Nicolas Borla
BBR 1 Ebene
Diff: mbed-os/rtos/ConditionVariable.h
- Revision:
- 0:fbdae7e6d805
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os/rtos/ConditionVariable.h Mon May 14 11:29:06 2018 +0000
@@ -0,0 +1,259 @@
+/* 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.
+ */
+#ifndef CONDITIONVARIABLE_H
+#define CONDITIONVARIABLE_H
+
+#include <stdint.h>
+#include "cmsis_os.h"
+#include "rtos/Mutex.h"
+#include "rtos/Semaphore.h"
+
+#include "platform/NonCopyable.h"
+
+namespace rtos {
+/** \addtogroup rtos */
+/** @{*/
+
+struct Waiter;
+
+/** This class provides a safe way to wait for or send notifications of condition changes
+ *
+ * This class is used in conjunction with a mutex to safely wait for or
+ * notify waiters of condition changes to a resource accessible by multiple
+ * threads.
+ *
+ * # Defined behavior
+ * - All threads waiting on the condition variable wake when
+ * ConditionVariable::notify_all is called.
+ * - If one or more threads are waiting on the condition variable at least
+ * one of them wakes when ConditionVariable::notify is called.
+ *
+ * # Undefined behavior
+ * - The thread which is unblocked on ConditionVariable::notify_one is
+ * undefined if there are multiple waiters.
+ * - The order which in which waiting threads acquire the condition variable's
+ * mutex after ConditionVariable::notify_all is called is undefined.
+ * - When ConditionVariable::notify_one or ConditionVariable::notify_all is
+ * called and there are one or more waiters and one or more threads attempting
+ * to acquire the condition variable's mutex the order in which the mutex is
+ * acquired is undefined.
+ * - The behavior of ConditionVariable::wait and ConditionVariable::wait_for
+ * is undefined if the condition variable's mutex is locked more than once by
+ * the calling thread.
+ * - Spurious notifications (not triggered by the application) can occur
+ * and it is not defined when these occur.
+ *
+ * @note Synchronization level: Thread safe
+ *
+ * Example:
+ * @code
+ * #include "mbed.h"
+ *
+ * Mutex mutex;
+ * ConditionVariable cond(mutex);
+ *
+ * // These variables are protected by locking mutex
+ * uint32_t count = 0;
+ * bool done = false;
+ *
+ * void worker_thread()
+ * {
+ * mutex.lock();
+ * do {
+ * printf("Worker: Count %lu\r\n", count);
+ *
+ * // Wait for a condition to change
+ * cond.wait();
+ *
+ * } while (!done);
+ * printf("Worker: Exiting\r\n");
+ * mutex.unlock();
+ * }
+ *
+ * int main() {
+ * Thread thread;
+ * thread.start(worker_thread);
+ *
+ * for (int i = 0; i < 5; i++) {
+ *
+ * mutex.lock();
+ * // Change count and notify waiters of this
+ * count++;
+ * printf("Main: Set count to %lu\r\n", count);
+ * cond.notify_all();
+ * mutex.unlock();
+ *
+ * wait(1.0);
+ * }
+ *
+ * mutex.lock();
+ * // Change done and notify waiters of this
+ * done = true;
+ * printf("Main: Set done\r\n");
+ * cond.notify_all();
+ * mutex.unlock();
+ *
+ * thread.join();
+ * }
+ * @endcode
+ */
+class ConditionVariable : private mbed::NonCopyable<ConditionVariable> {
+public:
+ /** Create and Initialize a ConditionVariable object
+ *
+ * @note You cannot call this function from ISR context.
+ */
+ ConditionVariable(Mutex &mutex);
+
+ /** Wait for a notification
+ *
+ * Wait until a notification occurs.
+ *
+ * @note - The thread calling this function must be the owner of the
+ * ConditionVariable's mutex and it must be locked exactly once
+ * @note - Spurious notifications can occur so the caller of this API
+ * should check to make sure the condition they are waiting on has
+ * been met
+ *
+ * Example:
+ * @code
+ * mutex.lock();
+ * while (!condition_met) {
+ * cond.wait();
+ * }
+ *
+ * function_to_handle_condition();
+ *
+ * mutex.unlock();
+ * @endcode
+ *
+ * @note You cannot call this function from ISR context.
+ */
+ void wait();
+
+ /** Wait for a notification until specified time
+ *
+ * @param millisec absolute end time referenced to Kernel::get_ms_count()
+ * @return true if a timeout occurred, false otherwise.
+ *
+ * @note - The thread calling this function must be the owner of the
+ * ConditionVariable's mutex and it must be locked exactly once
+ * @note - Spurious notifications can occur so the caller of this API
+ * should check to make sure the condition they are waiting on has
+ * been met
+ *
+ * Example:
+ * @code
+ * mutex.lock();
+ * uint64_t end_time = Kernel::get_ms_count() + COND_WAIT_TIMEOUT;
+ *
+ * while (!condition_met) {
+ * if (cond.wait_until(end_time)) {
+ * break;
+ * }
+ * }
+ *
+ * if (condition_met) {
+ * function_to_handle_condition();
+ * }
+ *
+ * mutex.unlock();
+ * @endcode
+ *
+ * @note You cannot call this function from ISR context.
+ */
+ bool wait_until(uint64_t millisec);
+
+ /** Wait for a notification or timeout
+ *
+ * @param millisec timeout value or osWaitForever in case of no time-out.
+ * @return true if a timeout occurred, false otherwise.
+ *
+ * @note - The thread calling this function must be the owner of the
+ * ConditionVariable's mutex and it must be locked exactly once
+ * @note - Spurious notifications can occur so the caller of this API
+ * should check to make sure the condition they are waiting on has
+ * been met
+ *
+ * Example:
+ * @code
+ * mutex.lock();
+ *
+ * while (!condition_met) {
+ * cond.wait_for(MAX_SLEEP_TIME);
+ * if (!condition_met) {
+ * do_other_work_while_condition_false();
+ * }
+ * }
+ *
+ * if (condition_met) {
+ * function_to_handle_condition();
+ * }
+ *
+ * mutex.unlock();
+ * @endcode
+ *
+ * @note You cannot call this function from ISR context.
+ */
+ bool wait_for(uint32_t millisec);
+
+ /** Notify one waiter on this condition variable that a condition changed.
+ *
+ * @note - The thread calling this function must be the owner of the ConditionVariable's mutex
+ *
+ * @note You cannot call this function from ISR context.
+ */
+ void notify_one();
+
+ /** Notify all waiters on this condition variable that a condition changed.
+ *
+ * @note - The thread calling this function must be the owner of the ConditionVariable's mutex
+ *
+ * @note You cannot call this function from ISR context.
+ */
+ void notify_all();
+
+ /** ConditionVariable destructor
+ *
+ * @note You cannot call this function from ISR context.
+ */
+ ~ConditionVariable();
+
+protected:
+ struct Waiter {
+ Waiter();
+ Semaphore sem;
+ Waiter *prev;
+ Waiter *next;
+ bool in_list;
+ };
+
+ static void _add_wait_list(Waiter **wait_list, Waiter *waiter);
+ static void _remove_wait_list(Waiter **wait_list, Waiter *waiter);
+ Mutex &_mutex;
+ Waiter *_wait_list;
+};
+
+}
+#endif
+
+/** @}*/