Commit Graph

2952 Commits

Author SHA1 Message Date
Linus Torvalds b69bea8a65 A set of fixes for lockdep, tracing and RCU:
- Prevent recursion by using raw_cpu_* operations
 
   - Fixup the interrupt state in the cpu idle code to be consistent
 
   - Push rcu_idle_enter/exit() invocations deeper into the idle path so
     that the lock operations are inside the RCU watching sections
 
   - Move trace_cpu_idle() into generic code so it's called before RCU goes
     idle.
 
   - Handle raw_local_irq* vs. local_irq* operations correctly
 
   - Move the tracepoints out from under the lockdep recursion handling
     which turned out to be fragile and inconsistent.
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Merge tag 'locking-urgent-2020-08-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking fixes from Thomas Gleixner:
 "A set of fixes for lockdep, tracing and RCU:

   - Prevent recursion by using raw_cpu_* operations

   - Fixup the interrupt state in the cpu idle code to be consistent

   - Push rcu_idle_enter/exit() invocations deeper into the idle path so
     that the lock operations are inside the RCU watching sections

   - Move trace_cpu_idle() into generic code so it's called before RCU
     goes idle.

   - Handle raw_local_irq* vs. local_irq* operations correctly

   - Move the tracepoints out from under the lockdep recursion handling
     which turned out to be fragile and inconsistent"

* tag 'locking-urgent-2020-08-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  lockdep,trace: Expose tracepoints
  lockdep: Only trace IRQ edges
  mips: Implement arch_irqs_disabled()
  arm64: Implement arch_irqs_disabled()
  nds32: Implement arch_irqs_disabled()
  locking/lockdep: Cleanup
  x86/entry: Remove unused THUNKs
  cpuidle: Move trace_cpu_idle() into generic code
  cpuidle: Make CPUIDLE_FLAG_TLB_FLUSHED generic
  sched,idle,rcu: Push rcu_idle deeper into the idle path
  cpuidle: Fixup IRQ state
  lockdep: Use raw_cpu_*() for per-cpu variables
2020-08-30 11:43:50 -07:00
Peter Zijlstra 9864f5b594 cpuidle: Move trace_cpu_idle() into generic code
Remove trace_cpu_idle() from the arch_cpu_idle() implementations and
put it in the generic code, right before disabling RCU. Gets rid of
more trace_*_rcuidle() users.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Marco Elver <elver@google.com>
Link: https://lkml.kernel.org/r/20200821085348.428433395@infradead.org
2020-08-26 12:41:54 +02:00
Peter Zijlstra 1098582a0f sched,idle,rcu: Push rcu_idle deeper into the idle path
Lots of things take locks, due to a wee bug, rcu_lockdep didn't notice
that the locking tracepoints were using RCU.

Push rcu_idle_{enter,exit}() as deep as possible into the idle paths,
this also resolves a lot of _rcuidle()/RCU_NONIDLE() usage.

Specifically, sched_clock_idle_wakeup_event() will use ktime which
will use seqlocks which will tickle lockdep, and
stop_critical_timings() uses lock.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Marco Elver <elver@google.com>
Link: https://lkml.kernel.org/r/20200821085348.310943801@infradead.org
2020-08-26 12:41:53 +02:00
Gustavo A. R. Silva df561f6688 treewide: Use fallthrough pseudo-keyword
Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
2020-08-23 17:36:59 -05:00
Linus Torvalds 1195d58f00 Two fixes: fix a new tracepoint's output value, and fix the formatting of show-state syslog printouts.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-urgent-2020-08-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Ingo Molnar:
 "Two fixes: fix a new tracepoint's output value, and fix the formatting
  of show-state syslog printouts"

* tag 'sched-urgent-2020-08-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/debug: Fix the alignment of the show-state debug output
  sched: Fix use of count for nr_running tracepoint
2020-08-15 10:36:40 -07:00
Libing Zhou cc172ff301 sched/debug: Fix the alignment of the show-state debug output
Current sysrq(t) output task fields name are not aligned with
actual task fields value, e.g.:

	kernel: sysrq: Show State
	kernel:  task                        PC stack   pid father
	kernel: systemd         S12456     1      0 0x00000000
	kernel: Call Trace:
	kernel: ? __schedule+0x240/0x740

To make it more readable, print fields name together with task fields
value in the same line, with fixed width:

	kernel: sysrq: Show State
	kernel: task:systemd         state:S stack:12920 pid:    1 ppid:     0 flags:0x00000000
	kernel: Call Trace:
	kernel: __schedule+0x282/0x620

Signed-off-by: Libing Zhou <libing.zhou@nokia-sbell.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200814030236.37835-1-libing.zhou@nokia-sbell.com
2020-08-14 12:36:18 +02:00
Linus Torvalds 6d2b84a4e5 This tree adds the sched_set_fifo*() encapsulation APIs to remove
static priority level knowledge from non-scheduler code.
 
 The three APIs for non-scheduler code to set SCHED_FIFO are:
 
  - sched_set_fifo()
  - sched_set_fifo_low()
  - sched_set_normal()
 
 These are two FIFO priority levels: default (high), and a 'low' priority level,
 plus sched_set_normal() to set the policy back to non-SCHED_FIFO.
 
 Since the changes affect a lot of non-scheduler code, we kept this in a separate
 tree.
 
 When merging to the latest upstream tree there's a conflict in drivers/spi/spi.c,
 which can be resolved via:
 
 	sched_set_fifo(ctlr->kworker_task);
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-fifo-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull sched/fifo updates from Ingo Molnar:
 "This adds the sched_set_fifo*() encapsulation APIs to remove static
  priority level knowledge from non-scheduler code.

  The three APIs for non-scheduler code to set SCHED_FIFO are:

   - sched_set_fifo()
   - sched_set_fifo_low()
   - sched_set_normal()

  These are two FIFO priority levels: default (high), and a 'low'
  priority level, plus sched_set_normal() to set the policy back to
  non-SCHED_FIFO.

  Since the changes affect a lot of non-scheduler code, we kept this in
  a separate tree"

* tag 'sched-fifo-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
  sched,tracing: Convert to sched_set_fifo()
  sched: Remove sched_set_*() return value
  sched: Remove sched_setscheduler*() EXPORTs
  sched,psi: Convert to sched_set_fifo_low()
  sched,rcutorture: Convert to sched_set_fifo_low()
  sched,rcuperf: Convert to sched_set_fifo_low()
  sched,locktorture: Convert to sched_set_fifo()
  sched,irq: Convert to sched_set_fifo()
  sched,watchdog: Convert to sched_set_fifo()
  sched,serial: Convert to sched_set_fifo()
  sched,powerclamp: Convert to sched_set_fifo()
  sched,ion: Convert to sched_set_normal()
  sched,powercap: Convert to sched_set_fifo*()
  sched,spi: Convert to sched_set_fifo*()
  sched,mmc: Convert to sched_set_fifo*()
  sched,ivtv: Convert to sched_set_fifo*()
  sched,drm/scheduler: Convert to sched_set_fifo*()
  sched,msm: Convert to sched_set_fifo*()
  sched,psci: Convert to sched_set_fifo*()
  sched,drbd: Convert to sched_set_fifo*()
  ...
2020-08-06 11:55:43 -07:00
Phil Auld a1bd06853e sched: Fix use of count for nr_running tracepoint
The count field is meant to tell if an update to nr_running
is an add or a subtract. Make it do so by adding the missing
minus sign.

Fixes: 9d246053a6 ("sched: Add a tracepoint to track rq->nr_running")
Signed-off-by: Phil Auld <pauld@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200805203138.1411-1-pauld@redhat.com
2020-08-06 09:36:59 +02:00
Linus Torvalds 0408497800 Power management updates for 5.9-rc1
- Make the Energy Model cover non-CPU devices (Lukasz Luba).
 
  - Add Ice Lake server idle states table to the intel_idle driver
    and eliminate a redundant static variable from it (Chen Yu,
    Rafael Wysocki).
 
