Merge tag 'sched_ext-for-7.0-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext fixes from Tejun Heo:

- Fix SCX_KICK_WAIT deadlock where multiple CPUs waiting

Merge tag 'sched_ext-for-7.0-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext fixes from Tejun Heo:

- Fix SCX_KICK_WAIT deadlock where multiple CPUs waiting for each other
in hardirq context form a cycle. Move the wait to a balance callback
which can drop the rq lock and process IPIs.

- Fix inconsistent NUMA node lookup in scx_select_cpu_dfl() where
the waker_node used cpu_to_node() while prev_cpu used
scx_cpu_node_if_enabled(), leading to undefined behavior when
per-node idle tracking is disabled.

* tag 'sched_ext-for-7.0-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
selftests/sched_ext: Add cyclic SCX_KICK_WAIT stress test
sched_ext: Fix SCX_KICK_WAIT deadlock by deferring wait to balance callback
sched_ext: Fix inconsistent NUMA node lookup in scx_select_cpu_dfl()

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selftests/sched_ext: Add cyclic SCX_KICK_WAIT stress test

Add a test that creates a 3-CPU kick_wait cycle (A->B->C->A). A BPF
scheduler kicks the next CPU in the ring with SCX_KICK_WAIT on every
enq

selftests/sched_ext: Add cyclic SCX_KICK_WAIT stress test

Add a test that creates a 3-CPU kick_wait cycle (A->B->C->A). A BPF
scheduler kicks the next CPU in the ring with SCX_KICK_WAIT on every
enqueue while userspace workers generate continuous scheduling churn via
sched_yield(). Without the preceding fix, this hangs the machine within seconds.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Tested-by: Christian Loehle <christian.loehle@arm.com>

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