lockmgr.h revision 110414
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/lockmgr.h 110414 2003-02-05 19:36:58Z julian $ 39 */ 40 41#ifndef _SYS_LOCKMGR_H_ 42#define _SYS_LOCKMGR_H_ 43 44struct mtx; 45 46/* 47 * The general lock structure. Provides for multiple shared locks, 48 * upgrading from shared to exclusive, and sleeping until the lock 49 * can be gained. 50 */ 51struct lock { 52 struct mtx *lk_interlock; /* lock on remaining fields */ 53 u_int lk_flags; /* see below */ 54 int lk_sharecount; /* # of accepted shared locks */ 55 int lk_waitcount; /* # of processes sleeping for lock */ 56 short lk_exclusivecount; /* # of recursive exclusive locks */ 57 short lk_prio; /* priority at which to sleep */ 58 const char *lk_wmesg; /* resource sleeping (for tsleep) */ 59 int lk_timo; /* maximum sleep time (for tsleep) */ 60 struct thread *lk_lockholder; /* thread of exclusive lock holder */ 61 struct lock *lk_newlock; /* lock taking over this lock */ 62#ifdef DEBUG_LOCKS 63 const char *lk_filename; 64 const char *lk_lockername; 65 int lk_lineno; 66 67 struct thread *lk_slockholder; 68 const char *lk_sfilename; 69 const char *lk_slockername; 70 int lk_slineno; 71#endif 72}; 73/* 74 * Lock request types: 75 * LK_SHARED - get one of many possible shared locks. If a process 76 * holding an exclusive lock requests a shared lock, the exclusive 77 * lock(s) will be downgraded to shared locks. 78 * LK_EXCLUSIVE - stop further shared locks, when they are cleared, 79 * grant a pending upgrade if it exists, then grant an exclusive 80 * lock. Only one exclusive lock may exist at a time, except that 81 * a process holding an exclusive lock may get additional exclusive 82 * locks if it explicitly sets the LK_CANRECURSE flag in the lock 83 * request, or if the LK_CANRECUSE flag was set when the lock was 84 * initialized. 85 * LK_UPGRADE - the process must hold a shared lock that it wants to 86 * have upgraded to an exclusive lock. Other processes may get 87 * exclusive access to the resource between the time that the upgrade 88 * is requested and the time that it is granted. 89 * LK_EXCLUPGRADE - the process must hold a shared lock that it wants to 90 * have upgraded to an exclusive lock. If the request succeeds, no 91 * other processes will have gotten exclusive access to the resource 92 * between the time that the upgrade is requested and the time that 93 * it is granted. However, if another process has already requested 94 * an upgrade, the request will fail (see error returns below). 95 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants 96 * to have downgraded to a shared lock. If the process holds multiple 97 * (recursive) exclusive locks, they will all be downgraded to shared 98 * locks. 99 * LK_RELEASE - release one instance of a lock. 100 * LK_DRAIN - wait for all activity on the lock to end, then mark it 101 * decommissioned. This feature is used before freeing a lock that 102 * is part of a piece of memory that is about to be freed. 103 * LK_EXCLOTHER - return for lockstatus(). Used when another process 104 * holds the lock exclusively. 105 * 106 * These are flags that are passed to the lockmgr routine. 107 */ 108#define LK_TYPE_MASK 0x0000000f /* type of lock sought */ 109#define LK_SHARED 0x00000001 /* shared lock */ 110#define LK_EXCLUSIVE 0x00000002 /* exclusive lock */ 111#define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */ 112#define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */ 113#define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */ 114#define LK_RELEASE 0x00000006 /* release any type of lock */ 115#define LK_DRAIN 0x00000007 /* wait for all lock activity to end */ 116#define LK_EXCLOTHER 0x00000008 /* other process holds lock */ 117/* 118 * External lock flags. 119 * 120 * The first three flags may be set in lock_init to set their mode permanently, 121 * or passed in as arguments to the lock manager. The LK_REENABLE flag may be 122 * set only at the release of a lock obtained by drain. 