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+/*-
+ * BSD LICENSE
+ *
+ * Copyright(c) 2010-2012 Intel Corporation. All rights reserved.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form 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.
+ * * Neither the name of Intel Corporation nor the names of its
+ * contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER 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.
+ *
+ * version: DPDK.L.1.2.3-3
+ */
+
+#ifndef _RTE_RWLOCK_H_
+#define _RTE_RWLOCK_H_
+
+/**
+ * @file
+ *
+ * RTE Read-Write Locks
+ *
+ * This file defines an API for read-write locks. The lock is used to
+ * protect data that allows multiple readers in parallel, but only
+ * one writer. All readers are blocked until the writer is finished
+ * writing.
+ *
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <rte_common.h>
+#include <rte_atomic.h>
+
+/**
+ * The rte_rwlock_t type.
+ *
+ * cnt is -1 when write lock is held, and > 0 when read locks are held.
+ */
+typedef struct {
+ volatile int32_t cnt; /**< -1 when W lock held, > 0 when R locks held. */
+} rte_rwlock_t;
+
+/**
+ * A static rwlock initializer.
+ */
+#define RTE_RWLOCK_INITIALIZER { 0 }
+
+/**
+ * Initialize the rwlock to an unlocked state.
+ *
+ * @param rwl
+ * A pointer to the rwlock structure.
+ */
+static inline void
+rte_rwlock_init(rte_rwlock_t *rwl)
+{
+ rwl->cnt = 0;
+}
+
+/**
+ * Take a read lock. Loop until the lock is held.
+ *
+ * @param rwl
+ * A pointer to a rwlock structure.
+ */
+static inline void
+rte_rwlock_read_lock(rte_rwlock_t *rwl)
+{
+ int32_t x;
+ int success = 0;
+
+ while (success == 0) {
+ x = rwl->cnt;
+ /* write lock is held */
+ if (x < 0) {
+ rte_pause();
+ continue;
+ }
+ success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
+ x, x + 1);
+ }
+}
+
+/**
+ * Release a read lock.
+ *
+ * @param rwl
+ * A pointer to the rwlock structure.
+ */
+static inline void
+rte_rwlock_read_unlock(rte_rwlock_t *rwl)
+{
+ /* in debug mode, we should check that rwl->cnt is > 0 */
+
+ /* same than atomic32_dec */
+ asm volatile(MPLOCKED
+ "decl %[cnt]"
+ : [cnt] "=m" (rwl->cnt) /* output (0) */
+ : "m" (rwl->cnt) /* input (1) */
+ ); /* no clobber-list */
+}
+
+/**
+ * Take a write lock. Loop until the lock is held.
+ *
+ * @param rwl
+ * A pointer to a rwlock structure.
+ */
+static inline void
+rte_rwlock_write_lock(rte_rwlock_t *rwl)
+{
+ int32_t x;
+ int success = 0;
+
+ while (success == 0) {
+ x = rwl->cnt;
+ /* a lock is held */
+ if (x != 0) {
+ rte_pause();
+ continue;
+ }
+ success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
+ 0, -1);
+ }
+}
+
+/**
+ * Release a write lock.
+ *
+ * @param rwl
+ * A pointer to a rwlock structure.
+ */
+static inline void
+rte_rwlock_write_unlock(rte_rwlock_t *rwl)
+{
+ /* in debug mode, we should check that rwl->cnt is < 0 */
+
+ /* same than atomic32_inc */
+ asm volatile(MPLOCKED
+ "incl %[cnt]"
+ : [cnt] "=m" (rwl->cnt) /* output (0) */
+ : "m" (rwl->cnt) /* input (1) */
+ ); /* no clobber-list */
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _RTE_RWLOCK_H_ */