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 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
33 * @(#)lock.h 8.12 (Berkeley) 5/19/95
34 * $FreeBSD: releng/7.4/sys/sys/lockmgr.h 211533 2010-08-20 20:58:57Z jhb $
35 */
36
37 #ifndef _SYS_LOCKMGR_H_
38 #define _SYS_LOCKMGR_H_
39
40 #ifdef DEBUG_LOCKS
41 #include <sys/stack.h> /* XXX */
42 #endif
43 #include <sys/queue.h>
44 #include <sys/_lock.h>
45
46 struct mtx;
47
48 /*
49 * The general lock structure. Provides for multiple shared locks,
50 * upgrading from shared to exclusive, and sleeping until the lock
51 * can be gained.
52 */
53 struct lock {
54 struct lock_object lk_object; /* common lock properties */
55 struct mtx *lk_interlock; /* lock on remaining fields */
56 u_int lk_flags; /* see below */
57 int lk_sharecount; /* # of accepted shared locks */
58 int lk_waitcount; /* # of processes sleeping for lock */
59 short lk_exclusivecount; /* # of recursive exclusive locks */
60 short lk_prio; /* priority at which to sleep */
61 int lk_timo; /* maximum sleep time (for tsleep) */
62 struct thread *lk_lockholder; /* thread of exclusive lock holder */
63 struct lock *lk_newlock; /* lock taking over this lock */
64
65 #ifdef DEBUG_LOCKS
66 struct stack lk_stack;
67 #endif
68 };
69
70 #define lk_wmesg lk_object.lo_name
71 /*
72 * Lock request types:
73 * LK_SHARED - get one of many possible shared locks. If a process
74 * holding an exclusive lock requests a shared lock, the exclusive
75 * lock(s) will be downgraded to shared locks.
76 * LK_EXCLUSIVE - stop further shared locks, when they are cleared,
77 * grant a pending upgrade if it exists, then grant an exclusive
78 * lock. Only one exclusive lock may exist at a time, except that
79 * a process holding an exclusive lock may get additional exclusive
80 * locks if it explicitly sets the LK_CANRECURSE flag in the lock
81 * request, or if the LK_CANRECUSE flag was set when the lock was
82 * initialized.
83 * LK_UPGRADE - the process must hold a shared lock that it wants to
84 * have upgraded to an exclusive lock. Other processes may get
85 * exclusive access to the resource between the time that the upgrade
86 * is requested and the time that it is granted.
87 * LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
88 * have upgraded to an exclusive lock. If the request succeeds, no
89 * other processes will have gotten exclusive access to the resource
90 * between the time that the upgrade is requested and the time that
91 * it is granted. However, if another process has already requested
92 * an upgrade, the request will fail (see error returns below).
93 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants
94 * to have downgraded to a shared lock. If the process holds multiple
95 * (recursive) exclusive locks, they will all be downgraded to shared
96 * locks.
97 * LK_RELEASE - release one instance of a lock.
98 * LK_DRAIN - wait for all activity on the lock to end, then mark it
99 * decommissioned. This feature is used before freeing a lock that
100 * is part of a piece of memory that is about to be freed.
101 * LK_EXCLOTHER - return for lockstatus(). Used when another process
102 * holds the lock exclusively.
103 *
104 * These are flags that are passed to the lockmgr routine.
105 */
106 #define LK_TYPE_MASK 0x0000000f /* type of lock sought */
107 #define LK_SHARED 0x00000001 /* shared lock */
108 #define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
109 #define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
110 #define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */
111 #define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
112 #define LK_RELEASE 0x00000006 /* release any type of lock */
113 #define LK_DRAIN 0x00000007 /* wait for all lock activity to end */
114 #define LK_EXCLOTHER 0x00000008 /* other process holds lock */
115 /*
116 * External lock flags.
117 *
118 * These may be set in lock_init to set their mode permanently,
119 * or passed in as arguments to the lock manager.
