bsd/sys/lock.h

   1 /*
   2  * Copyright (c) 2000-2005 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /* Copyright (c) 1995, 1997 Apple Computer, Inc. All Rights Reserved */
  29 /*
  30  * Copyright (c) 1995
  31  *      The Regents of the University of California.  All rights reserved.
  32  *
  33  * This code contains ideas from software contributed to Berkeley by
  34  * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
  35  * System project at Carnegie-Mellon University.
  36  *
  37  * Redistribution and use in source and binary forms, with or without
  38  * modification, are permitted provided that the following conditions
  39  * are met:
  40  * 1. Redistributions of source code must retain the above copyright
  41  *    notice, this list of conditions and the following disclaimer.
  42  * 2. Redistributions in binary form must reproduce the above copyright
  43  *    notice, this list of conditions and the following disclaimer in the
  44  *    documentation and/or other materials provided with the distribution.
  45  * 3. All advertising materials mentioning features or use of this software
  46  *    must display the following acknowledgement:
  47  *      This product includes software developed by the University of
  48  *      California, Berkeley and its contributors.
  49  * 4. Neither the name of the University nor the names of its contributors
  50  *    may be used to endorse or promote products derived from this software
  51  *    without specific prior written permission.
  52  *
  53  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  54  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  55  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  56  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  57  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  58  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  59  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  60  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  61  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  62  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  63  * SUCH DAMAGE.
  64  *
  65  *      @(#)lock.h      8.12 (Berkeley) 5/19/95
  66  */
  67
  68 #ifndef _SYS_LOCK_H_
  69 #define _SYS_LOCK_H_
  70
  71 #include <sys/appleapiopts.h>
  72 #include <sys/types.h>
  73 #include <sys/cdefs.h>
  74
  75 #ifdef KERNEL
  76
  77 #include <kern/locks.h>
  78
  79 #endif /* KERNEL */
  80
  81 #ifdef BSD_KERNEL_PRIVATE
  82 /*
  83  * The general lock structure.  Provides for multiple shared locks,
  84  * upgrading from shared to exclusive, and sleeping until the lock
  85  * can be gained. The simple locks are defined in <machine/param.h>.
  86  */
  87 struct lock__bsd__ {
  88         void * lk_interlock[10];                /* lock on remaining fields */
  89         u_int   lk_flags;               /* see below */
  90         int     lk_sharecount;          /* # of accepted shared locks */
  91         int     lk_waitcount;           /* # of processes sleeping for lock */
  92         short   lk_exclusivecount;      /* # of recursive exclusive locks */
  93         short   lk_prio;                /* priority at which to sleep */
  94         const char      *lk_wmesg;      /* resource sleeping (for tsleep) */
  95         int     lk_timo;                /* maximum sleep time (for tsleep) */
  96         pid_t   lk_lockholder;          /* pid of exclusive lock holder */
  97         void    *lk_lockthread;         /* thread which acquired excl lock */
  98 };
  99
 100 // LP64todo - should this move?
 101
 102 /* LP64 version of lock__bsd__.  all pointers
 103  * grow when we're dealing with a 64-bit process.
 104  * WARNING - keep in sync with lock__bsd__
 105  */
 106
 107 struct user_lock__bsd__ {
 108         user_addr_t     lk_interlock[10];   /* lock on remaining fields */
 109         u_int           lk_flags;                       /* see below */
 110         int                     lk_sharecount;          /* # of accepted shared locks */
 111         int                     lk_waitcount;           /* # of processes sleeping for lock */
 112         short           lk_exclusivecount;      /* # of recursive exclusive locks */
 113         short           lk_prio;                        /* priority at which to sleep */
 114         user_addr_t lk_wmesg;           /* resource sleeping (for tsleep) */
 115         int                     lk_timo;                        /* maximum sleep time (for tsleep) */
 116         pid_t           lk_lockholder;          /* pid of exclusive lock holder */
 117         user_addr_t     lk_lockthread;          /* thread which acquired excl lock */
 118 };
 119
 120 /*
 121  * Lock request types:
 122  *   LK_SHARED - get one of many possible shared locks. If a process
 123  *      holding an exclusive lock requests a shared lock, the exclusive
 124  *      lock(s) will be downgraded to shared locks.
 125  *   LK_EXCLUSIVE - stop further shared locks, when they are cleared,
 126  *      grant a pending upgrade if it exists, then grant an exclusive
 127  *      lock. Only one exclusive lock may exist at a time, except that
 128  *      a process holding an exclusive lock may get additional exclusive
 129  *      locks if it explicitly sets the LK_CANRECURSE flag in the lock
 130  *      request, or if the LK_CANRECUSE flag was set when the lock was
 131  *      initialized.
