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/*-
* BSD LICENSE
*
* Copyright(c) 2010-2014 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.
*/
#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)
{
rte_atomic32_dec((rte_atomic32_t *)(intptr_t)&rwl->cnt);
}
/**
* 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)
{
rte_atomic32_inc((rte_atomic32_t *)(intptr_t)&rwl->cnt);
}
/**
* Try to execute critical section in a hardware memory transaction, if it
* fails or not available take a read lock
*
* NOTE: An attempt to perform a HW I/O operation inside a hardware memory
* transaction always aborts the transaction since the CPU is not able to
* roll-back should the transaction fail. Therefore, hardware transactional
* locks are not advised to be used around rte_eth_rx_burst() and
* rte_eth_tx_burst() calls.
*
* @param rwl
* A pointer to a rwlock structure.
*/
static inline void
rte_rwlock_read_lock_tm(rte_rwlock_t *rwl);
/**
* Commit hardware memory transaction or release the read lock if the lock is used as a fall-back
*
* @param rwl
* A pointer to the rwlock structure.
*/
static inline void
rte_rwlock_read_unlock_tm(rte_rwlock_t *rwl);
/**
* Try to execute critical section in a hardware memory transaction, if it
* fails or not available take a write lock
*
* NOTE: An attempt to perform a HW I/O operation inside a hardware memory
* transaction always aborts the transaction since the CPU is not able to
* roll-back should the transaction fail. Therefore, hardware transactional
* locks are not advised to be used around rte_eth_rx_burst() and
* rte_eth_tx_burst() calls.
*
* @param rwl
* A pointer to a rwlock structure.
*/
static inline void
rte_rwlock_write_lock_tm(rte_rwlock_t *rwl);
/**
* Commit hardware memory transaction or release the write lock if the lock is used as a fall-back
*
* @param rwl
* A pointer to a rwlock structure.
*/
static inline void
rte_rwlock_write_unlock_tm(rte_rwlock_t *rwl);
#ifdef __cplusplus
}
#endif
#endif /* _RTE_RWLOCK_H_ */
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