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Linus Torvalds 5b33fc6492 sched_ext: Changes for v7.2
This depends on the BPF arena work in bpf-next and should be pulled after
 it. for-7.1-fixes was merged in a few times to avoid conflicts with the
 feature changes.
 
 - Most of this continues the in-development sub-scheduler support, which
   lets a root BPF scheduler delegate to nested sub-schedulers. The
   dispatch-path building blocks landed in 7.1. A follow-up patchset in
   development will complete enqueue-path support for hierarchical
   scheduling. This cycle adds most of that infrastructure:
 
   - Topological CPU IDs (cids): a dense, topology-ordered CPU numbering
     where the CPUs of a core, LLC, or NUMA node form contiguous ranges,
     so a topology unit becomes a (start, length) slice. Raw CPU numbers
     are sparse and don't track topological closeness, which makes them
     clumsy for sharding work across sub-schedulers and awkward in BPF.
 
   - cmask: bitmaps windowed over a slice of cid space, so a sub-scheduler
     can track, for example, the idle cids of its shard without a full
     NR_CPUS cpumask.
 
   - A struct_ops variant that cid-form sub-schedulers register with,
     along with the cid-form kfuncs they call.
 
   - BPF arena integration, which sub-scheduler support is built on. The
     bpf-next additions let the kernel read and write the BPF scheduler's
     arena directly, turning it into a real kernel/BPF shared-memory
     channel. Shared state like the per-CPU cmask now lives there.
 
   - scx_qmap is reworked to exercise the new arena and cid interfaces.
 
 - Exit-dump improvements: dump the faulting CPU first, expose the exit
   CPU to BPF and userspace, and normalize the dump header.
 
 - Misc kfuncs and cleanups: a task-ID lookup kfunc, __printf checking on
   the error and dump formatters, header reorganization, and assorted
   fixes.
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Merge tag 'sched_ext-for-7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext updates from Tejun Heo:
 "Most of this continues the in-development sub-scheduler support, which
  lets a root BPF scheduler delegate to nested sub-schedulers. The
  dispatch-path building blocks landed in 7.1. A follow-up patchset in
  development will complete enqueue-path support for hierarchical
  scheduling. This cycle adds most of that infrastructure:

   - Topological CPU IDs (cids): a dense, topology-ordered CPU numbering
     where the CPUs of a core, LLC, or NUMA node form contiguous ranges,
     so a topology unit becomes a (start, length) slice. Raw CPU numbers
     are sparse and don't track topological closeness, which makes them
     clumsy for sharding work across sub-schedulers and awkward in BPF.

   - cmask: bitmaps windowed over a slice of cid space, so a
     sub-scheduler can track, for example, the idle cids of its shard
     without a full NR_CPUS cpumask.

   - A struct_ops variant that cid-form sub-schedulers register with,
     along with the cid-form kfuncs they call.

   - BPF arena integration, which sub-scheduler support is built on. The
     bpf-next additions let the kernel read and write the BPF
     scheduler's arena directly, turning it into a real kernel/BPF
     shared-memory channel. Shared state like the per-CPU cmask now
     lives there.

   - scx_qmap is reworked to exercise the new arena and cid interfaces.

  Additionally:

   - Exit-dump improvements: dump the faulting CPU first, expose the
     exit CPU to BPF and userspace, and normalize the dump header.

   - Misc kfuncs and cleanups: a task-ID lookup kfunc, __printf checking
     on the error and dump formatters, header reorganization, and
     assorted fixes"

