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

Pull sched_ext updates from Tejun Heo:
"Most of this cycle completes the enqueue-path support for hierarc

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

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
...

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sched_ext: Rename balance-era identifiers to dispatch terms

sched_class->balance() is gone from sched_ext and what balance_one() does is
run dispatch to produce something pickable. Update the balanc

sched_ext: Rename balance-era identifiers to dispatch terms

sched_class->balance() is gone from sched_ext and what balance_one() does is
run dispatch to produce something pickable. Update the balance-era names to
dispatch terms:

- balance_one() -> dispatch_one()
- SCX_RQ_IN_BALANCE -> SCX_RQ_IN_DISPATCH

No BPF scheduler reads the flag. The enum autogen headers gain the new name
with the old entry retained like other removed enumerators, zero-filling at
load time. No functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>

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sched_ext: fix stale references in doc comments

- inlines.h: scx_bpf_dispatch() doesn't exist; the comment means
scx_bpf_sub_dispatch()
- internal.h: name %SCX_DEQ_SCHED_CHANGE instead of the neve

sched_ext: fix stale references in doc comments

- inlines.h: scx_bpf_dispatch() doesn't exist; the comment means
scx_bpf_sub_dispatch()
- internal.h: name %SCX_DEQ_SCHED_CHANGE instead of the never-defined
%SCX_DEQ_SAVE
- internal.h: @name shows up in the ops file in the scheduler's sysfs
directory, not a "kernel.sched_ext_ops" sysctl

Signed-off-by: Tao Cui <cuitao@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>

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Merge branch 'for-7.3' into for-7.3-arena-args

sched_ext: Merge branch 'for-7.2-fixes' into for-7.3

Pull to receive:

c10b216a072f ("sched/core: Handle pick_task() releasing the rq lock")
f3629c63a4af ("sched/core: Make core-sched flips wait f

sched_ext: Merge branch 'for-7.2-fixes' into for-7.3

Pull to receive:

c10b216a072f ("sched/core: Handle pick_task() releasing the rq lock")
f3629c63a4af ("sched/core: Make core-sched flips wait for in-flight selections")
ffaab58d2175 ("sched_ext: Replace SCX_RQ_BAL_KEEP with a dispatch verdict return")
3dd52416e44a ("sched_ext: Fix this_rq() assumptions in dispatch kfuncs")
f2da9587118d ("sched_ext: Count rq lock releases in rq->scx.lock_drop_seq")
d954004205c1 ("sched_ext: Fix rq->core_pick corruption under core scheduling")

for the pending core scheduling follow-ups and to resolve the conflicts
with the code reorganization and cap gate work on for-7.3.

ffaab58d2175 converts scx_dispatch_sched() to a dispatch verdict return
which for-7.3 moved from ext.c into inlines.h. Resolved by applying the
conversion to the relocated copy and combining balance_one()'s verdict
returns with the scx_task_can_stay_on_cpu() gate from the cap work.

ffaab58d2175 and 3dd52416e44a update scx_bpf_sub_dispatch() which
for-7.3 moved into sub.c. Resolved by applying the scx_locked_rq()
switch and the verdict test to the sub.c copy.

f2da9587118d instruments the open-coded lock releases in
consume_remote_task() which for-7.3 folded into switch_rq_lock().
Resolved by keeping the accounting in switch_rq_lock() which covers all
its callers.

d954004205c1 widens the put_prev_task_scx() WARN suppression to all
core-sched rqs on the same condition that for-7.3 gated with
scx_task_can_stay_on_cpu(). Resolved by combining both.

Signed-off-by: Tejun Heo <tj@kernel.org>

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sched_ext: Gate sub_dispatch_prev with CONFIG_EXT_SUB_SCHED

rq->scx.sub_dispatch_prev is sub-sched-only but was left unconditional. Move
it into the CONFIG_EXT_SUB_SCHED block next to ecaps_to_sync

sched_ext: Gate sub_dispatch_prev with CONFIG_EXT_SUB_SCHED

rq->scx.sub_dispatch_prev is sub-sched-only but was left unconditional. Move
it into the CONFIG_EXT_SUB_SCHED block next to ecaps_to_sync and gate its
updates.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

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sched_ext: Move scx_dispatch_sched() to a new inlines.h

scx_dispatch_sched() is common dispatch machinery and looks out of place in
sub.h, but it needs scx_cpu_arg() from cid.h and can't move into i

sched_ext: Move scx_dispatch_sched() to a new inlines.h

scx_dispatch_sched() is common dispatch machinery and looks out of place in
sub.h, but it needs scx_cpu_arg() from cid.h and can't move into internal.h
without creating a circular include. Add inlines.h on top of internal.h and
cid.h, and move the function there. The function was sub.h's only cid.h
user, so drop that include. Pure code move, no functional change.

v2: Host the function in a new inlines.h instead of at internal.h's tail,
which formed a circular include with cid.h. Drop sub.h's now-unused
cid.h include. (sashiko AI)

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

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