fn mark_futex_owner_died(entry: u64, futex_offset: i64, tid: u32)Expand description
Mark a futex as owner-died if the current thread still holds it.
Reads the futex value at (entry + futex_offset). If the lower 30 bits
match tid, sets bit 30 (FUTEX_OWNER_DIED) and does a FUTEX_WAKE.