bsd/sys/lock.h

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /* Copyright (c) 1995, 1997 Apple Computer, Inc. All Rights Reserved */
  23 /*
  24  * Copyright (c) 1995
  25  *      The Regents of the University of California.  All rights reserved.
  26  *
  27  * This code contains ideas from software contributed to Berkeley by
  28  * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
  29  * System project at Carnegie-Mellon University.
  30  *
  31  * Redistribution and use in source and binary forms, with or without
  32  * modification, are permitted provided that the following conditions
  33  * are met:
  34  * 1. Redistributions of source code must retain the above copyright
  35  *    notice, this list of conditions and the following disclaimer.
  36  * 2. Redistributions in binary form must reproduce the above copyright
  37  *    notice, this list of conditions and the following disclaimer in the
  38  *    documentation and/or other materials provided with the distribution.
  39  * 3. All advertising materials mentioning features or use of this software
  40  *    must display the following acknowledgement:
  41  *      This product includes software developed by the University of
  42  *      California, Berkeley and its contributors.
  43  * 4. Neither the name of the University nor the names of its contributors
  44  *    may be used to endorse or promote products derived from this software
  45  *    without specific prior written permission.
  46  *
  47  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  48  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  49  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  50  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  51  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  52  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  53  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  54  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  55  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  56  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  57  * SUCH DAMAGE.
  58  *
  59  *      @(#)lock.h      8.12 (Berkeley) 5/19/95
  60  */
  61
  62 #ifndef _SYS_LOCK_H_
  63 #define _SYS_LOCK_H_
  64 #ifdef KERNEL
  65
  66 #include <kern/simple_lock.h>
  67 #include <kern/simple_lock_types.h>
  68
  69 #if defined(simple_lock_init)
  70 #undef simple_lock_init
  71 #endif
  72 #define simple_lock_init(l)     usimple_lock_init((l),0)
  73
  74 #if defined(simple_lock)
  75 #undef simple_lock
  76 #endif
  77 #define simple_lock(l)         ((void) 1)
  78
  79 #if defined(simple_unlock)
  80 #undef simple_unlock
  81 #endif
  82 #define simple_unlock(l)        ((void) 1)
  83
  84 #if defined(simple_lock_try)
  85 #undef simple_lock_try
  86 #endif
  87 #define simple_lock_try(l)      1
  88
  89 #else /* KERNEL */
  90
  91 #ifndef _MACHINE_SIMPLE_LOCK_DATA_
  92 #define _MACHINE_SIMPLE_LOCK_DATA_
  93
  94 #include <mach/boolean.h>
  95
  96 #if defined(__ppc__)
  97 struct slock{
  98         volatile unsigned int lock_data[10];
  99 };
 100 #else
 101 struct slock{
 102         volatile unsigned int lock_data[9];
 103 };
 104 #endif
 105 typedef struct slock    simple_lock_data_t;
 106 typedef struct slock    *simple_lock_t;
 107 #define decl_simple_lock_data(class,name) \
 108 class   simple_lock_data_t      name;
 109
 110 #endif  /* _MACHINE_SIMPLE_LOCK_DATA_ */
 111
 112 #endif /* KERNEL */
 113 /*
 114  * The general lock structure.  Provides for multiple shared locks,
 115  * upgrading from shared to exclusive, and sleeping until the lock
 116  * can be gained. The simple locks are defined in <machine/param.h>.
 117  */
 118 struct lock__bsd__ {
 119         simple_lock_data_t
 120                 lk_interlock;           /* lock on remaining fields */
 121         u_int   lk_flags;               /* see below */
 122         int     lk_sharecount;          /* # of accepted shared locks */
 123         int     lk_waitcount;           /* # of processes sleeping for lock */
 124         short   lk_exclusivecount;      /* # of recursive exclusive locks */
 125         short   lk_prio;                /* priority at which to sleep */
 126         char    *lk_wmesg;              /* resource sleeping (for tsleep) */
 127         int     lk_timo;                /* maximum sleep time (for tsleep) */
 128         pid_t   lk_lockholder;          /* pid of exclusive lock holder */
 129         void    *lk_lockthread;         /* thread which acquired excl lock */
 130 };
 131 /*
 132  * Lock request types:
 133  *   LK_SHARED - get one of many possible shared locks. If a process
 134  *      holding an exclusive lock requests a shared lock, the exclusive
 135  *      lock(s) will be downgraded to shared locks.
 136  *   LK_EXCLUSIVE - stop further shared locks, when they are cleared,
 137  *      grant a pending upgrade if it exists, then grant an exclusive
 138  *      lock. Only one exclusive lock may exist at a time, except that
 139  *      a process holding an exclusive lock may get additional exclusive
 140  *      locks if it explicitly sets the LK_CANRECURSE flag in the lock
 141  *      request, or if the LK_CANRECUSE flag was set when the lock was
 142  *      initialized.
