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rtos/ConditionVariable.cpp
- Committer:
- kevman
- Date:
- 2018-11-28
- Revision:
- 0:38ceb79fef03
File content as of revision 0:38ceb79fef03:
/* mbed Microcontroller Library * Copyright (c) 2017-2017 ARM Limited * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ #include "rtos/ConditionVariable.h" #include "rtos/Kernel.h" #include "rtos/Thread.h" #include "mbed_error.h" #include "mbed_assert.h" namespace rtos { ConditionVariable::Waiter::Waiter(): sem(0), prev(NULL), next(NULL), in_list(false) { // No initialization to do } ConditionVariable::ConditionVariable(Mutex &mutex): _mutex(mutex), _wait_list(NULL) { // No initialization to do } void ConditionVariable::wait() { wait_for(osWaitForever); } bool ConditionVariable::wait_for(uint32_t millisec) { Waiter current_thread; MBED_ASSERT(_mutex.get_owner() == Thread::gettid()); MBED_ASSERT(_mutex._count == 1); _add_wait_list(&_wait_list, ¤t_thread); _mutex.unlock(); int32_t sem_count = current_thread.sem.wait(millisec); bool timeout = (sem_count > 0) ? false : true; _mutex.lock(); if (current_thread.in_list) { _remove_wait_list(&_wait_list, ¤t_thread); } return timeout; } bool ConditionVariable::wait_until(uint64_t millisec) { uint64_t now = Kernel::get_ms_count(); if (now >= millisec) { // Time has already passed - standard behaviour is to // treat as a "try". return wait_for(0); } else if (millisec - now >= osWaitForever) { // Exceeds maximum delay of underlying wait_for - // spuriously wake after 49 days, indicating no timeout. wait_for(osWaitForever - 1); return false; } else { return wait_for(millisec - now); } } void ConditionVariable::notify_one() { MBED_ASSERT(_mutex.get_owner() == Thread::gettid()); if (_wait_list != NULL) { _wait_list->sem.release(); _remove_wait_list(&_wait_list, _wait_list); } } void ConditionVariable::notify_all() { MBED_ASSERT(_mutex.get_owner() == Thread::gettid()); while (_wait_list != NULL) { _wait_list->sem.release(); _remove_wait_list(&_wait_list, _wait_list); } } void ConditionVariable::_add_wait_list(Waiter **wait_list, Waiter *waiter) { if (NULL == *wait_list) { // Nothing in the list so add it directly. // Update prev and next pointer to reference self *wait_list = waiter; waiter->next = waiter; waiter->prev = waiter; } else { // Add after the last element Waiter *first = *wait_list; Waiter *last = (*wait_list)->prev; // Update new entry waiter->next = first; waiter->prev = last; // Insert into the list first->prev = waiter; last->next = waiter; } waiter->in_list = true; } void ConditionVariable::_remove_wait_list(Waiter **wait_list, Waiter *waiter) { Waiter *prev = waiter->prev; Waiter *next = waiter->next; // Remove from list prev->next = waiter->next; next->prev = waiter->prev; *wait_list = waiter->next; if (*wait_list == waiter) { // This was the last element in the list *wait_list = NULL; } // Invalidate pointers waiter->next = NULL; waiter->prev = NULL; waiter->in_list = false; } ConditionVariable::~ConditionVariable() { MBED_ASSERT(NULL == _wait_list); } }