  - Eliminate all W=1 build warnings from cpufreq (Lee Jones).
 
  - Add support for Sapphire Rapids and for Power Limit 4 to the
    Intel RAPL power capping driver (Sumeet Pawnikar, Zhang Rui).
 
  - Fix function name in kerneldoc comments in the idle_inject power
    capping driver (Yangtao Li).
 
  - Fix locking issues with cpufreq governors and drop a redundant
    "weak" function definition from cpufreq (Viresh Kumar).
 
  - Rearrange cpufreq to register non-modular governors at the
    core_initcall level and allow the default cpufreq governor to
    be specified in the kernel command line (Quentin Perret).
 
  - Extend, fix and clean up the intel_pstate driver (Srinivas
    Pandruvada, Rafael Wysocki):
 
    * Add a new sysfs attribute for disabling/enabling CPU
      energy-efficiency optimizations in the processor.
 
    * Make the driver avoid enabling HWP if EPP is not supported.
 
    * Allow the driver to handle numeric EPP values in the sysfs
      interface and fix the setting of EPP via sysfs in the active
      mode.
 
    * Eliminate a static checker warning and clean up a kerneldoc
      comment.
 
  - Clean up some variable declarations in the powernv cpufreq
    driver (Wei Yongjun).
 
  - Fix up the ->enter_s2idle callback definition to cover the case
    when it points to the same function as ->idle correctly (Neal
    Liu).
 
  - Rearrange and clean up the PSCI cpuidle driver (Ulf Hansson).
 
  - Make the PM core emit "changed" uevent when adding/removing the
    "wakeup" sysfs attribute of devices (Abhishek Pandit-Subedi).
 
  - Add a helper macro for declaring PM callbacks and use it in the
    MMC jz4740 driver (Paul Cercueil).
 
  - Fix white space in some places in the hibernate code and make the
    system-wide PM code use "const char *" where appropriate (Xiang
    Chen, Alexey Dobriyan).
 
  - Add one more "unsafe" helper macro to the freezer to cover the NFS
    use case (He Zhe).
 
  - Change the language in the generic PM domains framework to use
    parent/child terminology and clean up a typo and some comment
    fromatting in that code (Kees Cook, Geert Uytterhoeven).
 
  - Update the operating performance points OPP framework (Lukasz
    Luba, Andrew-sh.Cheng, Valdis Kletnieks):
 
    * Refactor dev_pm_opp_of_register_em() and update related drivers.
 
    * Add a missing function export.
 
    * Allow disabled OPPs in dev_pm_opp_get_freq().
 
  - Update devfreq core and drivers (Chanwoo Choi, Lukasz Luba, Enric
    Balletbo i Serra, Dmitry Osipenko, Kieran Bingham, Marc Zyngier):
 
    * Add support for delayed timers to the devfreq core and make the
      Samsung exynos5422-dmc driver use it.
 
    * Unify sysfs interface to use "df-" as a prefix in instance names
      consistently.
 
    * Fix devfreq_summary debugfs node indentation.
 
    * Add the rockchip,pmu phandle to the rk3399_dmc driver DT
      bindings.
 
    * List Dmitry Osipenko as the Tegra devfreq driver maintainer.
 
    * Fix typos in the core devfreq code.
 
  - Update the pm-graph utility to version 5.7 including a number of
    fixes related to suspend-to-idle (Todd Brandt).
 
  - Fix coccicheck errors and warnings in the cpupower utility (Shuah
    Khan).
 
  - Replace HTTP links with HTTPs ones in multiple places (Alexander
    A. Klimov).
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Merge tag 'pm-5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull power management updates from Rafael Wysocki:
 "The most significant change here is the extension of the Energy Model
  to cover non-CPU devices (as well as CPUs) from Lukasz Luba.

  There is also some new hardware support (Ice Lake server idle states
  table for intel_idle, Sapphire Rapids and Power Limit 4 support in the
  RAPL driver), some new functionality in the existing drivers (eg. a
  new switch to disable/enable CPU energy-efficiency optimizations in
  intel_pstate, delayed timers in devfreq), some assorted fixes (cpufreq
  core, intel_pstate, intel_idle) and cleanups (eg. cpuidle-psci,
  devfreq), including the elimination of W=1 build warnings from cpufreq
  done by Lee Jones.

  Specifics:

   - Make the Energy Model cover non-CPU devices (Lukasz Luba).

   - Add Ice Lake server idle states table to the intel_idle driver and
     eliminate a redundant static variable from it (Chen Yu, Rafael
     Wysocki).

   - Eliminate all W=1 build warnings from cpufreq (Lee Jones).

   - Add support for Sapphire Rapids and for Power Limit 4 to the Intel
     RAPL power capping driver (Sumeet Pawnikar, Zhang Rui).

   - Fix function name in kerneldoc comments in the idle_inject power
     capping driver (Yangtao Li).

   - Fix locking issues with cpufreq governors and drop a redundant
     "weak" function definition from cpufreq (Viresh Kumar).

   - Rearrange cpufreq to register non-modular governors at the
     core_initcall level and allow the default cpufreq governor to be
     specified in the kernel command line (Quentin Perret).

   - Extend, fix and clean up the intel_pstate driver (Srinivas
     Pandruvada, Rafael Wysocki):

       * Add a new sysfs attribute for disabling/enabling CPU
         energy-efficiency optimizations in the processor.

       * Make the driver avoid enabling HWP if EPP is not supported.

       * Allow the driver to handle numeric EPP values in the sysfs
         interface and fix the setting of EPP via sysfs in the active
         mode.

       * Eliminate a static checker warning and clean up a kerneldoc
         comment.

   - Clean up some variable declarations in the powernv cpufreq driver
     (Wei Yongjun).

   - Fix up the ->enter_s2idle callback definition to cover the case
     when it points to the same function as ->idle correctly (Neal Liu).

   - Rearrange and clean up the PSCI cpuidle driver (Ulf Hansson).

   - Make the PM core emit "changed" uevent when adding/removing the
     "wakeup" sysfs attribute of devices (Abhishek Pandit-Subedi).

   - Add a helper macro for declaring PM callbacks and use it in the MMC
     jz4740 driver (Paul Cercueil).

   - Fix white space in some places in the hibernate code and make the
     system-wide PM code use "const char *" where appropriate (Xiang
     Chen, Alexey Dobriyan).

   - Add one more "unsafe" helper macro to the freezer to cover the NFS
     use case (He Zhe).

   - Change the language in the generic PM domains framework to use
     parent/child terminology and clean up a typo and some comment
     fromatting in that code (Kees Cook, Geert Uytterhoeven).

   - Update the operating performance points OPP framework (Lukasz Luba,
     Andrew-sh.Cheng, Valdis Kletnieks):

       * Refactor dev_pm_opp_of_register_em() and update related drivers.

       * Add a missing function export.

       * Allow disabled OPPs in dev_pm_opp_get_freq().

   - Update devfreq core and drivers (Chanwoo Choi, Lukasz Luba, Enric
     Balletbo i Serra, Dmitry Osipenko, Kieran Bingham, Marc Zyngier):

       * Add support for delayed timers to the devfreq core and make the
         Samsung exynos5422-dmc driver use it.

       * Unify sysfs interface to use "df-" as a prefix in instance
         names consistently.

       * Fix devfreq_summary debugfs node indentation.

       * Add the rockchip,pmu phandle to the rk3399_dmc driver DT
         bindings.

       * List Dmitry Osipenko as the Tegra devfreq driver maintainer.

       * Fix typos in the core devfreq code.

   - Update the pm-graph utility to version 5.7 including a number of
     fixes related to suspend-to-idle (Todd Brandt).

   - Fix coccicheck errors and warnings in the cpupower utility (Shuah
     Khan).

   - Replace HTTP links with HTTPs ones in multiple places (Alexander A.
     Klimov)"

* tag 'pm-5.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (71 commits)
  cpuidle: ACPI: fix 'return' with no value build warning
  cpufreq: intel_pstate: Fix EPP setting via sysfs in active mode
  cpufreq: intel_pstate: Rearrange the storing of new EPP values
  intel_idle: Customize IceLake server support
  PM / devfreq: Fix the wrong end with semicolon
  PM / devfreq: Fix indentaion of devfreq_summary debugfs node
  PM / devfreq: Clean up the devfreq instance name in sysfs attr
  memory: samsung: exynos5422-dmc: Add module param to control IRQ mode
  memory: samsung: exynos5422-dmc: Adjust polling interval and uptreshold
  memory: samsung: exynos5422-dmc: Use delayed timer as default
  PM / devfreq: Add support delayed timer for polling mode
  dt-bindings: devfreq: rk3399_dmc: Add rockchip,pmu phandle
  PM / devfreq: tegra: Add Dmitry as a maintainer
  PM / devfreq: event: Fix trivial spelling
  PM / devfreq: rk3399_dmc: Fix kernel oops when rockchip,pmu is absent
  cpuidle: change enter_s2idle() prototype
  cpuidle: psci: Prevent domain idlestates until consumers are ready
  cpuidle: psci: Convert PM domain to platform driver
  cpuidle: psci: Fix error path via converting to a platform driver
  cpuidle: psci: Fail cpuidle registration if set OSI mode failed
  ...
2020-08-03 20:28:08 -07:00
Linus Torvalds e4cbce4d13 The main changes in this cycle were:
- Improve uclamp performance by using a static key for the fast path
 
  - Add the "sched_util_clamp_min_rt_default" sysctl, to optimize for
    better power efficiency of RT tasks on battery powered devices.
    (The default is to maximize performance & reduce RT latencies.)
 
  - Improve utime and stime tracking accuracy, which had a fixed boundary
    of error, which created larger and larger relative errors as the values
    become larger. This is now replaced with more precise arithmetics,
    using the new mul_u64_u64_div_u64() helper in math64.h.
 
  - Improve the deadline scheduler, such as making it capacity aware
 
  - Improve frequency-invariant scheduling
 
  - Misc cleanups in energy/power aware scheduling
 
  - Add sched_update_nr_running tracepoint to track changes to nr_running
 
  - Documentation additions and updates
 
  - Misc cleanups and smaller fixes
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

 - Improve uclamp performance by using a static key for the fast path

 - Add the "sched_util_clamp_min_rt_default" sysctl, to optimize for
   better power efficiency of RT tasks on battery powered devices.
   (The default is to maximize performance & reduce RT latencies.)

 - Improve utime and stime tracking accuracy, which had a fixed boundary
   of error, which created larger and larger relative errors as the
   values become larger. This is now replaced with more precise
   arithmetics, using the new mul_u64_u64_div_u64() helper in math64.h.

 - Improve the deadline scheduler, such as making it capacity aware

 - Improve frequency-invariant scheduling

 - Misc cleanups in energy/power aware scheduling

 - Add sched_update_nr_running tracepoint to track changes to nr_running

 - Documentation additions and updates

 - Misc cleanups and smaller fixes

* tag 'sched-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
  sched/doc: Factorize bits between sched-energy.rst & sched-capacity.rst
  sched/doc: Document capacity aware scheduling
  sched: Document arch_scale_*_capacity()
  arm, arm64: Fix selection of CONFIG_SCHED_THERMAL_PRESSURE
  Documentation/sysctl: Document uclamp sysctl knobs
  sched/uclamp: Add a new sysctl to control RT default boost value
  sched/uclamp: Fix a deadlock when enabling uclamp static key
  sched: Remove duplicated tick_nohz_full_enabled() check
  sched: Fix a typo in a comment
  sched/uclamp: Remove unnecessary mutex_init()
  arm, arm64: Select CONFIG_SCHED_THERMAL_PRESSURE
  sched: Cleanup SCHED_THERMAL_PRESSURE kconfig entry
  arch_topology, sched/core: Cleanup thermal pressure definition
  trace/events/sched.h: fix duplicated word
  linux/sched/mm.h: drop duplicated words in comments
  smp: Fix a potential usage of stale nr_cpus
  sched/fair: update_pick_idlest() Select group with lowest group_util when idle_cpus are equal
  sched: nohz: stop passing around unused "ticks" parameter.
  sched: Better document ttwu()
  sched: Add a tracepoint to track rq->nr_running
  ...
2020-08-03 14:58:38 -07:00
Rafael J. Wysocki c81b30c895 Merge branch 'pm-cpufreq'
* pm-cpufreq: (24 commits)
  cpufreq: intel_pstate: Fix EPP setting via sysfs in active mode
  cpufreq: intel_pstate: Rearrange the storing of new EPP values
  cpufreq: intel_pstate: Avoid enabling HWP if EPP is not supported
  cpufreq: intel_pstate: Clean up aperf_mperf_shift description
  cpufreq: powernv: Make some symbols static
  cpufreq: amd_freq_sensitivity: Mark sometimes used ID structs as __maybe_unused
  cpufreq: intel_pstate: Supply struct attribute description for get_aperf_mperf_shift()
  cpufreq: pcc-cpufreq: Mark sometimes used ID structs as __maybe_unused
  cpufreq: powernow-k8: Mark 'hi' and 'lo' dummy variables as __always_unused
  cpufreq: acpi-cpufreq: Mark sometimes used ID structs as __maybe_unused
  cpufreq: acpi-cpufreq: Mark 'dummy' variable as __always_unused
  cpufreq: powernv-cpufreq: Fix a bunch of kerneldoc related issues
  cpufreq: pasemi: Include header file for {check,restore}_astate prototypes
  cpufreq: cpufreq_governor: Demote store_sampling_rate() header to standard comment block
  cpufreq: cpufreq: Demote lots of function headers unworthy of kerneldoc status
  cpufreq: freq_table: Demote obvious misuse of kerneldoc to standard comment blocks
  cpufreq: Replace HTTP links with HTTPS ones
  cpufreq: intel_pstate: Fix static checker warning for epp variable
  cpufreq: Remove the weakly defined cpufreq_default_governor()
  cpufreq: Specify default governor on command line
  ...
2020-08-03 13:12:36 +02:00
Rafael J. Wysocki 5b5642075c Merge branches 'pm-em' and 'pm-core'
* pm-em:
  OPP: refactor dev_pm_opp_of_register_em() and update related drivers
  Documentation: power: update Energy Model description
  PM / EM: change name of em_pd_energy to em_cpu_energy
  PM / EM: remove em_register_perf_domain
  PM / EM: add support for other devices than CPUs in Energy Model
  PM / EM: update callback structure and add device pointer
  PM / EM: introduce em_dev_register_perf_domain function
  PM / EM: change naming convention from 'capacity' to 'performance'

* pm-core:
  mmc: jz4740: Use pm_ptr() macro
  PM: Make *_DEV_PM_OPS macros use __maybe_unused
  PM: core: introduce pm_ptr() macro
2020-08-03 13:11:39 +02:00
Linus Torvalds c6fe44d96f list: add "list_del_init_careful()" to go with "list_empty_careful()"
That gives us ordering guarantees around the pair.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-08-02 20:39:44 -07:00
Valentin Schneider f4470cdf10 sched: Document arch_scale_*_capacity()
Rather that hide their purpose in some dark, damp corner of Documentation/,
add some documentation to the default implementations.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200731192016.7484-2-valentin.schneider@arm.com
2020-08-01 09:19:43 +02:00
Qais Yousef 13685c4a08 sched/uclamp: Add a new sysctl to control RT default boost value
RT tasks by default run at the highest capacity/performance level. When
uclamp is selected this default behavior is retained by enforcing the
requested uclamp.min (p->uclamp_req[UCLAMP_MIN]) of the RT tasks to be
uclamp_none(UCLAMP_MAX), which is SCHED_CAPACITY_SCALE; the maximum
value.

