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extern/STLport/5.2.1/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)
+#  ifndef _STLP_INTERNAL_CTIME
+#    include <stl/_ctime.h>
+#  endif
+#  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 defined (_STLP_USE_ATOMIC_SWAP_MUTEX)
+template<int __32bits>
+_STLP_STATIC_MUTEX
+_Atomic_swap_struct<__32bits>::_S_swap_lock _STLP_MUTEX_INITIALIZER;
+#  undef _STLP_USE_ATOMIC_SWAP_MUTEX
+#endif
+
+#if defined (_STLP_THREADS) && !defined (_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
+
+#if defined (_STLP_THREADS) && !defined (_STLP_USE_PTHREAD_SPINLOCK)
+
+#  if defined (_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, unsigned int& __iteration) {
+#  if defined (_STLP_WIN32THREADS)
+#    if defined (_WIN32_WINNT) && (_WIN32_WINNT >= 0x0400)
+  if (__iteration <= 4000) {
+    // Use SwitchToThread because 
+    // 1) Sleep(1) often takes ~15 ms
+    // 2) SwitchToThread yields to lower-priority threads
+    // 4000 is enough to avoid Sleep and is used just to prevent infinite looping
+    // This number is advised spin count for Heap management by Microsoft
+     SwitchToThread(); 
+  } else {
+#    endif
+    if (__log_nsec <= 21) {
+      /* Note from boost (www.boost.org):
+       * Changed from Sleep(0) to Sleep(1).
+       * 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));
+    }
+#    if defined (_WIN32_WINNT) && (_WIN32_WINNT >= 0x0400)
+    __iteration = 0; //reset to avoid sleeps sequence
+  }
+#    endif
+#  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, __i);
+    }
+  } /* first _Atomic_swap */
+#  endif
+}
+#endif // _STLP_USE_PTHREAD_SPINLOCK
+
+_STLP_END_NAMESPACE
+
+#endif /* _STLP_EXPOSE_GLOBALS_IMPLEMENTATION */
+#endif /*  _STLP_THREADS_C */
+
+// Local Variables:
+// mode:C++
+// End: