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* [patch] libstdc++/60421 (again) Loop in std::this_thread sleep functions
@ 2015-11-11 17:09 Jonathan Wakely
  0 siblings, 0 replies; only message in thread
From: Jonathan Wakely @ 2015-11-11 17:09 UTC (permalink / raw)
  To: libstdc++, gcc-patches

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This fixes part of PR 60421 by looping in this_thread::sleep_for when
it is interrupted by a signal, and looping in this_thread::sleep_until
to handle clock adjustments.

There are still problems with integer overflow/wrapping in sleep_for,
which still need to be addressed somehow. Maybe using the new
overflow-checking built-ins.

Tested powerpc64le-linux, committed to trunk.


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commit 1773ceda34abcbe088048786ac869ee1740ce1d9
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Nov 11 16:16:55 2015 +0000

    Loop in std::this_thread sleep functions
    
    	PR libstdc++/60421
    	* include/std/thread (this_thread::sleep_for): Retry on EINTR.
    	(this_thread::sleep_until): Retry if time not reached.
    	* src/c++11/thread.cc (__sleep_for): Retry on EINTR.
    	* testsuite/30_threads/this_thread/60421.cc: Test interruption and
    	non-steady clocks.

diff --git a/libstdc++-v3/include/std/thread b/libstdc++-v3/include/std/thread
index c67ec46..5940e6e 100644
--- a/libstdc++-v3/include/std/thread
+++ b/libstdc++-v3/include/std/thread
@@ -297,7 +297,8 @@ _GLIBCXX_END_NAMESPACE_VERSION
 	    static_cast<std::time_t>(__s.count()),
 	    static_cast<long>(__ns.count())
 	  };
-	::nanosleep(&__ts, 0);
+	while (::nanosleep(&__ts, &__ts) == -1 && errno == EINTR)
+	  { }
 #else
 	__sleep_for(__s, __ns);
 #endif
@@ -309,8 +310,17 @@ _GLIBCXX_END_NAMESPACE_VERSION
       sleep_until(const chrono::time_point<_Clock, _Duration>& __atime)
       {
 	auto __now = _Clock::now();
-	if (__now < __atime)
-	  sleep_for(__atime - __now);
+	if (_Clock::is_steady)
+	  {
+	    if (__now < __atime)
+	      sleep_for(__atime - __now);
+	    return;
+	  }
+	while (__now < __atime)
+	  {
+	    sleep_for(__atime - __now);
+	    __now = _Clock::now();
+	  }
       }
 
   _GLIBCXX_END_NAMESPACE_VERSION
diff --git a/libstdc++-v3/src/c++11/thread.cc b/libstdc++-v3/src/c++11/thread.cc
index e116afa..3407e80 100644
--- a/libstdc++-v3/src/c++11/thread.cc
+++ b/libstdc++-v3/src/c++11/thread.cc
@@ -221,7 +221,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	static_cast<std::time_t>(__s.count()),
 	static_cast<long>(__ns.count())
       };
-    ::nanosleep(&__ts, 0);
+    while (::nanosleep(&__ts, &__ts) == -1 && errno == EINTR)
+      { }
 #elif defined(_GLIBCXX_HAVE_SLEEP)
 # ifdef _GLIBCXX_HAVE_USLEEP
     ::sleep(__s.count());
diff --git a/libstdc++-v3/testsuite/30_threads/this_thread/60421.cc b/libstdc++-v3/testsuite/30_threads/this_thread/60421.cc
index ecc4deb..5dbf257 100644
--- a/libstdc++-v3/testsuite/30_threads/this_thread/60421.cc
+++ b/libstdc++-v3/testsuite/30_threads/this_thread/60421.cc
@@ -15,12 +15,19 @@
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
-// { dg-options "-std=gnu++11" }
+// { dg-do run { target *-*-freebsd* *-*-dragonfly* *-*-netbsd* *-*-linux* *-*-gnu* *-*-solaris* *-*-cygwin *-*-rtems* *-*-darwin* powerpc-ibm-aix* } }
+// { dg-options " -std=gnu++11 -pthread" { target *-*-freebsd* *-*-dragonfly* *-*-netbsd* *-*-linux* *-*-gnu* powerpc-ibm-aix* } }
+// { dg-options " -std=gnu++11 -pthreads" { target *-*-solaris* } }
+// { dg-options " -std=gnu++11 " { target *-*-cygwin *-*-rtems* *-*-darwin* } }
 // { dg-require-cstdint "" }
+// { dg-require-gthreads "" }
 // { dg-require-time "" }
 
 #include <thread>
 #include <chrono>
+#include <atomic>
+#include <cstdint>
+#include <signal.h>
 #include <testsuite_hooks.h>
 
 void
@@ -28,11 +35,64 @@ test01()
 {
   std::this_thread::sleep_for(std::chrono::seconds(0));
   std::this_thread::sleep_for(std::chrono::seconds(-1));
-  std::this_thread::sleep_for(std::chrono::duration<uint64_t>::zero());
+  std::this_thread::sleep_for(std::chrono::duration<std::uint64_t>::zero());
+}
+
+void
+test02()
+{
+  bool test __attribute__((unused)) = true;
+
+  // test interruption of this_thread::sleep_for() by a signal
+  struct sigaction sa{ };
+  sa.sa_handler = +[](int) { };
+  sigaction(SIGUSR1, &sa, 0);
+  bool result = false;
+  std::atomic<bool> sleeping{false};
+  std::thread t([&result, &sleeping] {
+    auto start = std::chrono::system_clock::now();
+    auto time = std::chrono::seconds(3);
+    sleeping = true;
+    std::this_thread::sleep_for(time);
+    result = std::chrono::system_clock::now() >= (start + time);
+  });
+  while (!sleeping) { }
+  std::this_thread::sleep_for(std::chrono::milliseconds(500));
+  pthread_kill(t.native_handle(), SIGUSR1);
+  t.join();
+  VERIFY( result );
+}
+
+struct slow_clock
+{
+  using rep = std::chrono::system_clock::rep;
+  using period = std::chrono::system_clock::period;
+  using duration = std::chrono::system_clock::duration;
+  using time_point = std::chrono::time_point<slow_clock, duration>;
+  static constexpr bool is_steady = false;
+
+  static time_point now()
+  {
+    auto real = std::chrono::system_clock::now();
+    return time_point{real.time_since_epoch() / 2};
+  }
+};
+
+void
+test03()
+{
+  bool test __attribute__((unused)) = true;
+
+  // test that this_thread::sleep_until() handles clock adjustments
+  auto when = slow_clock::now() + std::chrono::seconds(2);
+  std::this_thread::sleep_until(when);
+  VERIFY( slow_clock::now() >= when );
 }
 
 int
 main()
 {
   test01();
+  test02();
+  test03();
 }

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2015-11-11 17:09 [patch] libstdc++/60421 (again) Loop in std::this_thread sleep functions Jonathan Wakely

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