120 */
121 #define LK_EXTFLG_MASK 0x00000ff0 /* mask of external flags */
122 #define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
123 #define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
124 #define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
125 #define LK_NOSHARE 0x00000080 /* Only allow exclusive locks */
126 #define LK_TIMELOCK 0x00000100 /* use lk_timo, else no timeout */
127 /*
128 * Nonpersistent external flags.
129 */
130 #define LK_RETRY 0x00001000 /* vn_lock: retry until locked */
131 #define LK_INTERLOCK 0x00002000 /*
132 * unlock passed mutex after getting
133 * lk_interlock
134 */
135 /*
136 * Internal lock flags.
137 *
138 * These flags are used internally to the lock manager.
139 */
140 #define LK_WANT_UPGRADE 0x00010000 /* waiting for share-to-excl upgrade */
141 #define LK_WANT_EXCL 0x00020000 /* exclusive lock sought */
142 #define LK_HAVE_EXCL 0x00040000 /* exclusive lock obtained */
143 #define LK_WAITDRAIN 0x00080000 /* process waiting for lock to drain */
144 #define LK_DRAINING 0x00100000 /* lock is being drained */
145 #define LK_INTERNAL 0x00200000/* The internal lock is already held */
146 /*
147 * Internal state flags corresponding to lk_sharecount, and lk_waitcount
148 */
149 #define LK_SHARE_NONZERO 0x01000000
150 #define LK_WAIT_NONZERO 0x02000000
151
152
153 /*
154 * Lock return status.
155 *
156 * Successfully obtained locks return 0. Locks will always succeed
157 * unless one of the following is true:
158 * LK_FORCEUPGRADE is requested and some other process has already
159 * requested a lock upgrade (returns EBUSY).
160 * LK_WAIT is set and a sleep would be required (returns EBUSY).
161 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
162 * PCATCH is set in lock priority and a signal arrives (returns
163 * either EINTR or ERESTART if system calls is to be restarted).
164 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
165 * A failed lock attempt always returns a non-zero error value. No lock
166 * is held after an error return (in particular, a failed LK_UPGRADE
167 * or LK_FORCEUPGRADE will have released its shared access lock).
168 */
169
170 /*
171 * Indicator that no process holds exclusive lock
172 */
173 #define LK_KERNPROC ((struct thread *)-2)
174 #define LK_NOPROC ((struct thread *) -1)
175
176 #ifdef _KERNEL
177
178 #if !defined(LOCK_FILE) || !defined(LOCK_LINE)
179 #error "LOCK_FILE and LOCK_LINE not defined, include <sys/lock.h> before"
180 #endif
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, LOCK_FILE, \
193 LOCK_LINE); \
194 break; \
195 default: \
196 panic("unknown LOCKMGR_ASSERT at %s:%d", LOCK_FILE, \
197 LOCK_LINE); \
198 } \
199 } while (0)
200 #else /* INVARIANTS */
201 #define LOCKMGR_ASSERT(lkp, p, what)
202 #endif /* INVARIANTS */
203
204 struct thread;
205
206 void lockinit(struct lock *, int prio, const char *wmesg,
207 int timo, int flags);
208 void lockdestroy(struct lock *);
209
210 int _lockmgr(struct lock *, u_int flags,
211 struct mtx *, struct thread *p, char *file, int line);
212 void transferlockers(struct lock *, struct lock *);
213 void lockmgr_printinfo(struct lock *);
214 int lockstatus(struct lock *, struct thread *);
215 int lockcount(struct lock *);
216 int lockwaiters(struct lock *);
217 void lockallowshare(struct lock *);
218 void lockallowrecurse(struct lock *);
219 void lockdisablerecurse(struct lock *);
220
221 #define lockmgr(lock, flags, mtx, td) \
222 _lockmgr((lock), (flags), (mtx), (td), LOCK_FILE, LOCK_LINE)
223 #ifdef DDB
224 int lockmgr_chain(struct thread *td, struct thread **ownerp);
225 #endif
226
227 #endif /* !_KERNEL */
228
229 #endif /* !_SYS_LOCKMGR_H_ */
Cache object: f7b63d8a3136aa668bbf228d1d84d9fe
|