Commit Graph

911 Commits

Author SHA1 Message Date
Randy Dunlap
2064a5ab04 sched/core: Fix kernel-doc warnings after code movement
Fix the following kernel-doc warnings after code restructuring:

  ../kernel/sched/core.c:5113: warning: No description found for parameter 't'
  ../kernel/sched/core.c:5113: warning: Excess function parameter 'interval' description in 'sched_rr_get_interval'

	get rid of set_fs()")

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: abca5fc535 ("sched_rr_get_interval(): move compat to native,
Link: http://lkml.kernel.org/r/995c6ded-b32e-bbe4-d9f5-4d42d121aff1@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-12-11 16:10:42 +01:00
Linus Torvalds
93f30c73ec Merge branch 'misc.compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull compat and uaccess updates from Al Viro:

 - {get,put}_compat_sigset() series

 - assorted compat ioctl stuff

 - more set_fs() elimination

 - a few more timespec64 conversions

 - several removals of pointless access_ok() in places where it was
   followed only by non-__ variants of primitives

* 'misc.compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (24 commits)
  coredump: call do_unlinkat directly instead of sys_unlink
  fs: expose do_unlinkat for built-in callers
  ext4: take handling of EXT4_IOC_GROUP_ADD into a helper, get rid of set_fs()
  ipmi: get rid of pointless access_ok()
  pi433: sanitize ioctl
  cxlflash: get rid of pointless access_ok()
  mtdchar: get rid of pointless access_ok()
  r128: switch compat ioctls to drm_ioctl_kernel()
  selection: get rid of field-by-field copyin
  VT_RESIZEX: get rid of field-by-field copyin
  i2c compat ioctls: move to ->compat_ioctl()
  sched_rr_get_interval(): move compat to native, get rid of set_fs()
  mips: switch to {get,put}_compat_sigset()
  sparc: switch to {get,put}_compat_sigset()
  s390: switch to {get,put}_compat_sigset()
  ppc: switch to {get,put}_compat_sigset()
  parisc: switch to {get,put}_compat_sigset()
  get_compat_sigset()
  get rid of {get,put}_compat_itimerspec()
  io_getevents: Use timespec64 to represent timeouts
  ...
2017-11-17 11:54:55 -08:00
Linus Torvalds
22714a2ba4 Merge branch 'for-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo:
 "Cgroup2 cpu controller support is finally merged.

   - Basic cpu statistics support to allow monitoring by default without
     the CPU controller enabled.

   - cgroup2 cpu controller support.

   - /sys/kernel/cgroup files to help dealing with new / optional
     features"

* 'for-4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: export list of cgroups v2 features using sysfs
  cgroup: export list of delegatable control files using sysfs
  cgroup: mark @cgrp __maybe_unused in cpu_stat_show()
  MAINTAINERS: relocate cpuset.c
  cgroup, sched: Move basic cpu stats from cgroup.stat to cpu.stat
  sched: Implement interface for cgroup unified hierarchy
  sched: Misc preps for cgroup unified hierarchy interface
  sched/cputime: Add dummy cputime_adjust() implementation for CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
  cgroup: statically initialize init_css_set->dfl_cgrp
  cgroup: Implement cgroup2 basic CPU usage accounting
  cpuacct: Introduce cgroup_account_cputime[_field]()
  sched/cputime: Expose cputime_adjust()
2017-11-15 14:29:44 -08:00
Linus Torvalds
3e2014637c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
 "The main updates in this cycle were:

   - Group balancing enhancements and cleanups (Brendan Jackman)

   - Move CPU isolation related functionality into its separate
     kernel/sched/isolation.c file, with related 'housekeeping_*()'
     namespace and nomenclature et al. (Frederic Weisbecker)

   - Improve the interactive/cpu-intense fairness calculation (Josef
     Bacik)

   - Improve the PELT code and related cleanups (Peter Zijlstra)

   - Improve the logic of pick_next_task_fair() (Uladzislau Rezki)

   - Improve the RT IPI based balancing logic (Steven Rostedt)

   - Various micro-optimizations:

   - better !CONFIG_SCHED_DEBUG optimizations (Patrick Bellasi)

   - better idle loop (Cheng Jian)

   - ... plus misc fixes, cleanups and updates"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
  sched/core: Optimize sched_feat() for !CONFIG_SCHED_DEBUG builds
  sched/sysctl: Fix attributes of some extern declarations
  sched/isolation: Document isolcpus= boot parameter flags, mark it deprecated
  sched/isolation: Add basic isolcpus flags
  sched/isolation: Move isolcpus= handling to the housekeeping code
  sched/isolation: Handle the nohz_full= parameter
  sched/isolation: Introduce housekeeping flags
  sched/isolation: Split out new CONFIG_CPU_ISOLATION=y config from CONFIG_NO_HZ_FULL
  sched/isolation: Rename is_housekeeping_cpu() to housekeeping_cpu()
  sched/isolation: Use its own static key
  sched/isolation: Make the housekeeping cpumask private
  sched/isolation: Provide a dynamic off-case to housekeeping_any_cpu()
  sched/isolation, watchdog: Use housekeeping_cpumask() instead of ad-hoc version
  sched/isolation: Move housekeeping related code to its own file
  sched/idle: Micro-optimize the idle loop
  sched/isolcpus: Fix "isolcpus=" boot parameter handling when !CONFIG_CPUMASK_OFFSTACK
  x86/tsc: Append the 'tsc=' description for the 'tsc=unstable' boot parameter
  sched/rt: Simplify the IPI based RT balancing logic
  block/ioprio: Use a helper to check for RT prio
  sched/rt: Add a helper to test for a RT task
  ...
2017-11-13 13:37:52 -08:00
Patrick Bellasi
765cc3a4b2 sched/core: Optimize sched_feat() for !CONFIG_SCHED_DEBUG builds
When the kernel is compiled with !CONFIG_SCHED_DEBUG support, we expect that
all SCHED_FEAT are turned into compile time constants being propagated
to support compiler optimizations.