 132  *   LK_UPGRADE - the process must hold a shared lock that it wants to
 133  *      have upgraded to an exclusive lock. Other processes may get
 134  *      exclusive access to the resource between the time that the upgrade
 135  *      is requested and the time that it is granted.
 136  *   LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
 137  *      have upgraded to an exclusive lock. If the request succeeds, no
 138  *      other processes will have gotten exclusive access to the resource
 139  *      between the time that the upgrade is requested and the time that
 140  *      it is granted. However, if another process has already requested
 141  *      an upgrade, the request will fail (see error returns below).
 142  *   LK_DOWNGRADE - the process must hold an exclusive lock that it wants
 143  *      to have downgraded to a shared lock. If the process holds multiple
 144  *      (recursive) exclusive locks, they will all be downgraded to shared
 145  *      locks.
 146  *   LK_RELEASE - release one instance of a lock.
 147  *   LK_DRAIN - wait for all activity on the lock to end, then mark it
 148  *      decommissioned. This feature is used before freeing a lock that
 149  *      is part of a piece of memory that is about to be freed.
 150  *
 151  * These are flags that are passed to the lockmgr routine.
 152  */
 153 #define LK_TYPE_MASK    0x0000000f      /* type of lock sought */
 154 #define LK_SHARED       0x00000001      /* shared lock */
 155 #define LK_EXCLUSIVE    0x00000002      /* exclusive lock */
 156 #define LK_UPGRADE      0x00000003      /* shared-to-exclusive upgrade */
 157 #define LK_EXCLUPGRADE  0x00000004      /* first shared-to-exclusive upgrade */
 158 #define LK_DOWNGRADE    0x00000005      /* exclusive-to-shared downgrade */
 159 #define LK_RELEASE      0x00000006      /* release any type of lock */
 160 #define LK_DRAIN        0x00000007      /* wait for all lock activity to end */
 161 /*
 162  * External lock flags.
 163  *
 164  * The first three flags may be set in lock_init to set their mode permanently,
 165  * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
 166  * set only at the release of a lock obtained by drain.
 167  */
 168 #define LK_EXTFLG_MASK  0x00000070      /* mask of external flags */
 169 #define LK_NOWAIT       0x00000010      /* do not sleep to await lock */
 170 #define LK_SLEEPFAIL    0x00000020      /* sleep, then return failure */
 171 #define LK_CANRECURSE   0x00000040      /* allow recursive exclusive lock */
 172 #define LK_REENABLE     0x00000080      /* lock is be reenabled after drain */
 173 /*
 174  * Internal lock flags.
 175  *
 176  * These flags are used internally to the lock manager.
 177  */
 178 #define LK_WANT_UPGRADE 0x00000100      /* waiting for share-to-excl upgrade */
 179 #define LK_WANT_EXCL    0x00000200      /* exclusive lock sought */
 180 #define LK_HAVE_EXCL    0x00000400      /* exclusive lock obtained */
 181 #define LK_WAITDRAIN    0x00000800      /* process waiting for lock to drain */
 182 #define LK_DRAINING     0x00004000      /* lock is being drained */
 183 #define LK_DRAINED      0x00008000      /* lock has been decommissioned */
 184 /*
 185  * Control flags
 186  *
 187  * Non-persistent external flags.
 188  */
 189 #define LK_INTERLOCK    0x00010000      /* unlock passed simple lock after
 190                                            getting lk_interlock */
 191 #define LK_RETRY        0x00020000      /* vn_lock: retry until locked */
 192
 193 /*
 194  * Lock return status.
 195  *
 196  * Successfully obtained locks return 0. Locks will always succeed
 197  * unless one of the following is true:
 198  *      LK_FORCEUPGRADE is requested and some other process has already
 199  *          requested a lock upgrade (returns EBUSY).
 200  *      LK_WAIT is set and a sleep would be required (returns EBUSY).
 201  *      LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
 202  *      PCATCH is set in lock priority and a signal arrives (returns
 203  *          either EINTR or ERESTART if system calls is to be restarted).
 204  *      Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
 205  * A failed lock attempt always returns a non-zero error value. No lock
 206  * is held after an error return (in particular, a failed LK_UPGRADE
 207  * or LK_FORCEUPGRADE will have released its shared access lock).
 208  */
 209
 210 /*
 211  * Indicator that no process holds exclusive lock
 212  */
 213 #define LK_KERNPROC ((pid_t) -2)
 214 #define LK_NOPROC ((pid_t) -1)
 215
 216 struct proc;
 217
 218 void    lockinit(struct lock__bsd__ *, int prio, const char *wmesg, int timo,
 219                         int flags);
 220 int     lockmgr(struct lock__bsd__ *, u_int flags,
 221                         void *, struct proc *p);
 222 int     lockstatus(struct lock__bsd__ *);
 223
 224 #endif /* BSD_KERNEL_PRIVATE  */
 225
 226 #endif  /* _SYS_LOCK_H_ */