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Tejun Heo 5ebec443fb sched_ext: Exit dispatch and move operations immediately when aborting 
62dcbab8b0 ("sched_ext: Avoid live-locking bypass mode switching") introduced
the breather mechanism to inject delays during bypass mode switching. It
maintains operation semantics unchanged while reducing lock contention to avoid
live-locks on large NUMA systems.

However, the breather only activates when exiting the scheduler, so there's no
need to maintain operation semantics. Simplify by exiting dispatch and move
operations immediately when scx_aborting is set. In consume_dispatch_q(), break
out of the task iteration loop. In scx_dsq_move(), return early before
acquiring locks.

This also fixes cases the breather mechanism cannot handle. When a large system
has many runnable threads affinitized to different CPU subsets and the BPF
scheduler places them all into a single DSQ, many CPUs can scan the DSQ
concurrently for tasks they can run. This can cause DSQ and RQ locks to be held
for extended periods, leading to various failure modes. The breather cannot
solve this because once in the consume loop, there's no exit. The new mechanism
fixes this by exiting the loop immediately.

The bypass DSQ is exempted to ensure the bypass mechanism itself can make
progress.

v2: Use READ_ONCE() when reading scx_aborting (Andrea Righi).

Reported-by: Dan Schatzberg <schatzberg.dan@gmail.com>
Reviewed-by: Dan Schatzberg <schatzberg.dan@gmail.com>
Cc: Andrea Righi <arighi@nvidia.com>
Cc: Emil Tsalapatis <etsal@meta.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
History 2025-11-12 06:43:44 -10:00
arch sched_ext: Merge branch 'for-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup into for-6.19 2025-11-03 11:57:26 -10:00
block block-6.18-20251016 2025-10-17 08:31:26 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto This push contains the following changes: 2025-10-10 08:56:16 -07:00
Documentation Rust 'rustfmt' cleanup 2025-10-18 10:05:13 -10:00
drivers Hi, 2025-10-18 08:38:28 -10:00
fs Description for this pull request: 2025-10-18 07:23:59 -10:00
include sched_ext: Use per-CPU DSQs instead of per-node global DSQs in bypass mode 2025-11-12 06:43:44 -10:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/rw: check for NULL io_br_sel when putting a buffer 2025-10-15 13:38:53 -06:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel sched_ext: Exit dispatch and move operations immediately when aborting 2025-11-12 06:43:44 -10:00
lib lib/test_kho: use kho_preserve_vmalloc instead of storing addresses in fdt 2025-10-07 13:48:56 -07:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm slab: reset slab->obj_ext when freeing and it is OBJEXTS_ALLOC_FAIL 2025-10-16 15:16:45 +02:00
net bpf-fixes 2025-10-18 08:00:43 -10:00
rust rust: bitmap: fix formatting 2025-10-17 13:02:22 +02:00
samples Char/Misc/IIO/Binder changes for 6.18-rc1 2025-10-04 16:26:32 -07:00
scripts Kbuild fixes for 6.18 #1 2025-10-11 15:47:12 -07:00
security integrity-v6.18 2025-10-05 10:48:33 -07:00
sound ALSA: hda/realtek: Fix mute led for HP Omen 17-cb0xxx 2025-10-17 16:37:21 +02:00
tools sched_ext: Merge branch 'for-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup into for-6.19 2025-11-03 11:57:26 -10:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM x86 fixes for 6.18: 2025-10-18 10:25:43 +02:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.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 .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap Including fixes from CAN 2025-10-16 09:41:21 -07:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.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 USB/Thunderbolt changes for 6.18-rc1 2025-10-04 16:07:08 -07:00
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 Including fixes from CAN 2025-10-16 09:41:21 -07:00
Makefile Linux 6.18-rc2 2025-10-19 15:19:16 -10:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

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

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.