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37 * @(#)lock.h 8.12 (Berkeley) 5/19/95
38 * $FreeBSD: src/sys/sys/lock.h,v 1.17.2.3 2001/12/25 01:44:44 dillon Exp $
39 * $DragonFly: src/sys/sys/lock.h,v 1.3 2003/06/25 03:56:10 dillon Exp $
46 #include <machine/lock.h>
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. The simple locks are defined in <machine/param.h>.
56 struct simplelock lk_interlock; /* lock on remaining fields */
57 u_int lk_flags; /* see below */
58 int lk_sharecount; /* # of accepted shared locks */
59 int lk_waitcount; /* # of processes sleeping for lock */
60 short lk_exclusivecount; /* # of recursive exclusive locks */
61 short lk_prio; /* priority at which to sleep */
62 char *lk_wmesg; /* resource sleeping (for tsleep) */
63 int lk_timo; /* maximum sleep time (for tsleep) */
64 struct thread *lk_lockholder; /* thread of excl lock holder */
66 const char *lk_filename;
67 const char *lk_lockername;
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
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
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.
104 * These are flags that are passed to the lockmgr routine.
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 */
116 * External lock flags.
118 * The first three flags may be set in lock_init to set their mode permanently,
119 * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
120 * set only at the release of a lock obtained by drain.
122 #define LK_EXTFLG_MASK 0x03000070 /* mask of external flags */
123 #define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
124 #define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
125 #define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
126 #define LK_REENABLE 0x00000080 /* lock is be reenabled after drain */
127 #define LK_NOPAUSE 0x01000000 /* no spinloop */
128 #define LK_TIMELOCK 0x02000000
130 * Internal lock flags.
132 * These flags are used internally to the lock manager.
134 #define LK_WANT_UPGRADE 0x00000100 /* waiting for share-to-excl upgrade */
135 #define LK_WANT_EXCL 0x00000200 /* exclusive lock sought */
136 #define LK_HAVE_EXCL 0x00000400 /* exclusive lock obtained */
137 #define LK_WAITDRAIN 0x00000800 /* process waiting for lock to drain */
138 #define LK_DRAINING 0x00004000 /* lock is being drained */
142 * Non-persistent external flags.
144 #define LK_INTERLOCK 0x00010000 /* unlock passed simple lock after
145 getting lk_interlock */
146 #define LK_RETRY 0x00020000 /* vn_lock: retry until locked */
147 #define LK_NOOBJ 0x00040000 /* vget: don't create object */
148 #define LK_THISLAYER 0x00080000 /* vn_lock: lock/unlock only current layer */
151 * Internal state flags corresponding to lk_sharecount, and lk_waitcount
153 #define LK_SHARE_NONZERO 0x00100000
154 #define LK_WAIT_NONZERO 0x00200000
157 * Lock return status.
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).
174 * Indicator that no process holds exclusive lock
176 #define LK_KERNTHREAD ((struct thread *)-2)
177 #define LK_NOTHREAD ((struct thread *)-1)
179 void dumplockinfo(struct lock *lkp);
182 void lockinit __P((struct lock *, int prio, char *wmesg, int timo,
185 int debuglockmgr __P((struct lock *, u_int flags,
186 struct simplelock *, struct thread *p,
190 #define lockmgr(lockp, flags, slockp, td) \
191 debuglockmgr((lockp), (flags), (slockp), (td), \
192 "lockmgr", __FILE__, __LINE__)
194 int lockmgr __P((struct lock *, u_int flags,
195 struct simplelock *, struct thread *td));
197 void lockmgr_printinfo __P((struct lock *));
198 int lockstatus __P((struct lock *, struct thread *));
199 int lockcount __P((struct lock *));
201 #ifdef SIMPLELOCK_DEBUG
202 void _simple_unlock __P((struct simplelock *alp, const char *, int));
203 #define simple_unlock(alp) _simple_unlock(alp, __FILE__, __LINE__)
204 int _simple_lock_try __P((struct simplelock *alp, const char *, int));
205 #define simple_lock_try(alp) _simple_lock_try(alp, __FILE__, __LINE__)
206 void _simple_lock __P((struct simplelock *alp, const char *, int));
207 #define simple_lock(alp) _simple_lock(alp, __FILE__, __LINE__)
208 void simple_lock_init __P((struct simplelock *alp));
209 #else /* !SIMPLELOCK_DEBUG */
210 #if MAXCPU == 1 /* no multiprocessor locking is necessary */
211 #define NULL_SIMPLELOCKS
212 #define simple_lock_init(alp)
213 #define simple_lock(alp)
214 #define simple_lock_try(alp) (1) /* always succeeds */
215 #define simple_unlock(alp)
216 #endif /* MAXCPU == 1 */
217 #endif /* !SIMPLELOCK_DEBUG */
219 #endif /* !_LOCK_H_ */