[PATCH] PR libstdc++/80538 Only call sleep for non-zero values

[Jonathan Wakely <jwakely at redhat dot com>]

Avoid a system call when no sleep is required. Sleep in a loop (actually
two loops) to handle interruption by signals.

	PR libstdc++/80538
	* src/c++11/thread.cc (this_thread::__sleep_for)
	[_GLIBCXX_HAVE_SLEEP]: Only call sleep for non-zero values.
	Loop while sleep call is interrupted and until steady_clock
	shows requested duration has elapsed.
	(!_GLIBCXX_HAVE_USLEEP]: Use the _GLIBCXX_HAVE_SLEEP code path, but
	avoiding the usleep call.
	* testsuite/30_threads/this_thread/60421.cc: Test repeated
	signal interruptions.

Tested x86_64-linux (by manually fudging the configure macros to test
the !_GLIBCXX_USE_NANOSLEEP paths).

Committed to trunk.

Attachment: patch.txt
Description: Text document