Merge tag 'sched_ext-for-7.3-rc4-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext fixes from Tejun Heo:

- A task reenqueued while its dispatch was still completi

Merge tag 'sched_ext-for-7.3-rc4-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext fixes from Tejun Heo:

- A task reenqueued while its dispatch was still completing had its
queued state clobbered by the dispatcher, dropping every later
dispatch of the task. Wait for the in-flight dispatch to settle
first

- A wakeup activation on another CPU marked the destination runqueue as
mid-wakeup, stranding a pending local reenqueue. If the scheduler was
unloaded first, the stale request pointed into freed memory that the
next scheduler dereferenced

- ops.dequeue() ran with the source dispatch queue's lock held, so a
scheduler iterating that queue from the callback deadlocked the CPU

- Schedulers with their own CPU ID mapping had no way to learn a task's
initial CPU mask and rebuilt it themselves, which went wrong across
sub-scheduler enable and re-home. Pass it to ops.enable()

- A bypass dispatch event counter missed the dispatches made by the
end-of-dispatch fallback and under-reported

- Selftests for the dequeue locking and initial mask changes

* tag 'sched_ext-for-7.3-rc4-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
sched_ext: Count SCX_EV_SUB_BYPASS_DISPATCH in the dispatch fallback
selftests/sched_ext: Check the cmask cid-form ops.enable() receives
sched_ext: Pass the initial cmask to cid-form ops.enable()
selftests/sched_ext: Test that ops.dequeue() can iterate the consumed DSQ
sched_ext: Don't run ops.dequeue() with a DSQ lock held
sched_ext: Derive SCX_RQ_IN_WAKEUP from the core enqueue flags
sched_ext: Wait for SCX_OPSS_DISPATCHING before reenqueueing a task

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selftests/sched_ext: Test that ops.dequeue() can iterate the consumed DSQ

Add a scheduler whose ops.dequeue() iterates the source user DSQ with
bpf_iter_scx_dsq. The iteration takes the DSQ's raw sp

selftests/sched_ext: Test that ops.dequeue() can iterate the consumed DSQ

Add a scheduler whose ops.dequeue() iterates the source user DSQ with
bpf_iter_scx_dsq. The iteration takes the DSQ's raw spinlock; on a
kernel that runs ops.dequeue() while the consume path still holds that
lock, the first task consumed self-deadlocks the CPU with IRQs
disabled. The watchdog cannot recover from that state, so on an
unfixed kernel this test wedges the system instead of failing cleanly.
On a fixed kernel the scheduler runs clean and the test passes.

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

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