Specifically, we expect that code blocks like this:

   if (sched_feat(FEATURE_NAME) [&& <other_conditions>]) {
	/* FEATURE CODE */
   }

are turned into dead-code in case FEATURE_NAME defaults to FALSE, and thus
being removed by the compiler from the finale image.

For this mechanism to properly work it's required for the compiler to
have full access, from each translation unit, to whatever is the value
defined by the sched_feat macro. This macro is defined as:

   #define sched_feat(x) (sysctl_sched_features & (1UL << __SCHED_FEAT_##x))

and thus, the compiler can optimize that code only if the value of
sysctl_sched_features is visible within each translation unit.

Since:

   029632fbb ("sched: Make separate sched*.c translation units")

the scheduler code has been split into separate translation units
however the definition of sysctl_sched_features is part of
kernel/sched/core.c while, for all the other scheduler modules, it is
visible only via kernel/sched/sched.h as an:

   extern const_debug unsigned int sysctl_sched_features

Unfortunately, an extern reference does not allow the compiler to apply
constants propagation. Thus, on !CONFIG_SCHED_DEBUG kernel we still end up
with code to load a memory reference and (eventually) doing an unconditional
jump of a chunk of code.

This mechanism is unavoidable when sched_features can be turned on and off at
run-time. However, this is not the case for "production" kernels compiled with
!CONFIG_SCHED_DEBUG. In this case, sysctl_sched_features is just a constant value
which cannot be changed at run-time and thus memory loads and jumps can be
avoided altogether.

This patch fixes the case of !CONFIG_SCHED_DEBUG kernel by declaring a local version
of the sysctl_sched_features constant for each translation unit. This will
ultimately allow the compiler to perform constants propagation and dead-code
pruning.

Tests have been done, with !CONFIG_SCHED_DEBUG on a v4.14-rc8 with and without
the patch, by running 30 iterations of:

   perf bench sched messaging --pipe --thread --group 4 --loop 50000

on a 40 cores Intel(R) Xeon(R) CPU E5-2690 v2 @ 3.00GHz using the
powersave governor to rule out variations due to frequency scaling.

Statistics on the reported completion time:

                   count     mean       std     min       99%     max
  v4.14-rc8         30.0  15.7831  0.176032  15.442  16.01226  16.014
  v4.14-rc8+patch   30.0  15.5033  0.189681  15.232  15.93938  15.962

... show a 1.8% speedup on average completion time and 0.5% speedup in the
99 percentile.

Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Brendan Jackman <brendan.jackman@arm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: http://lkml.kernel.org/r/20171108184101.16006-1-patrick.bellasi@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-11-09 07:35:08 +01:00
Frederic Weisbecker
edb9382175 sched/isolation: Move isolcpus= handling to the housekeeping code
We want to centralize the isolation features, to be done by the housekeeping
subsystem and scheduler domain isolation is a significant part of it.

No intended behaviour change, we just reuse the housekeeping cpumask
and core code.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1509072159-31808-11-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-10-27 09:55:30 +02:00
Frederic Weisbecker
de201559df sched/isolation: Introduce housekeeping flags
Before we implement isolcpus under housekeeping, we need the isolation
features to be more finegrained. For example some people want NOHZ_FULL
without the full scheduler isolation, others want full scheduler
isolation without NOHZ_FULL.

So let's cut all these isolation features piecewise, at the risk of
overcutting it right now. We can still merge some flags later if they
always make sense together.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1509072159-31808-9-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-10-27 09:55:29 +02:00
Frederic Weisbecker
204c083a00 sched/isolation: Rename is_housekeeping_cpu() to housekeeping_cpu()
Fit it into the housekeeping_*() namespace.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1509072159-31808-7-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-10-27 09:55:28 +02:00
Frederic Weisbecker
7863406143 sched/isolation: Move housekeeping related code to its own file
The housekeeping code is currently tied to the NOHZ code. As we are
planning to make housekeeping independent from it, start with moving
the relevant code to its own file.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1509072159-31808-2-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-10-27 09:55:24 +02:00
Tejun Heo
d41bf8c9de cgroup, sched: Move basic cpu stats from cgroup.stat to cpu.stat
The basic cpu stat is currently shown with "cpu." prefix in
cgroup.stat, and the same information is duplicated in cpu.stat when
cpu controller is enabled.  This is ugly and not very scalable as we
want to expand the coverage of stat information which is always
available.

This patch makes cgroup core always create "cpu.stat" file and show
the basic cpu stat there and calls the cpu controller to show the
extra stats when enabled.  This ensures that the same information
isn't presented in multiple places and makes future expansion of basic
stats easier.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2017-10-26 10:56:33 -07:00
Paul E. McKenney
ad4e25a3a1 Merge branches 'doc.2017.10.20a', 'fixes.2017.10.19a', 'stall.2017.10.09a' and 'torture.2017.10.09a' into HEAD
doc.2017.10.20a: Documentation updates.
fixes.2017.10.19a: Miscellaneous fixes.
stall.2017.10.09a: RCU CPU stall-warning updates.
torture.2017.10.09a: Torture-test updates.
2017-10-20 11:11:15 -07:00
Paul E. McKenney
0032f4e889 rcutorture: Dump writer stack if stalled
Right now, rcutorture warns if an rcu_torture_writer() kthread stalls,
but this warning is not always all that helpful.  This commit therefore
makes the first such warning include a stack dump.

This in turn requires that sched_show_task() be exported to GPL modules,
so this commit makes that change as well.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-10-09 14:26:09 -07:00
Paul E. McKenney
f79c3ad618 sched,rcu: Make cond_resched() provide RCU quiescent state
There is some confusion as to which of cond_resched() or
cond_resched_rcu_qs() should be added to long in-kernel loops.
This commit therefore eliminates the decision by adding RCU quiescent
states to cond_resched().  This commit also simplifies the code that
used to interact with cond_resched_rcu_qs(), and that now interacts with
cond_resched(), to reduce its overhead.  This reduction is necessary to
allow the heavier-weight cond_resched_rcu_qs() mechanism to be invoked
everywhere that cond_resched() is invoked.

