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Diffstat (limited to 'sys/contrib/octeon-sdk/cvmx-rwlock.h')
| -rw-r--r-- | sys/contrib/octeon-sdk/cvmx-rwlock.h | 171 |
1 files changed, 171 insertions, 0 deletions
diff --git a/sys/contrib/octeon-sdk/cvmx-rwlock.h b/sys/contrib/octeon-sdk/cvmx-rwlock.h new file mode 100644 index 000000000000..d236d1990b5c --- /dev/null +++ b/sys/contrib/octeon-sdk/cvmx-rwlock.h @@ -0,0 +1,171 @@ +/***********************license start*************** + * Copyright (c) 2003-2010 Cavium Inc. (support@cavium.com). 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 Cavium Inc. 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, including technical data, may be subject to U.S. export control + * laws, including the U.S. Export Administration Act and its associated + * regulations, and may be subject to export or import regulations in other + * countries. + + * TO THE MAXIMUM EXTENT PERMITTED BY LAW, THE SOFTWARE IS PROVIDED "AS IS" + * AND WITH ALL FAULTS AND CAVIUM INC. MAKES NO PROMISES, REPRESENTATIONS OR + * WARRANTIES, EITHER EXPRESS, IMPLIED, STATUTORY, OR OTHERWISE, WITH RESPECT TO + * THE SOFTWARE, INCLUDING ITS CONDITION, ITS CONFORMITY TO ANY REPRESENTATION OR + * DESCRIPTION, OR THE EXISTENCE OF ANY LATENT OR PATENT DEFECTS, AND CAVIUM + * SPECIFICALLY DISCLAIMS ALL IMPLIED (IF ANY) WARRANTIES OF TITLE, + * MERCHANTABILITY, NONINFRINGEMENT, FITNESS FOR A PARTICULAR PURPOSE, LACK OF + * VIRUSES, ACCURACY OR COMPLETENESS, QUIET ENJOYMENT, QUIET POSSESSION OR + * CORRESPONDENCE TO DESCRIPTION. THE ENTIRE RISK ARISING OUT OF USE OR + * PERFORMANCE OF THE SOFTWARE LIES WITH YOU. + ***********************license end**************************************/ + + + + + + + +/** + * @file + * + * This file provides reader/writer locks. + * + * <hr>$Revision: 70030 $<hr> + * + * + */ + + +#ifndef __CVMX_RWLOCK_H__ +#define __CVMX_RWLOCK_H__ + +/* include to get atomic compare and store */ +#include "cvmx-atomic.h" + +#ifdef __cplusplus +extern "C" { +#endif + +/* Flags for lock value in rw lock structure */ +#define CVMX_RWLOCK_WRITE_FLAG 0x1 +#define CVMX_RWLOCK_READ_INC 0x2 + + +/* Writer preference locks (wp). Can be starved by writers. When a writer + * is waiting, no readers are given the lock until all writers are done. + */ +typedef struct +{ + volatile uint32_t lock; + volatile uint32_t write_req; + volatile uint32_t write_comp; +} cvmx_rwlock_wp_lock_t; + +/** + * Initialize a reader/writer lock. This must be done + * by a single core before used. + * + * @param lock pointer to rwlock structure + */ +static inline void cvmx_rwlock_wp_init(cvmx_rwlock_wp_lock_t *lock) +{ + lock->lock = 0; + lock->write_req = 0; + lock->write_comp = 0; +} + +/** + * Perform a reader lock. If a writer is pending, this + * will wait for that writer to complete before locking. + * + * NOTE: Each thread/process must only lock any rwlock + * once, or else a deadlock may result. + * + * @param lock pointer to rwlock structure + */ +static inline void cvmx_rwlock_wp_read_lock(cvmx_rwlock_wp_lock_t *lock) +{ + + /* Wait for outstanding write requests to be serviced */ + while (lock->write_req != lock->write_comp) + ; + /* Add ourselves to interested reader count */ + cvmx_atomic_add32_nosync((int32_t *)&(lock->lock), CVMX_RWLOCK_READ_INC); + /* Wait for writer to finish. No writer will start again + ** until after we are done since we have already incremented + ** the reader count + */ + while (lock->lock & CVMX_RWLOCK_WRITE_FLAG) + ; + +} + +/** + * Perform a reader unlock. + * + * @param lock pointer to rwlock structure + */ +static inline void cvmx_rwlock_wp_read_unlock(cvmx_rwlock_wp_lock_t *lock) +{ + /* Remove ourselves to reader count */ + cvmx_atomic_add32_nosync((int32_t *)&(lock->lock), -CVMX_RWLOCK_READ_INC); +} + +/** + * Perform a writer lock. Any readers that attempt + * to get a lock while there are any pending write locks + * will wait until all writers have completed. Starvation + * of readers by writers is possible and must be avoided + * by the application. + * + * @param lock pointer to rwlock structure + */ +static inline void cvmx_rwlock_wp_write_lock(cvmx_rwlock_wp_lock_t *lock) +{ + /* Get previous value of write requests */ + uint32_t prev_writers = ((uint32_t)cvmx_atomic_fetch_and_add32((int32_t *)&(lock->write_req), 1)); + /* Spin until our turn */ + while (prev_writers != lock->write_comp) + ; + /* Spin until no other readers or writers, then set write flag */ + while (!cvmx_atomic_compare_and_store32((uint32_t *)&(lock->lock), 0, CVMX_RWLOCK_WRITE_FLAG)) + ; + +} +/** + * Perform a writer unlock. + * + * @param lock pointer to rwlock structure + */ +static inline void cvmx_rwlock_wp_write_unlock(cvmx_rwlock_wp_lock_t *lock) +{ + /* Remove our writer flag */ + CVMX_SYNCWS; /* Make sure all writes in protected region are visible before unlock */ + cvmx_atomic_add32_nosync((int32_t *)&(lock->lock), -CVMX_RWLOCK_WRITE_FLAG); + cvmx_atomic_add32_nosync((int32_t *)&(lock->write_comp), 1); + CVMX_SYNCWS; /* push unlock writes out, but don't stall */ +} + +#ifdef __cplusplus +} +#endif + +#endif /* __CVMX_RWLOCK_H__ */ |