1 /* SPDX-License-Identifier: BSD-3-Clause
2 * Copyright(c) 2010-2014 Intel Corporation
11 * RTE Read-Write Locks
13 * This file defines an API for read-write locks. The lock is used to
14 * protect data that allows multiple readers in parallel, but only
15 * one writer. All readers are blocked until the writer is finished
24 #include <rte_common.h>
25 #include <rte_atomic.h>
26 #include <rte_pause.h>
29 * The rte_rwlock_t type.
31 * cnt is -1 when write lock is held, and > 0 when read locks are held.
34 volatile int32_t cnt; /**< -1 when W lock held, > 0 when R locks held. */
38 * A static rwlock initializer.
40 #define RTE_RWLOCK_INITIALIZER { 0 }
43 * Initialize the rwlock to an unlocked state.
46 * A pointer to the rwlock structure.
49 rte_rwlock_init(rte_rwlock_t *rwl)
55 * Take a read lock. Loop until the lock is held.
58 * A pointer to a rwlock structure.
61 rte_rwlock_read_lock(rte_rwlock_t *rwl)
66 while (success == 0) {
68 /* write lock is held */
73 success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
74 (uint32_t)x, (uint32_t)(x + 1));
80 * @b EXPERIMENTAL: this API may change without prior notice.
82 * try to take a read lock.
85 * A pointer to a rwlock structure.
87 * - zero if the lock is successfully taken
88 * - -EBUSY if lock could not be acquired for reading because a
89 * writer holds the lock
91 static inline __rte_experimental int
92 rte_rwlock_read_trylock(rte_rwlock_t *rwl)
97 while (success == 0) {
99 /* write lock is held */
102 success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
103 (uint32_t)x, (uint32_t)(x + 1));
109 * Release a read lock.
112 * A pointer to the rwlock structure.
115 rte_rwlock_read_unlock(rte_rwlock_t *rwl)
117 rte_atomic32_dec((rte_atomic32_t *)(intptr_t)&rwl->cnt);
122 * @b EXPERIMENTAL: this API may change without prior notice.
124 * try to take a write lock.
127 * A pointer to a rwlock structure.
129 * - zero if the lock is successfully taken
130 * - -EBUSY if lock could not be acquired for writing because
131 * it was already locked for reading or writing
133 static inline __rte_experimental int
134 rte_rwlock_write_trylock(rte_rwlock_t *rwl)
139 if (x != 0 || rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
140 0, (uint32_t)-1) == 0)
147 * Take a write lock. Loop until the lock is held.
150 * A pointer to a rwlock structure.
153 rte_rwlock_write_lock(rte_rwlock_t *rwl)
158 while (success == 0) {
165 success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
171 * Release a write lock.
174 * A pointer to a rwlock structure.
177 rte_rwlock_write_unlock(rte_rwlock_t *rwl)
179 rte_atomic32_inc((rte_atomic32_t *)(intptr_t)&rwl->cnt);
183 * Try to execute critical section in a hardware memory transaction, if it
184 * fails or not available take a read lock
186 * NOTE: An attempt to perform a HW I/O operation inside a hardware memory
187 * transaction always aborts the transaction since the CPU is not able to
188 * roll-back should the transaction fail. Therefore, hardware transactional
189 * locks are not advised to be used around rte_eth_rx_burst() and
190 * rte_eth_tx_burst() calls.
193 * A pointer to a rwlock structure.
196 rte_rwlock_read_lock_tm(rte_rwlock_t *rwl);
199 * Commit hardware memory transaction or release the read lock if the lock is used as a fall-back
202 * A pointer to the rwlock structure.
205 rte_rwlock_read_unlock_tm(rte_rwlock_t *rwl);
208 * Try to execute critical section in a hardware memory transaction, if it
209 * fails or not available take a write lock
211 * NOTE: An attempt to perform a HW I/O operation inside a hardware memory
212 * transaction always aborts the transaction since the CPU is not able to
213 * roll-back should the transaction fail. Therefore, hardware transactional
214 * locks are not advised to be used around rte_eth_rx_burst() and
215 * rte_eth_tx_burst() calls.
218 * A pointer to a rwlock structure.
221 rte_rwlock_write_lock_tm(rte_rwlock_t *rwl);
224 * Commit hardware memory transaction or release the write lock if the lock is used as a fall-back
227 * A pointer to a rwlock structure.
230 rte_rwlock_write_unlock_tm(rte_rwlock_t *rwl);
236 #endif /* _RTE_RWLOCK_H_ */