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Linus Torvalds 36ae1c45b2 Scheduler changes for v7.0:
Scheduler Kconfig space updates:
 
  - Further consolidate configurable preemption modes: reduce
    the number of architectures that are allowed to offer
    PREEMPT_NONE and PREEMPT_VOLUNTARY, reducing the number
    of preemption models from four to just two: 'full' and 'lazy'
    on up-to-date architectures (arm64, loongarch, powerpc,
    riscv, s390, x86).
 
    None and voluntary are only available as legacy features
    on platforms that don't implement lazy preemption yet,
    or which don't even support preemption.
 
    The goal is to eventually remove cond_resched() and
    voluntary preemption altogether.
 
    (Peter Zijlstra)
 
 RSEQ based 'scheduler time slice extension' support:
 
 This allows a thread to request a time slice extension when it
 enters a critical section to avoid contention on a resource when
 the thread is scheduled out inside of the critical section.
 
  - Add fields and constants for time slice extension
  - Provide static branch for time slice extensions
  - Add statistics for time slice extensions
  - Add prctl() to enable time slice extensions
  - Implement sys_rseq_slice_yield()
  - Implement syscall entry work for time slice extensions
  - Implement time slice extension enforcement timer
  - Reset slice extension when scheduled
  - Implement rseq_grant_slice_extension()
  - entry: Hook up rseq time slice extension
  - selftests: Implement time slice extension test
 
    (Thomas Gleixner)
 
  - Allow registering RSEQ with slice extension
  - Move slice_ext_nsec to debugfs
  - Lower default slice extension
  - selftests/rseq: Add rseq slice histogram script
 
    (Peter Zijlstra)
 
 Scheduler performance/scalability improvements:
 
  - Update rq->avg_idle when a task is moved to an idle CPU,
    which improves the scalability of various workloads.
    (Shubhang Kaushik)
 
  - Reorder fields in 'struct rq' for better caching
    (Blake Jones)
 
  - Fair scheduler SMP NOHZ balancing code speedups:
 
    - Move checking for nohz cpus after time check
    - Change likelyhood of nohz.nr_cpus
    - Remove nohz.nr_cpus and use weight of cpumask instead
 
      (Shrikanth Hegde)
 
  - Avoid false sharing for sched_clock_irqtime (Wangyang Guo)
 
  - Drop useless cpumask_empty() in find_energy_efficient_cpu()
  - Simplify task_numa_find_cpu()
  - Use cpumask_weight_and() in sched_balance_find_dst_group()
 
    (Yury Norov)
 
 DL scheduler updates:
 
  - Add a deadline server for sched_ext tasks (by Andrea Righi and
    Joel Fernandes, with fixes by Peter Zijlstra)
 
 RT scheduler updates:
 
  - Skip currently executing CPU in rto_next_cpu() (Chen Jinghuang)
 
 Entry code updates and performance improvements, which is part of the
 scheduler tree in this cycle due to interdependencies with the RSEQ
 based time slice extension work:
 
   - Remove unused syscall argument from syscall_trace_enter()
   - Rework syscall_exit_to_user_mode_work() for architecture reuse
   - Add arch_ptrace_report_syscall_entry/exit()
   - Inline syscall_exit_work() and syscall_trace_enter()
 
     (Jinjie Ruan)
 
 Scheduler core updates:
 
  - Rework sched_class::wakeup_preempt() and rq_modified_*()
  - Avoid rq->lock bouncing in sched_balance_newidle()
  - Rename rcu_dereference_check_sched_domain() =>
           rcu_dereference_sched_domain()
  - <linux/compiler_types.h>: Add the __signed_scalar_typeof() helper
 
    (Peter Zijlstra)
 
 Fair scheduler updates/refactoring:
 
  - Fold the sched_avg update
  - Change rcu_dereference_check_sched_domain() to rcu-sched
  - Switch to rcu_dereference_all()
  - Remove superfluous rcu_read_lock()
  - Limit hrtick work
 
