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527f2f9057
* Create a branch for some evul shell experiments. svn path=/branches/shell-experiments/; revision=61927
168 lines
4.9 KiB
C
168 lines
4.9 KiB
C
/*
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*
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*
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* Copyright (c) 1994
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* Hewlett-Packard Company
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*
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* Copyright (c) 1996,1997
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* Silicon Graphics Computer Systems, Inc.
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*
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* Copyright (c) 1997
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* Moscow Center for SPARC Technology
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*
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* Copyright (c) 1999
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* Boris Fomitchev
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*
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* This material is provided "as is", with absolutely no warranty expressed
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* or implied. Any use is at your own risk.
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*
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* Permission to use or copy this software for any purpose is hereby granted
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* without fee, provided the above notices are retained on all copies.
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* Permission to modify the code and to distribute modified code is granted,
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* provided the above notices are retained, and a notice that the code was
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* modified is included with the above copyright notice.
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*
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*/
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#ifndef _STLP_THREADS_C
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#define _STLP_THREADS_C
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#ifndef _STLP_INTERNAL_THREADS_H
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# include <stl/_threads.h>
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#endif
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#if defined (_STLP_EXPOSE_GLOBALS_IMPLEMENTATION)
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#if defined (_STLP_SGI_THREADS)
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# include <time.h>
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#elif defined (_STLP_UNIX)
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# ifndef _STLP_INTERNAL_CTIME
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# include <stl/_ctime.h>
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# endif
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# if defined (_STLP_USE_NAMESPACES) && !defined (_STLP_VENDOR_GLOBAL_CSTD)
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using _STLP_VENDOR_CSTD::time_t;
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# endif
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# include <sys/time.h>
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#endif
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_STLP_BEGIN_NAMESPACE
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#if defined (_STLP_USE_ATOMIC_SWAP_MUTEX)
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template<int __32bits>
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_STLP_STATIC_MUTEX
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_Atomic_swap_struct<__32bits>::_S_swap_lock _STLP_MUTEX_INITIALIZER;
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# undef _STLP_USE_ATOMIC_SWAP_MUTEX
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#endif
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#if defined (_STLP_THREADS) && !defined (_STLP_USE_PTHREAD_SPINLOCK)
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template <int __inst>
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unsigned _STLP_mutex_spin<__inst>::__max = _STLP_mutex_spin<__inst>::__low_max;
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template <int __inst>
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unsigned _STLP_mutex_spin<__inst>::__last = 0;
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#endif // _STLP_USE_PTHREAD_SPINLOCK
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#if defined (_STLP_THREADS) && !defined (_STLP_USE_PTHREAD_SPINLOCK)
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# if defined (_STLP_SPARC_SOLARIS_THREADS)
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// underground function in libc.so; we do not want dependance on librt
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extern "C" int __nanosleep(const struct timespec*, struct timespec*);
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# define _STLP_NANOSLEEP __nanosleep
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# else
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# define _STLP_NANOSLEEP nanosleep
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# endif
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template <int __inst>
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void _STLP_CALL
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_STLP_mutex_spin<__inst>::_S_nsec_sleep(int __log_nsec, unsigned int& __iteration) {
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# if defined (_STLP_WIN32THREADS)
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# if defined (_WIN32_WINNT) && (_WIN32_WINNT >= 0x0400)
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if (__iteration <= 4000) {
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// Use SwitchToThread because
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// 1) Sleep(1) often takes ~15 ms
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// 2) SwitchToThread yields to lower-priority threads
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// 4000 is enough to avoid Sleep and is used just to prevent infinite looping
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// This number is advised spin count for Heap management by Microsoft
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SwitchToThread();
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} else {
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# endif
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if (__log_nsec <= 21) {
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/* Note from boost (www.boost.org):
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* Changed from Sleep(0) to Sleep(1).
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* According to MSDN, Sleep(0) will never yield to a lower-priority thread,
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* whereas Sleep(1) will. Performance seems not to be affected. */
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Sleep(1);
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} else {
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Sleep(1 << (__log_nsec - 20));
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}
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# if defined (_WIN32_WINNT) && (_WIN32_WINNT >= 0x0400)
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__iteration = 0; //reset to avoid sleeps sequence
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}
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# endif
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# elif defined(_STLP_OS2THREADS)
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if (__log_nsec <= 20) {
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DosSleep(0);
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} else {
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DosSleep(1 << (__log_nsec - 20));
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}
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# elif defined (_STLP_UNIX)
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timespec __ts;
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/* Max sleep is 2**27nsec ~ 60msec */
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__ts.tv_sec = 0;
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__ts.tv_nsec = 1 << __log_nsec;
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_STLP_NANOSLEEP(&__ts, 0);
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# endif
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}
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template <int __inst>
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void _STLP_CALL
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_STLP_mutex_spin<__inst>::_M_do_lock(volatile __stl_atomic_t* __lock) {
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# if defined(_STLP_ATOMIC_EXCHANGE)
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if (_Atomic_swap(__lock, 1)) {
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unsigned __my_spin_max = _STLP_mutex_spin<0>::__max;
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unsigned __my_last_spins = _STLP_mutex_spin<0>::__last;
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volatile unsigned __junk = 17; // Value doesn't matter.
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unsigned __i;
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for (__i = 0; __i < __my_spin_max; ++__i) {
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if (__i < __my_last_spins/2 || *__lock) {
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__junk *= __junk; __junk *= __junk;
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__junk *= __junk; __junk *= __junk;
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} else {
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if (!_Atomic_swap(__lock, 1)) {
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// got it!
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// Spinning worked. Thus we're probably not being scheduled
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// against the other process with which we were contending.
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// Thus it makes sense to spin longer the next time.
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_STLP_mutex_spin<0>::__last = __i;
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_STLP_mutex_spin<0>::__max = _STLP_mutex_spin<0>::__high_max;
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return;
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}
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}
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}
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// We are probably being scheduled against the other process. Sleep.
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_STLP_mutex_spin<0>::__max = _STLP_mutex_spin<0>::__low_max;
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for (__i = 0 ;; ++__i) {
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int __log_nsec = __i + 6;
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if (__log_nsec > 27) __log_nsec = 27;
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if (!_Atomic_swap(__lock, 1)) {
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break;
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}
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_S_nsec_sleep(__log_nsec, __i);
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}
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} /* first _Atomic_swap */
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# endif
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}
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#endif // _STLP_USE_PTHREAD_SPINLOCK
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_STLP_END_NAMESPACE
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#endif /* _STLP_EXPOSE_GLOBALS_IMPLEMENTATION */
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#endif /* _STLP_THREADS_C */
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// Local Variables:
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// mode:C++
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// End:
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