This is also referred to as 'the default boost value of RT tasks'.

See commit 1a00d99997 ("sched/uclamp: Set default clamps for RT tasks").

On battery powered devices, it is desired to control this default
(currently hardcoded) behavior at runtime to reduce energy consumed by
RT tasks.

For example, a mobile device manufacturer where big.LITTLE architecture
is dominant, the performance of the little cores varies across SoCs, and
on high end ones the big cores could be too power hungry.

Given the diversity of SoCs, the new knob allows manufactures to tune
the best performance/power for RT tasks for the particular hardware they
run on.

They could opt to further tune the value when the user selects
a different power saving mode or when the device is actively charging.

The runtime aspect of it further helps in creating a single kernel image
that can be run on multiple devices that require different tuning.

Keep in mind that a lot of RT tasks in the system are created by the
kernel. On Android for instance I can see over 50 RT tasks, only
a handful of which created by the Android framework.

To control the default behavior globally by system admins and device
integrator, introduce the new sysctl_sched_uclamp_util_min_rt_default
to change the default boost value of the RT tasks.

I anticipate this to be mostly in the form of modifying the init script
of a particular device.

To avoid polluting the fast path with unnecessary code, the approach
taken is to synchronously do the update by traversing all the existing
tasks in the system. This could race with a concurrent fork(), which is
dealt with by introducing sched_post_fork() function which will ensure
the racy fork will get the right update applied.

Tested on Juno-r2 in combination with the RT capacity awareness [1].
By default an RT task will go to the highest capacity CPU and run at the
maximum frequency, which is particularly energy inefficient on high end
mobile devices because the biggest core[s] are 'huge' and power hungry.

With this patch the RT task can be controlled to run anywhere by
default, and doesn't cause the frequency to be maximum all the time.
Yet any task that really needs to be boosted can easily escape this
default behavior by modifying its requested uclamp.min value
(p->uclamp_req[UCLAMP_MIN]) via sched_setattr() syscall.

[1] 804d402fb6f6: ("sched/rt: Make RT capacity-aware")

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200716110347.19553-2-qais.yousef@arm.com
2020-07-29 13:51:47 +02:00
Qais Yousef e65855a52b sched/uclamp: Fix a deadlock when enabling uclamp static key
The following splat was caught when setting uclamp value of a task:

  BUG: sleeping function called from invalid context at ./include/linux/percpu-rwsem.h:49

   cpus_read_lock+0x68/0x130
   static_key_enable+0x1c/0x38
   __sched_setscheduler+0x900/0xad8

Fix by ensuring we enable the key outside of the critical section in
__sched_setscheduler()

Fixes: 46609ce227 ("sched/uclamp: Protect uclamp fast path code with static key")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200716110347.19553-4-qais.yousef@arm.com
2020-07-29 13:51:47 +02:00
Miaohe Lin 21a6ee14a8 sched: Remove duplicated tick_nohz_full_enabled() check
In sched_update_tick_dependency() there's two calls that check
whether nohz_full is enabled: tick_nohz_full_cpu() does it
implicitly, while there's also an explicit call to tick_nohz_full_enabled().

Remove the duplicated, open coded check.

[ mingo: Amended the changelog. ]

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/1595935075-14223-1-git-send-email-linmiaohe@huawei.com
2020-07-28 13:27:54 +02:00
Qinglang Miao 13efa61612 sched/uclamp: Remove unnecessary mutex_init()
The uclamp_mutex lock is initialized statically via DEFINE_MUTEX(),
it is unnecessary to initialize it runtime via mutex_init().

Signed-off-by: Qinglang Miao <miaoqinglang@huawei.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/20200725085629.98292-1-miaoqinglang@huawei.com
2020-07-25 12:10:36 +02:00
Chris Wilson 062d3f95b6 sched: Warn if garbage is passed to default_wake_function()
Since the default_wake_function() passes its flags onto
try_to_wake_up(), warn if those flags collide with internal values.

Given that the supplied flags are garbage, no repair can be done but at
least alert the user to the damage they are causing.

In the belief that these errors should be picked up during testing, the
warning is only compiled in under CONFIG_SCHED_DEBUG.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: https://lore.kernel.org/r/20200723201042.18861-1-chris@chris-wilson.co.uk
2020-07-24 14:40:25 +02:00
Valentin Schneider 25980c7a79 arch_topology, sched/core: Cleanup thermal pressure definition
The following commit:

  14533a16c4 ("thermal/cpu-cooling, sched/core: Move the arch_set_thermal_pressure() API to generic scheduler code")

moved the definition of arch_set_thermal_pressure() to sched/core.c, but
kept its declaration in linux/arch_topology.h. When building e.g. an x86
kernel with CONFIG_SCHED_THERMAL_PRESSURE=y, cpufreq_cooling.c ends up
getting the declaration of arch_set_thermal_pressure() from
include/linux/arch_topology.h, which is somewhat awkward.

On top of this, sched/core.c unconditionally defines
o The thermal_pressure percpu variable
o arch_set_thermal_pressure()

while arch_scale_thermal_pressure() does nothing unless redefined by the
architecture.

arch_*() functions are meant to be defined by architectures, so revert the
aforementioned commit and re-implement it in a way that keeps
arch_set_thermal_pressure() architecture-definable, and doesn't define the
thermal pressure percpu variable for kernels that don't need
it (CONFIG_SCHED_THERMAL_PRESSURE=n).

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200712165917.9168-2-valentin.schneider@arm.com
2020-07-22 10:22:05 +02:00
Peter Puhov 3edecfef02 sched/fair: update_pick_idlest() Select group with lowest group_util when idle_cpus are equal
In slow path, when selecting idlest group, if both groups have type
group_has_spare, only idle_cpus count gets compared.
As a result, if multiple tasks are created in a tight loop,
and go back to sleep immediately
(while waiting for all tasks to be created),
they may be scheduled on the same core, because CPU is back to idle
when the new fork happen.

For example:
sudo perf record -e sched:sched_wakeup_new -- \
                                  sysbench threads --threads=4 run
...
    total number of events:              61582
...
sudo perf script
sysbench 129378 [006] 74586.633466: sched:sched_wakeup_new:
                            sysbench:129380 [120] success=1 CPU:007
sysbench 129378 [006] 74586.634718: sched:sched_wakeup_new:
                            sysbench:129381 [120] success=1 CPU:007
sysbench 129378 [006] 74586.635957: sched:sched_wakeup_new:
                            sysbench:129382 [120] success=1 CPU:007
sysbench 129378 [006] 74586.637183: sched:sched_wakeup_new:
                            sysbench:129383 [120] success=1 CPU:007

This may have negative impact on performance for workloads with frequent
creation of multiple threads.

In this patch we are using group_util to select idlest group if both groups
have equal number of idle_cpus. Comparing the number of idle cpu is
not enough in this case, because the newly forked thread sleeps
immediately and before we select the cpu for the next one.
This is shown in the trace where the same CPU7 is selected for
all wakeup_new events.
That's why, looking at utilization when there is the same number of
CPU is a good way to see where the previous task was placed. Using
nr_running doesn't solve the problem because the newly forked task is not
running and the cpu would not have been idle in this case and an idle
CPU would have been selected instead.

With this patch newly created tasks would be better distributed.

