[opsiff]

Aligned with: https://gitee.com/anolis/cloud-kernel/pulls/4865/commits

Summary by Sourcery

Update scheduler and cgroup interfaces to support sched_ext scheduling classes and safer task lifecycle handling.

Bug Fixes:

• Make cgroup task iteration safe across interrupt contexts by preserving interrupt state while locking.
• Allow scheduler-specific fork cancellation and return errors from cgroup-aware scheduler fork setup.

Enhancements:

• Extend scheduler-class interfaces for task reweighting and class-transition handling, while centralizing load-average updates and cgroup weight conversions to support sched_ext integration.

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[sourcery-ai]

Reviewer's Guide

Updates the 6.6 scheduler and cgroup interfaces for sched_ext by adding scheduling-class lifecycle hooks, making fork setup cancellable, hardening cgroup iteration locking, and refactoring load-average and cgroup-weight handling into shared scheduler helpers.

Sequence diagram for cancellable scheduler fork setup

sequenceDiagram
    participant Fork as copy_process
    participant Scheduler as sched_cgroup_fork
    participant Cgroup as cgroup_cancel_fork
    participant Cancel as sched_cancel_fork

    Fork->>Scheduler: sched_cgroup_fork(p, args)
    alt scheduler fork setup fails
        Scheduler-->>Fork: return error
        Fork->>Cgroup: cgroup_cancel_fork(p, args)
    else later fork failure
        Scheduler-->>Fork: return 0
        Fork->>Cgroup: cgroup_cancel_fork(p, args)
    end
    Fork->>Cancel: sched_cancel_fork(p)

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Flow diagram for scheduler class transition handling

flowchart TD
    A[Scheduler changes task class] --> B[check_class_changing]
    B --> C{Previous class differs?}
    C -- No --> D[Continue scheduling update]
    C -- Yes --> E{New class has switching_to?}
    E -- No --> D
    E -- Yes --> F[Call switching_to]
    F --> D

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File-Level Changes

Change	Details	Files
Adds scheduler extension hooks and fork cancellation handling so scheduling classes can participate in task setup, class transitions, and task reweighting.	Make sched_cgroup_fork failure-aware and add sched_cancel_fork cleanup. Invoke a class hook when a task changes scheduling class. Move task reweighting behind sched_class->reweight_task and register the fair-class implementation. Relax scheduler class ordering checks from contiguous layout to relative ordering.	include/linux/sched/task.h kernel/fork.c kernel/sched/core.c kernel/sched/fair.c kernel/sched/sched.h kernel/sched/syscalls.c
Hardens cgroup task iteration against interrupt-context locking issues.	Replace irq-disabling spin-lock operations with irqsave/irqrestore around iterator state transitions. Represent iterator flags as an enum and scope their definitions under CONFIG_CGROUPS.	include/linux/cgroup.h kernel/cgroup/cgroup.c
Centralizes scheduler load and cgroup weight conversions while separating non-fair load-average updates.	Add shared conversion helpers for cgroup weights and use them for CPU weight reads and writes. Extract RT, deadline, thermal, and IRQ load-average updates into update_other_load_avgs(). Add normal_policy() and use it to restrict fair wakeup preemption to normal tasks.	kernel/sched/core.c kernel/sched/fair.c kernel/sched/sched.h kernel/sched/syscalls.c

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[Copilot]

🟡 Changes recommended

The new scheduler-class callbacks bypass existing reserved slots and break the preserved binary layout on KABI-enabled builds.

1 open issue

• Preserve sched_class ABI by using reserved tail slots · New

What changed in this PR

This PR prepares the scheduler and cgroup interfaces for sched_ext integration, adding lifecycle hooks and shared scheduler helpers.

Changes:

• Add scheduler-class reweighting and transition callbacks, plus fork cancellation and error-handling paths.
• Centralize non-fair load-average updates and cgroup weight conversions.
• Preserve interrupt state during cgroup task iteration.

File	Description
kernel/​sched/​syscalls.c	Add shared load-average updates and invoke the class-transition hook.
kernel/​sched/​sched.h	Define scheduler callbacks, policy helpers, and weight conversions.
kernel/​sched/​fair.c	Register fair-class reweighting and use shared helpers.
kernel/​sched/​core.c	Wire scheduler hooks, fork interfaces, and weight helpers.
kernel/​fork.c	Handle scheduler fork errors and cancellation cleanup.
kernel/​cgroup/​cgroup.c	Preserve interrupt state around iterator locks.
include/​linux/​sched/​task.h	Declare updated scheduler fork interfaces.
include/​linux/​cgroup.h	Expose weight constants unconditionally and convert iterator flags to an enum.

_{Review effort: Balanced}