The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/sys/lockf.h

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    1 /*-
    2  * Copyright (c) 1991, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software contributed to Berkeley by
    6  * Scooter Morris at Genentech Inc.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 4. Neither the name of the University nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  *
   32  *      @(#)lockf.h     8.1 (Berkeley) 6/11/93
   33  * $FreeBSD$
   34  */
   35 
   36 #ifndef _SYS_LOCKF_H_
   37 #define _SYS_LOCKF_H_
   38 
   39 #include <sys/queue.h>
   40 #include <sys/_lock.h>
   41 #include <sys/_sx.h>
   42 
   43 struct vop_advlock_args;
   44 struct vop_advlockasync_args;
   45 
   46 /*
   47  * The lockf_entry structure is a kernel structure which contains the
   48  * information associated with a byte range lock.  The lockf_entry
   49  * structures are linked into the inode structure. Locks are sorted by
   50  * the starting byte of the lock for efficiency.
   51  *
   52  * Active and pending locks on a vnode are organised into a
   53  * graph. Each pending lock has an out-going edge to each active lock
   54  * that blocks it.
   55  *
   56  * Locks:
   57  * (i)          locked by the vnode interlock
   58  * (s)          locked by state->ls_lock
   59  * (S)          locked by lf_lock_states_lock
   60  * (c)          const until freeing
   61  */
   62 struct lockf_edge {
   63         LIST_ENTRY(lockf_edge) le_outlink; /* (s) link from's out-edge list */
   64         LIST_ENTRY(lockf_edge) le_inlink; /* (s) link to's in-edge list */
   65         struct lockf_entry *le_from;    /* (c) out-going from here */
   66         struct lockf_entry *le_to;      /* (s) in-coming to here */
   67 };
   68 LIST_HEAD(lockf_edge_list, lockf_edge);
   69 
   70 struct lockf_entry {
   71         short   lf_flags;           /* (c) Semantics: F_POSIX, F_FLOCK, F_WAIT */
   72         short   lf_type;            /* (s) Lock type: F_RDLCK, F_WRLCK */
   73         off_t   lf_start;           /* (s) Byte # of the start of the lock */
   74         off_t   lf_end;             /* (s) Byte # of the end of the lock (OFF_MAX=EOF) */
   75         struct  lock_owner *lf_owner; /* (c) Owner of the lock */
   76         struct  vnode *lf_vnode;    /* (c) File being locked (only valid for active lock) */
   77         struct  inode *lf_inode;    /* (c) Back pointer to the inode */
   78         struct  task *lf_async_task;/* (c) Async lock callback */
   79         LIST_ENTRY(lockf_entry) lf_link;  /* (s) Linkage for lock lists */
   80         struct lockf_edge_list lf_outedges; /* (s) list of out-edges */
   81         struct lockf_edge_list lf_inedges; /* (s) list of out-edges */
   82 };
   83 LIST_HEAD(lockf_entry_list, lockf_entry);
   84 
   85 /*
   86  * Filesystem private node structures should include space for a
   87  * pointer to a struct lockf_state. This pointer is used by the lock
   88  * manager to track the locking state for a file.
   89  *
   90  * The ls_active list contains the set of active locks on the file. It
   91  * is strictly ordered by the lock's lf_start value. Each active lock
   92  * will have in-coming edges to any pending lock which it blocks.
   93  *
   94  * Lock requests which are blocked by some other active lock are
   95  * listed in ls_pending with newer requests first in the list. Lock
   96  * requests in this list will have out-going edges to each active lock
   97  * that blocks then. They will also have out-going edges to each
   98  * pending lock that is older in the queue - this helps to ensure
   99  * fairness when several processes are contenting to lock the same
  100  * record.
  101 
  102  * The value of ls_threads is the number of threads currently using
  103  * the state structure (typically either setting/clearing locks or
  104  * sleeping waiting to do so). This is used to defer freeing the
  105  * structure while some thread is still using it.
  106  */
  107 struct lockf {
  108         LIST_ENTRY(lockf) ls_link;      /* (S) all active lockf states */
  109         struct  sx      ls_lock;
  110         struct  lockf_entry_list ls_active; /* (s) Active locks */
  111         struct  lockf_entry_list ls_pending; /* (s) Pending locks */
  112         int             ls_threads;     /* (i) Thread count */
  113 };
  114 LIST_HEAD(lockf_list, lockf);
  115 
  116 int      lf_advlock(struct vop_advlock_args *, struct lockf **, u_quad_t);
  117 int      lf_advlockasync(struct vop_advlockasync_args *, struct lockf **, u_quad_t);
  118 int      lf_countlocks(int sysid);
  119 void     lf_clearremotesys(int sysid);
  120 
  121 #endif /* !_SYS_LOCKF_H_ */

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