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tools/sched_ext: scx_pair: fix stride == 0 crash on single-CPU systems

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nr_cpu_ids / 2 produces stride 0 on a single-CPU system, which later
causes SCX_BUG_ON(i == j) to fire. Validate stride after option
parsing to also catch invalid user-supplied values via -S.

Signed-off-by: David Carlier <devnexen@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
David Carlier 2026-02-17 20:08:36 +00:00 • committed by Tejun Heo
parent 55a24d9203
commit 625be3456b
1 changed files with 6 additions and 1 deletions
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7
tools/sched_ext/scx_pair.c
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@ -56,7 +56,6 @@ restart:
skel = SCX_OPS_OPEN(pair_ops, scx_pair);
skel->rodata->nr_cpu_ids = libbpf_num_possible_cpus();
assert(skel->rodata->nr_cpu_ids > 0);
skel->rodata->pair_batch_dur_ns = __COMPAT_ENUM_OR_ZERO("scx_public_consts", "SCX_SLICE_DFL");
/* pair up the earlier half to the latter by default, override with -s */
@ -76,6 +75,12 @@ restart:
}
}
/* Stride must be positive to pair distinct CPUs. */
if (stride <= 0) {
fprintf(stderr, "Invalid stride %d, must be positive\n", stride);
scx_pair__destroy(skel);
return -1;
}
bpf_map__set_max_entries(skel->maps.pair_ctx, skel->rodata->nr_cpu_ids / 2);
/* Resize arrays so their element count is equal to cpu count. */