123 */ 124#define LK_EXTFLG_MASK 0x03000070 /* mask of external flags */ 125#define LK_NOWAIT 0x00000010 /* do not sleep to await lock */ 126#define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */ 127#define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */ 128#define LK_REENABLE 0x00000080 /* lock is be reenabled after drain */ 129#define LK_NOPAUSE 0x01000000 /* no spinloop */ 130#define LK_TIMELOCK 0x02000000 /* use lk_timo, else no timeout */ 131/* 132 * Internal lock flags. 133 * 134 * These flags are used internally to the lock manager. 135 */ 136#define LK_WANT_UPGRADE 0x00000100 /* waiting for share-to-excl upgrade */ 137#define LK_WANT_EXCL 0x00000200 /* exclusive lock sought */ 138#define LK_HAVE_EXCL 0x00000400 /* exclusive lock obtained */ 139#define LK_WAITDRAIN 0x00000800 /* process waiting for lock to drain */ 140#define LK_DRAINING 0x00004000 /* lock is being drained */ 141/* 142 * Control flags 143 * 144 * Non-persistent external flags. 145 */ 146#define LK_INTERLOCK 0x00010000 /* 147 * unlock passed mutex after getting 148 * lk_interlock 149 */ 150#define LK_RETRY 0x00020000 /* vn_lock: retry until locked */ 151#define LK_THISLAYER 0x00040000 /* vn_lock: lock/unlock only current layer */ 152 153/* 154 * Internal state flags corresponding to lk_sharecount, and lk_waitcount 155 */ 156#define LK_SHARE_NONZERO 0x00100000 157#define LK_WAIT_NONZERO 0x00200000 158 159/* 160 * Lock return status. 161 * 162 * Successfully obtained locks return 0. Locks will always succeed 163 * unless one of the following is true: 164 * LK_FORCEUPGRADE is requested and some other process has already 165 * requested a lock upgrade (returns EBUSY). 166 * LK_WAIT is set and a sleep would be required (returns EBUSY). 167 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK). 168 * PCATCH is set in lock priority and a signal arrives (returns 169 * either EINTR or ERESTART if system calls is to be restarted). 170 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK). 171 * A failed lock attempt always returns a non-zero error value. No lock 172 * is held after an error return (in particular, a failed LK_UPGRADE 173 * or LK_FORCEUPGRADE will have released its shared access lock). 174 */ 175 176/* 177 * Indicator that no process holds exclusive lock 178 */ 179#define LK_KERNPROC ((struct thread *)-2) 180#define LK_NOPROC ((struct thread *) -1) 181 182#ifdef INVARIANTS 183#define LOCKMGR_ASSERT(lkp, what, p) do { \ 184 switch ((what)) { \ 185 case LK_SHARED: \ 186 if (lockstatus((lkp), (p)) == LK_SHARED) \ 187 break; \ 188 /* fall into exclusive */ \ 189 case LK_EXCLUSIVE: \ 190 if (lockstatus((lkp), (p)) != LK_EXCLUSIVE) \ 191 panic("lock %s %s not held at %s:%d", \ 192 (lkp)->lk_wmesg, #what, __FILE__, \ 193 __LINE__); \ 194 break; \ 195 default: \ 196 panic("unknown LOCKMGR_ASSERT at %s:%d", __FILE__, \ 197 __LINE__); \ 198 } \ 199} while (0) 200#else /* INVARIANTS */ 201#define LOCKMGR_ASSERT(lkp, p, what) 202#endif /* INVARIANTS */ 203 204void dumplockinfo(struct lock *lkp); 205struct thread; 206 207void lockinit(struct lock *, int prio, const char *wmesg, 208 int timo, int flags); 209void lockdestroy(struct lock *); 210 211#ifdef DEBUG_LOCKS 212int debuglockmgr(struct lock *, u_int flags, 213 struct mtx *, struct thread *p, 214 const char *, 215 const char *, 216 int); 217#define lockmgr(lockp, flags, slockp, proc) \ 218 debuglockmgr((lockp), (flags), (slockp), (proc), \ 219 "lockmgr", __FILE__, __LINE__) 220#else 221int lockmgr(struct lock *, u_int flags, 222 struct mtx *, struct thread *p); 223#endif 224void transferlockers(struct lock *, struct lock *); 225void lockmgr_printinfo(struct lock *); 226int lockstatus(struct lock *, struct thread *); 227int lockcount(struct lock *); 228 229#endif /* !_SYS_LOCKMGR_H_ */ 230