Attached is a regression test in the libc-test framework for the bug
fixed in commit 76ca7a5446a8aec2b671a401d5e1878c4704754e:

    fix failure of internal futex __timedwait to report ECANCELED
    
    as part of abstracting the futex wait, this function suppresses all
    futex error values which callers should not see using a whitelist
    approach. when the masked cancellation mode was added, the new
    ECANCELED error was not whitelisted. this omission caused the new
    pthread_cond_wait code using masked cancellation to exhibit a spurious
    wake (rather than acting on cancellation) when the request arrived
    after blocking on the cond var.

Rich