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components/libraries/mutex/nrf_mtx.h

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+/**
+ * Copyright (c) 2015 - 2020, Nordic Semiconductor ASA
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form, except as embedded into a Nordic
+ *    Semiconductor ASA integrated circuit in a product or a software update for
+ *    such product, must reproduce the above copyright notice, this list of
+ *    conditions and the following disclaimer in the documentation and/or other
+ *    materials provided with the distribution.
+ *
+ * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
+ *    contributors may be used to endorse or promote products derived from this
+ *    software without specific prior written permission.
+ *
+ * 4. This software, with or without modification, must only be used with a
+ *    Nordic Semiconductor ASA integrated circuit.
+ *
+ * 5. Any software provided in binary form under this license must not be reverse
+ *    engineered, decompiled, modified and/or disassembled.
+ *
+ * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
+ * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
+ * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+/** @file
+ * @defgroup nrf_mtx nRF Mutex
+ * @{
+ * @ingroup app_common
+ * @brief Mutex used for protecting resources.
+ *
+ * This module provides a mutex that can be used to ensure only one context may enter a critical
+ * section holding the lock.
+ */
+#ifndef NRF_MTX_H__
+#define NRF_MTX_H__
+
+#include <stdint.h>
+#include <stdbool.h>
+#include "nrf.h"
+#include "nrf_atomic.h"
+#include "nrf_assert.h"
+
+#define NRF_MTX_LOCKED      1
+#define NRF_MTX_UNLOCKED    0
+
+/**
+ * @brief Mutex data type.
+ *
+ * All fields in this struct are internal, and should never be modified outside of the nrf_mtx_*
+ * functions.
+ */
+typedef nrf_atomic_u32_t nrf_mtx_t;
+
+/**
+ * @brief Initialize mutex.
+ *
+ * This function _must_ be called before nrf_mtx_trylock() and nrf_mtx_unlock() functions.
+ *
+ * @param[in, out] p_mtx The mutex to be initialized.
+ */
+__STATIC_INLINE void nrf_mtx_init(nrf_mtx_t * p_mtx);
+
+
+/**
+ * @brief Destroy mutex.
+ *
+ * This function can be used in abort scenarios or when the mutex is no longer to be used.
+ *
+ * @param[in] p_mtx The mutex to be destroy.
+ */
+__STATIC_INLINE void nrf_mtx_destroy(nrf_mtx_t * p_mtx);
+
+/**
+ * @brief Try to lock a mutex.
+ *
+ * If the mutex is already held by another context, this function will return immediately.
+ *
+ * @param[in, out] p_mtx The mutex to be locked.
+ * @return true if lock was acquired, false if not
+ */
+__STATIC_INLINE bool nrf_mtx_trylock(nrf_mtx_t * p_mtx);
+
+/**
+ * @brief Unlock a mutex.
+ *
+ * This function _must_ only be called when holding the lock. Unlocking a mutex which you do not
+ * hold will give undefined behavior.
+ *
+ * @note Unlock must happen from the same context as the one used to lock the mutex.
+ *
+ * @param[in, out] p_mtx The mutex to be unlocked.
+ */
+__STATIC_INLINE void nrf_mtx_unlock(nrf_mtx_t * p_mtx);
+
+#ifndef SUPPRESS_INLINE_IMPLEMENTATION
+
+__STATIC_INLINE void nrf_mtx_init(nrf_mtx_t * p_mtx)
+{
+    ASSERT(p_mtx  != NULL);
+
+    *p_mtx = NRF_MTX_UNLOCKED;
+    __DMB();
+}
+
+__STATIC_INLINE void nrf_mtx_destroy(nrf_mtx_t * p_mtx)
+{
+    ASSERT(p_mtx  != NULL);
+
+    // Add memory barrier to ensure that any memory operations protected by the mutex complete
+    // before the mutex is destroyed.
+    __DMB();
+
+    *p_mtx = NRF_MTX_UNLOCKED;
+}
+
+__STATIC_INLINE bool nrf_mtx_trylock(nrf_mtx_t * p_mtx)
+{
+    ASSERT(p_mtx  != NULL);
+
+    uint32_t old_val = nrf_atomic_u32_fetch_store(p_mtx, NRF_MTX_LOCKED);
+
+    // Add memory barrier to ensure that the mutex is locked before any memory operations protected
+    // by the mutex are started.
+    __DMB();
+
+    return (old_val == NRF_MTX_UNLOCKED);
+}
+
+__STATIC_INLINE void nrf_mtx_unlock(nrf_mtx_t * p_mtx)
+{
+    ASSERT(p_mtx  != NULL);
+    ASSERT(*p_mtx == NRF_MTX_LOCKED);
+
+    // Add memory barrier to ensure that any memory operations protected by the mutex complete
+    // before the mutex is unlocked.
+    __DMB();
+
+    *p_mtx = NRF_MTX_UNLOCKED;
+}
+
+#endif //SUPPRESS_INLINE_IMPLEMENTATION
+
+#endif // NRF_MTX_H__
+/** @} */