lock.h revision 66296
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: head/sys/sys/lock.h 66296 2000-09-23 12:18:06Z ps $ 39 */ 40 41#ifndef _LOCK_H_ 42#define _LOCK_H_ 43 44 45#include <machine/lock.h> 46 47/* 48 * The general lock structure. Provides for multiple shared locks, 49 * upgrading from shared to exclusive, and sleeping until the lock 50 * can be gained. The simple locks are defined in <machine/param.h>. 51 */ 52struct lock { 53 struct simplelock lk_interlock; /* lock on remaining fields */ 54 u_int lk_flags; /* see below */ 55 int lk_sharecount; /* # of accepted shared locks */ 56 int lk_waitcount; /* # of processes sleeping for lock */ 57 short lk_exclusivecount; /* # of recursive exclusive locks */ 58 short lk_prio; /* priority at which to sleep */ 59 char *lk_wmesg; /* resource sleeping (for tsleep) */ 60 int lk_timo; /* maximum sleep time (for tsleep) */ 61 pid_t lk_lockholder; /* pid of exclusive lock holder */ 62#ifdef DEBUG_LOCKS 63 const char *lk_filename; 64 const char *lk_lockername; 65 int lk_lineno; 66#endif 67}; 68/* 69 * Lock request types: 70 * LK_SHARED - get one of many possible shared locks. If a process 71 * holding an exclusive lock requests a shared lock, the exclusive 72 * lock(s) will be downgraded to shared locks. 73 * LK_EXCLUSIVE - stop further shared locks, when they are cleared, 74 * grant a pending upgrade if it exists, then grant an exclusive 75 * lock. Only one exclusive lock may exist at a time, except that 76 * a process holding an exclusive lock may get additional exclusive 77 * locks if it explicitly sets the LK_CANRECURSE flag in the lock 78 * request, or if the LK_CANRECUSE flag was set when the lock was 79 * initialized. 80 * LK_UPGRADE - the process must hold a shared lock that it wants to 81 * have upgraded to an exclusive lock. Other processes may get 82 * exclusive access to the resource between the time that the upgrade 83 * is requested and the time that it is granted. 84 * LK_EXCLUPGRADE - the process must hold a shared lock that it wants to 85 * have upgraded to an exclusive lock. If the request succeeds, no 86 * other processes will have gotten exclusive access to the resource 87 * between the time that the upgrade is requested and the time that 88 * it is granted. However, if another process has already requested 89 * an upgrade, the request will fail (see error returns below). 90 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants 91 * to have downgraded to a shared lock. If the process holds multiple 92 * (recursive) exclusive locks, they will all be downgraded to shared 93 * locks. 94 * LK_RELEASE - release one instance of a lock. 95 * LK_DRAIN - wait for all activity on the lock to end, then mark it 96 * decommissioned. This feature is used before freeing a lock that 97 * is part of a piece of memory that is about to be freed. 98 * LK_EXCLOTHER - return for lockstatus(). Used when another process 99 * holds the lock exclusively. 100 * 101 * These are flags that are passed to the lockmgr routine. 102 */ 103#define LK_TYPE_MASK 0x0000000f /* type of lock sought */ 104#define LK_SHARED 0x00000001 /* shared lock */ 105#define LK_EXCLUSIVE 0x00000002 /* exclusive lock */ 106#define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */ 107#define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */ 108#define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */ 109#define LK_RELEASE 0x00000006 /* release any type of lock */ 110#define LK_DRAIN 0x00000007 /* wait for all lock activity to end */ 111#define LK_EXCLOTHER 0x00000008 /* other process holds lock */ 112/* 113 * External lock flags. 114 * 115 * The first three flags may be set in lock_init to set their mode permanently, 116 * or passed in as arguments to the lock manager. The LK_REENABLE flag may be 117 * set only at the release of a lock obtained by drain. 