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/lock.h

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    1 /* 
    2  * Copyright (c) 1995
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code contains ideas from software contributed to Berkeley by
    6  * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
    7  * System project at Carnegie-Mellon University.
    8  *
    9  * Redistribution and use in source and binary forms, with or without
   10  * modification, are permitted provided that the following conditions
   11  * are met:
   12  * 1. Redistributions of source code must retain the above copyright
   13  *    notice, this list of conditions and the following disclaimer.
   14  * 2. Redistributions in binary form must reproduce the above copyright
   15  *    notice, this list of conditions and the following disclaimer in the
   16  *    documentation and/or other materials provided with the distribution.
   17  * 3. All advertising materials mentioning features or use of this software
   18  *    must display the following acknowledgement:
   19  *      This product includes software developed by the University of
   20  *      California, Berkeley and its contributors.
   21  * 4. Neither the name of the University nor the names of its contributors
   22  *    may be used to endorse or promote products derived from this software
   23  *    without specific prior written permission.
   24  *
   25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   35  * SUCH DAMAGE.
   36  *
   37  *      @(#)lock.h      8.12 (Berkeley) 5/19/95
   38  * $FreeBSD: stable/3/sys/sys/lock.h 50583 1999-08-29 16:33:42Z peter $
   39  */
   40 
   41 #ifndef _LOCK_H_
   42 #define _LOCK_H_
   43 
   44 
   45 #include <machine/lock.h>
   46 
   47 /*
   48  * The general lock structure.  Provides for multiple shared locks,
   49  * upgrading from shared to exclusive, and sleeping until the lock
   50  * can be gained. The simple locks are defined in <machine/param.h>.
   51  */
   52 struct lock {
   53         struct  simplelock lk_interlock; /* lock on remaining fields */
   54         u_int   lk_flags;               /* see below */
   55         int     lk_sharecount;          /* # of accepted shared locks */
   56         int     lk_waitcount;           /* # of processes sleeping for lock */
   57         short   lk_exclusivecount;      /* # of recursive exclusive locks */
   58         short   lk_prio;                /* priority at which to sleep */
   59         char    *lk_wmesg;              /* resource sleeping (for tsleep) */
   60         int     lk_timo;                /* maximum sleep time (for tsleep) */
   61         pid_t   lk_lockholder;          /* pid of exclusive lock holder */
   62 #ifdef  DEBUG_LOCKS
   63         const char *lk_filename;
   64         const char *lk_lockername;
   65         int     lk_lineno;
   66 #endif
   67 };
   68 /*
   69  * Lock request types:
   70  *   LK_SHARED - get one of many possible shared locks. If a process
   71  *      holding an exclusive lock requests a shared lock, the exclusive
   72  *      lock(s) will be downgraded to shared locks.
   73  *   LK_EXCLUSIVE - stop further shared locks, when they are cleared,
   74  *      grant a pending upgrade if it exists, then grant an exclusive
   75  *      lock. Only one exclusive lock may exist at a time, except that
   76  *      a process holding an exclusive lock may get additional exclusive
   77  *      locks if it explicitly sets the LK_CANRECURSE flag in the lock
   78  *      request, or if the LK_CANRECUSE flag was set when the lock was
   79  *      initialized.
   80  *   LK_UPGRADE - the process must hold a shared lock that it wants to
   81  *      have upgraded to an exclusive lock. Other processes may get
   82  *      exclusive access to the resource between the time that the upgrade
   83  *      is requested and the time that it is granted.
   84  *   LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
   85  *      have upgraded to an exclusive lock. If the request succeeds, no
   86  *      other processes will have gotten exclusive access to the resource
   87  *      between the time that the upgrade is requested and the time that
   88  *      it is granted. However, if another process has already requested
   89  *      an upgrade, the request will fail (see error returns below).
   90  *   LK_DOWNGRADE - the process must hold an exclusive lock that it wants
   91  *      to have downgraded to a shared lock. If the process holds multiple
   92  *      (recursive) exclusive locks, they will all be downgraded to shared
   93  *      locks.
   94  *   LK_RELEASE - release one instance of a lock.
   95  *   LK_DRAIN - wait for all activity on the lock to end, then mark it
   96  *      decommissioned. This feature is used before freeing a lock that
   97  *      is part of a piece of memory that is about to be freed.
   98  *
   99  * These are flags that are passed to the lockmgr routine.
  100  */
  101 #define LK_TYPE_MASK    0x0000000f      /* type of lock sought */
  102 #define LK_SHARED       0x00000001      /* shared lock */
  103 #define LK_EXCLUSIVE    0x00000002      /* exclusive lock */
  104 #define LK_UPGRADE      0x00000003      /* shared-to-exclusive upgrade */
  105 #define LK_EXCLUPGRADE  0x00000004      /* first shared-to-exclusive upgrade */
  106 #define LK_DOWNGRADE    0x00000005      /* exclusive-to-shared downgrade */
  107 #define LK_RELEASE      0x00000006      /* release any type of lock */
  108 #define LK_DRAIN        0x00000007      /* wait for all lock activity to end */
  109 /*
  110  * External lock flags.
