FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/include/sys/rrwlock.h

     /*
      * CDDL HEADER START
      *
      * The contents of this file are subject to the terms of the
      * Common Development and Distribution License (the "License").
      * You may not use this file except in compliance with the License.
      *
      * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      * or https://opensource.org/licenses/CDDL-1.0.
     * See the License for the specific language governing permissions
     * and limitations under the License.
     *
     * When distributing Covered Code, include this CDDL HEADER in each
     * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     * If applicable, add the following below this CDDL HEADER, with the
     * fields enclosed by brackets "[]" replaced with your own identifying
     * information: Portions Copyright [yyyy] [name of copyright owner]
     *
     * CDDL HEADER END
     */
    /*
     * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
     * Use is subject to license terms.
     */
    /*
     * Copyright (c) 2012 by Delphix. All rights reserved.
     */
    
    #ifndef _SYS_RR_RW_LOCK_H
    #define _SYS_RR_RW_LOCK_H
    
    
    
    #ifdef  __cplusplus
    extern "C" {
    #endif
    
    #include <sys/inttypes.h>
    #include <sys/zfs_context.h>
    #include <sys/zfs_refcount.h>
    
    extern uint_t rrw_tsd_key;
    
    /*
     * A reader-writer lock implementation that allows re-entrant reads, but
     * still gives writers priority on "new" reads.
     *
     * See rrwlock.c for more details about the implementation.
     *
     * Fields of the rrwlock_t structure:
     * - rr_lock: protects modification and reading of rrwlock_t fields
     * - rr_cv: cv for waking up readers or waiting writers
     * - rr_writer: thread id of the current writer
     * - rr_anon_rount: number of active anonymous readers
     * - rr_linked_rcount: total number of non-anonymous active readers
     * - rr_writer_wanted: a writer wants the lock
     */
    typedef struct rrwlock {
            kmutex_t        rr_lock;
            kcondvar_t      rr_cv;
            kthread_t       *rr_writer;
            zfs_refcount_t  rr_anon_rcount;
            zfs_refcount_t  rr_linked_rcount;
            boolean_t       rr_writer_wanted;
            boolean_t       rr_track_all;
    } rrwlock_t;
    
    /*
     * 'tag' is used in reference counting tracking.  The
     * 'tag' must be the same in a rrw_enter() as in its
     * corresponding rrw_exit().
     */
    void rrw_init(rrwlock_t *rrl, boolean_t track_all);
    void rrw_destroy(rrwlock_t *rrl);
    void rrw_enter(rrwlock_t *rrl, krw_t rw, const void *tag);
    void rrw_enter_read(rrwlock_t *rrl, const void *tag);
    void rrw_enter_read_prio(rrwlock_t *rrl, const void *tag);
    void rrw_enter_write(rrwlock_t *rrl);
    void rrw_exit(rrwlock_t *rrl, const void *tag);
    boolean_t rrw_held(rrwlock_t *rrl, krw_t rw);
    void rrw_tsd_destroy(void *arg);
    
    #define RRW_READ_HELD(x)        rrw_held(x, RW_READER)
    #define RRW_WRITE_HELD(x)       rrw_held(x, RW_WRITER)
    #define RRW_LOCK_HELD(x) \
            (rrw_held(x, RW_WRITER) || rrw_held(x, RW_READER))
    
    /*
     * A reader-mostly lock implementation, tuning above reader-writer locks
     * for hightly parallel read acquisitions, pessimizing write acquisitions.
     *
     * This should be a prime number.  See comment in rrwlock.c near
     * RRM_TD_LOCK() for details.
     */
    #define RRM_NUM_LOCKS           17
    typedef struct rrmlock {
            rrwlock_t       locks[RRM_NUM_LOCKS];
    } rrmlock_t;
    
   void rrm_init(rrmlock_t *rrl, boolean_t track_all);
   void rrm_destroy(rrmlock_t *rrl);
   void rrm_enter(rrmlock_t *rrl, krw_t rw, const void *tag);
   void rrm_enter_read(rrmlock_t *rrl, const void *tag);
   void rrm_enter_write(rrmlock_t *rrl);
   void rrm_exit(rrmlock_t *rrl, const void *tag);
   boolean_t rrm_held(rrmlock_t *rrl, krw_t rw);
   
   #define RRM_READ_HELD(x)        rrm_held(x, RW_READER)
   #define RRM_WRITE_HELD(x)       rrm_held(x, RW_WRITER)
   #define RRM_LOCK_HELD(x) \
           (rrm_held(x, RW_WRITER) || rrm_held(x, RW_READER))
   
   #ifdef  __cplusplus
   }
   #endif
   
   #endif  /* _SYS_RR_RW_LOCK_H */

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