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6 * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
7 * System project at Carnegie-Mellon University.
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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 $
45 * A number of third party programs #include <sys/lock.h> for no good
46 * reason. Don't actually include anything unless we are the kernel.
48 #if defined(_KERNEL) || defined(_KERNEL_STRUCTURES)
50 #include <machine/lock.h>
51 #ifndef _SYS_THREAD_H_
52 #include <sys/thread.h> /* lwkt_token */
54 #ifndef _SYS_SPINLOCK_H_
55 #include <sys/spinlock.h>
59 * The general lock structure. Provides for multiple shared locks,
60 * upgrading from shared to exclusive, and sleeping until the lock
66 struct spinlock lk_spinlock; /* lock on remaining fields */
67 u_int lk_flags; /* see below */
68 int lk_sharecount; /* # of accepted shared locks */
69 int lk_waitcount; /* # of processes sleeping for lock */
70 short lk_exclusivecount; /* # of recursive exclusive locks */
72 const char *lk_wmesg; /* resource sleeping (for tsleep) */
73 int lk_timo; /* maximum sleep time (for tsleep) */
74 struct thread *lk_lockholder; /* thread of excl lock holder */
76 const char *lk_filename;
77 const char *lk_lockername;
83 * LK_SHARED - get one of many possible shared locks. If a process
84 * holding an exclusive lock requests a shared lock, the exclusive
85 * lock(s) will be downgraded to shared locks.
86 * LK_EXCLUSIVE - stop further shared locks, when they are cleared,
87 * grant a pending upgrade if it exists, then grant an exclusive
88 * lock. Only one exclusive lock may exist at a time, except that
89 * a process holding an exclusive lock may get additional exclusive
90 * locks if it explicitly sets the LK_CANRECURSE flag in the lock
91 * request, or if the LK_CANRECUSE flag was set when the lock was
93 * LK_UPGRADE - the process must hold a shared lock that it wants to
94 * have upgraded to an exclusive lock. Other processes may get
95 * exclusive access to the resource between the time that the upgrade
96 * is requested and the time that it is granted.
97 * LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
98 * have upgraded to an exclusive lock. If the request succeeds, no
99 * other processes will have gotten exclusive access to the resource
100 * between the time that the upgrade is requested and the time that
101 * it is granted. However, if another process has already requested
102 * an upgrade, the request will fail (see error returns below).
103 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants
104 * to have downgraded to a shared lock. If the process holds multiple
105 * (recursive) exclusive locks, they will all be downgraded to shared
107 * LK_RELEASE - release one instance of a lock.
108 * LK_EXCLOTHER - return for lockstatus(). Used when another process
109 * holds the lock exclusively.
111 * These are flags that are passed to the lockmgr routine.
113 #define LK_TYPE_MASK 0x0000000f /* type of lock sought */
114 #define LK_SHARED 0x00000001 /* shared lock */
115 #define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
116 #define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
117 #define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */
118 #define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
119 #define LK_RELEASE 0x00000006 /* release any type of lock */
120 #define LK_UNUSED07 0x00000007
121 #define LK_EXCLOTHER 0x00000008 /* other process holds lock */
123 * External lock flags.
125 * The first three flags may be set in lock_init to set their mode permanently,
126 * or passed in as arguments to the lock manager.
128 #define LK_EXTFLG_MASK 0x07000070 /* mask of external flags */
129 #define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
130 #define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
131 #define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
132 #define LK_UNUSED0080 0x00000080
133 #define LK_UNUSED0100x 0x01000000
134 #define LK_TIMELOCK 0x02000000
135 #define LK_PCATCH 0x04000000 /* timelocked with signal catching */
137 * Internal lock flags.
139 * These flags are used internally to the lock manager.
141 #define LK_WANT_UPGRADE 0x00000100 /* waiting for share-to-excl upgrade */
142 #define LK_WANT_EXCL 0x00000200 /* exclusive lock sought */
143 #define LK_HAVE_EXCL 0x00000400 /* exclusive lock obtained */
144 #define LK_UNUSED0800 0x00000800
145 #define LK_UNUSED4000 0x00004000
149 * Non-persistent external flags.
151 #define LK_UNUSED10000 0x00010000
152 #define LK_RETRY 0x00020000 /* vn_lock: retry until locked */
153 #define LK_NOOBJ 0x00040000 /* vget: don't create object */
154 #define LK_THISLAYER 0x00080000 /* vn_lock: lock/unlock only current layer */
157 * Internal state flags corresponding to lk_sharecount, and lk_waitcount
159 #define LK_SHARE_NONZERO 0x00100000
160 #define LK_WAIT_NONZERO 0x00200000
163 * Lock return status.
165 * Successfully obtained locks return 0. Locks will always succeed
166 * unless one of the following is true:
167 * LK_FORCEUPGRADE is requested and some other process has already
168 * requested a lock upgrade (returns EBUSY).
169 * LK_WAIT is set and a sleep would be required (returns EBUSY).
170 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
171 * PCATCH is set in lock priority and a signal arrives (returns
172 * either EINTR or ERESTART if system calls is to be restarted).
173 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
174 * A failed lock attempt always returns a non-zero error value. No lock
175 * is held after an error return (in particular, a failed LK_UPGRADE
176 * or LK_FORCEUPGRADE will have released its shared access lock).
180 * Indicator that no process holds exclusive lock
182 #define LK_KERNTHREAD ((struct thread *)-2)
183 #define LK_NOTHREAD ((struct thread *)-1)
187 void dumplockinfo(struct lock *lkp);
191 struct lock *la_lock;
196 void lockinit (struct lock *, const char *wmesg, int timo, int flags);
197 void lockreinit (struct lock *, const char *wmesg, int timo, int flags);
198 void lockuninit(struct lock *);
199 void lock_sysinit(struct lock_args *);
201 int debuglockmgr (struct lock *, u_int flags,
205 #define lockmgr(lockp, flags) \
206 debuglockmgr((lockp), (flags), "lockmgr", __FILE__, __LINE__)
208 int lockmgr (struct lock *, u_int flags);
210 void lockmgr_setexclusive_interlocked(struct lock *);
211 void lockmgr_clrexclusive_interlocked(struct lock *);
212 void lockmgr_kernproc (struct lock *);
213 void lockmgr_printinfo (struct lock *);
214 int lockstatus (struct lock *, struct thread *);
215 int lockowned (struct lock *);
216 int lockcount (struct lock *);
217 int lockcountnb (struct lock *);
219 #define LOCK_SYSINIT(name, lock, desc, flags) \
220 static struct lock_args name##_args = { \
225 SYSINIT(name##_lock_sysinit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, \
226 lock_sysinit, &name##_args); \
227 SYSUNINIT(name##_lock_sysuninit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, \
231 #endif /* _KERNEL || _KERNEL_STRUCTURES */
232 #endif /* _SYS_LOCK_H_ */