    (Peter Zijlstra)
 
  - Join two #ifdef CONFIG_FAIR_GROUP_SCHED blocks
  - Clean up comments in 'struct cfs_rq'
  - Separate se->vlag from se->vprot
  - Rename cfs_rq::avg_load to cfs_rq::sum_weight
  - Rename cfs_rq::avg_vruntime to ::sum_w_vruntime & helper functions
  - Introduce and use the vruntime_cmp() and vruntime_op() wrappers
    for wrapped-signed aritmetics
  - Sort out 'blocked_load*' namespace noise
 
    (Ingo Molnar)
 
 Scheduler debugging code updates:
 
  - Export hidden tracepoints to modules (Gabriele Monaco)
 
  - Convert copy_from_user() + kstrtouint() to kstrtouint_from_user()
    (Fushuai Wang)
 
  - Add assertions to QUEUE_CLASS (Peter Zijlstra)
 
  - hrtimer: Fix tracing oddity (Thomas Gleixner)
 
 Misc fixes and cleanups:
 
  - Re-evaluate scheduling when migrating queued tasks out of
    throttled cgroups (Zicheng Qu)
 
  - Remove task_struct->faults_disabled_mapping (Christoph Hellwig)
 
  - Fix math notation errors in avg_vruntime comment (Zhan Xusheng)
 
  - sched/cpufreq: Use %pe format for PTR_ERR() printing (zenghongling)
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2026-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:
 "Scheduler Kconfig space updates:

   - Further consolidate configurable preemption modes (Peter Zijlstra)

     Reduce the number of architectures that are allowed to offer
     PREEMPT_NONE and PREEMPT_VOLUNTARY, reducing the number of
     preemption models from four to just two: 'full' and 'lazy' on
     up-to-date architectures (arm64, loongarch, powerpc, riscv, s390,
     x86).

     None and voluntary are only available as legacy features on
     platforms that don't implement lazy preemption yet, or which don't
     even support preemption.

     The goal is to eventually remove cond_resched() and voluntary
     preemption altogether.

  RSEQ based 'scheduler time slice extension' support (Thomas Gleixner
  and Peter Zijlstra):

  This allows a thread to request a time slice extension when it enters
  a critical section to avoid contention on a resource when the thread
  is scheduled out inside of the critical section.

   - Add fields and constants for time slice extension
   - Provide static branch for time slice extensions
   - Add statistics for time slice extensions
   - Add prctl() to enable time slice extensions
   - Implement sys_rseq_slice_yield()
   - Implement syscall entry work for time slice extensions
   - Implement time slice extension enforcement timer
   - Reset slice extension when scheduled
   - Implement rseq_grant_slice_extension()
   - entry: Hook up rseq time slice extension
   - selftests: Implement time slice extension test
   - Allow registering RSEQ with slice extension
   - Move slice_ext_nsec to debugfs
   - Lower default slice extension
   - selftests/rseq: Add rseq slice histogram script

  Scheduler performance/scalability improvements:

   - Update rq->avg_idle when a task is moved to an idle CPU, which
     improves the scalability of various workloads (Shubhang Kaushik)

   - Reorder fields in 'struct rq' for better caching (Blake Jones)

   - Fair scheduler SMP NOHZ balancing code speedups (Shrikanth Hegde):
      - Move checking for nohz cpus after time check
      - Change likelyhood of nohz.nr_cpus
      - Remove nohz.nr_cpus and use weight of cpumask instead

   - Avoid false sharing for sched_clock_irqtime (Wangyang Guo)

   - Cleanups (Yury Norov):
      - Drop useless cpumask_empty() in find_energy_efficient_cpu()
      - Simplify task_numa_find_cpu()
      - Use cpumask_weight_and() in sched_balance_find_dst_group()

  DL scheduler updates:

