rte_rwlock.h File Reference

#include <errno.h>
#include <rte_branch_prediction.h>
#include <rte_common.h>
#include <rte_pause.h>

Go to the source code of this file.

Macros
#define	RTE_RWLOCK_WAIT   0x1 /* Writer is waiting */
#define	RTE_RWLOCK_INITIALIZER   { 0 }

Functions
static void	rte_rwlock_init (rte_rwlock_t *rwl)
static void	rte_rwlock_read_lock (rte_rwlock_t *rwl)
static int	rte_rwlock_read_trylock (rte_rwlock_t *rwl)
static void	rte_rwlock_read_unlock (rte_rwlock_t *rwl)
static int	rte_rwlock_write_trylock (rte_rwlock_t *rwl)
static void	rte_rwlock_write_lock (rte_rwlock_t *rwl)
static void	rte_rwlock_write_unlock (rte_rwlock_t *rwl)
static void	rte_rwlock_read_lock_tm (rte_rwlock_t *rwl)
static void	rte_rwlock_read_unlock_tm (rte_rwlock_t *rwl)
static void	rte_rwlock_write_lock_tm (rte_rwlock_t *rwl)
static void	rte_rwlock_write_unlock_tm (rte_rwlock_t *rwl)

Detailed Description

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.

This version does not give preference to readers or writers and does not starve either readers or writers.

See also: https://locklessinc.com/articles/locks/

Definition in file rte_rwlock.h.

Macro Definition Documentation

RTE_RWLOCK_WAIT

#define RTE_RWLOCK_WAIT   0x1 /* Writer is waiting */

The rte_rwlock_t type.

Readers increment the counter by RTE_RWLOCK_READ (4) Writers set the RTE_RWLOCK_WRITE bit when lock is held and set the RTE_RWLOCK_WAIT bit while waiting.

31 2 1 0 +----------------—+-+-+ | readers | | | +----------------—+-+-+ ^ ^ | | WRITE: lock held -—/ | WAIT: writer pending –/

Definition at line 52 of file rte_rwlock.h.

RTE_RWLOCK_INITIALIZER

#define RTE_RWLOCK_INITIALIZER   { 0 }

A static rwlock initializer.

Definition at line 65 of file rte_rwlock.h.

Function Documentation

rte_rwlock_init()

static void rte_rwlock_init ( rte_rwlock_t *  rwl )

inlinestatic

Initialize the rwlock to an unlocked state.

Parameters

rwl	A pointer to the rwlock structure.

Definition at line 74 of file rte_rwlock.h.

rte_rwlock_read_lock()

static void rte_rwlock_read_lock ( rte_rwlock_t *  rwl )

inlinestatic

Take a read lock. Loop until the lock is held.

Note

The RW lock isn't recursive, so calling this function on the same lock twice without releasing it could potentially result in a deadlock scenario when a write lock is involved.

Parameters

rwl	A pointer to a rwlock structure.

Definition at line 90 of file rte_rwlock.h.

rte_rwlock_read_trylock()

static int rte_rwlock_read_trylock ( rte_rwlock_t *  rwl )

inlinestatic

Try to take a read lock.

Parameters

rwl	A pointer to a rwlock structure.

Returns

• zero if the lock is successfully taken
• -EBUSY if lock could not be acquired for reading because a writer holds the lock

Definition at line 125 of file rte_rwlock.h.

rte_rwlock_read_unlock()

static void rte_rwlock_read_unlock ( rte_rwlock_t *  rwl )

inlinestatic

Release a read lock.

Parameters

rwl	A pointer to the rwlock structure.

Definition at line 156 of file rte_rwlock.h.

rte_rwlock_write_trylock()

static int rte_rwlock_write_trylock ( rte_rwlock_t *  rwl )

inlinestatic

Try to take a write lock.

Parameters

rwl	A pointer to a rwlock structure.

Returns

• zero if the lock is successfully taken
• -EBUSY if lock could not be acquired for writing because it was already locked for reading or writing

Definition at line 172 of file rte_rwlock.h.

rte_rwlock_write_lock()

static void rte_rwlock_write_lock ( rte_rwlock_t *  rwl )

inlinestatic

Take a write lock. Loop until the lock is held.

Parameters

rwl	A pointer to a rwlock structure.

Definition at line 192 of file rte_rwlock.h.

rte_rwlock_write_unlock()

static void rte_rwlock_write_unlock ( rte_rwlock_t *  rwl )

inlinestatic

Release a write lock.

Parameters

rwl	A pointer to a rwlock structure.

Definition at line 225 of file rte_rwlock.h.

rte_rwlock_read_lock_tm()

static void rte_rwlock_read_lock_tm ( rte_rwlock_t *  rwl )

inlinestatic

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.

Parameters

rwl	A pointer to a rwlock structure.

rte_rwlock_read_unlock_tm()

static void rte_rwlock_read_unlock_tm ( rte_rwlock_t *  rwl )

inlinestatic

Commit hardware memory transaction or release the read lock if the lock is used as a fall-back

Parameters

rwl	A pointer to the rwlock structure.

rte_rwlock_write_lock_tm()

static void rte_rwlock_write_lock_tm ( rte_rwlock_t *  rwl )

inlinestatic

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.

Parameters

rwl	A pointer to a rwlock structure.

rte_rwlock_write_unlock_tm()

static void rte_rwlock_write_unlock_tm ( rte_rwlock_t *  rwl )

inlinestatic

Commit hardware memory transaction or release the write lock if the lock is used as a fall-back

Parameters

rwl	A pointer to a rwlock structure.