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Linus Torvalds a60ce761d9 Updates for the time/timer core subsystem:
- Harden the user space controllable hrtimer interfaces further to
     protect against unpriviledged DoS attempts by arming timers in the past.
 
   - Add per-capacity hierarchies to the timer migration code to prevent
     timer migration accross different capacity domains. This code has been
     disabled last minute as there is a pathological problem with SoCs which
     advertise a larger number of capacity domains. The problem is under
     investigation and the code won't be active before v7.3, but that turned
     out to be less intrusive than a full revert as it preserves the
     preparatory steps and allows people to work on the final resolution
 
   - Export time namespace functionality as a recent user can be built as a
     module.
 
   - Initialize the jiffies clocksource before using it. The recent
     hardening against time moving backward requires that the related
     members of struct clocksource have been initialized, otherwise it
     clamps the readout to 0, which makes time stand sill and causes boot
     delays.
 
   - Fix a more than twenty year old PID reference count leak in an error
     path of the POSIX CPU timer code.
 
   - The usual small fixes, improvements and cleanups all over the place.
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Merge tag 'timers-core-2026-06-13' of gitolite.kernel.org:pub/scm/linux/kernel/git/tip/tip

Pull timer core updates from Thomas Gleixner:
 "Updates for the time/timer core subsystem:

   - Harden the user space controllable hrtimer interfaces further to
     protect against unpriviledged DoS attempts by arming timers in the
     past.

   - Add per-capacity hierarchies to the timer migration code to prevent
     timer migration accross different capacity domains. This code has
     been disabled last minute as there is a pathological problem with
     SoCs which advertise a larger number of capacity domains. The
     problem is under investigation and the code won't be active before
     v7.3, but that turned out to be less intrusive than a full revert
     as it preserves the preparatory steps and allows people to work on
     the final resolution

   - Export time namespace functionality as a recent user can be built
     as a module.

   - Initialize the jiffies clocksource before using it. The recent
     hardening against time moving backward requires that the related
     members of struct clocksource have been initialized, otherwise it
     clamps the readout to 0, which makes time stand sill and causes
     boot delays.

   - Fix a more than twenty year old PID reference count leak in an
     error path of the POSIX CPU timer code.

   - The usual small fixes, improvements and cleanups all over the
     place"

* tag 'timers-core-2026-06-13' of gitolite.kernel.org:pub/scm/linux/kernel/git/tip/tip: (31 commits)
  posix-cpu-timers: Fix pid refcount leak in do_cpu_nanosleep() error path
  time/jiffies: Register jiffies clocksource before usage
  timers/migration: Temporarily disable per capacity hierarchies
  timers/migration: Turn tmigr_hierarchy level_list into a flexible array
  timers/migration: Deactivate per-capacity hierarchies under nohz_full
  timers/migration: Fix hotplug migrator selection target on asymetric capacity machines
  ntsync: Honour caller's time namespace for absolute MONOTONIC timeouts
  time/namespace: Export init_time_ns and do_timens_ktime_to_host()
  timers/migration: Update stale @online doc to @available
  timers: Fix flseep() typo in kernel-doc comment
  hrtimer: Fix the bogus return type of __hrtimer_start_range_ns()
  hrtimer: Return ktime_t from hrtimer_get_next_event()/hrtimer_next_event_without()
  clocksource: Clean up clocksource_update_freq() functions
  alarmtimer: Remove stale return description from alarm_handle_timer()
  selftests/posix_timers: Use CLOCK_THREAD_CPUTIME_ID for ITIMER_PROF measurements
  scripts/timers: Add timer_migration_tree.py
  timers/migration: Handle capacity in connect tracepoints
  timers/migration: Split per-capacity hierarchies
  timers/migration: Track CPUs in a hierarchy
  timers/migration: Abstract out hierarchy to prepare for CPU capacity awareness
  ...
2026-06-15 13:39:12 +05:30
arch Updates for clocksource/clockevent drivers: 2026-06-15 13:34:03 +05:30
block block-7.1-20260529 2026-05-29 10:41:07 -07:00
certs Clang build fixes for 7.1 2026-04-24 09:29:51 -07:00
crypto crypto/krb5, rxrpc: Fix lack of pre-decrypt/pre-verify length checks 2026-05-20 16:36:45 -07:00
Documentation Updates for clocksource/clockevent drivers: 2026-06-15 13:34:03 +05:30
drivers Updates for the time/timer core subsystem: 2026-06-15 13:39:12 +05:30
fs Updates for the time/timer core subsystem: 2026-06-15 13:39:12 +05:30
include Updates for the time/timer core subsystem: 2026-06-15 13:39:12 +05:30
init Rust changes for v7.2 2026-06-15 09:25:48 +05:30
io_uring io_uring-7.1-20260611 2026-06-12 10:49:59 -07:00
ipc kernel-7.2-rc1.misc 2026-06-15 03:05:50 +05:30
kernel Updates for the time/timer core subsystem: 2026-06-15 13:39:12 +05:30
lib vfs-7.2-rc1.misc 2026-06-15 03:59:45 +05:30
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 Driver core changes for 7.2-rc1 2026-06-15 12:41:17 +05:30
net Updates for the time/timer core subsystem: 2026-06-15 13:39:12 +05:30
rust Driver core changes for 7.2-rc1 2026-06-15 12:41:17 +05:30
samples Driver core changes for 7.2-rc1 2026-06-15 12:41:17 +05:30
scripts Updates for the time/timer core subsystem: 2026-06-15 13:39:12 +05:30
security Kbuild / Kconfig changes for 7.2 2026-06-15 05:01:15 +05:30
sound ASoC: Fixes for v7.1 2026-06-11 21:29:47 +02:00
tools Updates for the time/timer core subsystem: 2026-06-15 13:39:12 +05:30
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 scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 MAINTAINERS: update Baoquan He's email address 2026-06-03 16:25:50 -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 Delete some obsolete networking code 2026-04-24 09:41:58 -07:00
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 Two small updates to the SMP/hotplug subsystem: 2026-06-15 13:30:04 +05:30
Makefile Rust changes for v7.2 2026-06-15 09:25:48 +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