  111  *
  112  * The first three flags may be set in lock_init to set their mode permanently,
  113  * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
  114  * set only at the release of a lock obtained by drain.
  115  */
  116 #define LK_EXTFLG_MASK  0x01000070      /* mask of external flags */
  117 #define LK_NOWAIT       0x00000010      /* do not sleep to await lock */
  118 #define LK_SLEEPFAIL    0x00000020      /* sleep, then return failure */
  119 #define LK_CANRECURSE   0x00000040      /* allow recursive exclusive lock */
  120 #define LK_REENABLE     0x00000080      /* lock is be reenabled after drain */
  121 #define LK_NOPAUSE      0x01000000      /* no spinloop */
  122 /*
  123  * Internal lock flags.
  124  *
  125  * These flags are used internally to the lock manager.
  126  */
  127 #define LK_WANT_UPGRADE 0x00000100      /* waiting for share-to-excl upgrade */
  128 #define LK_WANT_EXCL    0x00000200      /* exclusive lock sought */
  129 #define LK_HAVE_EXCL    0x00000400      /* exclusive lock obtained */
  130 #define LK_WAITDRAIN    0x00000800      /* process waiting for lock to drain */
  131 #define LK_DRAINING     0x00004000      /* lock is being drained */
  132 #define LK_DRAINED      0x00008000      /* lock has been decommissioned */
  133 /*
  134  * Control flags
  135  *
  136  * Non-persistent external flags.
  137  */
  138 #define LK_INTERLOCK    0x00010000 /* unlock passed simple lock after
  139                                    getting lk_interlock */
  140 #define LK_RETRY        0x00020000 /* vn_lock: retry until locked */
  141 #define LK_NOOBJ        0x00040000 /* vget: don't create object */
  142 
  143 /*
  144  * Internal state flags corresponding to lk_sharecount, and lk_waitcount
  145  */
  146 #define LK_SHARE_NONZERO 0x00100000
  147 #define LK_WAIT_NONZERO  0x00200000
  148 
  149 /*
  150  * Lock return status.
  151  *
  152  * Successfully obtained locks return 0. Locks will always succeed
  153  * unless one of the following is true:
  154  *      LK_FORCEUPGRADE is requested and some other process has already
  155  *          requested a lock upgrade (returns EBUSY).
  156  *      LK_WAIT is set and a sleep would be required (returns EBUSY).
  157  *      LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
  158  *      PCATCH is set in lock priority and a signal arrives (returns
  159  *          either EINTR or ERESTART if system calls is to be restarted).
  160  *      Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
  161  * A failed lock attempt always returns a non-zero error value. No lock
  162  * is held after an error return (in particular, a failed LK_UPGRADE
  163  * or LK_FORCEUPGRADE will have released its shared access lock).
  164  */
  165 
  166 /*
  167  * Indicator that no process holds exclusive lock
  168  */
  169 #define LK_KERNPROC ((pid_t) -2)
  170 #define LK_NOPROC ((pid_t) -1)
  171 
  172 void dumplockinfo(struct lock *lkp);
  173 struct proc;
  174 
  175 void    lockinit __P((struct lock *, int prio, char *wmesg, int timo,
  176                         int flags));
  177 #ifdef DEBUG_LOCKS
  178 int     debuglockmgr __P((struct lock *, u_int flags,
  179                         struct simplelock *, struct proc *p,
  180                         const char *,
  181                         const char *,
  182                         int));
  183 #define lockmgr(lockp, flags, slockp, proc) \
  184         debuglockmgr((lockp), (flags), (slockp), (proc), \
  185             "lockmgr", __FILE__, __LINE__)
  186 #else
  187 int     lockmgr __P((struct lock *, u_int flags,
  188                         struct simplelock *, struct proc *p));
  189 #endif
  190 void    lockmgr_printinfo __P((struct lock *));
  191 int     lockstatus __P((struct lock *));
  192 
  193 #ifdef SIMPLELOCK_DEBUG
  194 void _simple_unlock __P((struct simplelock *alp, const char *, int));
  195 #define simple_unlock(alp) _simple_unlock(alp, __FILE__, __LINE__)
  196 int _simple_lock_try __P((struct simplelock *alp, const char *, int));
  197 #define simple_lock_try(alp) _simple_lock_try(alp, __FILE__, __LINE__)
  198 void _simple_lock __P((struct simplelock *alp, const char *, int));
  199 #define simple_lock(alp) _simple_lock(alp, __FILE__, __LINE__)
  200 void simple_lock_init __P((struct simplelock *alp));
  201 #else /* !SIMPLELOCK_DEBUG */
  202 #if NCPUS == 1 /* no multiprocessor locking is necessary */
  203 #define NULL_SIMPLELOCKS
  204 #define simple_lock_init(alp)
  205 #define simple_lock(alp)
  206 #define simple_lock_try(alp)    (1)     /* always succeeds */
  207 #define simple_unlock(alp)
  208 #endif /* NCPUS == 1 */
  209 #endif /* !SIMPLELOCK_DEBUG */
  210 
  211 #endif /* !_LOCK_H_ */

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