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STLPORT/stlport/stl/_threads.c

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+/*
+ *
+ *
+ * Copyright (c) 1994
+ * Hewlett-Packard Company
+ *
+ * Copyright (c) 1996,1997
+ * Silicon Graphics Computer Systems, Inc.
+ *
+ * Copyright (c) 1997
+ * Moscow Center for SPARC Technology
+ *
+ * Copyright (c) 1999 
+ * Boris Fomitchev
+ *
+ * This material is provided "as is", with absolutely no warranty expressed
+ * or implied. Any use is at your own risk.
+ *
+ * Permission to use or copy this software for any purpose is hereby granted 
+ * without fee, provided the above notices are retained on all copies.
+ * Permission to modify the code and to distribute modified code is granted,
+ * provided the above notices are retained, and a notice that the code was
+ * modified is included with the above copyright notice.
+ *
+ */
+#ifndef _STLP_THREADS_C
+#define _STLP_THREADS_C
+
+#ifndef _STLP_INTERNAL_THREADS_H
+# include <stl/_threads.h>
+#endif
+
+# if defined (_STLP_EXPOSE_GLOBALS_IMPLEMENTATION)
+
+# if defined(_STLP_SGI_THREADS)
+#  include <time.h>
+# elif defined (_STLP_UNIX)
+#  include <ctime>
+# if defined (_STLP_USE_NAMESPACES) && ! defined (_STLP_VENDOR_GLOBAL_CSTD)
+using _STLP_VENDOR_CSTD::time_t;
+# endif
+#  include <sys/time.h>
+# endif
+
+_STLP_BEGIN_NAMESPACE
+
+# if (_STLP_STATIC_TEMPLATE_DATA > 0)
+
+#  ifdef _STLP_THREADS
+#  if !defined(_STLP_ATOMIC_EXCHANGE) && (defined(_STLP_PTHREADS) || defined(_STLP_UITHREADS) || defined(_STLP_OS2THREADS) || defined(_STLP_USE_PTHREAD_SPINLOCK))
+template<int __dummy>
+_STLP_STATIC_MUTEX
+_Swap_lock_struct<__dummy>::_S_swap_lock _STLP_MUTEX_INITIALIZER;
+#  endif
+#  endif //_STLP_THREADS
+
+#  ifndef _STLP_USE_PTHREAD_SPINLOCK
+template <int __inst>
+unsigned _STLP_mutex_spin<__inst>::__max = _STLP_mutex_spin<__inst>::__low_max;
+
+template <int __inst>
+unsigned _STLP_mutex_spin<__inst>::__last = 0;
+#  endif // _STLP_USE_PTHREAD_SPINLOCK
+
+# else /* ( _STLP_STATIC_TEMPLATE_DATA > 0 ) */
+
+#  if defined(_STLP_PTHREADS) || defined(_STLP_UITHREADS) || defined(_STLP_OS2THREADS)
+__DECLARE_INSTANCE(_STLP_STATIC_MUTEX, _Swap_lock_struct<0>::_S_swap_lock, 
+                   _STLP_MUTEX_INITIALIZER  );
+#  endif /* _STLP_PTHREADS */
+
+#  ifndef _STLP_USE_PTHREAD_SPINLOCK
+__DECLARE_INSTANCE(unsigned, _STLP_mutex_spin<0>::__max,  =30);
+__DECLARE_INSTANCE(unsigned, _STLP_mutex_spin<0>::__last, =0);
+#  endif // _STLP_USE_PTHREAD_SPINLOCK
+
+# endif /* ( _STLP_STATIC_TEMPLATE_DATA > 0 ) */
+
+#ifndef _STLP_USE_PTHREAD_SPINLOCK
+
+#ifdef _STLP_SPARC_SOLARIS_THREADS
+// underground function in libc.so; we do not want dependance on librt
+extern "C" int __nanosleep(const struct timespec*, struct timespec*);
+# define _STLP_NANOSLEEP __nanosleep
+#else
+# define _STLP_NANOSLEEP nanosleep
+#endif
+
+template <int __inst>
+void _STLP_CALL
+_STLP_mutex_spin<__inst>::_S_nsec_sleep(int __log_nsec) {
+#     if defined(_STLP_WIN32THREADS)
+	  if (__log_nsec <= 20) {
+        // Note from boost (www.boost.org): 
+        // Changed to Sleep(1) from Sleep(0).
+        // According to MSDN, Sleep(0) will never yield
+        // to a lower-priority thread, whereas Sleep(1)
+        // will. Performance seems not to be affected.
+	      Sleep(1);
+	  } else {
+	      Sleep(1 << (__log_nsec - 20));
+	  }
+#    elif defined(_STLP_OS2THREADS)
+      if (__log_nsec <= 20) {
+         DosSleep(0);
+      } else {
+         DosSleep(1 << (__log_nsec - 20));
+      }
+#     elif defined (_STLP_UNIX)
+          timespec __ts;
+          /* Max sleep is 2**27nsec ~ 60msec      */
+          __ts.tv_sec = 0;
+          __ts.tv_nsec = 1 << __log_nsec;
+          _STLP_NANOSLEEP(&__ts, 0);
+#     endif
+  }
+
+
+template <int __inst>
+void  _STLP_CALL
+_STLP_mutex_spin<__inst>::_M_do_lock(volatile __stl_atomic_t* __lock)
+{
+#if defined(_STLP_ATOMIC_EXCHANGE)
+  if (_Atomic_swap(__lock, 1)) {
+    unsigned __my_spin_max = _STLP_mutex_spin<0>::__max;
+    unsigned __my_last_spins = _STLP_mutex_spin<0>::__last;
+    volatile unsigned __junk = 17; 	// Value doesn't matter.
+    unsigned  __i;
+    
+    for (__i = 0; __i < __my_spin_max; ++__i) {
+      if (__i < __my_last_spins/2 || *__lock) {
+        __junk *= __junk; __junk *= __junk;
+        __junk *= __junk; __junk *= __junk;
+      } else {
+        if (!_Atomic_swap(__lock, 1)) {
+          // got it!
+          // Spinning worked.  Thus we're probably not being scheduled
+          // against the other process with which we were contending.
+          // Thus it makes sense to spin longer the next time.
+          _STLP_mutex_spin<0>::__last = __i;
+          _STLP_mutex_spin<0>::__max = _STLP_mutex_spin<0>::__high_max;
+	    return;
+        }
+      }
+    }
+    
+    // We are probably being scheduled against the other process.  Sleep.
+    _STLP_mutex_spin<0>::__max = _STLP_mutex_spin<0>::__low_max;
+    
+    for (__i = 0 ;; ++__i) {
+      int __log_nsec = __i + 6;
+      
+      if (__log_nsec > 27) __log_nsec = 27;
+      if (!_Atomic_swap(__lock, 1)) {
+	  break;
+      }
+      _S_nsec_sleep(__log_nsec);
+    }
+    
+  } /* first _Atomic_swap */
+# endif
+}
+#endif // _STLP_USE_PTHREAD_SPINLOCK
+
+_STLP_END_NAMESPACE
+
+# endif /* BUILDING_STLPORT */
+#endif /*  _STLP_THREADS_C */
+
+// Local Variables:
+// mode:C++
+// End: