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 * $FreeBSD$
35 */
36
37 #ifndef _SYS_LOCKMGR_H_
38 #define _SYS_LOCKMGR_H_
39
40 struct mtx;
41
42 /*
43 * The general lock structure. Provides for multiple shared locks,
44 * upgrading from shared to exclusive, and sleeping until the lock
45 * can be gained.
46 */
47 struct lock {
48 struct mtx *lk_interlock; /* lock on remaining fields */
49 u_int lk_flags; /* see below */
50 int lk_sharecount; /* # of accepted shared locks */
51 int lk_waitcount; /* # of processes sleeping for lock */
52 short lk_exclusivecount; /* # of recursive exclusive locks */
53 short lk_prio; /* priority at which to sleep */
54 const char *lk_wmesg; /* resource sleeping (for tsleep) */
55 int lk_timo; /* maximum sleep time (for tsleep) */
56 struct thread *lk_lockholder; /* thread of exclusive lock holder */
57 struct lock *lk_newlock; /* lock taking over this lock */
58 #ifdef DEBUG_LOCKS
59 const char *lk_filename;
60 const char *lk_lockername;
61 int lk_lineno;
62
63 struct thread *lk_slockholder;
64 const char *lk_sfilename;
65 const char *lk_slockername;
66 int lk_slineno;
67 #endif
68 };
69 /*
70 * Lock request types:
71 * LK_SHARED - get one of many possible shared locks. If a process
72 * holding an exclusive lock requests a shared lock, the exclusive
73 * lock(s) will be downgraded to shared locks.
74 * LK_EXCLUSIVE - stop further shared locks, when they are cleared,
75 * grant a pending upgrade if it exists, then grant an exclusive
76 * lock. Only one exclusive lock may exist at a time, except that
77 * a process holding an exclusive lock may get additional exclusive
78 * locks if it explicitly sets the LK_CANRECURSE flag in the lock
79 * request, or if the LK_CANRECUSE flag was set when the lock was
80 * initialized.
81 * LK_UPGRADE - the process must hold a shared lock that it wants to
82 * have upgraded to an exclusive lock. Other processes may get
83 * exclusive access to the resource between the time that the upgrade
84 * is requested and the time that it is granted.
85 * LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
86 * have upgraded to an exclusive lock. If the request succeeds, no
87 * other processes will have gotten exclusive access to the resource
88 * between the time that the upgrade is requested and the time that
89 * it is granted. However, if another process has already requested
90 * an upgrade, the request will fail (see error returns below).
91 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants
92 * to have downgraded to a shared lock. If the process holds multiple
93 * (recursive) exclusive locks, they will all be downgraded to shared
94 * locks.
95 * LK_RELEASE - release one instance of a lock.
96 * LK_DRAIN - wait for all activity on the lock to end, then mark it
97 * decommissioned. This feature is used before freeing a lock that
98 * is part of a piece of memory that is about to be freed.
99 * LK_EXCLOTHER - return for lockstatus(). Used when another process
100 * holds the lock exclusively.
101 *
102 * These are flags that are passed to the lockmgr routine.
103 */
104 #define LK_TYPE_MASK 0x0000000f /* type of lock sought */
105 #define LK_SHARED 0x00000001 /* shared lock */
106 #define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
107 #define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
108 #define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */
109 #define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
110 #define LK_RELEASE 0x00000006 /* release any type of lock */
111 #define LK_DRAIN 0x00000007 /* wait for all lock activity to end */
112 #define LK_EXCLOTHER 0x00000008 /* other process holds lock */
113 /*
114 * External lock flags.
115 *
116 * The first three flags may be set in lock_init to set their mode permanently,
117 * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
118 * set only at the release of a lock obtained by drain.
119 */
120 #define LK_EXTFLG_MASK 0x03000070 /* mask of external flags */
121 #define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
122 #define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
123 #define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
124 #define LK_REENABLE 0x00000080 /* lock is be reenabled after drain */
125 #define LK_NOPAUSE 0x01000000 /* no spinloop */
126 #define LK_TIMELOCK 0x02000000 /* use lk_timo, else no timeout */
127 /*
128 * Internal lock flags.
