linux-rng/Documentation/scheduler, branch master

Merge tag 'sched_ext-for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

2026-08-20T18:01:37Z

Pull sched_ext updates from Tejun Heo: "Most of this cycle completes the enqueue-path support for hierarchical sub-scheduling, which makes sub-scheduler support feature complete: a root BPF scheduler can now hand a cgroup subtree over to a nested sub-scheduler together with revocable CPU grants, and the sub-scheduler owns all scheduling decisions for its tasks on those CPUs. Development volume was high and a number of changes plugging holes in the new support landed late in the cycle. Also included are core scheduling fixes that were completed too late for the v7.2 release and are routed through this pull request. Sub-scheduler CPU delegation: - Parent schedulers now grant and revoke per-CPU capabilities (enqueueing, preemption, CPU frequency control) on their children, enforced on every path a scheduler can reach a CPU through. Previously only dispatching could be delegated; this lets sub-schedulers fully schedule their CPUs. - Rescue execution: a task whose scheduler doesn't have access to the CPUs the task needs to run on starved until the watchdog ejected the whole scheduler. The kernel now runs such tasks directly on a small bandwidth budget, turning a scheduler-killing failure into bounded degradation. - Cgroup integration: tasks migrating across a sub-scheduler boundary weren't re-homed to the new owner, causing wrong-scheduler scheduling and a use-after-free. Sub-schedulers now take over their cgroup subtree and receive its cgroup callbacks. - Arena objects now cross the kernel/BPF boundary as typed pointer arguments, translated transparently by the BPF tree's new arena argument support, replacing untyped arguments with manual translation. - scx_qmap now demonstrates full hierarchical sub-scheduling. Other fixes and updates: - Robustness improvements: the abort path is now NMI-safe, fixing deadlocks when errors are raised from NMI context and making hardlockup recovery direct. Reenqueue loops that could monopolize a CPU ahead of the watchdog now eject the offending scheduler, and stalls are blamed on the scheduler actually responsible. - Hardening: BPF-writable arena memory is validated before kernel use, and task slice and vtime writes got explicit synchronization rules, closing corruption vectors open to buggy or malicious schedulers. - Core scheduling: sched_ext dispatching can drop the rq lock inside the core-wide pick, which let interleaving selections corrupt each other's state and hard-hang the machine. The selection now restarts when the lock was released. The task ordering callback was also invoked with its arguments swapped, and the default ordering is updated to work across sub-scheduler boundaries. The fixes are marked for stable. - Other fixes headed for stable: a task init leak on fork failure during enable, tooling compat macros that silently failed to detect newer kernels, and a crash on reenqueueing against a destroyed dispatch queue. - Tooling: scx_pair moves off deprecated callbacks, and the deprecated scx_bpf_cpu_rq() kfunc is removed" * tag 'sched_ext-for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: (144 commits) sched_ext: Drop the dead SCX_DEQ_CORE_SCHED_EXEC test in dequeue_task_scx() sched_ext: Make core-sched task ordering hierarchy-aware sched_ext: Use runnable_at for the default core-sched task ordering sched_ext: Fix inverted ops.core_sched_before() invocation sched_ext: Move the config-off sub-cap kfunc stubs into sub.c sched_ext: Rename balance-era identifiers to dispatch terms sched_ext: Drop the stale keep_prev fixup in dispatch_pick() sched_ext: Keep kick_sync waiting on the rq's own CPU sched_ext: Make SCHED_CLASS_EXT select GENERIC_ALLOCATOR sched_ext/scx_flatcg: Fix cvtime true-up on slice expiry sched_ext: Don't BUG_ON a destroyed DSQ in process_deferred_reenq_users sched_ext: Fix scx_bpf_dsq_move_to_local___v2 compat detection sched_ext: Make scx_bpf_events() read the calling scheduler's counters sched_ext: Drop unlocked scx_rq_clock_invalidate() from scx_root_disable() selftests/sched_ext: Fix flaky ddsp failure tests on busy systems selftests/sched_ext: Make numa idle validation race-free sched_ext: Fix scx_bpf_dsq_reenq___compat kfunc extern prototype sched_ext/scx_flatcg: expire cached hweights on weight changes sched_ext: Fix exit_task leak on fork failure during enable sched_ext: fix stale references in doc comments ...

Merge tag 'docs-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/docs/linux

2026-08-20T17:31:50Z

Pull documentation updates from Jonathan Corbet: "It has been a not-too-busy cycle for docs; here's the highlights: - A (hopefully) consensus change to our LLM-attribution requirements, removing the specific model name from the Assisted-by tag - A couple of new realtime documents - Various docs-build-system fixes - Ongoing work with the Chinese, Portuguese, and Japanese translations ...and lots of typo fixes, grammar tweaks, etc" * tag 'docs-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/docs/linux: (85 commits) Doc: admin-guide: pm: Remove unnecessary backticks and fix a spell Documentation: Extend the real-time hardware bits with some firmware bits docs: pt_BR: Reorganize process/index.rst to follow english structure docs: conf.py: fix the 'utf-8' typo doc tools: fix 'path' typos Documentation: real-time: Add kernel configuration guide docs: python: abi_regex: convert adjacent index placeholders docs: python: abi_regex: catch the right exception for a bad regex docs: sphinx-build-wrapper: include localversion in kernel version string Documentation: html: adjust sidebar section titles styling Documentation: html: show sections in the sidebar checkpatch.pl: adapt to new Assisted-by: format MAINTAINERS: update Traditional Chinese documentation maintainers docs: pt_BR: process: Translate CVE documentation docs: pt_BR: translate the management-style.rst to Brazilian Portuguese docs: xforms_lists: support DEFINE_IDTENTRY_IRQ() coding-assistants: simplify attribution docs: translations: pt_BR: translate email-clients.rst docs: pt_BR: process: Translate the security-bugs.rst doc:it_IT: align doc-guide translation ...

Documentation: sched_ext: fix events sysfs path and show_state example

2026-08-14T19:10:03Z

The events file is under the scheduler's sysfs kobject (/sys/kernel/sched_ext/root/events for the root scheduler), not the nonexistent "/events" path. Also add the missing "aborting" line to the scx_show_state.py example. Signed-off-by: Tao Cui Signed-off-by: Tejun Heo

sched_ext: Bound per-task reenqueues and eject the owning scheduler

2026-07-26T21:12:19Z

Unlike local reenqueues, cap rejections have no repeat limit. A malfunctioning scheduler can keep re-inserting a task to a cid it lacks caps on, cycling the task through reject and reenqueue. This was assumed safe because a task that never runs trips the stall watchdog. However, the reenqueue irq_work re-arms itself and outranks the timer vector, blocking everything else on the CPU including stall detection and recovery, until the NMI hardlockup detector fires. Local reenqueues already have a repeat cap, SCX_REENQ_LOCAL_MAX_REPEAT, which needs generalizing to cover all reenqueues. It also has an attribution problem. Counted per-cpu on root, it tears down the whole hierarchy even when a sub-scheduler caused the repeated reenqueues. Generalize by bounding every reenqueue with one per-task counter. reenq_cnt is bumped in scx_do_enqueue_task() on each SCX_ENQ_REENQ, the single path every reenqueue producer passes through, and cleared in clr_task_runnable() when the task is picked to run and in scx_disable_task() when it leaves the scheduler's control. Past SCX_REENQ_MAX_REPEAT the task's owning scheduler is ejected with a new SCX_EXIT_ERROR_REENQ and the task is left stranded to be picked up during sched exit. The SCX_EV_REENQ_LOCAL_REPEAT event becomes SCX_EV_REENQ_REPEAT, counting repeat reenqueues from all sources. v2: Count SCX_EV_REENQ_REPEAT only when a reenqueue leads to another reenqueue, not on every reenqueue. v3: - Also clear reenq_cnt in scx_disable_task() so that the count doesn't carry over to the next owner across sched class switches, scheduler replacement or sub-scheduler rehoming (Andrea Righi). - Update the stale SCX_EV_REENQ_LOCAL_REPEAT references in sched-ext.rst (Andrea Righi). Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi

sched/Documentation: fix code

2026-07-15T16:51:28Z

checkpatch.pl returns 'trailing statements should be on next line' for this file. Do as told. Signed-off-by: Manuel Ebner Acked-by: Randy Dunlap Tested-by: Randy Dunlap Signed-off-by: Jonathan Corbet Message-ID: <20260703115114.229848-3-manuelebner@mailbox.org>

sched/doc: Fix stale em_pd_energy() reference in sched-energy

2026-07-15T16:51:28Z

The scheduler energy-aware placement documentation refers to the em_pd_energy() API, which was renamed to em_cpu_energy() in commit f0b5694791ce ("PM / EM: change name of em_pd_energy to em_cpu_energy"). Update the reference to the current name. em_cpu_energy() is the EM helper that compute_energy() in kernel/sched/fair.c calls to estimate a performance domain's energy consumption (defined in include/linux/energy_model.h). Sync the zh_CN translation, which carries the same stale name. Signed-off-by: Liang Luo Reviewed-by: Dongliang Mu Reviewed-by: Lukasz Luba Reviewed-by: Alex Shi Signed-off-by: Jonathan Corbet Message-ID: <20260707085335.2942128-1-luoliang@kylinos.cn>

sched_ext: Documentation: Fix ops table header reference

2026-07-07T22:23:33Z

The "Where to Look" and "ABI Instability" sections state that the ops table is defined in include/linux/sched/ext.h. However, struct sched_ext_ops is actually defined in kernel/sched/ext/internal.h, along with the SCX_OPS_* flags; include/linux/sched/ext.h holds the core data structures (struct sched_ext_entity, struct scx_dispatch_q, ...) and the DSQ constants. Point the ops table references to the correct header. Signed-off-by: Liang Luo Reviewed-by: Andrea Righi Signed-off-by: Tejun Heo

sched_ext: Move sources under kernel/sched/ext/

2026-06-22T15:32:56Z

The sched_ext sources had grown to ten ext* files directly under kernel/sched/. Move them into a new kernel/sched/ext/ subdirectory and drop the now-redundant ext_ prefix. ext.c/h keep their names. kernel/sched/ext.{c,h} -> kernel/sched/ext/ext.{c,h} kernel/sched/ext_internal.h -> kernel/sched/ext/internal.h kernel/sched/ext_types.h -> kernel/sched/ext/types.h kernel/sched/ext_idle.{c,h} -> kernel/sched/ext/idle.{c,h} kernel/sched/ext_cid.{c,h} -> kernel/sched/ext/cid.{c,h} kernel/sched/ext_arena.{c,h} -> kernel/sched/ext/arena.{c,h} The include paths in build_policy.c and sched.h, the MAINTAINERS glob, and a few documentation and comment references are updated to match. No code or symbol changes. Suggested-by: Linus Torvalds Reviewed-by: Andrea Righi Signed-off-by: Tejun Heo

Merge tag 'sched_ext-for-7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

2026-06-17T11:10:11Z

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 ...

Documentation/scheduler: Fix duplicated word in sched-deadline

2026-05-03T14:49:11Z

The SCHED_DEADLINE documentation has a duplicated the in the CPU affinity section. Remove the extra word. Signed-off-by: Miles Krause Signed-off-by: Jonathan Corbet Message-ID: <20260429222435.2041-1-mileskrause5200@gmail.com>