sys/sys/lock.h

   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: src/sys/sys/lock.h,v 1.17.2.3 2001/12/25 01:44:44 dillon Exp $
  39  * $DragonFly: src/sys/sys/lock.h,v 1.12 2006/03/02 19:08:00 dillon Exp $
  40  */
  41
  42 #ifndef _SYS_LOCK_H_
  43 #define _SYS_LOCK_H_
  44
  45 /*
  46  * A number of third party programs #include <sys/lock.h> for no good
  47  * reason.  Don't actually include anything unless we are the kernel.
  48  */
  49 #if defined(_KERNEL) || defined(_KERNEL_STRUCTURES)
  50
  51 #include <machine/lock.h>
  52 #ifndef _SYS_THREAD_H_
  53 #include <sys/thread.h>         /* lwkt_token */
  54 #endif
  55 #ifndef _SYS_SPINLOCK_H_
  56 #include <sys/spinlock.h>
  57 #endif
  58
  59 /*
  60  * The general lock structure.  Provides for multiple shared locks,
  61  * upgrading from shared to exclusive, and sleeping until the lock
  62  * can be gained.
  63  */
  64 struct thread;
  65
  66 struct lock {
  67         struct spinlock lk_spinlock;    /* lock on remaining fields */
  68         u_int   lk_flags;               /* see below */
  69         int     lk_sharecount;          /* # of accepted shared locks */
  70         int     lk_waitcount;           /* # of processes sleeping for lock */
  71         short   lk_exclusivecount;      /* # of recursive exclusive locks */
  72         short   lk_unused1;
  73         char    *lk_wmesg;              /* resource sleeping (for tsleep) */
  74         int     lk_timo;                /* maximum sleep time (for tsleep) */
  75         struct thread *lk_lockholder;   /* thread of excl lock holder */
  76 #ifdef  DEBUG_LOCKS
  77         const char *lk_filename;
  78         const char *lk_lockername;
  79         int     lk_lineno;
  80 #endif
  81 };
  82 /*
  83  * Lock request types:
  84  *   LK_SHARED - get one of many possible shared locks. If a process
  85  *      holding an exclusive lock requests a shared lock, the exclusive
  86  *      lock(s) will be downgraded to shared locks.
  87  *   LK_EXCLUSIVE - stop further shared locks, when they are cleared,
  88  *      grant a pending upgrade if it exists, then grant an exclusive
  89  *      lock. Only one exclusive lock may exist at a time, except that
  90  *      a process holding an exclusive lock may get additional exclusive
  91  *      locks if it explicitly sets the LK_CANRECURSE flag in the lock
  92  *      request, or if the LK_CANRECUSE flag was set when the lock was
  93  *      initialized.
  94  *   LK_UPGRADE - the process must hold a shared lock that it wants to
  95  *      have upgraded to an exclusive lock. Other processes may get
  96  *      exclusive access to the resource between the time that the upgrade
  97  *      is requested and the time that it is granted.
  98  *   LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
  99  *      have upgraded to an exclusive lock. If the request succeeds, no
 100  *      other processes will have gotten exclusive access to the resource
 101  *      between the time that the upgrade is requested and the time that
 102  *      it is granted. However, if another process has already requested
 103  *      an upgrade, the request will fail (see error returns below).
 104  *   LK_DOWNGRADE - the process must hold an exclusive lock that it wants
 105  *      to have downgraded to a shared lock. If the process holds multiple
 106  *      (recursive) exclusive locks, they will all be downgraded to shared
 107  *      locks.
 108  *   LK_RELEASE - release one instance of a lock.
 109  *   LK_DRAIN - wait for all activity on the lock to end, then mark it
 110  *      decommissioned. This feature is used before freeing a lock that
 111  *      is part of a piece of memory that is about to be freed.
 112  *   LK_EXCLOTHER - return for lockstatus().  Used when another process
 113  *      holds the lock exclusively.
 114  *
 115  * These are flags that are passed to the lockmgr routine.
 116  */
 117 #define LK_TYPE_MASK    0x0000000f      /* type of lock sought */
 118 #define LK_SHARED       0x00000001      /* shared lock */
 119 #define LK_EXCLUSIVE    0x00000002      /* exclusive lock */
 120 #define LK_UPGRADE      0x00000003      /* shared-to-exclusive upgrade */
 121 #define LK_EXCLUPGRADE  0x00000004      /* first shared-to-exclusive upgrade */
 122 #define LK_DOWNGRADE    0x00000005      /* exclusive-to-shared downgrade */
 123 #define LK_RELEASE      0x00000006      /* release any type of lock */
 124 #define LK_DRAIN        0x00000007      /* wait for all lock activity to end */
 125 #define LK_EXCLOTHER    0x00000008      /* other process holds lock */
 126 /*
 127  * External lock flags.