   - Add a deadline server for sched_ext tasks (by Andrea Righi and Joel
     Fernandes, with fixes by Peter Zijlstra)

  RT scheduler updates:

   - Skip currently executing CPU in rto_next_cpu() (Chen Jinghuang)

  Entry code updates and performance improvements (Jinjie Ruan)

  This is part of the scheduler tree in this cycle due to inter-
  dependencies with the RSEQ based time slice extension work:

    - Remove unused syscall argument from syscall_trace_enter()
    - Rework syscall_exit_to_user_mode_work() for architecture reuse
    - Add arch_ptrace_report_syscall_entry/exit()
    - Inline syscall_exit_work() and syscall_trace_enter()

  Scheduler core updates (Peter Zijlstra):

   - Rework sched_class::wakeup_preempt() and rq_modified_*()
   - Avoid rq->lock bouncing in sched_balance_newidle()
   - Rename rcu_dereference_check_sched_domain() =>
            rcu_dereference_sched_domain()
   - <linux/compiler_types.h>: Add the __signed_scalar_typeof() helper

  Fair scheduler updates/refactoring (Peter Zijlstra and Ingo Molnar):

   - Fold the sched_avg update
   - Change rcu_dereference_check_sched_domain() to rcu-sched
   - Switch to rcu_dereference_all()
   - Remove superfluous rcu_read_lock()
   - Limit hrtick work
   - Join two #ifdef CONFIG_FAIR_GROUP_SCHED blocks
   - Clean up comments in 'struct cfs_rq'
   - Separate se->vlag from se->vprot
   - Rename cfs_rq::avg_load to cfs_rq::sum_weight
   - Rename cfs_rq::avg_vruntime to ::sum_w_vruntime & helper functions
   - Introduce and use the vruntime_cmp() and vruntime_op() wrappers for
     wrapped-signed aritmetics
   - Sort out 'blocked_load*' namespace noise

  Scheduler debugging code updates:

   - Export hidden tracepoints to modules (Gabriele Monaco)

   - Convert copy_from_user() + kstrtouint() to kstrtouint_from_user()
     (Fushuai Wang)

   - Add assertions to QUEUE_CLASS (Peter Zijlstra)

   - hrtimer: Fix tracing oddity (Thomas Gleixner)

  Misc fixes and cleanups:

   - Re-evaluate scheduling when migrating queued tasks out of throttled
     cgroups (Zicheng Qu)

   - Remove task_struct->faults_disabled_mapping (Christoph Hellwig)

   - Fix math notation errors in avg_vruntime comment (Zhan Xusheng)

   - sched/cpufreq: Use %pe format for PTR_ERR() printing
     (zenghongling)"