129 *
130 * These flags are used internally to the lock manager.
131 */
132 #define LK_WANT_UPGRADE 0x00000100 /* waiting for share-to-excl upgrade */
133 #define LK_WANT_EXCL 0x00000200 /* exclusive lock sought */
134 #define LK_HAVE_EXCL 0x00000400 /* exclusive lock obtained */
135 #define LK_WAITDRAIN 0x00000800 /* process waiting for lock to drain */
136 #define LK_DRAINING 0x00004000 /* lock is being drained */
137 /*
138 * Control flags
139 *
140 * Non-persistent external flags.
141 */
142 #define LK_INTERLOCK 0x00010000 /*
143 * unlock passed mutex after getting
144 * lk_interlock
145 */
146 #define LK_RETRY 0x00020000 /* vn_lock: retry until locked */
147 #define LK_THISLAYER 0x00040000 /* vn_lock: lock/unlock only current layer */
148 #define LK_INTERNAL 0x00080000/* The internal lock is already held */
149
150 /*
151 * Internal state flags corresponding to lk_sharecount, and lk_waitcount
152 */
153 #define LK_SHARE_NONZERO 0x00100000
154 #define LK_WAIT_NONZERO 0x00200000
155
156 /*
157 * Lock return status.
158 *
159 * Successfully obtained locks return 0. Locks will always succeed
160 * unless one of the following is true:
161 * LK_FORCEUPGRADE is requested and some other process has already
162 * requested a lock upgrade (returns EBUSY).
163 * LK_WAIT is set and a sleep would be required (returns EBUSY).
164 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
165 * PCATCH is set in lock priority and a signal arrives (returns
166 * either EINTR or ERESTART if system calls is to be restarted).
167 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
168 * A failed lock attempt always returns a non-zero error value. No lock
169 * is held after an error return (in particular, a failed LK_UPGRADE
170 * or LK_FORCEUPGRADE will have released its shared access lock).
171 */
172
173 /*
174 * Indicator that no process holds exclusive lock
175 */
176 #define LK_KERNPROC ((struct thread *)-2)
177 #define LK_NOPROC ((struct thread *) -1)
178
179 #ifdef INVARIANTS
180 #define LOCKMGR_ASSERT(lkp, what, p) do { \
181 switch ((what)) { \
182 case LK_SHARED: \
183 if (lockstatus((lkp), (p)) == LK_SHARED) \
184 break; \
185 /* fall into exclusive */ \
186 case LK_EXCLUSIVE: \
187 if (lockstatus((lkp), (p)) != LK_EXCLUSIVE) \
188 panic("lock %s %s not held at %s:%d", \
189 (lkp)->lk_wmesg, #what, __FILE__, \
190 __LINE__); \
191 break; \
192 default: \
193 panic("unknown LOCKMGR_ASSERT at %s:%d", __FILE__, \
194 __LINE__); \
195 } \
196 } while (0)
197 #else /* INVARIANTS */
198 #define LOCKMGR_ASSERT(lkp, p, what)
199 #endif /* INVARIANTS */
200
201 void dumplockinfo(struct lock *lkp);
202 struct thread;
203
204 void lockinit(struct lock *, int prio, const char *wmesg,
205 int timo, int flags);
206 void lockdestroy(struct lock *);
207
208 #ifdef DEBUG_LOCKS
209 int debuglockmgr(struct lock *, u_int flags,
210 struct mtx *, struct thread *p,
211 const char *,
212 const char *,
213 int);
214 #define lockmgr(lockp, flags, slockp, proc) \
215 debuglockmgr((lockp), (flags), (slockp), (proc), \
216 "lockmgr", __FILE__, __LINE__)
217 #else
218 int lockmgr(struct lock *, u_int flags,
219 struct mtx *, struct thread *p);
220 #endif
221 void transferlockers(struct lock *, struct lock *);
222 void lockmgr_printinfo(struct lock *);
223 int lockstatus(struct lock *, struct thread *);
224 int lockcount(struct lock *);
225
226 #endif /* !_SYS_LOCKMGR_H_ */
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