 128  *
 129  * The first three flags may be set in lock_init to set their mode permanently,
 130  * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
 131  * set only at the release of a lock obtained by drain.
 132  */
 133 #define LK_EXTFLG_MASK  0x07000070      /* mask of external flags */
 134 #define LK_NOWAIT       0x00000010      /* do not sleep to await lock */
 135 #define LK_SLEEPFAIL    0x00000020      /* sleep, then return failure */
 136 #define LK_CANRECURSE   0x00000040      /* allow recursive exclusive lock */
 137 #define LK_REENABLE     0x00000080      /* lock is be reenabled after drain */
 138 #define LK_NOPAUSE      0x01000000      /* no spinloop */
 139 #define LK_TIMELOCK     0x02000000
 140 #define LK_PCATCH       0x04000000      /* timelocked with signal catching */
 141 /*
 142  * Internal lock flags.
 143  *
 144  * These flags are used internally to the lock manager.
 145  */
 146 #define LK_WANT_UPGRADE 0x00000100      /* waiting for share-to-excl upgrade */
 147 #define LK_WANT_EXCL    0x00000200      /* exclusive lock sought */
 148 #define LK_HAVE_EXCL    0x00000400      /* exclusive lock obtained */
 149 #define LK_WAITDRAIN    0x00000800      /* process waiting for lock to drain */
 150 #define LK_DRAINING     0x00004000      /* lock is being drained */
 151 /*
 152  * Control flags
 153  *
 154  * Non-persistent external flags.
 155  */
 156 #define LK_INTERLOCK    0x00010000 /* unlock passed simple lock after
 157                                       getting lk_spinlock */
 158 #define LK_RETRY        0x00020000 /* vn_lock: retry until locked */
 159 #define LK_NOOBJ        0x00040000 /* vget: don't create object */
 160 #define LK_THISLAYER    0x00080000 /* vn_lock: lock/unlock only current layer */
 161
 162 /*
 163  * Internal state flags corresponding to lk_sharecount, and lk_waitcount
 164  */
 165 #define LK_SHARE_NONZERO 0x00100000
 166 #define LK_WAIT_NONZERO  0x00200000
 167
 168 /*
 169  * Lock return status.
 170  *
 171  * Successfully obtained locks return 0. Locks will always succeed
 172  * unless one of the following is true:
 173  *      LK_FORCEUPGRADE is requested and some other process has already
 174  *          requested a lock upgrade (returns EBUSY).
 175  *      LK_WAIT is set and a sleep would be required (returns EBUSY).
 176  *      LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
 177  *      PCATCH is set in lock priority and a signal arrives (returns
 178  *          either EINTR or ERESTART if system calls is to be restarted).
 179  *      Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
 180  * A failed lock attempt always returns a non-zero error value. No lock
 181  * is held after an error return (in particular, a failed LK_UPGRADE
 182  * or LK_FORCEUPGRADE will have released its shared access lock).
 183  */
 184
 185 /*
 186  * Indicator that no process holds exclusive lock
 187  */
 188 #define LK_KERNTHREAD ((struct thread *)-2)
 189 #define LK_NOTHREAD ((struct thread *)-1)
 190
 191 #ifdef _KERNEL
 192
 193 void dumplockinfo(struct lock *lkp);
 194 struct proc;
 195
 196 void    lockinit (struct lock *, char *wmesg, int timo, int flags);
 197 void    lockreinit (struct lock *, char *wmesg, int timo, int flags);
 198 #ifdef DEBUG_LOCKS
 199 int     debuglockmgr (struct lock *, u_int flags,
 200                         struct spinlock *, struct thread *p,
 201                         const char *,
 202                         const char *,
 203                         int);
 204 #define lockmgr(lockp, flags, slockp, td) \
 205         debuglockmgr((lockp), (flags), (slockp), (td), \
 206             "lockmgr", __FILE__, __LINE__)
 207 #else
 208 int     lockmgr (struct lock *, u_int flags,
 209                         struct spinlock *, struct thread *td);
 210 #endif
 211 void    lockmgr_printinfo (struct lock *);
 212 int     lockstatus (struct lock *, struct thread *);
 213 int     lockcount (struct lock *);
 214 int     lockcountnb (struct lock *);
 215
 216 #endif /* _KERNEL */
 217 #endif /* _KERNEL || _KERNEL_STRUCTURES */
 218 #endif /* _SYS_LOCK_H_ */
 219