* tag 'sched-core-2026-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (64 commits)
  sched: Re-evaluate scheduling when migrating queued tasks out of throttled cgroups
  sched/cpufreq: Use %pe format for PTR_ERR() printing
  sched/rt: Skip currently executing CPU in rto_next_cpu()
  sched/clock: Avoid false sharing for sched_clock_irqtime
  selftests/sched_ext: Add test for DL server total_bw consistency
  selftests/sched_ext: Add test for sched_ext dl_server
  sched/debug: Fix dl_server (re)start conditions
  sched/debug: Add support to change sched_ext server params
  sched_ext: Add a DL server for sched_ext tasks
  sched/debug: Stop and start server based on if it was active
  sched/debug: Fix updating of ppos on server write ops
  sched/deadline: Clear the defer params
  entry: Inline syscall_exit_work() and syscall_trace_enter()
  entry: Add arch_ptrace_report_syscall_entry/exit()
  entry: Rework syscall_exit_to_user_mode_work() for architecture reuse
  entry: Remove unused syscall argument from syscall_trace_enter()
  sched: remove task_struct->faults_disabled_mapping
  sched: Update rq->avg_idle when a task is moved to an idle CPU
  selftests/rseq: Add rseq slice histogram script
  hrtimer: Fix trace oddity
  ...
2026-02-10 12:50:10 -08:00
arch Scheduler changes for v7.0: 2026-02-10 12:50:10 -08:00
block The kthread code provides an infrastructure which manages the preferred 2026-02-09 19:57:30 -08:00
certs modsign: Enable ML-DSA module signing 2026-02-02 16:57:39 +00:00
crypto Locking updates for v6.20: 2026-02-10 12:28:44 -08:00
Documentation Scheduler changes for v7.0: 2026-02-10 12:50:10 -08:00
drivers Locking updates for v6.20: 2026-02-10 12:28:44 -08:00
fs Locking updates for v6.20: 2026-02-10 12:28:44 -08:00
include Scheduler changes for v7.0: 2026-02-10 12:50:10 -08:00
init Scheduler changes for v7.0: 2026-02-10 12:50:10 -08:00
io_uring for-7.0/block-20260206 2026-02-09 17:57:21 -08:00
ipc mqueue: switch to CLASS(filename) 2026-01-16 12:52:04 -05:00
kernel Scheduler changes for v7.0: 2026-02-10 12:50:10 -08:00
lib Locking updates for v6.20: 2026-02-10 12:28:44 -08:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm Locking updates for v6.20: 2026-02-10 12:28:44 -08:00
net Locking updates for v6.20: 2026-02-10 12:28:44 -08:00
rust Locking updates for v6.20: 2026-02-10 12:28:44 -08:00
samples samples: rust: remove imports available via prelude 2026-01-26 18:15:20 +01:00
scripts Scheduler changes for v7.0: 2026-02-10 12:50:10 -08:00
security Locking updates for v6.20: 2026-02-10 12:28:44 -08:00
sound ALSA: hda/realtek: Enable headset mic for Acer Nitro 5 2026-02-05 09:05:10 +01:00
tools Scheduler changes for v7.0: 2026-02-10 12:50:10 -08:00
usr initramfs: add gen_init_cpio to hostprogs unconditionally 2025-11-26 21:55:40 +01:00
virt Performance events changes for v7.0: 2026-02-10 12:00:46 -08:00
.clang-format s390/pci: Fix cyclic dead-lock in zpci_zdev_put() and zpci_scan_devices() 2025-12-14 11:03:58 +01:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: kbuild: add proc macro library support 2025-11-24 17:15:36 +01:00
.mailmap Rust changes for v6.20 / v7.0 2026-02-10 11:53:01 -08:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS A slightly calmer cycle for docs this time around, though there is still a 2026-02-09 20:53:18 -08:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS Locking updates for v6.20: 2026-02-10 12:28:44 -08:00
Makefile Locking updates for v6.20: 2026-02-10 12:28:44 -08:00
README docs: add AI Coding Assistants documentation 2026-01-06 14:55:06 -07:00

Linux kernel
============

The Linux kernel is the core of any Linux operating system. It manages hardware,
system resources, and provides the fundamental services for all other software.

Quick Start
-----------

* Report a bug: See Documentation/admin-guide/reporting-issues.rst
* Get the latest kernel: https://kernel.org
* Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst
* Join the community: https://lore.kernel.org/

Essential Documentation
-----------------------

All users should be familiar with:

* Building requirements: Documentation/process/changes.rst
* Code of Conduct: Documentation/process/code-of-conduct.rst
* License: See COPYING

Documentation can be built with make htmldocs or viewed online at:
https://www.kernel.org/doc/html/latest/


Who Are You?
============

Find your role below:

* New Kernel Developer - Getting started with kernel development
* Academic Researcher - Studying kernel internals and architecture
* Security Expert - Hardening and vulnerability analysis
* Backport/Maintenance Engineer - Maintaining stable kernels
* System Administrator - Configuring and troubleshooting
* Maintainer - Leading subsystems and reviewing patches
* Hardware Vendor - Writing drivers for new hardware
* Distribution Maintainer - Packaging kernels for distros
* AI Coding Assistant - LLMs and AI-powered development tools


