[PATCH] libstdc++: 60241.cc: tolerate slightly shorter aggregate sleep

[Sebastian Huber]

On 22/06/2022 08:01, Alexandre Oliva via Gcc-patches wrote:
> 
> On rtems under qemu, the frequently-interrupted nanosleep ends up
> sleeping shorter than expected, by a margin of less than 0,3%.
> 
> I figured failing the library test over a system (emulator?) bug is
> undesirable, so I put in some tolerance for the drift.
> 
> Regstrapped on x86_64-linux-gnu, also tested with a cross to
> aarch64-rtems6.  Ok to install?
> 
> PS: I see nothing wrong with the implementation of clock_nanosleep (used
> by nanosleep) on rtems6 that could cause it to wake up too early.  I
> suspect some artifact of the emulation environment.
> 
> 
> for  libstdc++-v3/ChangeLog
> 
> 	* testsuite/30_threads/this_thread/60421.cc: Tolerate a
> 	slightly early wakeup.
> ---
>   .../testsuite/30_threads/this_thread/60421.cc      |    3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/libstdc++-v3/testsuite/30_threads/this_thread/60421.cc b/libstdc++-v3/testsuite/30_threads/this_thread/60421.cc
> index 12dbeba1cc492..f3a5af453c4ad 100644
> --- a/libstdc++-v3/testsuite/30_threads/this_thread/60421.cc
> +++ b/libstdc++-v3/testsuite/30_threads/this_thread/60421.cc
> @@ -51,9 +51,10 @@ test02()
>     std::thread t([&result, &sleeping] {
>       auto start = std::chrono::system_clock::now();
>       auto time = std::chrono::seconds(3);
> +    auto tolerance = std::chrono::milliseconds(10);
>       sleeping = true;
>       std::this_thread::sleep_for(time);
> -    result = std::chrono::system_clock::now() >= (start + time);
> +    result = std::chrono::system_clock::now() + tolerance >= (start + time);
>       sleeping = false;
>     });
>     while (!sleeping)

This looks like a bug in RTEMS or the BSP for the test platform. I would 
first investigate this and then change the test which looks all right to me.

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