With this patch:
sudo perf record -e sched:sched_wakeup_new -- \
                                    sysbench threads --threads=4 run
...
    total number of events:              74401
...
sudo perf script
sysbench 129455 [006] 75232.853257: sched:sched_wakeup_new:
                            sysbench:129457 [120] success=1 CPU:008
sysbench 129455 [006] 75232.854489: sched:sched_wakeup_new:
                            sysbench:129458 [120] success=1 CPU:009
sysbench 129455 [006] 75232.855732: sched:sched_wakeup_new:
                            sysbench:129459 [120] success=1 CPU:010
sysbench 129455 [006] 75232.856980: sched:sched_wakeup_new:
                            sysbench:129460 [120] success=1 CPU:011

We tested this patch with following benchmarks:
master: 'commit b3a9e3b962 ("Linux 5.8-rc1")'

100 iterations of: perf bench -f simple futex wake -s -t 128 -w 1
Lower result is better
|         |   BASELINE |   +PATCH |   DELTA (%) |
|---------|------------|----------|-------------|
| mean    |      0.33  |    0.313 |      +5.152 |
| std (%) |     10.433 |    7.563 |             |

100 iterations of: sysbench threads --threads=8 run
Higher result is better
|         |   BASELINE |   +PATCH |   DELTA (%) |
|---------|------------|----------|-------------|
| mean    |   5235.02  | 5863.73  |      +12.01 |
| std (%) |      8.166 |   10.265 |             |

100 iterations of: sysbench mutex --mutex-num=1 --threads=8 run
Lower result is better
|         |   BASELINE |   +PATCH |   DELTA (%) |
|---------|------------|----------|-------------|
| mean    |      0.413 |    0.404 |      +2.179 |
| std (%) |      3.791 |    1.816 |             |

Signed-off-by: Peter Puhov <peter.puhov@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200714125941.4174-1-peter.puhov@linaro.org
2020-07-22 10:22:04 +02:00
Paul Gortmaker 46132e3ac5 sched: nohz: stop passing around unused "ticks" parameter.
The "ticks" parameter was added in commit 0f004f5a69 ("sched: Cure more
NO_HZ load average woes") since calc_global_nohz() was called and needed
the "ticks" argument.

But in commit c308b56b53 ("sched: Fix nohz load accounting -- again!")
it became unused as the function calc_global_nohz() dropped using "ticks".

Fixes: c308b56b53 ("sched: Fix nohz load accounting -- again!")
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/1593628458-32290-1-git-send-email-paul.gortmaker@windriver.com
2020-07-22 10:22:04 +02:00
Peter Zijlstra 58877d347b sched: Better document ttwu()
Dave hit the problem fixed by commit:

  b6e13e8582 ("sched/core: Fix ttwu() race")

and failed to understand much of the code involved. Per his request a
few comments to (hopefully) clarify things.

Requested-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200702125211.GQ4800@hirez.programming.kicks-ass.net
2020-07-22 10:22:03 +02:00
Peter Zijlstra 015dc08918 Merge branch 'sched/urgent' 2020-07-22 10:22:02 +02:00
Peter Zijlstra d136122f58 sched: Fix race against ptrace_freeze_trace()
There is apparently one site that violates the rule that only current
and ttwu() will modify task->state, namely ptrace_{,un}freeze_traced()
will change task->state for a remote task.

Oleg explains:

  "TASK_TRACED/TASK_STOPPED was always protected by siglock. In
particular, ttwu(__TASK_TRACED) must be always called with siglock
held. That is why ptrace_freeze_traced() assumes it can safely do
s/TASK_TRACED/__TASK_TRACED/ under spin_lock(siglock)."

This breaks the ordering scheme introduced by commit:

  dbfb089d36 ("sched: Fix loadavg accounting race")

Specifically, the reload not matching no longer implies we don't have
to block.

Simply things by noting that what we need is a LOAD->STORE ordering
and this can be provided by a control dependency.

So replace:

	prev_state = prev->state;
	raw_spin_lock(&rq->lock);
	smp_mb__after_spinlock(); /* SMP-MB */
	if (... && prev_state && prev_state == prev->state)
		deactivate_task();

with:

	prev_state = prev->state;
	if (... && prev_state) /* CTRL-DEP */
		deactivate_task();

Since that already implies the 'prev->state' load must be complete
before allowing the 'prev->on_rq = 0' store to become visible.

Fixes: dbfb089d36 ("sched: Fix loadavg accounting race")
Reported-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Tested-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Tested-by: Christian Brauner <christian.brauner@ubuntu.com>
2020-07-22 10:22:00 +02:00
Vincent Guittot 01cfcde9c2 sched/fair: handle case of task_h_load() returning 0
task_h_load() can return 0 in some situations like running stress-ng
mmapfork, which forks thousands of threads, in a sched group on a 224 cores
system. The load balance doesn't handle this correctly because
env->imbalance never decreases and it will stop pulling tasks only after
reaching loop_max, which can be equal to the number of running tasks of
the cfs. Make sure that imbalance will be decreased by at least 1.

misfit task is the other feature that doesn't handle correctly such
situation although it's probably more difficult to face the problem
because of the smaller number of CPUs and running tasks on heterogenous
system.

We can't simply ensure that task_h_load() returns at least one because it
would imply to handle underflow in other places.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: <stable@vger.kernel.org> # v4.4+
Link: https://lkml.kernel.org/r/20200710152426.16981-1-vincent.guittot@linaro.org
2020-07-16 23:19:48 +02:00
Phil Auld 9d246053a6 sched: Add a tracepoint to track rq->nr_running
Add a bare tracepoint trace_sched_update_nr_running_tp which tracks
->nr_running CPU's rq. This is used to accurately trace this data and
provide a visualization of scheduler imbalances in, for example, the
form of a heat map.  The tracepoint is accessed by loading an external
kernel module. An example module (forked from Qais' module and including
the pelt related tracepoints) can be found at:

  https://github.com/auldp/tracepoints-helpers.git

A script to turn the trace-cmd report output into a heatmap plot can be
found at:

  https://github.com/jirvoz/plot-nr-running

The tracepoints are added to add_nr_running() and sub_nr_running() which
are in kernel/sched/sched.h. In order to avoid CREATE_TRACE_POINTS in
the header a wrapper call is used and the trace/events/sched.h include
is moved before sched.h in kernel/sched/core.

Signed-off-by: Phil Auld <pauld@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200629192303.GC120228@lorien.usersys.redhat.com
2020-07-08 11:39:02 +02:00
Qais Yousef 46609ce227 sched/uclamp: Protect uclamp fast path code with static key
There is a report that when uclamp is enabled, a netperf UDP test
regresses compared to a kernel compiled without uclamp.

https://lore.kernel.org/lkml/20200529100806.GA3070@suse.de/

While investigating the root cause, there were no sign that the uclamp
code is doing anything particularly expensive but could suffer from bad
cache behavior under certain circumstances that are yet to be
understood.

https://lore.kernel.org/lkml/20200616110824.dgkkbyapn3io6wik@e107158-lin/

To reduce the pressure on the fast path anyway, add a static key that is
by default will skip executing uclamp logic in the
enqueue/dequeue_task() fast path until it's needed.

As soon as the user start using util clamp by:

	1. Changing uclamp value of a task with sched_setattr()
	2. Modifying the default sysctl_sched_util_clamp_{min, max}
	3. Modifying the default cpu.uclamp.{min, max} value in cgroup

We flip the static key now that the user has opted to use util clamp.
Effectively re-introducing uclamp logic in the enqueue/dequeue_task()
fast path. It stays on from that point forward until the next reboot.

This should help minimize the effect of util clamp on workloads that
don't need it but still allow distros to ship their kernels with uclamp
compiled in by default.

SCHED_WARN_ON() in uclamp_rq_dec_id() was removed since now we can end
up with unbalanced call to uclamp_rq_dec_id() if we flip the key while
a task is running in the rq. Since we know it is harmless we just
quietly return if we attempt a uclamp_rq_dec_id() when
rq->uclamp[].bucket[].tasks is 0.

In schedutil, we introduce a new uclamp_is_enabled() helper which takes
the static key into account to ensure RT boosting behavior is retained.

The following results demonstrates how this helps on 2 Sockets Xeon E5
2x10-Cores system.

