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/6.4/sys/sys/lockmgr.h 163178 2006-10-09 20:04:46Z tegge $
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
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 struct thread *lk_lockholder; /* thread of exclusive lock holder */
61 struct lock *lk_newlock; /* lock taking over this lock */
62 #ifdef DEBUG_LOCKS
63 struct stack lk_stack;
64 #endif
65 };
66 /*
67 * Lock request types:
68 * LK_SHARED - get one of many possible shared locks. If a process
69 * holding an exclusive lock requests a shared lock, the exclusive
70 * lock(s) will be downgraded to shared locks.
71 * LK_EXCLUSIVE - stop further shared locks, when they are cleared,
72 * grant a pending upgrade if it exists, then grant an exclusive
73 * lock. Only one exclusive lock may exist at a time, except that
74 * a process holding an exclusive lock may get additional exclusive
75 * locks if it explicitly sets the LK_CANRECURSE flag in the lock
76 * request, or if the LK_CANRECUSE flag was set when the lock was
77 * initialized.
78 * LK_UPGRADE - the process must hold a shared lock that it wants to
79 * have upgraded to an exclusive lock. Other processes may get
80 * exclusive access to the resource between the time that the upgrade
81 * is requested and the time that it is granted.
82 * LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
83 * have upgraded to an exclusive lock. If the request succeeds, no
84 * other processes will have gotten exclusive access to the resource
85 * between the time that the upgrade is requested and the time that
86 * it is granted. However, if another process has already requested
87 * an upgrade, the request will fail (see error returns below).
88 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants
89 * to have downgraded to a shared lock. If the process holds multiple
90 * (recursive) exclusive locks, they will all be downgraded to shared
91 * locks.
92 * LK_RELEASE - release one instance of a lock.
93 * LK_DRAIN - wait for all activity on the lock to end, then mark it
94 * decommissioned. This feature is used before freeing a lock that
95 * is part of a piece of memory that is about to be freed.
96 * LK_EXCLOTHER - return for lockstatus(). Used when another process
97 * holds the lock exclusively.
98 *
99 * These are flags that are passed to the lockmgr routine.
100 */
101 #define LK_TYPE_MASK 0x0000000f /* type of lock sought */
102 #define LK_SHARED 0x00000001 /* shared lock */
103 #define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
104 #define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
105 #define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */
106 #define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
107 #define LK_RELEASE 0x00000006 /* release any type of lock */
108 #define LK_DRAIN 0x00000007 /* wait for all lock activity to end */
109 #define LK_EXCLOTHER 0x00000008 /* other process holds lock */
110 /*
111 * External lock flags.
112 *
113 * These may be set in lock_init to set their mode permanently,
114 * or passed in as arguments to the lock manager.
115 */
116 #define LK_EXTFLG_MASK 0x00000ff0 /* mask of external flags */
117 #define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
118 #define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
119 #define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
120 #define LK_NOSHARE 0x00000080 /* Only allow exclusive locks */
121 #define LK_TIMELOCK 0x00000100 /* use lk_timo, else no timeout */
122 /*
123 * Nonpersistent external flags.
124 */
125 #define LK_RETRY 0x00001000 /* vn_lock: retry until locked */
126 #define LK_INTERLOCK 0x00002000 /*
127 * unlock passed mutex after getting
128 * lk_interlock
129 */
130 /*
131 * Internal lock flags.
132 *
133 * These flags are used internally to the lock manager.
134 */
135 #define LK_WANT_UPGRADE 0x00010000 /* waiting for share-to-excl upgrade */
136 #define LK_WANT_EXCL 0x00020000 /* exclusive lock sought */
137 #define LK_HAVE_EXCL 0x00040000 /* exclusive lock obtained */
138 #define LK_WAITDRAIN 0x00080000 /* process waiting for lock to drain */
139 #define LK_DRAINING 0x00100000 /* lock is being drained */
140 #define LK_INTERNAL 0x00200000/* The internal lock is already held */
141 /*
142 * Internal state flags corresponding to lk_sharecount, and lk_waitcount
143 */
144 #define LK_SHARE_NONZERO 0x01000000
145 #define LK_WAIT_NONZERO 0x02000000
146
147
148 /*
149 * Lock return status.
150 *
151 * Successfully obtained locks return 0. Locks will always succeed
152 * unless one of the following is true:
153 * LK_FORCEUPGRADE is requested and some other process has already
154 * requested a lock upgrade (returns EBUSY).
155 * LK_WAIT is set and a sleep would be required (returns EBUSY).
156 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
157 * PCATCH is set in lock priority and a signal arrives (returns
158 * either EINTR or ERESTART if system calls is to be restarted).
159 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
160 * A failed lock attempt always returns a non-zero error value. No lock
161 * is held after an error return (in particular, a failed LK_UPGRADE
162 * or LK_FORCEUPGRADE will have released its shared access lock).
163 */
164
165 /*
166 * Indicator that no process holds exclusive lock
167 */
168 #define LK_KERNPROC ((struct thread *)-2)
169 #define LK_NOPROC ((struct thread *) -1)
170
171 #ifdef INVARIANTS
172 #define LOCKMGR_ASSERT(lkp, what, p) do { \
173 switch ((what)) { \
174 case LK_SHARED: \
175 if (lockstatus((lkp), (p)) == LK_SHARED) \
176 break; \
177 /* fall into exclusive */ \
178 case LK_EXCLUSIVE: \
179 if (lockstatus((lkp), (p)) != LK_EXCLUSIVE) \
180 panic("lock %s %s not held at %s:%d", \
181 (lkp)->lk_wmesg, #what, __FILE__, \
182 __LINE__); \
183 break; \
184 default: \
185 panic("unknown LOCKMGR_ASSERT at %s:%d", __FILE__, \
186 __LINE__); \
187 } \
188 } while (0)
189 #else /* INVARIANTS */
190 #define LOCKMGR_ASSERT(lkp, p, what)
191 #endif /* INVARIANTS */
192
193 void dumplockinfo(struct lock *lkp);
194 struct thread;
195
196 void lockinit(struct lock *, int prio, const char *wmesg,
197 int timo, int flags);
198 void lockdestroy(struct lock *);
199
200 int lockmgr(struct lock *, u_int flags,
201 struct mtx *, struct thread *p);
202 void transferlockers(struct lock *, struct lock *);
203 void lockmgr_printinfo(struct lock *);
204 int lockstatus(struct lock *, struct thread *);
205 int lockcount(struct lock *);
206 int lockwaiters(struct lock *);
207 #ifdef DDB
208 int lockmgr_chain(struct thread *td, struct thread **ownerp);
209 #endif
210
211 #endif /* !_SYS_LOCKMGR_H_ */
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