118 */ 119#define LK_EXTFLG_MASK 0x01000070 /* mask of external flags */ 120#define LK_NOWAIT 0x00000010 /* do not sleep to await lock */ 121#define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */ 122#define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */ 123#define LK_REENABLE 0x00000080 /* lock is be reenabled after drain */ 124#define LK_NOPAUSE 0x01000000 /* no spinloop */ 125/* 126 * Internal lock flags. 127 * 128 * These flags are used internally to the lock manager. 129 */ 130#define LK_WANT_UPGRADE 0x00000100 /* waiting for share-to-excl upgrade */ 131#define LK_WANT_EXCL 0x00000200 /* exclusive lock sought */ 132#define LK_HAVE_EXCL 0x00000400 /* exclusive lock obtained */ 133#define LK_WAITDRAIN 0x00000800 /* process waiting for lock to drain */ 134#define LK_DRAINING 0x00004000 /* lock is being drained */ 135/* 136 * Control flags 137 * 138 * Non-persistent external flags. 139 */ 140#define LK_INTERLOCK 0x00010000 /* unlock passed simple lock after 141 getting lk_interlock */ 142#define LK_RETRY 0x00020000 /* vn_lock: retry until locked */ 143#define LK_NOOBJ 0x00040000 /* vget: don't create object */ 144 145/* 146 * Internal state flags corresponding to lk_sharecount, and lk_waitcount 147 */ 148#define LK_SHARE_NONZERO 0x00100000 149#define LK_WAIT_NONZERO 0x00200000 150 151/* 152 * Lock return status. 153 * 154 * Successfully obtained locks return 0. Locks will always succeed 155 * unless one of the following is true: 156 * LK_FORCEUPGRADE is requested and some other process has already 157 * requested a lock upgrade (returns EBUSY). 158 * LK_WAIT is set and a sleep would be required (returns EBUSY). 159 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK). 160 * PCATCH is set in lock priority and a signal arrives (returns 161 * either EINTR or ERESTART if system calls is to be restarted). 162 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK). 163 * A failed lock attempt always returns a non-zero error value. No lock 164 * is held after an error return (in particular, a failed LK_UPGRADE 165 * or LK_FORCEUPGRADE will have released its shared access lock). 166 */ 167 168/* 169 * Indicator that no process holds exclusive lock 170 */ 171#define LK_KERNPROC ((pid_t) -2) 172#define LK_NOPROC ((pid_t) -1) 173 174void dumplockinfo(struct lock *lkp); 175struct proc; 176 177void lockinit __P((struct lock *, int prio, char *wmesg, int timo, 178 int flags)); 179#ifdef DEBUG_LOCKS 180int debuglockmgr __P((struct lock *, u_int flags, 181 struct simplelock *, struct proc *p, 182 const char *, 183 const char *, 184 int)); 185#define lockmgr(lockp, flags, slockp, proc) \ 186 debuglockmgr((lockp), (flags), (slockp), (proc), \ 187 "lockmgr", __FILE__, __LINE__) 188#else 189int lockmgr __P((struct lock *, u_int flags, 190 struct simplelock *, struct proc *p)); 191#endif 192void lockmgr_printinfo __P((struct lock *)); 193int lockstatus __P((struct lock *, struct proc *)); 194int lockcount __P((struct lock *)); 195 196#ifdef SIMPLELOCK_DEBUG 197void _simple_unlock __P((struct simplelock *alp, const char *, int)); 198#define simple_unlock(alp) _simple_unlock(alp, __FILE__, __LINE__) 199int _simple_lock_try __P((struct simplelock *alp, const char *, int)); 200#define simple_lock_try(alp) _simple_lock_try(alp, __FILE__, __LINE__) 201void _simple_lock __P((struct simplelock *alp, const char *, int)); 202#define simple_lock(alp) _simple_lock(alp, __FILE__, __LINE__) 203void simple_lock_init __P((struct simplelock *alp)); 204#else /* !SIMPLELOCK_DEBUG */ 205#if MAXCPU == 1 /* no multiprocessor locking is necessary */ 206#define NULL_SIMPLELOCKS 207#define simple_lock_init(alp) 208#define simple_lock(alp) 209#define simple_lock_try(alp) (1) /* always succeeds */ 210#define simple_unlock(alp) 211#endif /* MAXCPU == 1 */ 212#endif /* !SIMPLELOCK_DEBUG */ 213 214#endif /* !_LOCK_H_ */ 215