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/lockmgr.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: releng/5.0/sys/sys/lockmgr.h 107414 2002-11-30 19:00:51Z mckusick $
   39  */
   40 
   41 #ifndef _SYS_LOCKMGR_H_
   42 #define _SYS_LOCKMGR_H_
   43 
   44 struct  mtx;
   45 
   46 /*
   47  * The general lock structure.  Provides for multiple shared locks,
   48  * upgrading from shared to exclusive, and sleeping until the lock
   49  * can be gained.
   50  */
   51 struct lock {
   52         struct  mtx *lk_interlock;      /* lock on remaining fields */
   53         u_int   lk_flags;               /* see below */
   54         int     lk_sharecount;          /* # of accepted shared locks */
   55         int     lk_waitcount;           /* # of processes sleeping for lock */
   56         short   lk_exclusivecount;      /* # of recursive exclusive locks */
   57         short   lk_prio;                /* priority at which to sleep */
   58         const char *lk_wmesg;           /* resource sleeping (for tsleep) */
   59         int     lk_timo;                /* maximum sleep time (for tsleep) */
   60         pid_t   lk_lockholder;          /* pid of exclusive lock holder */
   61         struct  lock *lk_newlock;       /* lock taking over this lock */
   62 #ifdef  DEBUG_LOCKS
   63         const char *lk_filename;
   64         const char *lk_lockername;
   65         int     lk_lineno;
   66 
   67         pid_t   lk_slockholder;
   68         const char *lk_sfilename;
   69         const char *lk_slockername;
   70         int     lk_slineno;
   71 #endif
   72 };
   73 /*
   74  * Lock request types:
   75  *   LK_SHARED - get one of many possible shared locks. If a process
   76  *      holding an exclusive lock requests a shared lock, the exclusive
   77  *      lock(s) will be downgraded to shared locks.
   78  *   LK_EXCLUSIVE - stop further shared locks, when they are cleared,
   79  *      grant a pending upgrade if it exists, then grant an exclusive
   80  *      lock. Only one exclusive lock may exist at a time, except that
   81  *      a process holding an exclusive lock may get additional exclusive
   82  *      locks if it explicitly sets the LK_CANRECURSE flag in the lock
   83  *      request, or if the LK_CANRECUSE flag was set when the lock was
   84  *      initialized.
   85  *   LK_UPGRADE - the process must hold a shared lock that it wants to
   86  *      have upgraded to an exclusive lock. Other processes may get
   87  *      exclusive access to the resource between the time that the upgrade
   88  *      is requested and the time that it is granted.
   89  *   LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
   90  *      have upgraded to an exclusive lock. If the request succeeds, no
   91  *      other processes will have gotten exclusive access to the resource
   92  *      between the time that the upgrade is requested and the time that
   93  *      it is granted. However, if another process has already requested
   94  *      an upgrade, the request will fail (see error returns below).
   95  *   LK_DOWNGRADE - the process must hold an exclusive lock that it wants
   96  *      to have downgraded to a shared lock. If the process holds multiple
   97  *      (recursive) exclusive locks, they will all be downgraded to shared
   98  *      locks.
   99  *   LK_RELEASE - release one instance of a lock.
  100  *   LK_DRAIN - wait for all activity on the lock to end, then mark it
  101  *      decommissioned. This feature is used before freeing a lock that
  102  *      is part of a piece of memory that is about to be freed.
  103  *   LK_EXCLOTHER - return for lockstatus().  Used when another process
  104  *      holds the lock exclusively.
  105  *
  106  * These are flags that are passed to the lockmgr routine.
  107  */
  108 #define LK_TYPE_MASK    0x0000000f      /* type of lock sought */
  109 #define LK_SHARED       0x00000001      /* shared lock */
  110 #define LK_EXCLUSIVE    0x00000002      /* exclusive lock */
  111 #define LK_UPGRADE      0x00000003      /* shared-to-exclusive upgrade */
  112 #define LK_EXCLUPGRADE  0x00000004      /* first shared-to-exclusive upgrade */
  113 #define LK_DOWNGRADE    0x00000005      /* exclusive-to-shared downgrade */
  114 #define LK_RELEASE      0x00000006      /* release any type of lock */
  115 #define LK_DRAIN        0x00000007      /* wait for all lock activity to end */
  116 #define LK_EXCLOTHER    0x00000008      /* other process holds lock */
  117 /*
  118  * External lock flags.
  119  *
  120  * The first three flags may be set in lock_init to set their mode permanently,
  121  * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
  122  * set only at the release of a lock obtained by drain.
  123  */
  124 #define LK_EXTFLG_MASK  0x03000070      /* mask of external flags */
  125 #define LK_NOWAIT       0x00000010      /* do not sleep to await lock */
  126 #define LK_SLEEPFAIL    0x00000020      /* sleep, then return failure */
  127 #define LK_CANRECURSE   0x00000040      /* allow recursive exclusive lock */
  128 #define LK_REENABLE     0x00000080      /* lock is be reenabled after drain */
  129 #define LK_NOPAUSE      0x01000000      /* no spinloop */
  130 #define LK_TIMELOCK     0x02000000      /* use lk_timo, else no timeout */
  131 /*
  132  * Internal lock flags.
  133  *
  134  * These flags are used internally to the lock manager.
  135  */
  136 #define LK_WANT_UPGRADE 0x00000100      /* waiting for share-to-excl upgrade */
  137 #define LK_WANT_EXCL    0x00000200      /* exclusive lock sought */
  138 #define LK_HAVE_EXCL    0x00000400      /* exclusive lock obtained */
  139 #define LK_WAITDRAIN    0x00000800      /* process waiting for lock to drain */
  140 #define LK_DRAINING     0x00004000      /* lock is being drained */
  141 /*
  142  * Control flags
  143  *
  144  * Non-persistent external flags.
  145  */
  146 #define LK_INTERLOCK    0x00010000 /*
  147                                     * unlock passed mutex after getting
  148                                     * lk_interlock
  149                                     */
  150 #define LK_RETRY        0x00020000 /* vn_lock: retry until locked */
  151 #define LK_THISLAYER    0x00040000 /* vn_lock: lock/unlock only current layer */
  152 
  153 /*
  154  * Internal state flags corresponding to lk_sharecount, and lk_waitcount
  155  */
  156 #define LK_SHARE_NONZERO 0x00100000
  157 #define LK_WAIT_NONZERO  0x00200000
  158 
  159 /*
  160  * Lock return status.
  161  *
  162  * Successfully obtained locks return 0. Locks will always succeed
  163  * unless one of the following is true:
  164  *      LK_FORCEUPGRADE is requested and some other process has already
  165  *          requested a lock upgrade (returns EBUSY).
  166  *      LK_WAIT is set and a sleep would be required (returns EBUSY).
  167  *      LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
  168  *      PCATCH is set in lock priority and a signal arrives (returns
  169  *          either EINTR or ERESTART if system calls is to be restarted).
  170  *      Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
  171  * A failed lock attempt always returns a non-zero error value. No lock
  172  * is held after an error return (in particular, a failed LK_UPGRADE
  173  * or LK_FORCEUPGRADE will have released its shared access lock).
  174  */
  175 
  176 /*
  177  * Indicator that no process holds exclusive lock
  178  */
  179 #define LK_KERNPROC ((pid_t) -2)
  180 #define LK_NOPROC ((pid_t) -1)
  181 
  182 #ifdef INVARIANTS
  183 #define LOCKMGR_ASSERT(lkp, what, p) do {                               \
  184         switch ((what)) {                                               \
  185         case LK_SHARED:                                                 \
  186                 if (lockstatus((lkp), (p)) == LK_SHARED)                \
  187                         break;                                          \
  188                 /* fall into exclusive */                               \
  189         case LK_EXCLUSIVE:                                              \
  190                 if (lockstatus((lkp), (p)) != LK_EXCLUSIVE)             \
  191                         panic("lock %s %s not held at %s:%d",           \
  192                             (lkp)->lk_wmesg, #what, __FILE__,           \
  193                             __LINE__);                                  \
  194                 break;                                                  \
  195         default:                                                        \
  196                 panic("unknown LOCKMGR_ASSERT at %s:%d", __FILE__,      \
  197                     __LINE__);                                          \
  198         }                                                               \
  199 } while (0)
  200 #else   /* INVARIANTS */
  201 #define LOCKMGR_ASSERT(lkp, p, what)
  202 #endif  /* INVARIANTS */
  203 
  204 void dumplockinfo(struct lock *lkp);
  205 struct thread;
  206 
  207 void    lockinit(struct lock *, int prio, const char *wmesg,
  208                         int timo, int flags);
  209 void    lockdestroy(struct lock *);
  210 
  211 #ifdef DEBUG_LOCKS
  212 int     debuglockmgr(struct lock *, u_int flags,
  213                         struct mtx *, struct thread *p,
  214                         const char *,
  215                         const char *,
  216                         int);
  217 #define lockmgr(lockp, flags, slockp, proc) \
  218         debuglockmgr((lockp), (flags), (slockp), (proc), \
  219             "lockmgr", __FILE__, __LINE__)
  220 #else
  221 int     lockmgr(struct lock *, u_int flags,
  222                         struct mtx *, struct thread *p);
  223 #endif
  224 void    transferlockers(struct lock *, struct lock *);
  225 void    lockmgr_printinfo(struct lock *);
  226 int     lockstatus(struct lock *, struct thread *);
  227 int     lockcount(struct lock *);
  228 
  229 #endif /* !_SYS_LOCKMGR_H_ */

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