[Deepin-Kernel-SIG] [linux 6.18-y] [BORE] linux6.18.22-bore-6.6.3

[opsiff]

update to linux6.18.22-bore-6.6.3

Summary by Sourcery

Update BORE scheduler integration and safeguards while bumping to version 6.6.3.

Bug Fixes:

• Prevent potential invalid list access when traversing descendant tasks in the BORE burst-cache path.
• Limit burst-cache thread-group scans to avoid excessive iteration in large thread groups.
• Preserve and correctly adjust virtual lag for the currently running entity when reweighting under CONFIG_SCHED_BORE to maintain proper deadlines.

Enhancements:

• Strengthen child-counting and descendant traversal in BORE scheduling logic by using READ_ONCE and null-safe list helpers.
• Bump SCHED_BORE version identifier from 6.6.2 to 6.6.3.

[sourcery-ai]

Reviewer's Guide

Updates the BORE scheduler integration to version 6.6.3, tightening child/descendant traversal to be RCU-safe and bounded by a scan limit, and adjusting CFS entity reweighting to correctly preserve and restore vlag/vruntime when BORE is enabled.

Flow diagram for RCU-safe descendant traversal in inherit_from_ancestor_hub

flowchart TD
  A_start["Start inherit_from_ancestor_hub for_each_child"] --> B_init["scan_count = 0"]
  B_init --> C_loop_start{"Next direct_child?"}

  C_loop_start -- "No" --> Z_end["Return count"]
  C_loop_start -- "Yes" --> D_limits

  D_limits{"Count/scan limits reached?"} -->|"count >= BURST_CACHE_SAMPLE_LIMIT"| Z_end
  D_limits -->|"scan_count++ >= BURST_CACHE_SCAN_LIMIT"| Z_end
  D_limits -->|"Within limits"| E_set_desc

  E_set_desc["descendant = direct_child"] --> F_desc_loop{"count_children_upto2(descendant) == 1"}

  F_desc_loop -- "No" --> G_check_eligible
  F_desc_loop -- "Yes" --> H_next_desc

  H_next_desc["next_descendant = list_first_or_null_rcu(descendant->children)"] --> I_next_null{"next_descendant is NULL?"}
  I_next_null -- "Yes" --> G_check_eligible
  I_next_null -- "No" --> J_update_desc["descendant = next_descendant"] --> F_desc_loop

  G_check_eligible{"task_is_bore_eligible(descendant)?"} -->|"No"| C_loop_start
  G_check_eligible -->|"Yes"| K_inc_count["count++"] --> C_loop_start

  Z_end --> A_done["End inherit_from_ancestor_hub"]

Loading

File-Level Changes

Change	Details	Files
Harden BORE child/descendant traversal to be RCU-safe and avoid invalid list access.	Refactor count_children_upto2 to READ_ONCE() the first and second child list pointers instead of dereferencing next directly. Change descendant walking loop to use list_first_or_null_rcu when following children and break out if no next descendant is found. Add a scan_count limit to the descendant traversal loop by reusing BURST_CACHE_SCAN_LIMIT to avoid unbounded walks.	kernel/sched/bore.c
Bound BORE thread-group burst cache sampling by a scan limit.	Introduce scan_count in inherit_from_thread_group to cap the number of scanned threads using BURST_CACHE_SCAN_LIMIT. Short-circuit the thread iteration when either the sample or scan limit is reached.	kernel/sched/bore.c
Adjust reweight_entity behavior under CONFIG_SCHED_BORE to preserve vlag/vruntime for the current entity instead of re-placing it.	Capture se->vlag before reweighting when the entity is on the runqueue and BORE is enabled. For the current entity, restore vruntime based on the saved vlag and avoid calling place_entity, updating deadline only if it was relative. Keep existing place_entity path for non-current entities or when BORE is disabled.	kernel/sched/fair.c
Bump the exposed BORE scheduler version string to 6.6.3.	Update SCHED_BORE_VERSION macro from 6.6.2 to 6.6.3.	include/linux/sched/bore.h

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[sourcery-ai]

Hey - I've left some high level feedback:

• The new use of list_first_or_null_rcu() in inherit_from_ancestor_hub() assumes an RCU read-side critical section; double-check that the full traversal (including the for_each_child macro and descendant loop) is always executed under rcu_read_lock(), or switch to a non-RCU list helper if that guarantee does not hold.
• The CONFIG_SCHED_BORE ifdefs added to reweight_entity() significantly change the vruntime/deadline adjustment path for curr entities; it would be helpful to briefly justify in a comment why curr is treated specially here (restoring vlag_unscaled and bypassing place_entity) to make the interaction with protect_slice() and rel_deadline clearer for future readers.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The new use of list_first_or_null_rcu() in inherit_from_ancestor_hub() assumes an RCU read-side critical section; double-check that the full traversal (including the for_each_child macro and descendant loop) is always executed under rcu_read_lock(), or switch to a non-RCU list helper if that guarantee does not hold.
- The CONFIG_SCHED_BORE ifdefs added to reweight_entity() significantly change the vruntime/deadline adjustment path for curr entities; it would be helpful to briefly justify in a comment why curr is treated specially here (restoring vlag_unscaled and bypassing place_entity) to make the interaction with protect_slice() and rel_deadline clearer for future readers.

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[Copilot]

Pull request overview

Updates the BORE scheduler integration in the CFS/EEVDF codepaths while bumping the in-tree BORE version to 6.6.3, focusing on safer traversal/scan bounds and preserving scheduling invariants during reweighting.

Changes:

• Adjust reweight_entity() under CONFIG_SCHED_BORE to preserve/compensate virtual lag for the currently running entity.
• Harden BORE burst-cache traversal by using READ_ONCE() and list_first_or_null_rcu(), and add a scan limit for large thread groups.
• Bump SCHED_BORE_VERSION from 6.6.2 to 6.6.3.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
kernel/sched/fair.c	Updates CFS entity reweighting to preserve current entity timing/lag properties under BORE.
kernel/sched/bore.c	Makes descendant traversal null-safe and limits scanning in burst-cache inheritance logic.
include/linux/sched/bore.h	Bumps the reported BORE version string to 6.6.3.

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[Copilot]

The #endif comment says "!CONFIG_SCHED_BORE" but the corresponding conditional is "#ifdef CONFIG_SCHED_BORE". Please update the trailing comment to match the actual condition to avoid confusion during future maintenance (and keep it consistent with kernel style expectations).

[Copilot]

Same issue here: the trailing #endif comment says "!CONFIG_SCHED_BORE" even though the block is guarded by "#ifdef CONFIG_SCHED_BORE". Please correct the comment to match the conditional for clarity.

[Copilot]

The trailing #endif comment here also uses "!CONFIG_SCHED_BORE" while closing an "#ifdef CONFIG_SCHED_BORE" block. Please fix the comment to avoid misleading readers.

[opsiff]

/test-ok