| /* |
| Copyright 2005-2010 Intel Corporation. All Rights Reserved. |
| |
| This file is part of Threading Building Blocks. |
| |
| Threading Building Blocks is free software; you can redistribute it |
| and/or modify it under the terms of the GNU General Public License |
| version 2 as published by the Free Software Foundation. |
| |
| Threading Building Blocks is distributed in the hope that it will be |
| useful, but WITHOUT ANY WARRANTY; without even the implied warranty |
| of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with Threading Building Blocks; if not, write to the Free Software |
| Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| |
| As a special exception, you may use this file as part of a free software |
| library without restriction. Specifically, if other files instantiate |
| templates or use macros or inline functions from this file, or you compile |
| this file and link it with other files to produce an executable, this |
| file does not by itself cause the resulting executable to be covered by |
| the GNU General Public License. This exception does not however |
| invalidate any other reasons why the executable file might be covered by |
| the GNU General Public License. |
| */ |
| |
| #ifndef __TBB_spin_mutex_H |
| #define __TBB_spin_mutex_H |
| |
| #include <cstddef> |
| #include <new> |
| #include "aligned_space.h" |
| #include "tbb_stddef.h" |
| #include "tbb_machine.h" |
| #include "tbb_profiling.h" |
| |
| namespace tbb { |
| |
| //! A lock that occupies a single byte. |
| /** A spin_mutex is a spin mutex that fits in a single byte. |
| It should be used only for locking short critical sections |
| (typically <20 instructions) when fairness is not an issue. |
| If zero-initialized, the mutex is considered unheld. |
| @ingroup synchronization */ |
| class spin_mutex { |
| //! 0 if lock is released, 1 if lock is acquired. |
| unsigned char flag; |
| |
| public: |
| //! Construct unacquired lock. |
| /** Equivalent to zero-initialization of *this. */ |
| spin_mutex() : flag(0) { |
| #if TBB_USE_THREADING_TOOLS |
| internal_construct(); |
| #endif |
| } |
| |
| //! Represents acquisition of a mutex. |
| class scoped_lock : internal::no_copy { |
| private: |
| //! Points to currently held mutex, or NULL if no lock is held. |
| spin_mutex* my_mutex; |
| |
| //! Value to store into spin_mutex::flag to unlock the mutex. |
| uintptr_t my_unlock_value; |
| |
| //! Like acquire, but with ITT instrumentation. |
| void __TBB_EXPORTED_METHOD internal_acquire( spin_mutex& m ); |
| |
| //! Like try_acquire, but with ITT instrumentation. |
| bool __TBB_EXPORTED_METHOD internal_try_acquire( spin_mutex& m ); |
| |
| //! Like release, but with ITT instrumentation. |
| void __TBB_EXPORTED_METHOD internal_release(); |
| |
| friend class spin_mutex; |
| |
| public: |
| //! Construct without acquiring a mutex. |
| scoped_lock() : my_mutex(NULL), my_unlock_value(0) {} |
| |
| //! Construct and acquire lock on a mutex. |
| scoped_lock( spin_mutex& m ) { |
| #if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT |
| my_mutex=NULL; |
| internal_acquire(m); |
| #else |
| my_unlock_value = __TBB_LockByte(m.flag); |
| my_mutex=&m; |
| #endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT*/ |
| } |
| |
| //! Acquire lock. |
| void acquire( spin_mutex& m ) { |
| #if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT |
| internal_acquire(m); |
| #else |
| my_unlock_value = __TBB_LockByte(m.flag); |
| my_mutex = &m; |
| #endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT*/ |
| } |
| |
| //! Try acquiring lock (non-blocking) |
| /** Return true if lock acquired; false otherwise. */ |
| bool try_acquire( spin_mutex& m ) { |
| #if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT |
| return internal_try_acquire(m); |
| #else |
| bool result = __TBB_TryLockByte(m.flag); |
| if( result ) { |
| my_unlock_value = 0; |
| my_mutex = &m; |
| } |
| return result; |
| #endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT*/ |
| } |
| |
| //! Release lock |
| void release() { |
| #if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT |
| internal_release(); |
| #else |
| __TBB_store_with_release(my_mutex->flag, static_cast<unsigned char>(my_unlock_value)); |
| my_mutex = NULL; |
| #endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */ |
| } |
| |
| //! Destroy lock. If holding a lock, releases the lock first. |
| ~scoped_lock() { |
| if( my_mutex ) { |
| #if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT |
| internal_release(); |
| #else |
| __TBB_store_with_release(my_mutex->flag, static_cast<unsigned char>(my_unlock_value)); |
| #endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */ |
| } |
| } |
| }; |
| |
| void __TBB_EXPORTED_METHOD internal_construct(); |
| |
| // Mutex traits |
| static const bool is_rw_mutex = false; |
| static const bool is_recursive_mutex = false; |
| static const bool is_fair_mutex = false; |
| |
| // ISO C++0x compatibility methods |
| |
| //! Acquire lock |
| void lock() { |
| #if TBB_USE_THREADING_TOOLS |
| aligned_space<scoped_lock,1> tmp; |
| new(tmp.begin()) scoped_lock(*this); |
| #else |
| __TBB_LockByte(flag); |
| #endif /* TBB_USE_THREADING_TOOLS*/ |
| } |
| |
| //! Try acquiring lock (non-blocking) |
| /** Return true if lock acquired; false otherwise. */ |
| bool try_lock() { |
| #if TBB_USE_THREADING_TOOLS |
| aligned_space<scoped_lock,1> tmp; |
| return (new(tmp.begin()) scoped_lock)->internal_try_acquire(*this); |
| #else |
| return __TBB_TryLockByte(flag); |
| #endif /* TBB_USE_THREADING_TOOLS*/ |
| } |
| |
| //! Release lock |
| void unlock() { |
| #if TBB_USE_THREADING_TOOLS |
| aligned_space<scoped_lock,1> tmp; |
| scoped_lock& s = *tmp.begin(); |
| s.my_mutex = this; |
| s.my_unlock_value = 0; |
| s.internal_release(); |
| #else |
| __TBB_store_with_release(flag, 0); |
| #endif /* TBB_USE_THREADING_TOOLS */ |
| } |
| |
| friend class scoped_lock; |
| }; |
| |
| __TBB_DEFINE_PROFILING_SET_NAME(spin_mutex) |
| |
| } // namespace tbb |
| |
| #endif /* __TBB_spin_mutex_H */ |