sched_ext: Wait for SCX_OPSS_DISPATCHING before moving tasks off DSQs

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A task can be found on a non-local DSQ while the CPU which dispatched it
is still running ops.dequeue() and hasn't cleared SCX_OPSS_DISPATCHING.
The DSQ consume and move paths don't wait for the dispatch to finish and
can operate on the task concurrently with the dispatcher.

Call scx_wait_dispatching() in scx_move_local_task_to_local_dsq(),
unlink_dsq_and_switch_rq_lock() and move_task_between_dsqs() before they
operate on the task. In scx_move_local_task_to_local_dsq(), wait before
scx_resolve_local_dsq() as it may update p->scx.flags.

Fixes: ebf1ccff79 ("sched_ext: Fix ops.dequeue() semantics")
Fixes: cb86607ada ("sched_ext: Don't run ops.dequeue() with a DSQ lock held")
Cc: stable@vger.kernel.org # v7.1+
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Assisted-by: Claude:claude-opus-5.5
Signed-off-by: Kuba Piecuch <jpiecuch@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

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Kuba Piecuch 2026-10-12 21:07:46 +00:00 • committed by Tejun Heo

parent 18f5c699d1

commit 2935062be7

1 changed files with 12 additions and 3 deletions

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kernel/sched/ext/ext.c

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