[PATCH] libstdc++: testsuite: tolerate non-cancelling sleep

[PATCH] libstdc++: testsuite: tolerate non-cancelling sleep

[Alexandre Oliva]

Though sleep, nanosleep and clock_nanosleep are all POSIX cancellation
points, not all target systems follow this POSIX requirement.
30_threads/thread/native_handle/cancel.cc will run until it times out
on such systems.

Rather than failing a C++ library test because of a limitation of the
target system, this patch gives the test a chance to successfully
exercise the features it intends to exercise, by introducing a
cancellation point in a loop that would otherwise run indefinitely on
systems exhibiting this limitation.

Regstrapped on x86_64-linux-gnu, also tested with a cross to
aarch64-rtems6.  Ok to install?


for  libstdc++-v3/ChangeLog

	* testsuite/30_threads/thread/native_handle/cancel.cc: Add an
	explicit cancellation point in case sleep_for lacks one.
---
 .../30_threads/thread/native_handle/cancel.cc      |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/testsuite/30_threads/thread/native_handle/cancel.cc b/libstdc++-v3/testsuite/30_threads/thread/native_handle/cancel.cc
index dca162b3ace1d..3cef97e8c53de 100644
--- a/libstdc++-v3/testsuite/30_threads/thread/native_handle/cancel.cc
+++ b/libstdc++-v3/testsuite/30_threads/thread/native_handle/cancel.cc
@@ -30,7 +30,11 @@ void f(std::atomic<bool>& started)
 {
   started = true;
   while (true)
-    std::this_thread::sleep_for(std::chrono::milliseconds(100));
+    {
+      std::this_thread::sleep_for(std::chrono::milliseconds(100));
+      // In case the target system doesn't make sleep a cancellation point...
+      pthread_testcancel();
+    }
 }
 
 int main()

-- 
Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
   Free Software Activist                       GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts.  Ask me about <https://stallmansupport.org>

Re: [PATCH] libstdc++: testsuite: tolerate non-cancelling sleep

[Jonathan Wakely]

On Wed, 22 Jun 2022 at 06:26, Alexandre Oliva via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
>
> Though sleep, nanosleep and clock_nanosleep are all POSIX cancellation
> points, not all target systems follow this POSIX requirement.
> 30_threads/thread/native_handle/cancel.cc will run until it times out
> on such systems.
>
> Rather than failing a C++ library test because of a limitation of the
> target system, this patch gives the test a chance to successfully
> exercise the features it intends to exercise, by introducing a
> cancellation point in a loop that would otherwise run indefinitely on
> systems exhibiting this limitation.
>
> Regstrapped on x86_64-linux-gnu, also tested with a cross to
> aarch64-rtems6.  Ok to install?

OK, thanks.

This test is already explicitly pthread-specific, so there's no
problem using pthread_testcancel there. It already uses
pthread_cancel, and is gated by:
// { dg-require-effective-target pthread }