* tag 'sched_ext-for-7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: (59 commits)
  sched_ext: Add scx_arena_to_kaddr() / scx_kaddr_to_arena()
  sched_ext: Make scx_bpf_kick_cid() return s32
  sched_ext: Add scx_cmask_test() and scx_cmask_for_each_cid()
  tools/sched_ext: Order single-cid cmask helpers as (cid, mask)
  sched_ext: Order single-cid cmask helpers as (cid, mask)
  selftests/sched_ext: Fix dsq_move_to_local check
  sched_ext: Guard BPF arena helper calls to fix 32-bit build
  sched_ext: idle: Fix errno loss in scx_idle_init()
  sched_ext: Convert ops.set_cmask() to arena-resident cmask
  sched_ext: Sub-allocator over kernel-claimed BPF arena pages
  sched_ext: Require an arena for cid-form schedulers
  sched_ext: Add cmask mask ops
  sched_ext: Track bits[] storage size in struct scx_cmask
  sched_ext: Rename scx_cmask.nr_bits to nr_cids
  tools/sched_ext: scx_qmap: Fix qa arena placement
  sched_ext: Mark !CONFIG_EXT_SUB_SCHED dummy stubs static inline
  sched_ext: Replace tryget_task_struct() with get_task_struct()
  sched_ext: Add scx_task_iter_relock() and use it in scx_root_enable_workfn()
  sched_ext: Fix ops_cid layout assert
  sched_ext: Use offsetofend on both sides of the ops_cid layout assert
  ...
2026-06-17 12:10:11 +01:00
arch bitmap updates for v7.2 2026-06-17 11:38:38 +01:00
block - small cleanups in dm-vdo, dm-raid, dm-cache, dm-zoned-metadata 2026-06-16 13:20:54 +05:30
certs Clang build fixes for 7.1 2026-04-24 09:29:51 -07:00
crypto Networking changes for 7.2. 2026-06-17 08:17:00 +01:00
Documentation sched_ext: Changes for v7.2 2026-06-17 12:10:11 +01:00
drivers workqueue: Changes for v7.2 2026-06-17 11:57:44 +01:00
fs workqueue: Changes for v7.2 2026-06-17 11:57:44 +01:00
include sched_ext: Changes for v7.2 2026-06-17 12:10:11 +01:00
init Bootconfig updates for v7.2 2026-06-16 17:29:24 +05:30
io_uring Networking changes for 7.2. 2026-06-17 08:17:00 +01:00
ipc kernel-7.2-rc1.misc 2026-06-15 03:05:50 +05:30
kernel sched_ext: Changes for v7.2 2026-06-17 12:10:11 +01:00
lib workqueue: Changes for v7.2 2026-06-17 11:57:44 +01:00
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 for-7.2/block-20260615 2026-06-16 13:02:47 +05:30
net bpf-next-7.2 2026-06-17 09:18:14 +01:00
rust Modules changes for v7.2-rc1 2026-06-17 11:35:58 +01:00
samples Driver core changes for 7.2-rc1 2026-06-15 12:41:17 +05:30
scripts linux_kselftest-kunit-7.2-rc1 2026-06-16 16:33:57 +05:30
security Networking changes for 7.2. 2026-06-17 08:17:00 +01:00
sound sound updates for 7.2-rc1 2026-06-17 11:18:45 +01:00
tools sched_ext: Changes for v7.2 2026-06-17 12:10:11 +01:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt vfs-7.2-rc1.misc 2026-06-15 03:59:45 +05:30
.clang-format Devicetree updates for v7.0: 2026-02-11 18:27:08 -08:00
.clippy.toml rust: bump Clippy's MSRV and clean incompatible_msrv allows 2026-04-07 09:51:39 +02:00
.cocciconfig
.editorconfig editorconfig: add rst extension 2026-01-26 19:07:09 -08:00
.get_maintainer.ignore .get_maintainer.ignore: add myself 2026-04-02 16:48:25 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Rust changes for v7.2 2026-06-15 09:25:48 +05:30
.mailmap mailmap: add entry for Jesse Brandeburg 2026-06-15 12:59:04 -07:00
.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 fbdev fixes & cleanups for 7.2-rc1: 2026-06-16 08:28:41 +05:30
Kbuild checksyscalls: move instance functionality into generic code 2026-04-05 09:21:32 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS bitmap updates for v7.2 2026-06-17 11:38:38 +01:00
Makefile slab changes for 7.2 2026-06-16 08:44:43 +05:30
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