re PR libstdc++/40088 (Creating a std::ostringstream object locks a global mutex)

2009-12-18  Jimmy Guo  <jguo@yahoo-inc.com>

	PR libstdc++/40088
	* src/locale_init.cc (locale::locale()): Optimize the common case
	where _S_global still points to _S_classic.

From-SVN: r155342

9 files changed, 44 insertions, 18 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index d6b934c..2077dc1 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,9 @@
+2009-12-18  Jimmy Guo  <jguo@yahoo-inc.com>
+
+	PR libstdc++/40088
+	* src/locale_init.cc (locale::locale()): Optimize the common case
+	where _S_global still points to _S_classic.
+
 2009-12-17  Dave Korn  <dave.korn.cygwin@gmail.com>
 
 	PR target/42377
diff --git a/libstdc++-v3/include/std/condition_variable b/libstdc++-v3/include/std/condition_variable
index f87eb1b..f5e4db15 100644
--- a/libstdc++-v3/include/std/condition_variable
+++ b/libstdc++-v3/include/std/condition_variable
@@ -50,6 +50,9 @@ namespace std
    * @{
    */
 
+  /// cv_status
+  enum class cv_status { no_timeout, timeout };
+  
   /// condition_variable
   class condition_variable
   {
@@ -84,13 +87,13 @@ namespace std
       }
 
     template<typename _Duration>
-      bool
+      cv_status
       wait_until(unique_lock<mutex>& __lock,
 		 const chrono::time_point<__clock_t, _Duration>& __atime)
       { return __wait_until_impl(__lock, __atime); }
 
     template<typename _Clock, typename _Duration>
-      bool
+      cv_status
       wait_until(unique_lock<mutex>& __lock,
 		 const chrono::time_point<_Clock, _Duration>& __atime)
       {
@@ -110,14 +113,14 @@ namespace std
 		 _Predicate __p)
       {
 	while (!__p())
-	  if (!wait_until(__lock, __atime))
+	  if (wait_until(__lock, __atime) == cv_status::timeout)
 	    return __p();
 
 	return true;
       }
 
     template<typename _Rep, typename _Period>
-      bool
+      cv_status
       wait_for(unique_lock<mutex>& __lock,
 	       const chrono::duration<_Rep, _Period>& __rtime)
       { return wait_until(__lock, __clock_t::now() + __rtime); }
@@ -135,7 +138,7 @@ namespace std
 
   private:
     template<typename _Clock, typename _Duration>
-      bool
+      cv_status
       __wait_until_impl(unique_lock<mutex>& __lock,
 			const chrono::time_point<_Clock, _Duration>& __atime)
       {
@@ -154,7 +157,8 @@ namespace std
 	__gthread_cond_timedwait(&_M_cond, __lock.mutex()->native_handle(),
 				 &__ts);
 
-	return _Clock::now() < __atime;
+	return (_Clock::now() < __atime
+		? cv_status::no_timeout : cv_status::timeout);
       }
   };
 
@@ -189,7 +193,7 @@ namespace std
       wait(_Lock& __lock, _Predicate __p);
 
     template<typename _Lock, typename _Clock, typename _Duration>
-      bool
+      cv_status
       wait_until(_Lock& __lock,
 		 const chrono::time_point<_Clock, _Duration>& __atime);
 
@@ -201,7 +205,7 @@ namespace std
 		 _Predicate __p);
 
     template<typename _Lock, typename _Rep, typename _Period>
-      bool
+      cv_status
       wait_for(_Lock& __lock, const chrono::duration<_Rep, _Period>& __rtime);
 
     template<typename _Lock, typename _Rep,
diff --git a/libstdc++-v3/src/locale_init.cc b/libstdc++-v3/src/locale_init.cc
index 1a47974..893b606 100644
--- a/libstdc++-v3/src/locale_init.cc
+++ b/libstdc++-v3/src/locale_init.cc
@@ -208,9 +208,25 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
   locale::locale() throw() : _M_impl(0)
   { 
     _S_initialize();
-    __gnu_cxx::__scoped_lock sentry(get_locale_mutex());
-    _S_global->_M_add_reference();
+
+    // Checked locking to optimize the common case where _S_global
+    // still points to _S_classic (locale::_S_initialize_once()):
+    // - If they are the same, just increment the reference count and
+    //   we are done.  This effectively constructs a C locale object
+    //   identical to the static c_locale.
+    // - Otherwise, _S_global can and may be destroyed due to
+    //   locale::global() call on another thread, in which case we
+    //   fall back to lock protected access to both _S_global and
+    //   its reference count.
     _M_impl = _S_global;
+    if (_M_impl == _S_classic)
+      _M_impl->_M_add_reference();
+    else
+      {
+        __gnu_cxx::__scoped_lock sentry(get_locale_mutex());
+        _S_global->_M_add_reference();
+        _M_impl = _S_global;
+      }
   }
 
   locale
diff --git a/libstdc++-v3/testsuite/30_threads/condition_variable/cons/assign_neg.cc b/libstdc++-v3/testsuite/30_threads/condition_variable/cons/assign_neg.cc
index 04e492b..9e9ad8a 100644
--- a/libstdc++-v3/testsuite/30_threads/condition_variable/cons/assign_neg.cc
+++ b/libstdc++-v3/testsuite/30_threads/condition_variable/cons/assign_neg.cc
@@ -32,4 +32,4 @@ void test01()
 }
 
