core/sched.c: fix undefined behavior on 8-bit/16-bit #18573
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An `1 << x` with `x >= 15` is undefined behavior on 8-bit / 16-bit machines (which typically have `sizeof(int) == 2`). Using `1UL << x` is safe for `x <= 31`, which is large enough to make use of the full 32 bits in `runqueue_bitcache`. In addition, a `static_assert()` is added to enforce that `SCHED_PRIO_LEVELS` is never set to anything larger than 32.
maribu
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Type: bug
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Area: core
benpicco
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Sep 10, 2022
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Contribution description
An
1 << xwithx >= 15is undefined behavior on 8-bit / 16-bit machines (which typically havesizeof(int) == 2).Using
1UL << xis safe forx <= 31, which is large enough to make use of the full 32 bits inrunqueue_bitcache.In addition, a
static_assert()is added to enforce thatSCHED_PRIO_LEVELSis never set to anything larger than 32.Testing procedure
Code review should be sufficient IMO.
Issues/PRs references
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