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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
45 #include <machine/lock.h>
48 * The general lock structure. Provides for multiple shared locks,
49 * upgrading from shared to exclusive, and sleeping until the lock
50 * can be gained. The simple locks are defined in <machine/param.h>.
53 struct simplelock lk_interlock; /* lock on remaining fields */
54 u_int lk_flags; /* see below */
55 int lk_sharecount; /* # of accepted shared locks */
56 int lk_waitcount; /* # of processes sleeping for lock */
57 short lk_exclusivecount; /* # of recursive exclusive locks */
58 short lk_prio; /* priority at which to sleep */
59 char *lk_wmesg; /* resource sleeping (for tsleep) */
60 int lk_timo; /* maximum sleep time (for tsleep) */
61 pid_t lk_lockholder; /* pid of exclusive lock holder */
63 const char *lk_filename;
64 const char *lk_lockername;
70 * LK_SHARED - get one of many possible shared locks. If a process
71 * holding an exclusive lock requests a shared lock, the exclusive
72 * lock(s) will be downgraded to shared locks.
73 * LK_EXCLUSIVE - stop further shared locks, when they are cleared,
74 * grant a pending upgrade if it exists, then grant an exclusive
75 * lock. Only one exclusive lock may exist at a time, except that
76 * a process holding an exclusive lock may get additional exclusive
77 * locks if it explicitly sets the LK_CANRECURSE flag in the lock
78 * request, or if the LK_CANRECUSE flag was set when the lock was
80 * LK_UPGRADE - the process must hold a shared lock that it wants to
81 * have upgraded to an exclusive lock. Other processes may get
82 * exclusive access to the resource between the time that the upgrade
83 * is requested and the time that it is granted.
84 * LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
85 * have upgraded to an exclusive lock. If the request succeeds, no
86 * other processes will have gotten exclusive access to the resource
87 * between the time that the upgrade is requested and the time that
88 * it is granted. However, if another process has already requested
89 * an upgrade, the request will fail (see error returns below).
90 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants
91 * to have downgraded to a shared lock. If the process holds multiple
92 * (recursive) exclusive locks, they will all be downgraded to shared
94 * LK_RELEASE - release one instance of a lock.
95 * LK_DRAIN - wait for all activity on the lock to end, then mark it
96 * decommissioned. This feature is used before freeing a lock that
97 * is part of a piece of memory that is about to be freed.
98 * LK_EXCLOTHER - return for lockstatus(). Used when another process
99 * holds the lock exclusively.
101 * These are flags that are passed to the lockmgr routine.
103 #define LK_TYPE_MASK 0x0000000f /* type of lock sought */
104 #define LK_SHARED 0x00000001 /* shared lock */
105 #define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
106 #define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
107 #define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */
108 #define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
109 #define LK_RELEASE 0x00000006 /* release any type of lock */
110 #define LK_DRAIN 0x00000007 /* wait for all lock activity to end */
111 #define LK_EXCLOTHER 0x00000008 /* other process holds lock */
113 * External lock flags.
115 * The first three flags may be set in lock_init to set their mode permanently,
116 * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
117 * set only at the release of a lock obtained by drain.
119 #define LK_EXTFLG_MASK 0x01000070 /* mask of external flags */
120 #define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
121 #define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
122 #define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
123 #define LK_REENABLE 0x00000080 /* lock is be reenabled after drain */
124 #define LK_NOPAUSE 0x01000000 /* no spinloop */
126 * Internal lock flags.
128 * These flags are used internally to the lock manager.
130 #define LK_WANT_UPGRADE 0x00000100 /* waiting for share-to-excl upgrade */
131 #define LK_WANT_EXCL 0x00000200 /* exclusive lock sought */
132 #define LK_HAVE_EXCL 0x00000400 /* exclusive lock obtained */
133 #define LK_WAITDRAIN 0x00000800 /* process waiting for lock to drain */
134 #define LK_DRAINING 0x00004000 /* lock is being drained */
138 * Non-persistent external flags.
140 #define LK_INTERLOCK 0x00010000 /* unlock passed simple lock after
141 getting lk_interlock */
142 #define LK_RETRY 0x00020000 /* vn_lock: retry until locked */
143 #define LK_NOOBJ 0x00040000 /* vget: don't create object */
146 * Internal state flags corresponding to lk_sharecount, and lk_waitcount
148 #define LK_SHARE_NONZERO 0x00100000
149 #define LK_WAIT_NONZERO 0x00200000
152 * Lock return status.
154 * Successfully obtained locks return 0. Locks will always succeed
155 * unless one of the following is true:
156 * LK_FORCEUPGRADE is requested and some other process has already
157 * requested a lock upgrade (returns EBUSY).
158 * LK_WAIT is set and a sleep would be required (returns EBUSY).
159 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
160 * PCATCH is set in lock priority and a signal arrives (returns
161 * either EINTR or ERESTART if system calls is to be restarted).
162 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
163 * A failed lock attempt always returns a non-zero error value. No lock
164 * is held after an error return (in particular, a failed LK_UPGRADE
165 * or LK_FORCEUPGRADE will have released its shared access lock).
169 * Indicator that no process holds exclusive lock
171 #define LK_KERNPROC ((pid_t) -2)
172 #define LK_NOPROC ((pid_t) -1)
174 void dumplockinfo(struct lock *lkp);
177 void lockinit __P((struct lock *, int prio, char *wmesg, int timo,
180 int debuglockmgr __P((struct lock *, u_int flags,
181 struct simplelock *, struct proc *p,
185 #define lockmgr(lockp, flags, slockp, proc) \
186 debuglockmgr((lockp), (flags), (slockp), (proc), \
187 "lockmgr", __FILE__, __LINE__)
189 int lockmgr __P((struct lock *, u_int flags,
190 struct simplelock *, struct proc *p));
192 void lockmgr_printinfo __P((struct lock *));
193 int lockstatus __P((struct lock *, struct proc *));
194 int lockcount __P((struct lock *));
196 #ifdef SIMPLELOCK_DEBUG
197 void _simple_unlock __P((struct simplelock *alp, const char *, int));
198 #define simple_unlock(alp) _simple_unlock(alp, __FILE__, __LINE__)
199 int _simple_lock_try __P((struct simplelock *alp, const char *, int));
200 #define simple_lock_try(alp) _simple_lock_try(alp, __FILE__, __LINE__)
201 void _simple_lock __P((struct simplelock *alp, const char *, int));
202 #define simple_lock(alp) _simple_lock(alp, __FILE__, __LINE__)
203 void simple_lock_init __P((struct simplelock *alp));
204 #else /* !SIMPLELOCK_DEBUG */
205 #if NCPUS == 1 /* no multiprocessor locking is necessary */
206 #define NULL_SIMPLELOCKS
207 #define simple_lock_init(alp)
208 #define simple_lock(alp)
209 #define simple_lock_try(alp) (1) /* always succeeds */
210 #define simple_unlock(alp)
211 #endif /* NCPUS == 1 */
212 #endif /* !SIMPLELOCK_DEBUG */
214 #endif /* !_LOCK_H_ */