 // { dg-error "used here" "" { target *-*-* } 31 }
-// { dg-error "deleted function" "" { target *-*-* } 67 }
+// { dg-error "deleted function" "" { target *-*-* } 70 }
diff --git a/libstdc++-v3/testsuite/30_threads/condition_variable/cons/copy_neg.cc b/libstdc++-v3/testsuite/30_threads/condition_variable/cons/copy_neg.cc
index 0d06628..5765351 100644
--- a/libstdc++-v3/testsuite/30_threads/condition_variable/cons/copy_neg.cc
+++ b/libstdc++-v3/testsuite/30_threads/condition_variable/cons/copy_neg.cc
@@ -31,4 +31,4 @@ void test01()
 }
 
 // { dg-error "used here" "" { target *-*-* } 30 }
-// { dg-error "deleted function" "" { target *-*-* } 66 }
+// { dg-error "deleted function" "" { target *-*-* } 69 }
diff --git a/libstdc++-v3/testsuite/30_threads/condition_variable/members/1.cc b/libstdc++-v3/testsuite/30_threads/condition_variable/members/1.cc
index 4dea137..127960a 100644
--- a/libstdc++-v3/testsuite/30_threads/condition_variable/members/1.cc
+++ b/libstdc++-v3/testsuite/30_threads/condition_variable/members/1.cc
@@ -40,8 +40,8 @@ int main()
       std::unique_lock<std::mutex> l(m);
 
       auto then = std::chrono::system_clock::now();
-      bool result = c1.wait_for(l, ms);
-      VERIFY( !result );
+      std::cv_status result = c1.wait_for(l, ms);
+      VERIFY( result == std::cv_status::timeout );
       VERIFY( (std::chrono::system_clock::now() - then) >= ms );
       VERIFY( l.owns_lock() );
     }
diff --git a/libstdc++-v3/testsuite/30_threads/condition_variable/members/2.cc b/libstdc++-v3/testsuite/30_threads/condition_variable/members/2.cc
index fe17666..ab2e877 100644
--- a/libstdc++-v3/testsuite/30_threads/condition_variable/members/2.cc
+++ b/libstdc++-v3/testsuite/30_threads/condition_variable/members/2.cc
@@ -40,8 +40,8 @@ int main()
       std::unique_lock<std::mutex> l(m);
 
       auto then = std::chrono::monotonic_clock::now();
-      bool result = c1.wait_until(l, then + ms);
-      VERIFY( !result );
+      std::cv_status result = c1.wait_until(l, then + ms);
+      VERIFY( result == std::cv_status::timeout );
       VERIFY( (std::chrono::monotonic_clock::now() - then) >= ms );
       VERIFY( l.owns_lock() );
     }
diff --git a/libstdc++-v3/testsuite/30_threads/condition_variable_any/cons/assign_neg.cc b/libstdc++-v3/testsuite/30_threads/condition_variable_any/cons/assign_neg.cc
index 473f326..14990a2 100644
--- a/libstdc++-v3/testsuite/30_threads/condition_variable_any/cons/assign_neg.cc
+++ b/libstdc++-v3/testsuite/30_threads/condition_variable_any/cons/assign_neg.cc
@@ -32,4 +32,4 @@ void test01()
 }
 
 // { dg-error "used here" "" { target *-*-* } 31 }
-// { dg-error "deleted function" "" { target *-*-* } 175 }
+// { dg-error "deleted function" "" { target *-*-* } 179 }
diff --git a/libstdc++-v3/testsuite/30_threads/condition_variable_any/cons/copy_neg.cc b/libstdc++-v3/testsuite/30_threads/condition_variable_any/cons/copy_neg.cc
index 1d06c2d..1a48a9e 100644
--- a/libstdc++-v3/testsuite/30_threads/condition_variable_any/cons/copy_neg.cc
+++ b/libstdc++-v3/testsuite/30_threads/condition_variable_any/cons/copy_neg.cc
@@ -31,4 +31,4 @@ void test01()
 }
 
 // { dg-error "used here" "" { target *-*-* } 30 }
-// { dg-error "deleted function" "" { target *-*-* } 174 }
+// { dg-error "deleted function" "" { target *-*-* } 178 }