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6 * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
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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 1.11 2005/11/19 17:19:48 dillon Exp $
46 * A number of third party programs #include <sys/lock.h> for no good
47 * reason. Don't actually include anything unless we are the kernel.
49 #if defined(_KERNEL) || defined(_KERNEL_STRUCTURES)
51 #include <machine/lock.h>
52 #ifndef _SYS_THREAD_H_
53 #include <sys/thread.h> /* lwkt_token */
55 #ifndef _SYS_SPINLOCK_H_
56 #include <sys/spinlock.h>
60 * The general lock structure. Provides for multiple shared locks,
61 * upgrading from shared to exclusive, and sleeping until the lock
67 struct spinlock lk_spinlock; /* lock on remaining fields */
68 u_int lk_flags; /* see below */
69 int lk_sharecount; /* # of accepted shared locks */
70 int lk_waitcount; /* # of processes sleeping for lock */
71 short lk_exclusivecount; /* # of recursive exclusive locks */
72 short lk_prio; /* tsleep flags */
73 char *lk_wmesg; /* resource sleeping (for tsleep) */
74 int lk_timo; /* maximum sleep time (for tsleep) */
75 struct thread *lk_lockholder; /* thread of excl lock holder */
77 const char *lk_filename;
78 const char *lk_lockername;
84 * LK_SHARED - get one of many possible shared locks. If a process
85 * holding an exclusive lock requests a shared lock, the exclusive
86 * lock(s) will be downgraded to shared locks.
87 * LK_EXCLUSIVE - stop further shared locks, when they are cleared,
88 * grant a pending upgrade if it exists, then grant an exclusive
89 * lock. Only one exclusive lock may exist at a time, except that
90 * a process holding an exclusive lock may get additional exclusive
91 * locks if it explicitly sets the LK_CANRECURSE flag in the lock
92 * request, or if the LK_CANRECUSE flag was set when the lock was
94 * LK_UPGRADE - the process must hold a shared lock that it wants to
95 * have upgraded to an exclusive lock. Other processes may get
96 * exclusive access to the resource between the time that the upgrade
97 * is requested and the time that it is granted.
98 * LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
99 * have upgraded to an exclusive lock. If the request succeeds, no
100 * other processes will have gotten exclusive access to the resource
101 * between the time that the upgrade is requested and the time that
102 * it is granted. However, if another process has already requested
103 * an upgrade, the request will fail (see error returns below).
104 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants
105 * to have downgraded to a shared lock. If the process holds multiple
106 * (recursive) exclusive locks, they will all be downgraded to shared
108 * LK_RELEASE - release one instance of a lock.
109 * LK_DRAIN - wait for all activity on the lock to end, then mark it
110 * decommissioned. This feature is used before freeing a lock that
111 * is part of a piece of memory that is about to be freed.
112 * LK_EXCLOTHER - return for lockstatus(). Used when another process
113 * holds the lock exclusively.
115 * These are flags that are passed to the lockmgr routine.
117 #define LK_TYPE_MASK 0x0000000f /* type of lock sought */
118 #define LK_SHARED 0x00000001 /* shared lock */
119 #define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
120 #define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
121 #define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */
122 #define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
123 #define LK_RELEASE 0x00000006 /* release any type of lock */
124 #define LK_DRAIN 0x00000007 /* wait for all lock activity to end */
125 #define LK_EXCLOTHER 0x00000008 /* other process holds lock */
127 * External lock flags.
129 * The first three flags may be set in lock_init to set their mode permanently,
130 * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
131 * set only at the release of a lock obtained by drain.
133 #define LK_EXTFLG_MASK 0x03000070 /* mask of external flags */
134 #define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
135 #define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
136 #define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
137 #define LK_REENABLE 0x00000080 /* lock is be reenabled after drain */
138 #define LK_NOPAUSE 0x01000000 /* no spinloop */
139 #define LK_TIMELOCK 0x02000000
141 * Internal lock flags.
143 * These flags are used internally to the lock manager.
145 #define LK_WANT_UPGRADE 0x00000100 /* waiting for share-to-excl upgrade */
146 #define LK_WANT_EXCL 0x00000200 /* exclusive lock sought */
147 #define LK_HAVE_EXCL 0x00000400 /* exclusive lock obtained */
148 #define LK_WAITDRAIN 0x00000800 /* process waiting for lock to drain */
149 #define LK_DRAINING 0x00004000 /* lock is being drained */
153 * Non-persistent external flags.
155 #define LK_INTERLOCK 0x00010000 /* unlock passed simple lock after
156 getting lk_spinlock */
157 #define LK_RETRY 0x00020000 /* vn_lock: retry until locked */
158 #define LK_NOOBJ 0x00040000 /* vget: don't create object */
159 #define LK_THISLAYER 0x00080000 /* vn_lock: lock/unlock only current layer */
162 * Internal state flags corresponding to lk_sharecount, and lk_waitcount
164 #define LK_SHARE_NONZERO 0x00100000
165 #define LK_WAIT_NONZERO 0x00200000
168 * Lock return status.
170 * Successfully obtained locks return 0. Locks will always succeed
171 * unless one of the following is true:
172 * LK_FORCEUPGRADE is requested and some other process has already
173 * requested a lock upgrade (returns EBUSY).
174 * LK_WAIT is set and a sleep would be required (returns EBUSY).
175 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
176 * PCATCH is set in lock priority and a signal arrives (returns
177 * either EINTR or ERESTART if system calls is to be restarted).
178 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
179 * A failed lock attempt always returns a non-zero error value. No lock
180 * is held after an error return (in particular, a failed LK_UPGRADE
181 * or LK_FORCEUPGRADE will have released its shared access lock).
185 * Indicator that no process holds exclusive lock
187 #define LK_KERNTHREAD ((struct thread *)-2)
188 #define LK_NOTHREAD ((struct thread *)-1)
192 void dumplockinfo(struct lock *lkp);
195 void lockinit (struct lock *, int prio, char *wmesg, int timo, int flags);
196 void lockreinit (struct lock *, int prio, char *wmesg, int timo, int flags);
198 int debuglockmgr (struct lock *, u_int flags,
199 struct spinlock *, struct thread *p,
203 #define lockmgr(lockp, flags, slockp, td) \
204 debuglockmgr((lockp), (flags), (slockp), (td), \
205 "lockmgr", __FILE__, __LINE__)
207 int lockmgr (struct lock *, u_int flags,
208 struct spinlock *, struct thread *td);
210 void lockmgr_printinfo (struct lock *);
211 int lockstatus (struct lock *, struct thread *);
212 int lockcount (struct lock *);
213 int lockcountnb (struct lock *);
216 #endif /* _KERNEL || _KERNEL_STRUCTURES */
217 #endif /* _SYS_LOCK_H_ */