit Mallick 
Cc: Arjan van de Ven 
Cc: Jon Masters 
Cc: Waiman Long 
Cc: Greg KH 
Cc: Dave Stewart 
Cc: Kees Cook 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181125185004.430168326@linutronix.de

Merge tag 'pm-4.20-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

2018-10-30T16:08:07+00:00

Pull more power management updates from Rafael Wysocki:
 "These remove a questionable heuristic from the menu cpuidle governor,
  fix a recent build regression in the intel_pstate driver, clean up ARM
  big-Little support in cpufreq and fix up hung task watchdog's
  interaction with system-wide power management transitions.

  Specifics:

   - Fix build regression in the intel_pstate driver that doesn't build
     without CONFIG_ACPI after recent changes (Dominik Brodowski).

   - One of the heuristics in the menu cpuidle governor is based on a
     function returning 0 most of the time, so drop it and clean up the
     scheduler code related to it (Daniel Lezcano).

   - Prevent the arm_big_little cpufreq driver from being used on ARM64
     which is not suitable for it and drop the arm_big_little_dt driver
     that is not used any more (Sudeep Holla).

   - Prevent the hung task watchdog from triggering during resume from
     system-wide sleep states by disabling it before freezing tasks and
     enabling it again after they have been thawed (Vitaly Kuznetsov)"

* tag 'pm-4.20-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  kernel: hung_task.c: disable on suspend
  cpufreq: remove unused arm_big_little_dt driver
  cpufreq: drop ARM_BIG_LITTLE_CPUFREQ support for ARM64
  cpufreq: intel_pstate: Fix compilation for !CONFIG_ACPI
  cpuidle: menu: Remove get_loadavg() from the performance multiplier
  sched: Factor out nr_iowait and nr_iowait_cpu