lock.h revision 27657
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 * $Id: lock.h,v 1.5 1997/07/23 20:40:52 fsmp Exp $ 39 */ 40 41#ifndef _LOCK_H_ 42#define _LOCK_H_ 43 44/* 45 * The general lock structure. Provides for multiple shared locks, 46 * upgrading from shared to exclusive, and sleeping until the lock 47 * can be gained. The simple locks are defined in <machine/param.h>. 48 */ 49struct lock { 50 struct simplelock lk_interlock; /* lock on remaining fields */ 51 u_int lk_flags; /* see below */ 52 int lk_sharecount; /* # of accepted shared locks */ 53 int lk_waitcount; /* # of processes sleeping for lock */ 54 short lk_exclusivecount; /* # of recursive exclusive locks */ 55 short lk_prio; /* priority at which to sleep */ 56 char *lk_wmesg; /* resource sleeping (for tsleep) */ 57 int lk_timo; /* maximum sleep time (for tsleep) */ 58 pid_t lk_lockholder; /* pid of exclusive lock holder */ 59}; 60/* 61 * Lock request types: 62 * LK_SHARED - get one of many possible shared locks. If a process 63 * holding an exclusive lock requests a shared lock, the exclusive 64 * lock(s) will be downgraded to shared locks. 65 * LK_EXCLUSIVE - stop further shared locks, when they are cleared, 66 * grant a pending upgrade if it exists, then grant an exclusive 67 * lock. Only one exclusive lock may exist at a time, except that 68 * a process holding an exclusive lock may get additional exclusive 69 * locks if it explicitly sets the LK_CANRECURSE flag in the lock 70 * request, or if the LK_CANRECUSE flag was set when the lock was 71 * initialized. 72 * LK_UPGRADE - the process must hold a shared lock that it wants to 73 * have upgraded to an exclusive lock. Other processes may get 74 * exclusive access to the resource between the time that the upgrade 75 * is requested and the time that it is granted. 76 * LK_EXCLUPGRADE - the process must hold a shared lock that it wants to 77 * have upgraded to an exclusive lock. If the request succeeds, no 78 * other processes will have gotten exclusive access to the resource 79 * between the time that the upgrade is requested and the time that 80 * it is granted. However, if another process has already requested 81 * an upgrade, the request will fail (see error returns below). 82 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants 83 * to have downgraded to a shared lock. If the process holds multiple 84 * (recursive) exclusive locks, they will all be downgraded to shared 85 * locks. 86 * LK_RELEASE - release one instance of a lock. 87 * LK_DRAIN - wait for all activity on the lock to end, then mark it 88 * decommissioned. This feature is used before freeing a lock that 89 * is part of a piece of memory that is about to be freed. 90 * 91 * These are flags that are passed to the lockmgr routine. 92 */ 93#define LK_TYPE_MASK 0x0000000f /* type of lock sought */ 94#define LK_SHARED 0x00000001 /* shared lock */ 95#define LK_EXCLUSIVE 0x00000002 /* exclusive lock */ 96#define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */ 97#define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */ 98#define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */ 99#define LK_RELEASE 0x00000006 /* release any type of lock */ 100#define LK_DRAIN 0x00000007 /* wait for all lock activity to end */ 101/* 102 * External lock flags. 103 * 104 * The first three flags may be set in lock_init to set their mode permanently, 105 * or passed in as arguments to the lock manager. The LK_REENABLE flag may be 106 * set only at the release of a lock obtained by drain. 107 */ 108#define LK_EXTFLG_MASK 0x00000070 /* mask of external flags */ 109#define LK_NOWAIT 0x00000010 /* do not sleep to await lock */ 110#define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */ 111#define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */ 112#define LK_REENABLE 0x00000080 /* lock is be reenabled after drain */ 113/* 114 * Internal lock flags. 115 * 116 * These flags are used internally to the lock manager. 117 */ 118#define LK_WANT_UPGRADE 0x00000100 /* waiting for share-to-excl upgrade */ 119#define LK_WANT_EXCL 0x00000200 /* exclusive lock sought */ 120#define LK_HAVE_EXCL 0x00000400 /* exclusive lock obtained */ 121#define LK_WAITDRAIN 0x00000800 /* process waiting for lock to drain */ 122#define LK_DRAINING 0x00004000 /* lock is being drained */ 123#define LK_DRAINED 0x00008000 /* lock has been decommissioned */ 124/* 125 * Control flags 126 * 127 * Non-persistent external flags. 128 */ 129#define LK_INTERLOCK 0x00010000 /* unlock passed simple lock after 130 getting lk_interlock */ 131#define LK_RETRY 0x00020000 /* vn_lock: retry until locked */ 132 133/* 134 * Lock return status. 135 * 136 * Successfully obtained locks return 0. Locks will always succeed 137 * unless one of the following is true: 138 * LK_FORCEUPGRADE is requested and some other process has already 139 * requested a lock upgrade (returns EBUSY). 140 * LK_WAIT is set and a sleep would be required (returns EBUSY). 141 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK). 142 * PCATCH is set in lock priority and a signal arrives (returns 143 * either EINTR or ERESTART if system calls is to be restarted). 144 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK). 145 * A failed lock attempt always returns a non-zero error value. No lock 146 * is held after an error return (in particular, a failed LK_UPGRADE 147 * or LK_FORCEUPGRADE will have released its shared access lock). 148 */ 149 150/* 151 * Indicator that no process holds exclusive lock 152 */ 153#define LK_KERNPROC ((pid_t) -2) 154#define LK_NOPROC ((pid_t) -1) 155 156struct proc; 157 158void lockinit __P((struct lock *, int prio, char *wmesg, int timo, 159 int flags)); 160int lockmgr __P((__volatile struct lock *, u_int flags, 161 struct simplelock *, struct proc *p)); 162void lockmgr_printinfo __P((struct lock *)); 163int lockstatus __P((struct lock *)); 164 165#ifdef SIMPLELOCK_DEBUG 166void _simple_unlock __P((__volatile struct simplelock *alp, const char *, int)); 167#define simple_unlock(alp) _simple_unlock(alp, __FILE__, __LINE__) 168int _simple_lock_try __P((__volatile struct simplelock *alp, const char *, int)); 169#define simple_lock_try(alp) _simple_lock_try(alp, __FILE__, __LINE__) 170void _simple_lock __P((__volatile struct simplelock *alp, const char *, int)); 171#define simple_lock(alp) _simple_lock(alp, __FILE__, __LINE__) 172void simple_lock_init __P((struct simplelock *alp)); 173#else /* !SIMPLELOCK_DEBUG */ 174#if NCPUS == 1 /* no multiprocessor locking is necessary */ 175#define simple_lock_init(alp) 176#define simple_lock(alp) 177#define simple_lock_try(alp) (1) /* always succeeds */ 178#define simple_unlock(alp) 179#endif /* NCPUS == 1 */ 180#endif /* !SIMPLELOCK_DEBUG */ 181 182#endif /* !_LOCK_H_ */ 183