For Specific Users
==================

New Kernel Developer
--------------------

Welcome! Start your kernel development journey here:

* Getting Started: Documentation/process/development-process.rst
* Your First Patch: Documentation/process/submitting-patches.rst
* Coding Style: Documentation/process/coding-style.rst
* Build System: Documentation/kbuild/index.rst
* Development Tools: Documentation/dev-tools/index.rst
* Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst
* Core APIs: Documentation/core-api/index.rst

Academic Researcher
-------------------

Explore the kernel's architecture and internals:

* Researcher Guidelines: Documentation/process/researcher-guidelines.rst
* Memory Management: Documentation/mm/index.rst
* Scheduler: Documentation/scheduler/index.rst
* Networking Stack: Documentation/networking/index.rst
* Filesystems: Documentation/filesystems/index.rst
* RCU (Read-Copy Update): Documentation/RCU/index.rst
* Locking Primitives: Documentation/locking/index.rst
* Power Management: Documentation/power/index.rst

Security Expert
---------------

Security documentation and hardening guides:

* Security Documentation: Documentation/security/index.rst
* LSM Development: Documentation/security/lsm-development.rst
* Self Protection: Documentation/security/self-protection.rst
* Reporting Vulnerabilities: Documentation/process/security-bugs.rst
* CVE Procedures: Documentation/process/cve.rst
* Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst
* Security Features: Documentation/userspace-api/seccomp_filter.rst

Backport/Maintenance Engineer
-----------------------------

Maintain and stabilize kernel versions:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* Backporting Guide: Documentation/process/backporting.rst
* Applying Patches: Documentation/process/applying-patches.rst
* Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git for Maintainers: Documentation/maintainer/configure-git.rst

System Administrator
--------------------

Configure, tune, and troubleshoot Linux systems:

* Admin Guide: Documentation/admin-guide/index.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst
* Tracing/Debugging: Documentation/trace/index.rst
* Performance Security: Documentation/admin-guide/perf-security.rst
* Hardware Monitoring: Documentation/hwmon/index.rst

Maintainer
----------

Lead kernel subsystems and manage contributions:

* Maintainer Handbook: Documentation/maintainer/index.rst
* Pull Requests: Documentation/maintainer/pull-requests.rst
* Managing Patches: Documentation/maintainer/modifying-patches.rst
* Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst
* Development Process: Documentation/process/maintainer-handbooks.rst
* Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git Configuration: Documentation/maintainer/configure-git.rst

Hardware Vendor
---------------

Write drivers and support new hardware:

* Driver API Guide: Documentation/driver-api/index.rst
* Driver Model: Documentation/driver-api/driver-model/driver.rst
* Device Drivers: Documentation/driver-api/infrastructure.rst
* Bus Types: Documentation/driver-api/driver-model/bus.rst
* Device Tree Bindings: Documentation/devicetree/bindings/
* Power Management: Documentation/driver-api/pm/index.rst
* DMA API: Documentation/core-api/dma-api.rst

Distribution Maintainer
-----------------------

Package and distribute the kernel:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* ABI Documentation: Documentation/ABI/README
* Kernel Configuration: Documentation/kbuild/kconfig.rst
* Module Signing: Documentation/admin-guide/module-signing.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst

AI Coding Assistant
-------------------

CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and
follow the AI coding assistants documentation before contributing to the Linux
kernel:

* Documentation/process/coding-assistants.rst

This documentation contains essential requirements about licensing, attribution,
and the Developer Certificate of Origin that all AI tools must comply with.


Communication and Support
=========================

* Mailing Lists: https://lore.kernel.org/
* IRC: #kernelnewbies on irc.oftc.net
* Bugzilla: https://bugzilla.kernel.org/
* MAINTAINERS file: Lists subsystem maintainers and mailing lists
* Email Clients: Documentation/process/email-clients.rst