Re: [PATCH 1/5] Improve libstdc++-v3 async test

[Jonathan Wakely <jwakely at redhat dot com>]

On 07/01/18 20:55 +0000, Mike Crowe wrote:
> Add tests for waiting for the future using both std::chrono::steady_clock
> and std::chrono::system_clock in preparation for dealing with those clocks
> properly in futex.cc.
> ---
> libstdc++-v3/testsuite/30_threads/async/async.cc | 36 ++++++++++++++++++++++++
> 1 file changed, 36 insertions(+)
>
> diff --git a/libstdc++-v3/testsuite/30_threads/async/async.cc b/libstdc++-v3/testsuite/30_threads/async/async.cc
> index 8071cb133fc..7326c5f7cd6 100644
> --- a/libstdc++-v3/testsuite/30_threads/async/async.cc
> +++ b/libstdc++-v3/testsuite/30_threads/async/async.cc
> @@ -52,17 +52,53 @@ void test02()
>   VERIFY( status == std::future_status::timeout );
>   status = f1.wait_until(std::chrono::system_clock::now());
>   VERIFY( status == std::future_status::timeout );
> +  status = f1.wait_until(std::chrono::steady_clock::now());
> +  VERIFY( status == std::future_status::timeout );
>   l.unlock();  // allow async thread to proceed
>   f1.wait();   // wait for it to finish
>   status = f1.wait_for(std::chrono::milliseconds(0));
>   VERIFY( status == std::future_status::ready );
>   status = f1.wait_until(std::chrono::system_clock::now());
>   VERIFY( status == std::future_status::ready );
> +  status = f1.wait_until(std::chrono::steady_clock::now());
> +  VERIFY( status == std::future_status::ready );
> +}
> +
> +void work03()
> +{
> +    std::this_thread::sleep_for(std::chrono::seconds(15));

I don't think we want 15s - 20s pauses in the testsuite.

Could the sleep_for be 5s, with waits of 500ms, 1s, and then 10s, so
the expected wait is only 5s?

I don't think it's the end of the world if the test occasionally
fails on very loaded machines.


> +}
> +
> +// This test is slow in order to try and avoid failing on a loaded
> +// machine. Nevertheless, it could still fail if the kernel decides
> +// not to schedule us for several seconds. It also assumes that no-one
> +// will change CLOCK_REALTIME whilst the test is running.
> +template<typename CLOCK>
> +void test03()
> +{
> +  auto const start = CLOCK::now();
> +  future<void> f1 = async(launch::async, &work03);
> +  std::future_status status;
> +
> +  status = f1.wait_for(std::chrono::seconds(5));
> +  VERIFY( status == std::future_status::timeout );
> +
> +  status = f1.wait_until(start + std::chrono::seconds(10));
> +  VERIFY( status == std::future_status::timeout );
> +
> +  status = f1.wait_until(start + std::chrono::seconds(25));
> +  VERIFY( status == std::future_status::ready );
> +
> +  auto const elapsed = CLOCK::now() - start;
> +  VERIFY( elapsed >= std::chrono::seconds(15) );
> +  VERIFY( elapsed < std::chrono::seconds(20) );
> }
>
> int main()
> {
>   test01();
>   test02();
> +  test03<std::chrono::system_clock>();
> +  test03<std::chrono::steady_clock>();
>   return 0;
> }
> --
> 2.11.0