213 lines
6.6 KiB
C++
213 lines
6.6 KiB
C++
/*
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Copyright (c) 2005-2017 Intel Corporation
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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#ifndef __TBB_spin_mutex_H
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#define __TBB_spin_mutex_H
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#include <cstddef>
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#include <new>
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#include "aligned_space.h"
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#include "tbb_stddef.h"
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#include "tbb_machine.h"
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#include "tbb_profiling.h"
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#include "internal/_mutex_padding.h"
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namespace tbb {
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//! A lock that occupies a single byte.
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/** A spin_mutex is a spin mutex that fits in a single byte.
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It should be used only for locking short critical sections
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(typically less than 20 instructions) when fairness is not an issue.
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If zero-initialized, the mutex is considered unheld.
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@ingroup synchronization */
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class spin_mutex : internal::mutex_copy_deprecated_and_disabled {
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//! 0 if lock is released, 1 if lock is acquired.
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__TBB_atomic_flag flag;
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public:
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//! Construct unacquired lock.
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/** Equivalent to zero-initialization of *this. */
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spin_mutex() : flag(0) {
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#if TBB_USE_THREADING_TOOLS
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internal_construct();
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#endif
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}
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//! Represents acquisition of a mutex.
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class scoped_lock : internal::no_copy {
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private:
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//! Points to currently held mutex, or NULL if no lock is held.
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spin_mutex* my_mutex;
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//! Value to store into spin_mutex::flag to unlock the mutex.
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/** This variable is no longer used. Instead, 0 and 1 are used to
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represent that the lock is free and acquired, respectively.
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We keep the member variable here to ensure backward compatibility */
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__TBB_Flag my_unlock_value;
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//! Like acquire, but with ITT instrumentation.
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void __TBB_EXPORTED_METHOD internal_acquire( spin_mutex& m );
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//! Like try_acquire, but with ITT instrumentation.
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bool __TBB_EXPORTED_METHOD internal_try_acquire( spin_mutex& m );
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//! Like release, but with ITT instrumentation.
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void __TBB_EXPORTED_METHOD internal_release();
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friend class spin_mutex;
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public:
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//! Construct without acquiring a mutex.
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scoped_lock() : my_mutex(NULL), my_unlock_value(0) {}
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//! Construct and acquire lock on a mutex.
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scoped_lock( spin_mutex& m ) : my_unlock_value(0) {
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internal::suppress_unused_warning(my_unlock_value);
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#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
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my_mutex=NULL;
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internal_acquire(m);
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#else
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my_mutex=&m;
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__TBB_LockByte(m.flag);
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#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT*/
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}
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//! Acquire lock.
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void acquire( spin_mutex& m ) {
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#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
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internal_acquire(m);
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#else
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my_mutex = &m;
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__TBB_LockByte(m.flag);
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#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT*/
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}
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//! Try acquiring lock (non-blocking)
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/** Return true if lock acquired; false otherwise. */
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bool try_acquire( spin_mutex& m ) {
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#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
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return internal_try_acquire(m);
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#else
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bool result = __TBB_TryLockByte(m.flag);
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if( result )
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my_mutex = &m;
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return result;
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#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT*/
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}
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//! Release lock
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void release() {
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#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
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internal_release();
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#else
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__TBB_UnlockByte(my_mutex->flag);
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my_mutex = NULL;
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#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */
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}
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//! Destroy lock. If holding a lock, releases the lock first.
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~scoped_lock() {
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if( my_mutex ) {
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#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
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internal_release();
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#else
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__TBB_UnlockByte(my_mutex->flag);
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#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */
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}
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}
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};
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//! Internal constructor with ITT instrumentation.
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void __TBB_EXPORTED_METHOD internal_construct();
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// Mutex traits
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static const bool is_rw_mutex = false;
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static const bool is_recursive_mutex = false;
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static const bool is_fair_mutex = false;
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// ISO C++0x compatibility methods
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//! Acquire lock
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void lock() {
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#if TBB_USE_THREADING_TOOLS
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aligned_space<scoped_lock> tmp;
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new(tmp.begin()) scoped_lock(*this);
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#else
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__TBB_LockByte(flag);
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#endif /* TBB_USE_THREADING_TOOLS*/
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}
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//! Try acquiring lock (non-blocking)
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/** Return true if lock acquired; false otherwise. */
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bool try_lock() {
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#if TBB_USE_THREADING_TOOLS
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aligned_space<scoped_lock> tmp;
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return (new(tmp.begin()) scoped_lock)->internal_try_acquire(*this);
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#else
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return __TBB_TryLockByte(flag);
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#endif /* TBB_USE_THREADING_TOOLS*/
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}
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//! Release lock
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void unlock() {
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#if TBB_USE_THREADING_TOOLS
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aligned_space<scoped_lock> tmp;
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scoped_lock& s = *tmp.begin();
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s.my_mutex = this;
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s.internal_release();
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#else
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__TBB_UnlockByte(flag);
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#endif /* TBB_USE_THREADING_TOOLS */
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}
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friend class scoped_lock;
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}; // end of spin_mutex
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__TBB_DEFINE_PROFILING_SET_NAME(spin_mutex)
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} // namespace tbb
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#if ( __TBB_x86_32 || __TBB_x86_64 )
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#include "internal/_x86_eliding_mutex_impl.h"
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#endif
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namespace tbb {
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//! A cross-platform spin mutex with speculative lock acquisition.
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/** On platforms with proper HW support, this lock may speculatively execute
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its critical sections, using HW mechanisms to detect real data races and
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ensure atomicity of the critical sections. In particular, it uses
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Intel(R) Transactional Synchronization Extensions (Intel(R) TSX).
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Without such HW support, it behaves like a spin_mutex.
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It should be used for locking short critical sections where the lock is
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contended but the data it protects are not. If zero-initialized, the
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mutex is considered unheld.
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@ingroup synchronization */
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#if ( __TBB_x86_32 || __TBB_x86_64 )
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typedef interface7::internal::padded_mutex<interface7::internal::x86_eliding_mutex,false> speculative_spin_mutex;
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#else
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typedef interface7::internal::padded_mutex<spin_mutex,false> speculative_spin_mutex;
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#endif
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__TBB_DEFINE_PROFILING_SET_NAME(speculative_spin_mutex)
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} // namespace tbb
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#endif /* __TBB_spin_mutex_H */
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