sched_ext: Authorize remote-move inserts against the placing scheduler

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scx_local_or_reject_dsq() authorizes a local-DSQ insert against the caps
of the scheduler doing the insert. On the consume/dispatch paths that is
the scheduler running balance_one(), passed down through
scx_consume_dispatch_q() and move_local_task_to_local_dsq(), so the check
is correct.

The remote-move path loses it. move_remote_task_to_local_dsq()
re-activates @p on the destination rq through enqueue_task_scx(), which
reconstructs the scheduler from the task, i.e. @p's owner. When an
ancestor places a descendant's task - e.g. draining a bypassed
sub-scheduler - the owner is a sub-scheduler of the placer, so
authorizing against the owner checks a narrower cap set and can
spuriously reject a task the placer is entitled to run.

Carry the placing scheduler across the activate_task() boundary the same
way enq_flags already are, via a per-rq field set only for the duration
of the re-activation, and have scx_local_or_reject_dsq() authorize
against it. The placer's caps are a superset of the owner's, so this
admits what the placer may run and keeps rejecting what it may not.

v2: Document @sch in move_remote_task_to_local_dsq()'s kerneldoc. (Andrea)

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

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This commit is contained in:

Tejun Heo 2026-07-13 22:18:44 -10:00

parent 6ea3be3680

commit f2c9f5155b

3 changed files with 25 additions and 15 deletions

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28

kernel/sched/ext/ext.c

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9

kernel/sched/ext/sub.c

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3

kernel/sched/sched.h

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