Tejun Heo e6979d05c6 tools/sched_ext: scx - Fix cmask_subset(), cmask_equal() and cmask_weight() ... cmask_equal(), cmask_weight() and cmask_subset() bounded their word walks with CMASK_NR_WORDS(nr_cids), which pads by one word and can't tell the last word in use without @base. The walks could thus cover a slack word past the active range, which cmask_reframe() leaves non-zero: a stale bit there gave cmask_equal() a spurious mismatch, cmask_weight() an inflated count, and cmask_subset() a spurious violation. cmask_subset() could also read @b->bits[] one word past its allocation (within the arena's fault-recovered range, so harmless), and deviated from the kernel scx_cmask_subset() by failing any @a range that doesn't nest inside @b's even when the overhanging bits are all clear. Bound the cmask_equal() and cmask_weight() walks by the words the range actually spans, with early returns for empty ranges. Rewrite cmask_subset() to match the kernel semantics: scan @a's overhangs for set bits with cmask_next_set() and walk the words of the range intersection. cmask_subset() moves below cmask_next_set(), which it now uses. Padding bits don't need masking as every cmask helper keeps them clear. Fixes: a58e6b79b4 ("sched_ext: Add cmask, a base-windowed bitmap over cid space") Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Andrea Righi <arighi@nvidia.com>		2026-07-09 11:08:41 -10:00
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bpf-compat/gnu
scx	tools/sched_ext: scx - Fix cmask_subset(), cmask_equal() and cmask_weight()	2026-07-09 11:08:41 -10:00