Part of that reduction in overhead converts the jiffies_till_sched_qs
kernel parameter to read-only at runtime, thus eliminating the need for
bounds checking.

Reported-by: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
[ paulmck: Keep PREEMPT=n cond_resched a no-op, per Peter Zijlstra. ]
2017-10-09 14:25:17 -07:00
Paul E. McKenney
7c2102e56a sched: Make resched_cpu() unconditional
The current implementation of synchronize_sched_expedited() incorrectly
assumes that resched_cpu() is unconditional, which it is not.  This means
that synchronize_sched_expedited() can hang when resched_cpu()'s trylock
fails as follows (analysis by Neeraj Upadhyay):

o	CPU1 is waiting for expedited wait to complete:

	sync_rcu_exp_select_cpus
	     rdp->exp_dynticks_snap & 0x1   // returns 1 for CPU5
	     IPI sent to CPU5

	synchronize_sched_expedited_wait
		 ret = swait_event_timeout(rsp->expedited_wq,
					   sync_rcu_preempt_exp_done(rnp_root),
					   jiffies_stall);

	expmask = 0x20, CPU 5 in idle path (in cpuidle_enter())

o	CPU5 handles IPI and fails to acquire rq lock.

	Handles IPI
	     sync_sched_exp_handler
		 resched_cpu
		     returns while failing to try lock acquire rq->lock
		 need_resched is not set

o	CPU5 calls  rcu_idle_enter() and as need_resched is not set, goes to
	idle (schedule() is not called).

o	CPU 1 reports RCU stall.

Given that resched_cpu() is now used only by RCU, this commit fixes the
assumption by making resched_cpu() unconditional.

Reported-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Suggested-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
2017-10-09 14:24:14 -07:00
Tejun Heo
0d5936344f sched: Implement interface for cgroup unified hierarchy
There are a couple interface issues which can be addressed in cgroup2
interface.

* Stats from cpuacct being reported separately from the cpu stats.

* Use of different time units.  Writable control knobs use
  microseconds, some stat fields use nanoseconds while other cpuacct
  stat fields use centiseconds.

* Control knobs which can't be used in the root cgroup still show up
  in the root.

* Control knob names and semantics aren't consistent with other
  controllers.

This patchset implements cpu controller's interface on cgroup2 which
adheres to the controller file conventions described in
Documentation/cgroups/cgroup-v2.txt.  Overall, the following changes
are made.

* cpuacct is implictly enabled and disabled by cpu and its information
  is reported through "cpu.stat" which now uses microseconds for all
  time durations.  All time duration fields now have "_usec" appended
  to them for clarity.

  Note that cpuacct.usage_percpu is currently not included in
  "cpu.stat".  If this information is actually called for, it will be
  added later.

* "cpu.shares" is replaced with "cpu.weight" and operates on the
  standard scale defined by CGROUP_WEIGHT_MIN/DFL/MAX (1, 100, 10000).
  The weight is scaled to scheduler weight so that 100 maps to 1024
  and the ratio relationship is preserved - if weight is W and its
  scaled value is S, W / 100 == S / 1024.  While the mapped range is a
  bit smaller than the orignal scheduler weight range, the dead zones
  on both sides are relatively small and covers wider range than the
  nice value mappings.  This file doesn't make sense in the root
  cgroup and isn't created on root.

* "cpu.weight.nice" is added. When read, it reads back the nice value
  which is closest to the current "cpu.weight".  When written, it sets
  "cpu.weight" to the weight value which matches the nice value.  This
  makes it easy to configure cgroups when they're competing against
  threads in threaded subtrees.

* "cpu.cfs_quota_us" and "cpu.cfs_period_us" are replaced by "cpu.max"
  which contains both quota and period.

v4: - Use cgroup2 basic usage stat as the information source instead
      of cpuacct.

v3: - Added "cpu.weight.nice" to allow using nice values when
      configuring the weight.  The feature is requested by PeterZ.
    - Merge the patch to enable threaded support on cpu and cpuacct.
    - Dropped the bits about getting rid of cpuacct from patch
      description as there is a pretty strong case for making cpuacct
      an implicit controller so that basic cpu usage stats are always
      available.
    - Documentation updated accordingly.  "cpu.rt.max" section is
      dropped for now.

v2: - cpu_stats_show() was incorrectly using CONFIG_FAIR_GROUP_SCHED
      for CFS bandwidth stats and also using raw division for u64.
      Use CONFIG_CFS_BANDWITH and do_div() instead.  "cpu.rt.max" is
      not included yet.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
2017-09-29 14:30:37 -07:00
Tejun Heo
a1f7164c7b sched: Misc preps for cgroup unified hierarchy interface
Make the following changes in preparation for the cpu controller
interface implementation for cgroup2.  This patch doesn't cause any
functional differences.

* s/cpu_stats_show()/cpu_cfs_stat_show()/

* s/cpu_files/cpu_legacy_files/

v2: Dropped cpuacct changes as it won't be used by cpu controller
    interface anymore.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
2017-09-29 14:30:36 -07:00
Vincent Guittot
9059393e4e sched/fair: Use reweight_entity() for set_user_nice()
Now that we directly change load_avg and propagate that change into
the sums, sys_nice() and co should do the same, otherwise its possible
to confuse load accounting when we migrate near the weight change.

Fixes-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
[ Added changelog, fixed the call condition. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/20170517095045.GA8420@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-09-29 19:35:14 +02:00
Peter Zijlstra
5d68cc95fb sched/debug: Ignore TASK_IDLE for SysRq-W
Markus reported that tasks in TASK_IDLE state are reported by SysRq-W,
which results in undesirable clutter.

Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-09-29 11:02:57 +02:00
Al Viro
abca5fc535 sched_rr_get_interval(): move compat to native, get rid of set_fs()
switch to using timespec64 internally, while we are at it

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-09-20 00:30:57 -04:00
Peter Zijlstra
4ff9083b8a sched/core: WARN() when migrating to an offline CPU
Migrating tasks to offline CPUs is a pretty big fail, warn about it.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.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/20170907150614.094206976@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-09-12 17:41:04 +02:00
Peter Zijlstra
50e7663233 sched/cpuset/pm: Fix cpuset vs. suspend-resume bugs
Cpusets vs. suspend-resume is _completely_ broken. And it got noticed
because it now resulted in non-cpuset usage breaking too.

On suspend cpuset_cpu_inactive() doesn't call into
cpuset_update_active_cpus() because it doesn't want to move tasks about,
there is no need, all tasks are frozen and won't run again until after
we've resumed everything.

But this means that when we finally do call into
cpuset_update_active_cpus() after resuming the last frozen cpu in
cpuset_cpu_active(), the top_cpuset will not have any difference with
the cpu_active_mask and this it will not in fact do _anything_.

So the cpuset configuration will not be restored. This was largely
hidden because we would unconditionally create identity domains and
mobile users would not in fact use cpusets much. And servers what do use
cpusets tend to not suspend-resume much.

An addition problem is that we'd not in fact wait for the cpuset work to
finish before resuming the tasks, allowing spurious migrations outside
of the specified domains.

Fix the rebuild by introducing cpuset_force_rebuild() and fix the
ordering with cpuset_wait_for_hotplug().

Reported-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: deb7aa308e ("cpuset: reorganize CPU / memory hotplug handling")
Link: http://lkml.kernel.org/r/20170907091338.orwxrqkbfkki3c24@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-09-07 11:45:21 +02:00
Linus Torvalds
5f82e71a00 Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Ingo Molnar:

 - Add 'cross-release' support to lockdep, which allows APIs like
   completions, where it's not the 'owner' who releases the lock, to be
   tracked. It's all activated automatically under
   CONFIG_PROVE_LOCKING=y.

 - Clean up (restructure) the x86 atomics op implementation to be more
   readable, in preparation of KASAN annotations. (Dmitry Vyukov)

 - Fix static keys (Paolo Bonzini)

 - Add killable versions of down_read() et al (Kirill Tkhai)

 - Rework and fix jump_label locking (Marc Zyngier, Paolo Bonzini)

 - Rework (and fix) tlb_flush_pending() barriers (Peter Zijlstra)

 - Remove smp_mb__before_spinlock() and convert its usages, introduce
   smp_mb__after_spinlock() (Peter Zijlstra)

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (56 commits)
  locking/lockdep/selftests: Fix mixed read-write ABBA tests
  sched/completion: Avoid unnecessary stack allocation for COMPLETION_INITIALIZER_ONSTACK()
  acpi/nfit: Fix COMPLETION_INITIALIZER_ONSTACK() abuse
  locking/pvqspinlock: Relax cmpxchg's to improve performance on some architectures
  smp: Avoid using two cache lines for struct call_single_data
  locking/lockdep: Untangle xhlock history save/restore from task independence
  locking/refcounts, x86/asm: Disable CONFIG_ARCH_HAS_REFCOUNT for the time being
  futex: Remove duplicated code and fix undefined behaviour
  Documentation/locking/atomic: Finish the document...
  locking/lockdep: Fix workqueue crossrelease annotation
  workqueue/lockdep: 'Fix' flush_work() annotation
  locking/lockdep/selftests: Add mixed read-write ABBA tests
  mm, locking/barriers: Clarify tlb_flush_pending() barriers
  locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE and CONFIG_LOCKDEP_COMPLETIONS truly non-interactive
  locking/lockdep: Explicitly initialize wq_barrier::done::map
  locking/lockdep: Rename CONFIG_LOCKDEP_COMPLETE to CONFIG_LOCKDEP_COMPLETIONS
  locking/lockdep: Reword title of LOCKDEP_CROSSRELEASE config
  locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE part of CONFIG_PROVE_LOCKING
  locking/refcounts, x86/asm: Implement fast refcount overflow protection
  locking/lockdep: Fix the rollback and overwrite detection logic in crossrelease
  ...
2017-09-04 11:52:29 -07:00
Linus Torvalds
f213a6c84c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
 "The main changes in this cycle were:

   - fix affine wakeups (Peter Zijlstra)

   - improve CPU onlining (and general bootup) scalability on systems
     with ridiculous number (thousands) of CPUs (Peter Zijlstra)

   - sched/numa updates (Rik van Riel)

   - sched/deadline updates (Byungchul Park)

   - sched/cpufreq enhancements and related cleanups (Viresh Kumar)

   - sched/debug enhancements (Xie XiuQi)

   - various fixes"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
  sched/debug: Optimize sched_domain sysctl generation
  sched/topology: Avoid pointless rebuild
  sched/topology, cpuset: Avoid spurious/wrong domain rebuilds
  sched/topology: Improve comments
  sched/topology: Fix memory leak in __sdt_alloc()
  sched/completion: Document that reinit_completion() must be called after complete_all()
  sched/autogroup: Fix error reporting printk text in autogroup_create()
  sched/fair: Fix wake_affine() for !NUMA_BALANCING
  sched/debug: Intruduce task_state_to_char() helper function
  sched/debug: Show task state in /proc/sched_debug
  sched/debug: Use task_pid_nr_ns in /proc/$pid/sched
  sched/core: Remove unnecessary initialization init_idle_bootup_task()
  sched/deadline: Change return value of cpudl_find()
  sched/deadline: Make find_later_rq() choose a closer CPU in topology
  sched/numa: Scale scan period with tasks in group and shared/private
  sched/numa: Slow down scan rate if shared faults dominate
  sched/pelt: Fix false running accounting
  sched: Mark pick_next_task_dl() and build_sched_domain() as static
  sched/cpupri: Don't re-initialize 'struct cpupri'
  sched/deadline: Don't re-initialize 'struct cpudl'
  ...
2017-09-04 09:10:24 -07:00
Ingo Molnar
94edf6f3c2 Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
Pull RCU updates from Paul E. McKenney:

 - Removal of spin_unlock_wait()
 - SRCU updates
 - Torture-test updates
 - Documentation updates
 - Miscellaneous fixes
 - CPU-hotplug fixes
 - Miscellaneous non-RCU fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-08-21 09:45:19 +02:00
Paul E. McKenney
656e7c0c0a Merge branches 'doc.2017.08.17a', 'fixes.2017.08.17a', 'hotplug.2017.07.25b', 'misc.2017.08.17a', 'spin_unlock_wait_no.2017.08.17a', 'srcu.2017.07.27c' and 'torture.2017.07.24c' into HEAD
doc.2017.08.17a: Documentation updates.
fixes.2017.08.17a: RCU fixes.
hotplug.2017.07.25b: CPU-hotplug updates.
misc.2017.08.17a: Miscellaneous fixes outside of RCU (give or take conflicts).
spin_unlock_wait_no.2017.08.17a: Remove spin_unlock_wait().
srcu.2017.07.27c: SRCU updates.
torture.2017.07.24c: Torture-test updates.
2017-08-17 08:10:04 -07:00
Mathieu Desnoyers
22e4ebb975 membarrier: Provide expedited private command
Implement MEMBARRIER_CMD_PRIVATE_EXPEDITED with IPIs using cpumask built
from all runqueues for which current thread's mm is the same as the
thread calling sys_membarrier. It executes faster than the non-expedited
variant (no blocking). It also works on NOHZ_FULL configurations.

Scheduler-wise, it requires a memory barrier before and after context
switching between processes (which have different mm). The memory
barrier before context switch is already present. For the barrier after
context switch:

* Our TSO archs can do RELEASE without being a full barrier. Look at
  x86 spin_unlock() being a regular STORE for example.  But for those
  archs, all atomics imply smp_mb and all of them have atomic ops in
  switch_mm() for mm_cpumask(), and on x86 the CR3 load acts as a full
  barrier.

* From all weakly ordered machines, only ARM64 and PPC can do RELEASE,
  the rest does indeed do smp_mb(), so there the spin_unlock() is a full
  barrier and we're good.

* ARM64 has a very heavy barrier in switch_to(), which suffices.

* PPC just removed its barrier from switch_to(), but appears to be
  talking about adding something to switch_mm(). So add a
  smp_mb__after_unlock_lock() for now, until this is settled on the PPC
  side.

Changes since v3:
- Properly document the memory barriers provided by each architecture.

Changes since v2:
- Address comments from Peter Zijlstra,
- Add smp_mb__after_unlock_lock() after finish_lock_switch() in
  finish_task_switch() to add the memory barrier we need after storing
  to rq->curr. This is much simpler than the previous approach relying
  on atomic_dec_and_test() in mmdrop(), which actually added a memory
  barrier in the common case of switching between userspace processes.
- Return -EINVAL when MEMBARRIER_CMD_SHARED is used on a nohz_full
  kernel, rather than having the whole membarrier system call returning
  -ENOSYS. Indeed, CMD_PRIVATE_EXPEDITED is compatible with nohz_full.
  Adapt the CMD_QUERY mask accordingly.

Changes since v1:
- move membarrier code under kernel/sched/ because it uses the
  scheduler runqueue,
- only add the barrier when we switch from a kernel thread. The case
  where we switch from a user-space thread is already handled by
  the atomic_dec_and_test() in mmdrop().
- add a comment to mmdrop() documenting the requirement on the implicit
  memory barrier.

CC: Peter Zijlstra <peterz@infradead.org>
CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: Andrew Hunter <ahh@google.com>
CC: Maged Michael <maged.michael@gmail.com>
CC: gromer@google.com
CC: Avi Kivity <avi@scylladb.com>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <paulus@samba.org>
CC: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Dave Watson <davejwatson@fb.com>
2017-08-17 07:28:05 -07:00
Paul E. McKenney
23a9b748a3 sched: Replace spin_unlock_wait() with lock/unlock pair
There is no agreed-upon definition of spin_unlock_wait()'s semantics,
and it appears that all callers could do just as well with a lock/unlock
pair.  This commit therefore replaces the spin_unlock_wait() call in
do_task_dead() with spin_lock() followed immediately by spin_unlock().
This should be safe from a performance perspective because the lock is
this tasks ->pi_lock, and this is called only after the task exits.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
[ paulmck: Drop smp_mb() based on Peter Zijlstra's analysis:
  http://lkml.kernel.org/r/20170811144150.26gowhxte7ri5fpk@hirez.programming.kicks-ass.net ]
2017-08-11 13:09:14 -07:00
Peter Zijlstra
d89e588ca4 locking: Introduce smp_mb__after_spinlock()
Since its inception, our understanding of ACQUIRE, esp. as applied to
spinlocks, has changed somewhat. Also, I wonder if, with a simple
change, we cannot make it provide more.

The problem with the comment is that the STORE done by spin_lock isn't
itself ordered by the ACQUIRE, and therefore a later LOAD can pass over
it and cross with any prior STORE, rendering the default WMB
insufficient (pointed out by Alan).

Now, this is only really a problem on PowerPC and ARM64, both of
which already defined smp_mb__before_spinlock() as a smp_mb().

At the same time, we can get a much stronger construct if we place
that same barrier _inside_ the spin_lock(). In that case we upgrade
the RCpc spinlock to an RCsc.  That would make all schedule() calls
fully transitive against one another.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-08-10 12:29:02 +02:00
Xie XiuQi
20435d84e5 sched/debug: Intruduce task_state_to_char() helper function
Now that we have more than one place to get the task state,
intruduce the task_state_to_char() helper function to save some code.