                                   nouclamp                 uclamp      uclamp-static-key
Hmean     send-64         162.43 (   0.00%)      157.84 *  -2.82%*      163.39 *   0.59%*
Hmean     send-128        324.71 (   0.00%)      314.78 *  -3.06%*      326.18 *   0.45%*
Hmean     send-256        641.55 (   0.00%)      628.67 *  -2.01%*      648.12 *   1.02%*
Hmean     send-1024      2525.28 (   0.00%)     2448.26 *  -3.05%*     2543.73 *   0.73%*
Hmean     send-2048      4836.14 (   0.00%)     4712.08 *  -2.57%*     4867.69 *   0.65%*
Hmean     send-3312      7540.83 (   0.00%)     7425.45 *  -1.53%*     7621.06 *   1.06%*
Hmean     send-4096      9124.53 (   0.00%)     8948.82 *  -1.93%*     9276.25 *   1.66%*
Hmean     send-8192     15589.67 (   0.00%)    15486.35 *  -0.66%*    15819.98 *   1.48%*
Hmean     send-16384    26386.47 (   0.00%)    25752.25 *  -2.40%*    26773.74 *   1.47%*

The perf diff between nouclamp and uclamp-static-key when uclamp is
disabled in the fast path:

     8.73%     -1.55%  [kernel.kallsyms]        [k] try_to_wake_up
     0.07%     +0.04%  [kernel.kallsyms]        [k] deactivate_task
     0.13%     -0.02%  [kernel.kallsyms]        [k] activate_task

The diff between nouclamp and uclamp-static-key when uclamp is enabled
in the fast path:

     8.73%     -0.72%  [kernel.kallsyms]        [k] try_to_wake_up
     0.13%     +0.39%  [kernel.kallsyms]        [k] activate_task
     0.07%     +0.38%  [kernel.kallsyms]        [k] deactivate_task

Fixes: 69842cba9a ("sched/uclamp: Add CPU's clamp buckets refcounting")
Reported-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://lkml.kernel.org/r/20200630112123.12076-3-qais.yousef@arm.com
2020-07-08 11:39:01 +02:00
Qais Yousef d81ae8aac8 sched/uclamp: Fix initialization of struct uclamp_rq
struct uclamp_rq was zeroed out entirely in assumption that in the first
call to uclamp_rq_inc() they'd be initialized correctly in accordance to
default settings.

But when next patch introduces a static key to skip
uclamp_rq_{inc,dec}() until userspace opts in to use uclamp, schedutil
will fail to perform any frequency changes because the
rq->uclamp[UCLAMP_MAX].value is zeroed at init and stays as such. Which
means all rqs are capped to 0 by default.

Fix it by making sure we do proper initialization at init without
relying on uclamp_rq_inc() doing it later.

Fixes: 69842cba9a ("sched/uclamp: Add CPU's clamp buckets refcounting")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://lkml.kernel.org/r/20200630112123.12076-2-qais.yousef@arm.com
2020-07-08 11:39:01 +02:00
Peter Zijlstra 85c2ce9104 sched, vmlinux.lds: Increase STRUCT_ALIGNMENT to 64 bytes for GCC-4.9
For some mysterious reason GCC-4.9 has a 64 byte section alignment for
structures, all other GCC versions (and Clang) tested (including 4.8
and 5.0) are fine with the 32 bytes alignment.

Getting this right is important for the new SCHED_DATA macro that
creates an explicitly ordered array of 'struct sched_class' in the
linker script and expect pointer arithmetic to work.

Fixes: c3a340f7e7 ("sched: Have sched_class_highest define by vmlinux.lds.h")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200630144905.GX4817@hirez.programming.kicks-ass.net
2020-07-08 11:39:00 +02:00
Peter Zijlstra faa2fd7cba Merge branch 'sched/urgent' 2020-07-08 11:38:59 +02:00
Mathieu Desnoyers ce3614daab sched: Fix unreliable rseq cpu_id for new tasks
While integrating rseq into glibc and replacing glibc's sched_getcpu
implementation with rseq, glibc's tests discovered an issue with
incorrect __rseq_abi.cpu_id field value right after the first time
a newly created process issues sched_setaffinity.

For the records, it triggers after building glibc and running tests, and
then issuing:

  for x in {1..2000} ; do posix/tst-affinity-static  & done

and shows up as:

error: Unexpected CPU 2, expected 0
error: Unexpected CPU 2, expected 0
error: Unexpected CPU 2, expected 0
error: Unexpected CPU 2, expected 0
error: Unexpected CPU 138, expected 0
error: Unexpected CPU 138, expected 0
error: Unexpected CPU 138, expected 0
error: Unexpected CPU 138, expected 0

This is caused by the scheduler invoking __set_task_cpu() directly from
sched_fork() and wake_up_new_task(), thus bypassing rseq_migrate() which
is done by set_task_cpu().

Add the missing rseq_migrate() to both functions. The only other direct
use of __set_task_cpu() is done by init_idle(), which does not involve a
user-space task.

Based on my testing with the glibc test-case, just adding rseq_migrate()
to wake_up_new_task() is sufficient to fix the observed issue. Also add
it to sched_fork() to keep things consistent.

The reason why this never triggered so far with the rseq/basic_test
selftest is unclear.

The current use of sched_getcpu(3) does not typically require it to be
always accurate. However, use of the __rseq_abi.cpu_id field within rseq
critical sections requires it to be accurate. If it is not accurate, it
can cause corruption in the per-cpu data targeted by rseq critical
sections in user-space.

Reported-By: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-By: Florian Weimer <fweimer@redhat.com>
Cc: stable@vger.kernel.org # v4.18+
Link: https://lkml.kernel.org/r/20200707201505.2632-1-mathieu.desnoyers@efficios.com
2020-07-08 11:38:50 +02:00
Peter Zijlstra dbfb089d36 sched: Fix loadavg accounting race
The recent commit:

  c6e7bd7afa ("sched/core: Optimize ttwu() spinning on p->on_cpu")

moved these lines in ttwu():

	p->sched_contributes_to_load = !!task_contributes_to_load(p);
	p->state = TASK_WAKING;

up before:

	smp_cond_load_acquire(&p->on_cpu, !VAL);

into the 'p->on_rq == 0' block, with the thinking that once we hit
schedule() the current task cannot change it's ->state anymore. And
while this is true, it is both incorrect and flawed.

It is incorrect in that we need at least an ACQUIRE on 'p->on_rq == 0'
to avoid weak hardware from re-ordering things for us. This can fairly
easily be achieved by relying on the control-dependency already in
place.

The second problem, which makes the flaw in the original argument, is
that while schedule() will not change prev->state, it will read it a
number of times (arguably too many times since it's marked volatile).
The previous condition 'p->on_cpu == 0' was sufficient because that
indicates schedule() has completed, and will no longer read
prev->state. So now the trick is to make this same true for the (much)
earlier 'prev->on_rq == 0' case.

Furthermore, in order to make the ordering stick, the 'prev->on_rq = 0'
assignment needs to he a RELEASE, but adding additional ordering to
schedule() is an unwelcome proposition at the best of times, doubly so
for mere accounting.

Luckily we can push the prev->state load up before rq->lock, with the
only caveat that we then have to re-read the state after. However, we
know that if it changed, we no longer have to worry about the blocking
path. This gives us the required ordering, if we block, we did the
prev->state load before an (effective) smp_mb() and the p->on_rq store
needs not change.

With this we end up with the effective ordering:

	LOAD p->state           LOAD-ACQUIRE p->on_rq == 0
	MB
	STORE p->on_rq, 0       STORE p->state, TASK_WAKING

which ensures the TASK_WAKING store happens after the prev->state
load, and all is well again.

Fixes: c6e7bd7afa ("sched/core: Optimize ttwu() spinning on p->on_cpu")
Reported-by: Dave Jones <davej@codemonkey.org.uk>
Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Dave Jones <davej@codemonkey.org.uk>
Tested-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Link: https://lkml.kernel.org/r/20200707102957.GN117543@hirez.programming.kicks-ass.net
2020-07-08 11:38:49 +02:00
Quentin Perret 10dd8573b0 cpufreq: Register governors at core_initcall
Currently, most CPUFreq governors are registered at the core_initcall
time when the given governor is the default one, and the module_init
time otherwise.

