selftests/sched_ext: Make allowed_cpus idle validation race-free

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A remotely selected CPU can be re-advertised as idle by an idle-to-idle
re-pick before the BPF program validates the selection. Checking that
the selected CPU remains absent from the idle mask is therefore
inherently racy.

Validate a stable local invariant instead: a CPU executing
ops.select_cpu() or ops.enqueue() in a non-idle scheduling context must
not be advertised as idle. Read the idle mask without modifying it and
also validate selected CPUs against the requested domain and task
affinity.

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

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Andrea Righi 2026-08-03 08:08:13 +02:00 • committed by Tejun Heo

parent ba190ed3f4

commit 12da4723b6

1 changed files with 42 additions and 7 deletions

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tools/testing/selftests/sched_ext/allowed_cpus.bpf.c

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