No functionality changed.

Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <cj.chengjian@huawei.com>
Cc: <huawei.libin@huawei.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/1502095463-160172-3-git-send-email-xiexiuqi@huawei.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-08-10 12:18:20 +02:00
Cheng Jian
18f08dae19 sched/core: Remove unnecessary initialization init_idle_bootup_task()
init_idle_bootup_task( ) is called in rest_init( ) to switch
the scheduling class of the boot thread to the idle class.

the function only sets:

    idle->sched_class = &idle_sched_class;

which has been set in init_idle() called by sched_init():

    /*
     * The idle tasks have their own, simple scheduling class:
     */
    idle->sched_class = &idle_sched_class;

We've already set the boot thread to idle class in
start_kernel()->sched_init()->init_idle()
so it's unnecessary to set it again in
start_kernel()->rest_init()->init_idle_bootup_task()

Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <akpm@linux-foundation.org>
Cc: <huawei.libin@huawei.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/1501838377-109720-1-git-send-email-cj.chengjian@huawei.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-08-10 12:18:18 +02:00
Viresh Kumar
5b713a3d94 sched/core: Reuse put_prev_task()
Reuse put_prev_task() instead of copying its implementation.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: linaro-kernel@lists.linaro.org
Link: http://lkml.kernel.org/r/e2e50578223d05c5e90a9feb964fe1ec5d09a052.1495603536.git.viresh.kumar@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-08-10 12:18:10 +02:00
Tejun Heo
955dbdf4ce sched: Allow migrating kthreads into online but inactive CPUs
Per-cpu workqueues have been tripping CPU affinity sanity checks while
a CPU is being offlined.  A per-cpu kworker ends up running on a CPU
which isn't its target CPU while the CPU is online but inactive.

While the scheduler allows kthreads to wake up on an online but
inactive CPU, it doesn't allow a running kthread to be migrated to
such a CPU, which leads to an odd situation where setting affinity on
a sleeping and running kthread leads to different results.

Each mem-reclaim workqueue has one rescuer which guarantees forward
progress and the rescuer needs to bind itself to the CPU which needs
help in making forward progress; however, due to the above issue,
while set_cpus_allowed_ptr() succeeds, the rescuer doesn't end up on
the correct CPU if the CPU is in the process of going offline,
tripping the sanity check and executing the work item on the wrong
CPU.

This patch updates __migrate_task() so that kthreads can be migrated
into an inactive but online CPU.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-07-28 13:49:53 -07:00
Jonathan Corbet
bf50f0e8a0 sched/core: Fix some documentation build warnings
The kerneldoc comments for try_to_wake_up_local() were out of date, leading
to these documentation build warnings:

  ./kernel/sched/core.c:2080: warning: No description found for parameter 'rf'
  ./kernel/sched/core.c:2080: warning: Excess function parameter 'cookie' description in 'try_to_wake_up_local'

Update the comment to reflect current reality and give us some peace and
quiet.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-doc@vger.kernel.org
Link: http://lkml.kernel.org/r/20170724135628.695cecfc@lwn.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-07-25 11:17:02 +02:00
Linus Torvalds
9bd42183b9 Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
 "The main changes in this cycle were:

   - Add the SYSTEM_SCHEDULING bootup state to move various scheduler
     debug checks earlier into the bootup. This turns silent and
     sporadically deadly bugs into nice, deterministic splats. Fix some
     of the splats that triggered. (Thomas Gleixner)

   - A round of restructuring and refactoring of the load-balancing and
     topology code (Peter Zijlstra)

   - Another round of consolidating ~20 of incremental scheduler code
     history: this time in terms of wait-queue nomenclature. (I didn't
     get much feedback on these renaming patches, and we can still
     easily change any names I might have misplaced, so if anyone hates
     a new name, please holler and I'll fix it.) (Ingo Molnar)

   - sched/numa improvements, fixes and updates (Rik van Riel)

   - Another round of x86/tsc scheduler clock code improvements, in hope
     of making it more robust (Peter Zijlstra)

   - Improve NOHZ behavior (Frederic Weisbecker)

   - Deadline scheduler improvements and fixes (Luca Abeni, Daniel
     Bristot de Oliveira)

   - Simplify and optimize the topology setup code (Lauro Ramos
     Venancio)

   - Debloat and decouple scheduler code some more (Nicolas Pitre)

   - Simplify code by making better use of llist primitives (Byungchul
     Park)

   - ... plus other fixes and improvements"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (103 commits)
  sched/cputime: Refactor the cputime_adjust() code
  sched/debug: Expose the number of RT/DL tasks that can migrate
  sched/numa: Hide numa_wake_affine() from UP build
  sched/fair: Remove effective_load()
  sched/numa: Implement NUMA node level wake_affine()
  sched/fair: Simplify wake_affine() for the single socket case
  sched/numa: Override part of migrate_degrades_locality() when idle balancing
  sched/rt: Move RT related code from sched/core.c to sched/rt.c
  sched/deadline: Move DL related code from sched/core.c to sched/deadline.c
  sched/cpuset: Only offer CONFIG_CPUSETS if SMP is enabled
  sched/fair: Spare idle load balancing on nohz_full CPUs
  nohz: Move idle balancer registration to the idle path
  sched/loadavg: Generalize "_idle" naming to "_nohz"
  sched/core: Drop the unused try_get_task_struct() helper function
  sched/fair: WARN() and refuse to set buddy when !se->on_rq
  sched/debug: Fix SCHED_WARN_ON() to return a value on !CONFIG_SCHED_DEBUG as well
  sched/wait: Disambiguate wq_entry->task_list and wq_head->task_list naming
  sched/wait: Move bit_wait_table[] and related functionality from sched/core.c to sched/wait_bit.c
  sched/wait: Split out the wait_bit*() APIs from <linux/wait.h> into <linux/wait_bit.h>
  sched/wait: Re-adjust macro line continuation backslashes in <linux/wait.h>
  ...
2017-07-03 13:08:04 -07:00
Linus Torvalds
330e9e4625 Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU updates from Ingo Molnar:
 "The sole purpose of these changes is to shrink and simplify the RCU
  code base, which has suffered from creeping bloat over the past couple
  of years. The end result is a net removal of ~2700 lines of code:

     79 files changed, 1496 insertions(+), 4211 deletions(-)

  Plus there's a marked reduction in the Kconfig space complexity as
  well, here's the number of matches on 'grep RCU' in the .config:

                               before       after

     x86-defconfig                 17          15
     x86-allmodconfig              33          20"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (86 commits)
  rcu: Remove RCU CPU stall warnings from Tiny RCU
  rcu: Remove event tracing from Tiny RCU
  rcu: Move RCU debug Kconfig options to kernel/rcu
  rcu: Move RCU non-debug Kconfig options to kernel/rcu
  rcu: Eliminate NOCBs CPU-state Kconfig options
  rcu: Remove debugfs tracing
  srcu: Remove Classic SRCU
  srcu: Fix rcutorture-statistics typo
  rcu: Remove SPARSE_RCU_POINTER Kconfig option
  rcu: Remove the now-obsolete PROVE_RCU_REPEATEDLY Kconfig option
  rcu: Remove typecheck() from RCU locking wrapper functions
  rcu: Remove #ifdef moving rcu_end_inkernel_boot from rcupdate.h
  rcu: Remove nohz_full full-system-idle state machine
  rcu: Remove the RCU_KTHREAD_PRIO Kconfig option
  rcu: Remove *_SLOW_* Kconfig options
  srcu: Use rnp->lock wrappers to replace explicit memory barriers
  rcu: Move rnp->lock wrappers for SRCU use
  rcu: Convert rnp->lock wrappers to macros for SRCU use
  rcu: Refactor #includes from include/linux/rcupdate.h
  bcm47xx: Fix build regression
  ...
2017-07-03 11:34:53 -07:00
Nicolas Pitre
8887cd9903 sched/rt: Move RT related code from sched/core.c to sched/rt.c
This helps making sched/core.c smaller and hopefully easier to understand and maintain.

Signed-off-by: Nicolas Pitre <nico@linaro.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/20170621182203.30626-3-nicolas.pitre@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-23 10:46:45 +02:00
Nicolas Pitre
06a76fe08d sched/deadline: Move DL related code from sched/core.c to sched/deadline.c
This helps making sched/core.c smaller and hopefully easier to understand and maintain.

Signed-off-by: Nicolas Pitre <nico@linaro.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/20170621182203.30626-2-nicolas.pitre@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-23 10:46:45 +02:00
Nicolas Pitre
e1d4eeec5a sched/cpuset: Only offer CONFIG_CPUSETS if SMP is enabled
Make CONFIG_CPUSETS=y depend on SMP as this feature makes no sense
on UP. This allows for configuring out cpuset_cpumask_can_shrink()
and task_can_attach() entirely, which shrinks the kernel a bit.

Signed-off-by: Nicolas Pitre <nico@linaro.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/20170614171926.8345-2-nicolas.pitre@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-23 10:46:44 +02:00
Ingo Molnar
902b319413 Merge branch 'WIP.sched/core' into sched/core
Conflicts:
	kernel/sched/Makefile

Pick up the waitqueue related renames - it didn't get much feedback,
so it appears to be uncontroversial. Famous last words? ;-)

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-20 12:28:21 +02:00
Ingo Molnar
5822a454d6 sched/wait: Move bit_wait_table[] and related functionality from sched/core.c to sched/wait_bit.c
The key hashed waitqueue data structures and their initialization
was done in the main scheduler file for no good reason, move them
to sched/wait_bit.c instead.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-20 12:19:14 +02:00
Ingo Molnar
ac6424b981 sched/wait: Rename wait_queue_t => wait_queue_entry_t
Rename:

	wait_queue_t		=>	wait_queue_entry_t

'wait_queue_t' was always a slight misnomer: its name implies that it's a "queue",
but in reality it's a queue *entry*. The 'real' queue is the wait queue head,
which had to carry the name.

Start sorting this out by renaming it to 'wait_queue_entry_t'.

This also allows the real structure name 'struct __wait_queue' to
lose its double underscore and become 'struct wait_queue_entry',
which is the more canonical nomenclature for such data types.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-20 12:18:27 +02:00
Andy Lutomirski
252d2a4117 sched/core: Idle_task_exit() shouldn't use switch_mm_irqs_off()
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: f98db6013c ("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>
2017-06-11 10:58:17 +02:00
Paul E. McKenney
d7d34d5e46 sched: Rely on synchronize_rcu_mult() de-duplication
The synchronize_rcu_mult() function now detects duplicate requests
for the same grace-period flavor and waits only once for each flavor.
This commit therefore removes the ugly #ifdef from sched_cpu_deactivate()
because synchronize_rcu_mult(call_rcu, call_rcu_sched) now does what
the #ifdef used to be needed for.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
2017-06-08 08:25:39 -07:00
Nicolas Pitre
f5832c1998 sched/core: Omit building stop_sched_class when !SMP
The stop class is invoked through stop_machine only.
This is dead code on UP builds.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170529210302.26868-3-nicolas.pitre@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-08 10:32:04 +02:00
Daniel Bristot de Oliveira
3effcb4247 sched/deadline: Use the revised wakeup rule for suspending constrained dl tasks
We have been facing some problems with self-suspending constrained
deadline tasks. The main reason is that the original CBS was not
designed for such sort of tasks.

One problem reported by Xunlei Pang takes place when a task
suspends, and then is awakened before the deadline, but so close
to the deadline that its remaining runtime can cause the task
to have an absolute density higher than allowed. In such situation,
the original CBS assumes that the task is facing an early activation,
and so it replenishes the task and set another deadline, one deadline
in the future. This rule works fine for implicit deadline tasks.
Moreover, it allows the system to adapt the period of a task in which
the external event source suffered from a clock drift.