In preparation for letting users specify the default governor on the
kernel command line, change all of them to be registered at the
core_initcall unconditionally, as it is already the case for the
schedutil and performance governors. This will allow us to assume
that builtin governors have been registered before the built-in
CPUFreq drivers probe.

And since all governors have similar init/exit patterns now, introduce
two new macros, cpufreq_governor_{init,exit}(), to factorize the code.

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
[ rjw: Changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2020-07-02 13:03:30 +02:00
Linus Torvalds 91a9a90d04 Peter Zijlstra says:
The most anticipated fix in this pull request is probably the horrible build
 fix for the RANDSTRUCT fail that didn't make -rc2. Also included is the cleanup
 that removes those BUILD_BUG_ON()s and replaces it with ugly unions.
 
 Also included is the try_to_wake_up() race fix that was first triggered by
 Paul's RCU-torture runs, but was independently hit by Dave Chinner's fstest
 runs as well.
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Merge tag 'sched_urgent_for_5.8_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Borislav Petkov:
 "The most anticipated fix in this pull request is probably the horrible
  build fix for the RANDSTRUCT fail that didn't make -rc2. Also included
  is the cleanup that removes those BUILD_BUG_ON()s and replaces it with
  ugly unions.

  Also included is the try_to_wake_up() race fix that was first
  triggered by Paul's RCU-torture runs, but was independently hit by
  Dave Chinner's fstest runs as well"

* tag 'sched_urgent_for_5.8_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/cfs: change initial value of runnable_avg
  smp, irq_work: Continue smp_call_function*() and irq_work*() integration
  sched/core: s/WF_ON_RQ/WQ_ON_CPU/
  sched/core: Fix ttwu() race
  sched/core: Fix PI boosting between RT and DEADLINE tasks
  sched/deadline: Initialize ->dl_boosted
  sched/core: Check cpus_mask, not cpus_ptr in __set_cpus_allowed_ptr(), to fix mask corruption
  sched/core: Fix CONFIG_GCC_PLUGIN_RANDSTRUCT build fail
2020-06-28 10:37:39 -07:00
Vincent Guittot e21cf43406 sched/cfs: change initial value of runnable_avg
Some performance regression on reaim benchmark have been raised with
  commit 070f5e860e ("sched/fair: Take into account runnable_avg to classify group")

The problem comes from the init value of runnable_avg which is initialized
with max value. This can be a problem if the newly forked task is finally
a short task because the group of CPUs is wrongly set to overloaded and
tasks are pulled less agressively.

Set initial value of runnable_avg equals to util_avg to reflect that there
is no waiting time so far.

Fixes: 070f5e860e ("sched/fair: Take into account runnable_avg to classify group")
Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200624154422.29166-1-vincent.guittot@linaro.org
2020-06-28 17:01:20 +02:00
Peter Zijlstra 8c4890d1c3 smp, irq_work: Continue smp_call_function*() and irq_work*() integration
Instead of relying on BUG_ON() to ensure the various data structures
line up, use a bunch of horrible unions to make it all automatic.

Much of the union magic is to ensure irq_work and smp_call_function do
not (yet) see the members of their respective data structures change
name.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20200622100825.844455025@infradead.org
2020-06-28 17:01:20 +02:00
Peter Zijlstra 739f70b476 sched/core: s/WF_ON_RQ/WQ_ON_CPU/
Use a better name for this poorly named flag, to avoid confusion...

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20200622100825.785115830@infradead.org
2020-06-28 17:01:20 +02:00
Peter Zijlstra b6e13e8582 sched/core: Fix ttwu() race
Paul reported rcutorture occasionally hitting a NULL deref:

  sched_ttwu_pending()
    ttwu_do_wakeup()
      check_preempt_curr() := check_preempt_wakeup()
        find_matching_se()
          is_same_group()
            if (se->cfs_rq == pse->cfs_rq) <-- *BOOM*

Debugging showed that this only appears to happen when we take the new
code-path from commit:

  2ebb177175 ("sched/core: Offload wakee task activation if it the wakee is descheduling")

and only when @cpu == smp_processor_id(). Something which should not
be possible, because p->on_cpu can only be true for remote tasks.
Similarly, without the new code-path from commit:

  c6e7bd7afa ("sched/core: Optimize ttwu() spinning on p->on_cpu")

this would've unconditionally hit:

  smp_cond_load_acquire(&p->on_cpu, !VAL);

and if: 'cpu == smp_processor_id() && p->on_cpu' is possible, this
would result in an instant live-lock (with IRQs disabled), something
that hasn't been reported.

The NULL deref can be explained however if the task_cpu(p) load at the
beginning of try_to_wake_up() returns an old value, and this old value
happens to be smp_processor_id(). Further assume that the p->on_cpu
load accurately returns 1, it really is still running, just not here.

Then, when we enqueue the task locally, we can crash in exactly the
observed manner because p->se.cfs_rq != rq->cfs_rq, because p's cfs_rq
is from the wrong CPU, therefore we'll iterate into the non-existant
parents and NULL deref.

The closest semi-plausible scenario I've managed to contrive is
somewhat elaborate (then again, actual reproduction takes many CPU
hours of rcutorture, so it can't be anything obvious):

					X->cpu = 1
					rq(1)->curr = X

	CPU0				CPU1				CPU2

					// switch away from X
					LOCK rq(1)->lock
					smp_mb__after_spinlock
					dequeue_task(X)
					  X->on_rq = 9
					switch_to(Z)
					  X->on_cpu = 0
					UNLOCK rq(1)->lock

									// migrate X to cpu 0
									LOCK rq(1)->lock
									dequeue_task(X)
									set_task_cpu(X, 0)
									  X->cpu = 0
									UNLOCK rq(1)->lock

									LOCK rq(0)->lock
									enqueue_task(X)
									  X->on_rq = 1
									UNLOCK rq(0)->lock

	// switch to X
	LOCK rq(0)->lock
	smp_mb__after_spinlock
	switch_to(X)
	  X->on_cpu = 1
	UNLOCK rq(0)->lock

	// X goes sleep
	X->state = TASK_UNINTERRUPTIBLE
	smp_mb();			// wake X
					ttwu()
					  LOCK X->pi_lock
					  smp_mb__after_spinlock

					  if (p->state)

					  cpu = X->cpu; // =? 1

					  smp_rmb()

	// X calls schedule()
	LOCK rq(0)->lock
	smp_mb__after_spinlock
	dequeue_task(X)
	  X->on_rq = 0

					  if (p->on_rq)

					  smp_rmb();

					  if (p->on_cpu && ttwu_queue_wakelist(..)) [*]

					  smp_cond_load_acquire(&p->on_cpu, !VAL)

					  cpu = select_task_rq(X, X->wake_cpu, ...)
					  if (X->cpu != cpu)
	switch_to(Y)
	  X->on_cpu = 0
	UNLOCK rq(0)->lock

However I'm having trouble convincing myself that's actually possible
on x86_64 -- after all, every LOCK implies an smp_mb() there, so if ttwu
observes ->state != RUNNING, it must also observe ->cpu != 1.

(Most of the previous ttwu() races were found on very large PowerPC)

Nevertheless, this fully explains the observed failure case.

Fix it by ordering the task_cpu(p) load after the p->on_cpu load,
which is easy since nothing actually uses @cpu before this.

