[libcxx] [test] Make the condvar wait_for tests less brittle
These seem to fail occasionally (they are marked as possibly requiring
a retry).
When doing a condvar wait_for(), it can wake up before the timeout
as a spurious wakeup. In these cases, the wait_for() method returns that
the timeout wasn't hit, and the test reruns another wait_for().
On Windows, it seems like the wait_for() operation often can end up
returning slightly before the intended deadline - when intending to
wait for 250 milliseconds, it can return after e.g. 235 milliseconds.
In these cases, the wait_for() doesn't indicate a timeout.
Previously, the test then reran a new wait_for() for a full 250
milliseconds each time. So for N consecutive wakeups slightly too early,
we'd wait for (N+1)*250 milliseconds. Now it only reruns wait_for() for
the remaining intended wait duration.
Differential Revision: https://reviews.llvm.org/D99175
GitOrigin-RevId: 01aa9e1f6e7df5a936612084c73be704e300c881
2 files changed
