164 lines
4.8 KiB
C++
164 lines
4.8 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_queuing_rw_mutex_H
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#define __TBB_queuing_rw_mutex_H
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#include "tbb_config.h"
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#if !TBB_USE_EXCEPTIONS && _MSC_VER
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// Suppress "C++ exception handler used, but unwind semantics are not enabled" warning in STL headers
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#pragma warning (push)
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#pragma warning (disable: 4530)
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#endif
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#include <cstring>
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#if !TBB_USE_EXCEPTIONS && _MSC_VER
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#pragma warning (pop)
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#endif
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#include "atomic.h"
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#include "tbb_profiling.h"
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namespace tbb {
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//! Queuing reader-writer mutex with local-only spinning.
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/** Adapted from Krieger, Stumm, et al. pseudocode at
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http://www.eecg.toronto.edu/parallel/pubs_abs.html#Krieger_etal_ICPP93
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@ingroup synchronization */
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class queuing_rw_mutex : internal::mutex_copy_deprecated_and_disabled {
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public:
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//! Construct unacquired mutex.
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queuing_rw_mutex() {
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q_tail = NULL;
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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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//! Destructor asserts if the mutex is acquired, i.e. q_tail is non-NULL
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~queuing_rw_mutex() {
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#if TBB_USE_ASSERT
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__TBB_ASSERT( !q_tail, "destruction of an acquired mutex");
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#endif
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}
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//! The scoped locking pattern
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/** It helps to avoid the common problem of forgetting to release lock.
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It also nicely provides the "node" for queuing locks. */
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class scoped_lock: internal::no_copy {
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//! Initialize fields to mean "no lock held".
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void initialize() {
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my_mutex = NULL;
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#if TBB_USE_ASSERT
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my_state = 0xFF; // Set to invalid state
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internal::poison_pointer(my_next);
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internal::poison_pointer(my_prev);
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#endif /* TBB_USE_ASSERT */
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}
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public:
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//! Construct lock that has not acquired a mutex.
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/** Equivalent to zero-initialization of *this. */
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scoped_lock() {initialize();}
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//! Acquire lock on given mutex.
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scoped_lock( queuing_rw_mutex& m, bool write=true ) {
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initialize();
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acquire(m,write);
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}
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//! Release lock (if lock is held).
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~scoped_lock() {
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if( my_mutex ) release();
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}
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//! Acquire lock on given mutex.
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void acquire( queuing_rw_mutex& m, bool write=true );
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//! Acquire lock on given mutex if free (i.e. non-blocking)
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bool try_acquire( queuing_rw_mutex& m, bool write=true );
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//! Release lock.
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void release();
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//! Upgrade reader to become a writer.
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/** Returns whether the upgrade happened without releasing and re-acquiring the lock */
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bool upgrade_to_writer();
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//! Downgrade writer to become a reader.
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bool downgrade_to_reader();
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private:
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//! The pointer to the mutex owned, or NULL if not holding a mutex.
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queuing_rw_mutex* my_mutex;
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//! The pointer to the previous and next competitors for a mutex
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scoped_lock *__TBB_atomic my_prev, *__TBB_atomic my_next;
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typedef unsigned char state_t;
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//! State of the request: reader, writer, active reader, other service states
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atomic<state_t> my_state;
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//! The local spin-wait variable
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/** Corresponds to "spin" in the pseudocode but inverted for the sake of zero-initialization */
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unsigned char __TBB_atomic my_going;
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//! A tiny internal lock
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unsigned char my_internal_lock;
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//! Acquire the internal lock
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void acquire_internal_lock();
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//! Try to acquire the internal lock
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/** Returns true if lock was successfully acquired. */
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bool try_acquire_internal_lock();
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//! Release the internal lock
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void release_internal_lock();
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//! Wait for internal lock to be released
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void wait_for_release_of_internal_lock();
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//! A helper function
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void unblock_or_wait_on_internal_lock( uintptr_t );
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};
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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 = true;
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static const bool is_recursive_mutex = false;
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static const bool is_fair_mutex = true;
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private:
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//! The last competitor requesting the lock
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atomic<scoped_lock*> q_tail;
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};
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__TBB_DEFINE_PROFILING_SET_NAME(queuing_rw_mutex)
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} // namespace tbb
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#endif /* __TBB_queuing_rw_mutex_H */
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