 143  *   LK_UPGRADE - the process must hold a shared lock that it wants to
 144  *      have upgraded to an exclusive lock. Other processes may get
 145  *      exclusive access to the resource between the time that the upgrade
 146  *      is requested and the time that it is granted.
 147  *   LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
 148  *      have upgraded to an exclusive lock. If the request succeeds, no
 149  *      other processes will have gotten exclusive access to the resource
 150  *      between the time that the upgrade is requested and the time that
 151  *      it is granted. However, if another process has already requested
 152  *      an upgrade, the request will fail (see error returns below).
 153  *   LK_DOWNGRADE - the process must hold an exclusive lock that it wants
 154  *      to have downgraded to a shared lock. If the process holds multiple
 155  *      (recursive) exclusive locks, they will all be downgraded to shared
 156  *      locks.
 157  *   LK_RELEASE - release one instance of a lock.
 158  *   LK_DRAIN - wait for all activity on the lock to end, then mark it
 159  *      decommissioned. This feature is used before freeing a lock that
 160  *      is part of a piece of memory that is about to be freed.
 161  *
 162  * These are flags that are passed to the lockmgr routine.
 163  */
 164 #define LK_TYPE_MASK    0x0000000f      /* type of lock sought */
 165 #define LK_SHARED       0x00000001      /* shared lock */
 166 #define LK_EXCLUSIVE    0x00000002      /* exclusive lock */
 167 #define LK_UPGRADE      0x00000003      /* shared-to-exclusive upgrade */
 168 #define LK_EXCLUPGRADE  0x00000004      /* first shared-to-exclusive upgrade */
 169 #define LK_DOWNGRADE    0x00000005      /* exclusive-to-shared downgrade */
 170 #define LK_RELEASE      0x00000006      /* release any type of lock */
 171 #define LK_DRAIN        0x00000007      /* wait for all lock activity to end */
 172 /*
 173  * External lock flags.
 174  *
 175  * The first three flags may be set in lock_init to set their mode permanently,
 176  * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
 177  * set only at the release of a lock obtained by drain.
 178  */
 179 #define LK_EXTFLG_MASK  0x00000070      /* mask of external flags */
 180 #define LK_NOWAIT       0x00000010      /* do not sleep to await lock */
 181 #define LK_SLEEPFAIL    0x00000020      /* sleep, then return failure */
 182 #define LK_CANRECURSE   0x00000040      /* allow recursive exclusive lock */
 183 #define LK_REENABLE     0x00000080      /* lock is be reenabled after drain */
 184 /*
 185  * Internal lock flags.
 186  *
 187  * These flags are used internally to the lock manager.
 188  */
 189 #define LK_WANT_UPGRADE 0x00000100      /* waiting for share-to-excl upgrade */
 190 #define LK_WANT_EXCL    0x00000200      /* exclusive lock sought */
 191 #define LK_HAVE_EXCL    0x00000400      /* exclusive lock obtained */
 192 #define LK_WAITDRAIN    0x00000800      /* process waiting for lock to drain */
 193 #define LK_DRAINING     0x00004000      /* lock is being drained */
 194 #define LK_DRAINED      0x00008000      /* lock has been decommissioned */
 195 /*
 196  * Control flags
 197  *
 198  * Non-persistent external flags.
 199  */
 200 #define LK_INTERLOCK    0x00010000      /* unlock passed simple lock after
 201                                            getting lk_interlock */
 202 #define LK_RETRY        0x00020000      /* vn_lock: retry until locked */
 203
 204 /*
 205  * Lock return status.
 206  *
 207  * Successfully obtained locks return 0. Locks will always succeed
 208  * unless one of the following is true:
 209  *      LK_FORCEUPGRADE is requested and some other process has already
 210  *          requested a lock upgrade (returns EBUSY).
 211  *      LK_WAIT is set and a sleep would be required (returns EBUSY).
 212  *      LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
 213  *      PCATCH is set in lock priority and a signal arrives (returns
 214  *          either EINTR or ERESTART if system calls is to be restarted).
 215  *      Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
 216  * A failed lock attempt always returns a non-zero error value. No lock
 217  * is held after an error return (in particular, a failed LK_UPGRADE
 218  * or LK_FORCEUPGRADE will have released its shared access lock).
 219  */
 220
 221 /*
 222  * Indicator that no process holds exclusive lock
 223  */
 224 #define LK_KERNPROC ((pid_t) -2)
 225 #define LK_NOPROC ((pid_t) -1)
 226
 227 struct proc;
 228
 229 void    lockinit __P((struct lock__bsd__ *, int prio, char *wmesg, int timo,
 230                         int flags));
 231 int     lockmgr __P((struct lock__bsd__ *, u_int flags,
 232                         simple_lock_t, struct proc *p));
 233 int     lockstatus __P((struct lock__bsd__ *));
 234
 235 #endif  /* _SYS_LOCK_H_ */