Fixes: c6e7bd7afa ("sched/core: Optimize ttwu() spinning on p->on_cpu")
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200622125649.GC576871@hirez.programming.kicks-ass.net
2020-06-28 17:01:20 +02:00
Juri Lelli 740797ce3a sched/core: Fix PI boosting between RT and DEADLINE tasks
syzbot reported the following warning:

 WARNING: CPU: 1 PID: 6351 at kernel/sched/deadline.c:628
 enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504

At deadline.c:628 we have:

 623 static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
 624 {
 625 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 626 	struct rq *rq = rq_of_dl_rq(dl_rq);
 627
 628 	WARN_ON(dl_se->dl_boosted);
 629 	WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
        [...]
     }

Which means that setup_new_dl_entity() has been called on a task
currently boosted. This shouldn't happen though, as setup_new_dl_entity()
is only called when the 'dynamic' deadline of the new entity
is in the past w.r.t. rq_clock and boosted tasks shouldn't verify this
condition.

Digging through the PI code I noticed that what above might in fact happen
if an RT tasks blocks on an rt_mutex hold by a DEADLINE task. In the
first branch of boosting conditions we check only if a pi_task 'dynamic'
deadline is earlier than mutex holder's and in this case we set mutex
holder to be dl_boosted. However, since RT 'dynamic' deadlines are only
initialized if such tasks get boosted at some point (or if they become
DEADLINE of course), in general RT 'dynamic' deadlines are usually equal
to 0 and this verifies the aforementioned condition.

Fix it by checking that the potential donor task is actually (even if
temporary because in turn boosted) running at DEADLINE priority before
using its 'dynamic' deadline value.

Fixes: 2d3d891d33 ("sched/deadline: Add SCHED_DEADLINE inheritance logic")
Reported-by: syzbot+119ba87189432ead09b4@syzkaller.appspotmail.com
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Tested-by: Daniel Wagner <dwagner@suse.de>
Link: https://lkml.kernel.org/r/20181119153201.GB2119@localhost.localdomain
2020-06-28 17:01:20 +02:00
Juri Lelli ce9bc3b27f sched/deadline: Initialize ->dl_boosted
syzbot reported the following warning triggered via SYSC_sched_setattr():

  WARNING: CPU: 0 PID: 6973 at kernel/sched/deadline.c:593 setup_new_dl_entity /kernel/sched/deadline.c:594 [inline]
  WARNING: CPU: 0 PID: 6973 at kernel/sched/deadline.c:593 enqueue_dl_entity /kernel/sched/deadline.c:1370 [inline]
  WARNING: CPU: 0 PID: 6973 at kernel/sched/deadline.c:593 enqueue_task_dl+0x1c17/0x2ba0 /kernel/sched/deadline.c:1441

This happens because the ->dl_boosted flag is currently not initialized by
__dl_clear_params() (unlike the other flags) and setup_new_dl_entity()
rightfully complains about it.

Initialize dl_boosted to 0.

Fixes: 2d3d891d33 ("sched/deadline: Add SCHED_DEADLINE inheritance logic")
Reported-by: syzbot+5ac8bac25f95e8b221e7@syzkaller.appspotmail.com
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Daniel Wagner <dwagner@suse.de>
Link: https://lkml.kernel.org/r/20200617072919.818409-1-juri.lelli@redhat.com
2020-06-28 17:01:20 +02:00
Scott Wood fd844ba9ae sched/core: Check cpus_mask, not cpus_ptr in __set_cpus_allowed_ptr(), to fix mask corruption
This function is concerned with the long-term CPU mask, not the
transitory mask the task might have while migrate disabled.  Before
this patch, if a task was migrate-disabled at the time
__set_cpus_allowed_ptr() was called, and the new mask happened to be
equal to the CPU that the task was running on, then the mask update
would be lost.

Signed-off-by: Scott Wood <swood@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200617121742.cpxppyi7twxmpin7@linutronix.de
2020-06-28 17:01:20 +02:00
Rafael J. Wysocki 10e8b11eb3 cpuidle: Rearrange s2idle-specific idle state entry code
Implement call_cpuidle_s2idle() in analogy with call_cpuidle()
for the s2idle-specific idle state entry and invoke it from
cpuidle_idle_call() to make the s2idle-specific idle entry code
path look more similar to the "regular" idle entry one.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Chen Yu <yu.c.chen@intel.com>
2020-06-25 13:52:53 +02:00
Peng Wang 423d02e146 sched/fair: Optimize dequeue_task_fair()
While looking at enqueue_task_fair and dequeue_task_fair, it occurred
to me that dequeue_task_fair can also be optimized as Vincent described
in commit 7d148be69e ("sched/fair: Optimize enqueue_task_fair()").

When encountering throttled cfs_rq, dequeue_throttle label can ensure
se not to be NULL, and rq->nr_running remains unchanged, so we can also
skip the early balance check.

Signed-off-by: Peng Wang <rocking@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/701eef9a40de93dcf5fe7063fd607bca5db38e05.1592287263.git.rocking@linux.alibaba.com
2020-06-25 13:45:44 +02:00
Kirill Tkhai aa93cd53bc sched: Micro optimization in pick_next_task() and in check_preempt_curr()
This introduces an optimization based on xxx_sched_class addresses
in two hot scheduler functions: pick_next_task() and check_preempt_curr().

It is possible to compare pointers to sched classes to check, which
of them has a higher priority, instead of current iterations using
for_each_class().

One more result of the patch is that size of object file becomes a little
less (excluding added BUG_ON(), which goes in __init section):

$size kernel/sched/core.o
         text     data      bss	    dec	    hex	filename
before:  66446    18957	    676	  86079	  1503f	kernel/sched/core.o
after:   66398    18957	    676	  86031	  1500f	kernel/sched/core.o

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/711a9c4b-ff32-1136-b848-17c622d548f3@yandex.ru
2020-06-25 13:45:44 +02:00
Steven Rostedt (VMware) a87e749e8f sched: Remove struct sched_class::next field
Now that the sched_class descriptors are defined in order via the linker
script vmlinux.lds.h, there's no reason to have a "next" pointer to the
previous priroity structure. The order of the sturctures can be aligned as
an array, and used to index and find the next sched_class descriptor.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191219214558.845353593@goodmis.org
2020-06-25 13:45:44 +02:00
Steven Rostedt (VMware) c3a340f7e7 sched: Have sched_class_highest define by vmlinux.lds.h
Now that the sched_class descriptors are defined by the linker script, and
this needs to be aware of the existance of stop_sched_class when SMP is
enabled or not, as it is used as the "highest" priority when defined. Move
the declaration of sched_class_highest to the same location in the linker
script that inserts stop_sched_class, and this will also make it easier to
see what should be defined as the highest class, as this linker script
location defines the priorities as well.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191219214558.682913590@goodmis.org
2020-06-25 13:45:44 +02:00
Steven Rostedt (VMware) 590d697963 sched: Force the address order of each sched class descriptor
In order to make a micro optimization in pick_next_task(), the order of the
sched class descriptor address must be in the same order as their priority
to each other. That is:

 &idle_sched_class < &fair_sched_class < &rt_sched_class <
 &dl_sched_class < &stop_sched_class

In order to guarantee this order of the sched class descriptors, add each
one into their own data section and force the order in the linker script.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/157675913272.349305.8936736338884044103.stgit@localhost.localdomain
2020-06-25 13:45:43 +02:00
Lukasz Luba f0b5694791 PM / EM: change name of em_pd_energy to em_cpu_energy
Energy Model framework now supports other devices than CPUs. Refactor some
of the functions in order to prevent wrong usage. The old function
em_pd_energy has to generic name. It must not be used without proper
cpumask pointer, which is possible only for CPU devices. Thus, rename it
and add proper description to warn of potential wrong usage for other
devices.

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Quentin Perret <qperret@google.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2020-06-24 17:16:42 +02:00
Lukasz Luba 521b512b15 PM / EM: change naming convention from 'capacity' to 'performance'
The Energy Model uses concept of performance domain and capacity states in
order to calculate power used by CPUs. Change naming convention from
capacity to performance state would enable wider usage in future, e.g.
upcoming support for other devices other than CPUs.

Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Quentin Perret <qperret@google.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2020-06-24 17:14:07 +02:00