Mutex.h

/* mbed Microcontroller Library
 * Copyright (c) 2006-2019 ARM Limited
 * SPDX-License-Identifier: MIT
 *
 * 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 MUTEX_H
#define MUTEX_H
 
#include <stdint.h>
#include "rtos/mbed_rtos_types.h"
#include "rtos/internal/mbed_rtos1_types.h"
#include "rtos/internal/mbed_rtos_storage.h"
#include "rtos/Kernel.h"
 
#include "platform/NonCopyable.h"
#include "platform/ScopedLock.h"
#include "platform/mbed_toolchain.h"
 
namespace rtos {
/** \addtogroup rtos-public-api */
/** @{*/
 
class Mutex;
/** Typedef for the mutex lock
 *
 * Usage:
 * @code
 * void foo(Mutex &m) {
 *     ScopedMutexLock lock(m);
 *     // Mutex lock protects code in this block
 * }
 * @endcode
 */
typedef mbed::ScopedLock<Mutex> ScopedMutexLock;
 
/**
 * \defgroup rtos_Mutex Mutex class
 * @{
 */
 
/**
 * @brief The Mutex class is used to synchronize the execution of threads.
 *
 * \par
 * This is, for example, used to protect access to a shared resource.
 *
 * \par
 * In bare-metal builds, the Mutex class is a dummy, so lock() and unlock() are no-ops.
 *
 * \par
 * Mbed Mutexes are recursive. So, if you call the \c lock() function multiple times,
 * you must call \c unlock() the same number of times to unlock the mutex.  This means that it's okay to lock
 * a mutex, then call another function that also locks and unlocks the mutex, and the mutex won't actually
 * get unlocked until your function unlocks it.
 *
 * @note You cannot use member functions of this class in ISR context. If you require Mutex functionality within ISR handler, consider using @a Semaphore.
 *
 * @note
 * Memory considerations: The mutex control structures are created on the current thread's stack, both for the Mbed OS
 * and underlying RTOS objects (static or dynamic RTOS memory pools are not being used).
*/
class Mutex : private mbed::NonCopyable<Mutex> {
public:
    /** Create and Initialize a Mutex object
     *
     * @note You cannot call this function from ISR context.
    */
    Mutex();
 
    /** Create and Initialize a Mutex object
 
     @param name name to be used for this mutex. It has to stay allocated for the lifetime of the thread.
     @note You cannot call this function from ISR context.
    */
    Mutex(const char *name);
 
    /**
      Wait until a Mutex becomes available.
 
      @note You cannot call this function from ISR context.
     */
    void lock();
 
    /** Try to lock the mutex, and return immediately
      @return true if the mutex was acquired, false otherwise.
      @note equivalent to trylock_for(0)
 
      @note You cannot call this function from ISR context.
     */
    bool trylock();
 
    /** Try to lock the mutex for a specified time
      @param   millisec  timeout value.
      @return true if the mutex was acquired, false otherwise.
      @note the underlying RTOS may have a limit to the maximum wait time
            due to internal 32-bit computations, but this is guaranteed to work if the
            wait is <= 0x7fffffff milliseconds (~24 days). If the limit is exceeded,
            the lock attempt will time out earlier than specified.
 
      @note You cannot call this function from ISR context.
      @deprecated Pass a chrono duration, not an integer millisecond count. For example use `5s` rather than `5000`.
     */
    MBED_DEPRECATED_SINCE("mbed-os-6.0.0", "Pass a chrono duration, not an integer millisecond count. For example use `5s` rather than `5000`.")
    bool trylock_for(uint32_t millisec);
 
    /** Try to lock the mutex for a specified time
      @param   rel_time  timeout value.
      @return true if the mutex was acquired, false otherwise.
      @note the underlying RTOS may have a limit to the maximum wait time
            due to internal 32-bit computations, but this is guaranteed to work if the
            wait is <= 0x7fffffff milliseconds (~24 days). If the limit is exceeded,
            the lock attempt will time out earlier than specified.
 
      @note You cannot call this function from ISR context.
     */
    bool trylock_for(Kernel::Clock::duration_u32 rel_time);
 
    /** Try to lock the mutex until specified time
      @param   millisec  absolute timeout time, referenced to Kernel::get_ms_count()
      @return true if the mutex was acquired, false otherwise.
      @note the underlying RTOS may have a limit to the maximum wait time
            due to internal 32-bit computations, but this is guaranteed to work if the
            wait is <= 0x7fffffff milliseconds (~24 days). If the limit is exceeded,
            the lock attempt will time out earlier than specified.
 
      @note You cannot call this function from ISR context.
      @deprecated Pass a chrono time_point, not an integer millisecond count. For example use
                  `Kernel::Clock::now() + 5s` rather than `Kernel::get_ms_count() + 5000`.
     */
    MBED_DEPRECATED_SINCE("mbed-os-6.0.0", "Pass a chrono time_point, not an integer millisecond count. For example use `Kernel::Clock::now() + 5s` rather than `Kernel::get_ms_count() + 5000`.")
    bool trylock_until(uint64_t millisec);
 
    /** Try to lock the mutex until specified time
      @param   abs_time  absolute timeout time, referenced to Kernel::Clock
      @return true if the mutex was acquired, false otherwise.
      @note the underlying RTOS may have a limit to the maximum wait time
            due to internal 32-bit computations, but this is guaranteed to work if the
            wait is <= 0x7fffffff milliseconds (~24 days). If the limit is exceeded,
            the lock attempt will time out earlier than specified.
 
      @note You cannot call this function from ISR context.
     */
    bool trylock_until(Kernel::Clock::time_point abs_time);
 
    /**
      Unlock the mutex that has previously been locked by the same thread
 
      @note You cannot call this function from ISR context.
     */
    void unlock();
 
    /** Get the owner the this mutex
      @return  the current owner of this mutex.
 
      @note You cannot call this function from ISR context.
     */
    osThreadId_t get_owner();
 
    /** Mutex destructor
     *
     * @note You cannot call this function from ISR context.
     */
    ~Mutex();
 
private:
    void constructor(const char *name = nullptr);
    friend class ConditionVariable;
 
    osMutexId_t               _id;
    mbed_rtos_storage_mutex_t _obj_mem;
    uint32_t                  _count;
};
 
/** @}*/
/** @}*/
}
#endif