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MAKES NO PROMISES, REPRESENTATIONS OR 30 * WARRANTIES, EITHER EXPRESS, IMPLIED, STATUTORY, OR OTHERWISE, WITH RESPECT TO 31 * THE SOFTWARE, INCLUDING ITS CONDITION, ITS CONFORMITY TO ANY REPRESENTATION OR 32 * DESCRIPTION, OR THE EXISTENCE OF ANY LATENT OR PATENT DEFECTS, AND CAVIUM 33 * SPECIFICALLY DISCLAIMS ALL IMPLIED (IF ANY) WARRANTIES OF TITLE, 34 * MERCHANTABILITY, NONINFRINGEMENT, FITNESS FOR A PARTICULAR PURPOSE, LACK OF 35 * VIRUSES, ACCURACY OR COMPLETENESS, QUIET ENJOYMENT, QUIET POSSESSION OR 36 * CORRESPONDENCE TO DESCRIPTION. THE ENTIRE RISK ARISING OUT OF USE OR 37 * PERFORMANCE OF THE SOFTWARE LIES WITH YOU. 38 ***********************license end**************************************/ 39 40 41 42 43 44 45 46/** 47 * @file 48 * 49 * This file provides reader/writer locks. 50 * 51 * <hr>$Revision: 70030 $<hr> 52 * 53 * 54 */ 55 56 57#ifndef __CVMX_RWLOCK_H__ 58#define __CVMX_RWLOCK_H__ 59 60/* include to get atomic compare and store */ 61#include "cvmx-atomic.h" 62 63#ifdef __cplusplus 64extern "C" { 65#endif 66 67/* Flags for lock value in rw lock structure */ 68#define CVMX_RWLOCK_WRITE_FLAG 0x1 69#define CVMX_RWLOCK_READ_INC 0x2 70 71 72/* Writer preference locks (wp). Can be starved by writers. When a writer 73 * is waiting, no readers are given the lock until all writers are done. 74 */ 75typedef struct 76{ 77 volatile uint32_t lock; 78 volatile uint32_t write_req; 79 volatile uint32_t write_comp; 80} cvmx_rwlock_wp_lock_t; 81 82/** 83 * Initialize a reader/writer lock. This must be done 84 * by a single core before used. 85 * 86 * @param lock pointer to rwlock structure 87 */ 88static inline void cvmx_rwlock_wp_init(cvmx_rwlock_wp_lock_t *lock) 89{ 90 lock->lock = 0; 91 lock->write_req = 0; 92 lock->write_comp = 0; 93} 94 95/** 96 * Perform a reader lock. If a writer is pending, this 97 * will wait for that writer to complete before locking. 98 * 99 * NOTE: Each thread/process must only lock any rwlock 100 * once, or else a deadlock may result. 101 * 102 * @param lock pointer to rwlock structure 103 */ 104static inline void cvmx_rwlock_wp_read_lock(cvmx_rwlock_wp_lock_t *lock) 105{ 106 107 /* Wait for outstanding write requests to be serviced */ 108 while (lock->write_req != lock->write_comp) 109 ; 110 /* Add ourselves to interested reader count */ 111 cvmx_atomic_add32_nosync((int32_t *)&(lock->lock), CVMX_RWLOCK_READ_INC); 112 /* Wait for writer to finish. No writer will start again 113 ** until after we are done since we have already incremented 114 ** the reader count 115 */ 116 while (lock->lock & CVMX_RWLOCK_WRITE_FLAG) 117 ; 118 119} 120 121/** 122 * Perform a reader unlock. 123 * 124 * @param lock pointer to rwlock structure 125 */ 126static inline void cvmx_rwlock_wp_read_unlock(cvmx_rwlock_wp_lock_t *lock) 127{ 128 /* Remove ourselves to reader count */ 129 cvmx_atomic_add32_nosync((int32_t *)&(lock->lock), -CVMX_RWLOCK_READ_INC); 130} 131 132/** 133 * Perform a writer lock. Any readers that attempt 134 * to get a lock while there are any pending write locks 135 * will wait until all writers have completed. Starvation 136 * of readers by writers is possible and must be avoided 137 * by the application. 138 * 139 * @param lock pointer to rwlock structure 140 */ 141static inline void cvmx_rwlock_wp_write_lock(cvmx_rwlock_wp_lock_t *lock) 142{ 143 /* Get previous value of write requests */ 144 uint32_t prev_writers = ((uint32_t)cvmx_atomic_fetch_and_add32((int32_t *)&(lock->write_req), 1)); 145 /* Spin until our turn */ 146 while (prev_writers != lock->write_comp) 147 ; 148 /* Spin until no other readers or writers, then set write flag */ 149 while (!cvmx_atomic_compare_and_store32((uint32_t *)&(lock->lock), 0, CVMX_RWLOCK_WRITE_FLAG)) 150 ; 151 152} 153/** 154 * Perform a writer unlock. 155 * 156 * @param lock pointer to rwlock structure 157 */ 158static inline void cvmx_rwlock_wp_write_unlock(cvmx_rwlock_wp_lock_t *lock) 159{ 160 /* Remove our writer flag */ 161 CVMX_SYNCWS; /* Make sure all writes in protected region are visible before unlock */ 162 cvmx_atomic_add32_nosync((int32_t *)&(lock->lock), -CVMX_RWLOCK_WRITE_FLAG); 163 cvmx_atomic_add32_nosync((int32_t *)&(lock->write_comp), 1); 164 CVMX_SYNCWS; /* push unlock writes out, but don't stall */ 165} 166 167#ifdef __cplusplus 168} 169#endif 170 171#endif /* __CVMX_RWLOCK_H__ */ 172