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  * 4. Neither the name of the University nor the names of its contributors
   18  *    may be used to endorse or promote products derived from this software
   19  *    without specific prior written permission.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31  * SUCH DAMAGE.
   32  *
   33  *      @(#)lock.h      8.12 (Berkeley) 5/19/95
   34  * $FreeBSD$
   35  */
   36 
   37 #ifndef _SYS_LOCKMGR_H_
   38 #define _SYS_LOCKMGR_H_
   39 
   40 struct  mtx;
   41 
   42 /*
   43  * The general lock structure.  Provides for multiple shared locks,
   44  * upgrading from shared to exclusive, and sleeping until the lock
   45  * can be gained.
   46  */
   47 struct lock {
   48         struct  mtx *lk_interlock;      /* lock on remaining fields */
   49         u_int   lk_flags;               /* see below */
   50         int     lk_sharecount;          /* # of accepted shared locks */
   51         int     lk_waitcount;           /* # of processes sleeping for lock */
   52         short   lk_exclusivecount;      /* # of recursive exclusive locks */
   53         short   lk_prio;                /* priority at which to sleep */
   54         const char *lk_wmesg;           /* resource sleeping (for tsleep) */
   55         int     lk_timo;                /* maximum sleep time (for tsleep) */
   56         struct thread *lk_lockholder;   /* thread of exclusive lock holder */
   57         struct  lock *lk_newlock;       /* lock taking over this lock */
   58 #ifdef  DEBUG_LOCKS
   59         const char *lk_filename;
   60         const char *lk_lockername;
   61         int     lk_lineno;
   62 
   63         struct thread *lk_slockholder;
   64         const char *lk_sfilename;
   65         const char *lk_slockername;
   66         int     lk_slineno;
   67 #endif
   68 };
   69 /*
   70  * Lock request types:
   71  *   LK_SHARED - get one of many possible shared locks. If a process
   72  *      holding an exclusive lock requests a shared lock, the exclusive
   73  *      lock(s) will be downgraded to shared locks.
   74  *   LK_EXCLUSIVE - stop further shared locks, when they are cleared,
   75  *      grant a pending upgrade if it exists, then grant an exclusive
   76  *      lock. Only one exclusive lock may exist at a time, except that
   77  *      a process holding an exclusive lock may get additional exclusive
   78  *      locks if it explicitly sets the LK_CANRECURSE flag in the lock
   79  *      request, or if the LK_CANRECUSE flag was set when the lock was
   80  *      initialized.
   81  *   LK_UPGRADE - the process must hold a shared lock that it wants to
   82  *      have upgraded to an exclusive lock. Other processes may get
   83  *      exclusive access to the resource between the time that the upgrade
   84  *      is requested and the time that it is granted.
   85  *   LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
   86  *      have upgraded to an exclusive lock. If the request succeeds, no
   87  *      other processes will have gotten exclusive access to the resource
   88  *      between the time that the upgrade is requested and the time that
   89  *      it is granted. However, if another process has already requested
   90  *      an upgrade, the request will fail (see error returns below).
   91  *   LK_DOWNGRADE - the process must hold an exclusive lock that it wants
   92  *      to have downgraded to a shared lock. If the process holds multiple
   93  *      (recursive) exclusive locks, they will all be downgraded to shared
   94  *      locks.
   95  *   LK_RELEASE - release one instance of a lock.
   96  *   LK_DRAIN - wait for all activity on the lock to end, then mark it
   97  *      decommissioned. This feature is used before freeing a lock that
   98  *      is part of a piece of memory that is about to be freed.
   99  *   LK_EXCLOTHER - return for lockstatus().  Used when another process
  100  *      holds the lock exclusively.
  101  *
  102  * These are flags that are passed to the lockmgr routine.
  103  */
  104 #define LK_TYPE_MASK    0x0000000f      /* type of lock sought */
  105 #define LK_SHARED       0x00000001      /* shared lock */
  106 #define LK_EXCLUSIVE    0x00000002      /* exclusive lock */
  107 #define LK_UPGRADE      0x00000003      /* shared-to-exclusive upgrade */
  108 #define LK_EXCLUPGRADE  0x00000004      /* first shared-to-exclusive upgrade */
  109 #define LK_DOWNGRADE    0x00000005      /* exclusive-to-shared downgrade */
  110 #define LK_RELEASE      0x00000006      /* release any type of lock */
  111 #define LK_DRAIN        0x00000007      /* wait for all lock activity to end */
  112 #define LK_EXCLOTHER    0x00000008      /* other process holds lock */
  113 /*
  114  * External lock flags.
  115  *
  116  * The first three flags may be set in lock_init to set their mode permanently,
  117  * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
  118  * set only at the release of a lock obtained by drain.
  119  */
  120 #define LK_EXTFLG_MASK  0x03000070      /* mask of external flags */
  121 #define LK_NOWAIT       0x00000010      /* do not sleep to await lock */
  122 #define LK_SLEEPFAIL    0x00000020      /* sleep, then return failure */
  123 #define LK_CANRECURSE   0x00000040      /* allow recursive exclusive lock */
  124 #define LK_REENABLE     0x00000080      /* lock is be reenabled after drain */
  125 #define LK_NOPAUSE      0x01000000      /* no spinloop */
  126 #define LK_TIMELOCK     0x02000000      /* use lk_timo, else no timeout */
  127 /*
  128  * Internal lock flags.
  129  *
  130  * These flags are used internally to the lock manager.
  131  */
  132 #define LK_WANT_UPGRADE 0x00000100      /* waiting for share-to-excl upgrade */
  133 #define LK_WANT_EXCL    0x00000200      /* exclusive lock sought */
  134 #define LK_HAVE_EXCL    0x00000400      /* exclusive lock obtained */
  135 #define LK_WAITDRAIN    0x00000800      /* process waiting for lock to drain */
  136 #define LK_DRAINING     0x00004000      /* lock is being drained */
  137 /*
  138  * Control flags
  139  *
  140  * Non-persistent external flags.
  141  */
  142 #define LK_INTERLOCK    0x00010000 /*
  143                                     * unlock passed mutex after getting
  144                                     * lk_interlock
  145                                     */
  146 #define LK_RETRY        0x00020000 /* vn_lock: retry until locked */
  147 #define LK_THISLAYER    0x00040000 /* vn_lock: lock/unlock only current layer */
  148 #define LK_INTERNAL     0x00080000/* The internal lock is already held */
  149 
  150 /*
  151  * Internal state flags corresponding to lk_sharecount, and lk_waitcount
  152  */
  153 #define LK_SHARE_NONZERO 0x00100000
  154 #define LK_WAIT_NONZERO  0x00200000
  155 
  156 /*
  157  * Lock return status.
  158  *
  159  * Successfully obtained locks return 0. Locks will always succeed
  160  * unless one of the following is true:
  161  *      LK_FORCEUPGRADE is requested and some other process has already
  162  *          requested a lock upgrade (returns EBUSY).
  163  *      LK_WAIT is set and a sleep would be required (returns EBUSY).
  164  *      LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
  165  *      PCATCH is set in lock priority and a signal arrives (returns
  166  *          either EINTR or ERESTART if system calls is to be restarted).
  167  *      Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
  168  * A failed lock attempt always returns a non-zero error value. No lock
  169  * is held after an error return (in particular, a failed LK_UPGRADE
  170  * or LK_FORCEUPGRADE will have released its shared access lock).
  171  */
  172 
  173 /*
  174  * Indicator that no process holds exclusive lock
  175  */
  176 #define LK_KERNPROC ((struct thread *)-2)
  177 #define LK_NOPROC ((struct thread *) -1)
  178 
  179 #ifdef INVARIANTS
  180 #define LOCKMGR_ASSERT(lkp, what, p) do {                               \
  181         switch ((what)) {                                               \
  182         case LK_SHARED:                                                 \
  183                 if (lockstatus((lkp), (p)) == LK_SHARED)                \
  184                         break;                                          \
  185                 /* fall into exclusive */                               \
  186         case LK_EXCLUSIVE:                                              \
  187                 if (lockstatus((lkp), (p)) != LK_EXCLUSIVE)             \
  188                         panic("lock %s %s not held at %s:%d",           \
  189                             (lkp)->lk_wmesg, #what, __FILE__,           \
  190                             __LINE__);                                  \
  191                 break;                                                  \
  192         default:                                                        \
  193                 panic("unknown LOCKMGR_ASSERT at %s:%d", __FILE__,      \
  194                     __LINE__);                                          \
  195         }                                                               \
  196 } while (0)
  197 #else   /* INVARIANTS */
  198 #define LOCKMGR_ASSERT(lkp, p, what)
  199 #endif  /* INVARIANTS */
  200 
  201 void dumplockinfo(struct lock *lkp);
  202 struct thread;
  203 
  204 void    lockinit(struct lock *, int prio, const char *wmesg,
  205                         int timo, int flags);
  206 void    lockdestroy(struct lock *);
  207 
  208 #ifdef DEBUG_LOCKS
  209 int     debuglockmgr(struct lock *, u_int flags,
  210                         struct mtx *, struct thread *p,
  211                         const char *,
  212                         const char *,
  213                         int);
  214 #define lockmgr(lockp, flags, slockp, proc) \
  215         debuglockmgr((lockp), (flags), (slockp), (proc), \
  216             "lockmgr", __FILE__, __LINE__)
  217 #else
  218 int     lockmgr(struct lock *, u_int flags,
  219                         struct mtx *, struct thread *p);
  220 #endif
  221 void    transferlockers(struct lock *, struct lock *);
  222 void    lockmgr_printinfo(struct lock *);
  223 int     lockstatus(struct lock *, struct thread *);
  224 int     lockcount(struct lock *);
  225 
  226 #endif /* !_SYS_LOCKMGR_H_ */

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