sched_ext: Wait for SCX_OPSS_DISPATCHING before reenqueueing a task

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ebf1ccff79 ("sched_ext: Fix ops.dequeue() semantics") moved the final
ops_state store in scx_dispatch_enqueue() after the DSQ unlock so that the
custody update and ops.dequeue() precede it. A task can thus be found on a
DSQ while still SCX_OPSS_DISPATCHING.

The dequeue and core-sched pick paths wait for the state to clear in
ops_dequeue() but the reenqueue paths don't. A reenqueue in that window runs
ops.enqueue() and sets SCX_OPSS_QUEUED before the dispatch has completed.
The dispatcher's final store then overwrites it with SCX_OPSS_NONE and
finish_dispatch() drops every later dispatch of the task.

Wait for SCX_OPSS_DISPATCHING to clear before dequeueing a task for
reenqueue, the same way ops_dequeue() does.

Fixes: ebf1ccff79 ("sched_ext: Fix ops.dequeue() semantics")
Cc: stable@vger.kernel.org # v7.1+
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

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Tejun Heo 2026-09-15 12:34:44 -10:00

parent a9e3760b08

commit 7de9a6fb44

3 changed files with 15 additions and 0 deletions

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13

kernel/sched/ext/ext.c

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1

kernel/sched/ext/internal.h

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1

kernel/sched/ext/sub.c

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