However, this opens the window for bandwidth leakage for constrained
deadline tasks. For instance, a task with the following parameters:

  runtime   = 5 ms
  deadline  = 7 ms
  [density] = 5 / 7 = 0.71
  period    = 1000 ms

If the task runs for 1 ms, and then suspends for another 1ms,
it will be awakened with the following parameters:

  remaining runtime = 4
  laxity = 5

presenting a absolute density of 4 / 5 = 0.80.

In this case, the original CBS would assume the task had an early
wakeup. Then, CBS will reset the runtime, and the absolute deadline will
be postponed by one relative deadline, allowing the task to run.

The problem is that, if the task runs this pattern forever, it will keep
receiving bandwidth, being able to run 1ms every 2ms. Following this
behavior, the task would be able to run 500 ms in 1 sec. Thus running
more than the 5 ms / 1 sec the admission control allowed it to run.

Trying to address the self-suspending case, Luca Abeni, Giuseppe
Lipari, and Juri Lelli [1] revisited the CBS in order to deal with
self-suspending tasks. In the new approach, rather than
replenishing/postponing the absolute deadline, the revised wakeup rule
adjusts the remaining runtime, reducing it to fit into the allowed
density.

A revised version of the idea is:

At a given time t, the maximum absolute density of a task cannot be
higher than its relative density, that is:

  runtime / (deadline - t) <= dl_runtime / dl_deadline

Knowing the laxity of a task (deadline - t), it is possible to move
it to the other side of the equality, thus enabling to define max
remaining runtime a task can use within the absolute deadline, without
over-running the allowed density:

  runtime = (dl_runtime / dl_deadline) * (deadline - t)

For instance, in our previous example, the task could still run:

  runtime = ( 5 / 7 ) * 5
  runtime = 3.57 ms

Without causing damage for other deadline tasks. It is note worthy
that the laxity cannot be negative because that would cause a negative
runtime. Thus, this patch depends on the patch:

  df8eac8caf ("sched/deadline: Throttle a constrained deadline task activated after the deadline")

Which throttles a constrained deadline task activated after the
deadline.

Finally, it is also possible to use the revised wakeup rule for
all other tasks, but that would require some more discussions
about pros and cons.

Reported-by: Xunlei Pang <xpang@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
[peterz: replaced dl_is_constrained with dl_is_implicit]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luca Abeni <luca.abeni@santannapisa.it>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Romulo Silva de Oliveira <romulo.deoliveira@ufsc.br>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Link: http://lkml.kernel.org/r/5c800ab3a74a168a84ee5f3f84d12a02e11383be.1495803804.git.bristot@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-08 10:32:03 +02:00
Luca Abeni
daec579836 sched/deadline: Reclaim bandwidth not used by dl tasks
This commit introduces a per-runqueue "extra utilization" that can be
reclaimed by deadline tasks. In this way, the maximum fraction of CPU
time that can reclaimed by deadline tasks is fixed (and configurable)
and does not depend on the total deadline utilization.
The GRUB accounting rule is modified to add this "extra utilization"
to the inactive utilization of the runqueue, and to avoid reclaiming
more than a maximum fraction of the CPU time.

Tested-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Luca Abeni <luca.abeni@santannapisa.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Claudio Scordino <claudio@evidence.eu.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Link: http://lkml.kernel.org/r/1495138417-6203-10-git-send-email-luca.abeni@santannapisa.it
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-08 10:31:55 +02:00
Luca Abeni
2d4283e9d5 sched/deadline: Make GRUB a task's flag
This patch introduces the SCHED_FLAG_RECLAIM flag to specify
that a DL task is allowed to reclaim unused CPU time (using
the GRUB algorithm).

Tested-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Luca Abeni <luca.abeni@santannapisa.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Claudio Scordino <claudio@evidence.eu.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Link: http://lkml.kernel.org/r/1495138417-6203-7-git-send-email-luca.abeni@santannapisa.it
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-08 10:31:52 +02:00
Luca Abeni
4da3abcefe sched/deadline: Do not reclaim the whole CPU bandwidth
Original GRUB tends to reclaim 100% of the CPU time... And this
allows a CPU hog to starve non-deadline tasks.
To address this issue, allow the scheduler to reclaim only a
specified fraction of CPU time, stored in the new "bw_ratio"
field of the dl runqueue structure.

Tested-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Luca Abeni <luca.abeni@santannapisa.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Claudio Scordino <claudio@evidence.eu.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Link: http://lkml.kernel.org/r/1495138417-6203-6-git-send-email-luca.abeni@santannapisa.it
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-08 10:31:51 +02:00
Luca Abeni
c52f14d384 sched/deadline: Implement GRUB accounting
According to the GRUB (Greedy Reclaimation of Unused Bandwidth)
reclaiming algorithm, the runtime is not decreased as "dq = -dt",
but as "dq = -Uact dt" (where Uact is the per-runqueue active
utilization).
Hence, this commit modifies the runtime accounting rule in
update_curr_dl() to implement the GRUB rule.

Tested-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Luca Abeni <luca.abeni@santannapisa.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Claudio Scordino <claudio@evidence.eu.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Link: http://lkml.kernel.org/r/1495138417-6203-5-git-send-email-luca.abeni@santannapisa.it
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-08 10:31:51 +02:00
Luca Abeni
387e31300b sched/deadline: Fix the update of the total -deadline utilization
Now that the inactive timer can be armed to fire at the 0-lag time,
it is possible to use inactive_task_timer() to update the total
-deadline utilization (dl_b->total_bw) at the correct time, fixing
dl_overflow() and __setparam_dl().

Tested-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Luca Abeni <luca.abeni@santannapisa.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Claudio Scordino <claudio@evidence.eu.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Link: http://lkml.kernel.org/r/1495138417-6203-4-git-send-email-luca.abeni@santannapisa.it
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-06-08 10:31:50 +02:00