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

[Alexandre Oliva <oliva@adacore.com>]

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)


-- 
Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
   Free Software Activist                       GNU Toolchain Engineer
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