libstdc++: testsuite: async.cc early timeout

The async call and future variable initialization may take a while to
complete on uniprocessors, especially if the async call and other
unrelated processes run before context switches back to the main
thread.

Taking steady_begin only then sometimes causes the 11*100ms in the
slow clock, counted from before the async call, to not be enough for
the measured wait to last 1s in the steady clock.  I've seen it fall
short of 1s by as little as a third of a tenth of a second in some
cases, but in one surprisingly extreme case the elapsed wait time got
only up to 216.7ms.

Initializing both timestamps next to each other, before the async
call, appears to avoid the problem entirely.  I've renamed the
variable moved out of the block so as to avoid name hiding in the
subsequent block, that has another steady_begin variable.

The second wait fails a lot less frequently, but the 2s limit has been
exceeded, so I'm bumping up the max sleep to ~4s, and the tolerance to
3s.


for  libstdc++-v3/ChangeLog

	* testsuite/30_threads/async/async.cc (test04): Initialize
	steady_start, renamed from steady_begin, next to slow_start.
	Increase tolerance for final wait.

0 files changed, 0 insertions, 0 deletions