FreeBSD/Linux Kernel Cross Reference
sys/sys/lockmgr.h
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: releng/5.0/sys/sys/lockmgr.h 107414 2002-11-30 19:00:51Z mckusick $
39 */
40
41 #ifndef _SYS_LOCKMGR_H_
42 #define _SYS_LOCKMGR_H_
43
44 struct 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 */
51 struct 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 pid_t lk_lockholder; /* pid 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 pid_t 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 ((pid_t) -2)
180 #define LK_NOPROC ((pid_t) -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
204 void dumplockinfo(struct lock *lkp);
205 struct thread;
206
207 void lockinit(struct lock *, int prio, const char *wmesg,
208 int timo, int flags);
209 void lockdestroy(struct lock *);
210
211 #ifdef DEBUG_LOCKS
212 int 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
221 int lockmgr(struct lock *, u_int flags,
222 struct mtx *, struct thread *p);
223 #endif
224 void transferlockers(struct lock *, struct lock *);
225 void lockmgr_printinfo(struct lock *);
226 int lockstatus(struct lock *, struct thread *);
227 int lockcount(struct lock *);
228
229 #endif /* !_SYS_LOCKMGR_H_ */
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