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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
47 * The general lock structure. Provides for multiple shared locks,
48 * upgrading from shared to exclusive, and sleeping until the lock
52 struct mtx *lk_interlock; /* lock on remaining fields */
53 u_int lk_flags; /* see below */
54 int lk_sharecount; /* # of accepted shared locks */
55 int lk_waitcount; /* # of processes sleeping for lock */
56 short lk_exclusivecount; /* # of recursive exclusive locks */
57 short lk_prio; /* priority at which to sleep */
58 char *lk_wmesg; /* resource sleeping (for tsleep) */
59 int lk_timo; /* maximum sleep time (for tsleep) */
60 pid_t lk_lockholder; /* pid of exclusive lock holder */
62 const char *lk_filename;
63 const char *lk_lockername;
69 * LK_SHARED - get one of many possible shared locks. If a process
70 * holding an exclusive lock requests a shared lock, the exclusive
71 * lock(s) will be downgraded to shared locks.
72 * LK_EXCLUSIVE - stop further shared locks, when they are cleared,
73 * grant a pending upgrade if it exists, then grant an exclusive
74 * lock. Only one exclusive lock may exist at a time, except that
75 * a process holding an exclusive lock may get additional exclusive
76 * locks if it explicitly sets the LK_CANRECURSE flag in the lock
77 * request, or if the LK_CANRECUSE flag was set when the lock was
79 * LK_UPGRADE - the process must hold a shared lock that it wants to
80 * have upgraded to an exclusive lock. Other processes may get
81 * exclusive access to the resource between the time that the upgrade
82 * is requested and the time that it is granted.
83 * LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
84 * have upgraded to an exclusive lock. If the request succeeds, no
85 * other processes will have gotten exclusive access to the resource
86 * between the time that the upgrade is requested and the time that
87 * it is granted. However, if another process has already requested
88 * an upgrade, the request will fail (see error returns below).
89 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants
90 * to have downgraded to a shared lock. If the process holds multiple
91 * (recursive) exclusive locks, they will all be downgraded to shared
93 * LK_RELEASE - release one instance of a lock.
94 * LK_DRAIN - wait for all activity on the lock to end, then mark it
95 * decommissioned. This feature is used before freeing a lock that
96 * is part of a piece of memory that is about to be freed.
97 * LK_EXCLOTHER - return for lockstatus(). Used when another process
98 * holds the lock exclusively.
100 * These are flags that are passed to the lockmgr routine.
102 #define LK_TYPE_MASK 0x0000000f /* type of lock sought */
103 #define LK_SHARED 0x00000001 /* shared lock */
104 #define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
105 #define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
106 #define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */
107 #define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
108 #define LK_RELEASE 0x00000006 /* release any type of lock */
109 #define LK_DRAIN 0x00000007 /* wait for all lock activity to end */
110 #define LK_EXCLOTHER 0x00000008 /* other process holds lock */
112 * External lock flags.
114 * The first three flags may be set in lock_init to set their mode permanently,
115 * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
116 * set only at the release of a lock obtained by drain.
118 #define LK_EXTFLG_MASK 0x01000070 /* mask of external flags */
119 #define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
120 #define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
121 #define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
122 #define LK_REENABLE 0x00000080 /* lock is be reenabled after drain */
123 #define LK_NOPAUSE 0x01000000 /* no spinloop */
125 * Internal lock flags.
127 * These flags are used internally to the lock manager.
129 #define LK_WANT_UPGRADE 0x00000100 /* waiting for share-to-excl upgrade */
130 #define LK_WANT_EXCL 0x00000200 /* exclusive lock sought */
131 #define LK_HAVE_EXCL 0x00000400 /* exclusive lock obtained */
132 #define LK_WAITDRAIN 0x00000800 /* process waiting for lock to drain */
133 #define LK_DRAINING 0x00004000 /* lock is being drained */
137 * Non-persistent external flags.
139 #define LK_INTERLOCK 0x00010000 /*
140 * unlock passed mutex after getting
143 #define LK_RETRY 0x00020000 /* vn_lock: retry until locked */
144 #define LK_NOOBJ 0x00040000 /* vget: don't create object */
145 #define LK_THISLAYER 0x00080000 /* vn_lock: lock/unlock only current layer */
148 * Internal state flags corresponding to lk_sharecount, and lk_waitcount
150 #define LK_SHARE_NONZERO 0x00100000
151 #define LK_WAIT_NONZERO 0x00200000
154 * Lock return status.
156 * Successfully obtained locks return 0. Locks will always succeed
157 * unless one of the following is true:
158 * LK_FORCEUPGRADE is requested and some other process has already
159 * requested a lock upgrade (returns EBUSY).
160 * LK_WAIT is set and a sleep would be required (returns EBUSY).
161 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
162 * PCATCH is set in lock priority and a signal arrives (returns
163 * either EINTR or ERESTART if system calls is to be restarted).
164 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
165 * A failed lock attempt always returns a non-zero error value. No lock
166 * is held after an error return (in particular, a failed LK_UPGRADE
167 * or LK_FORCEUPGRADE will have released its shared access lock).
171 * Indicator that no process holds exclusive lock
173 #define LK_KERNPROC ((pid_t) -2)
174 #define LK_NOPROC ((pid_t) -1)
177 #define LOCKMGR_ASSERT(lkp, what, p) do { \
180 if (lockstatus((lkp), (p)) == LK_SHARED) \
182 /* fall into exclusive */ \
184 if (lockstatus((lkp), (p)) != LK_EXCLUSIVE) \
185 panic("lock %s %s not held at %s:%d", \
186 (lkp)->lk_wmesg, #what, __FILE__, \
190 panic("unknown LOCKMGR_ASSERT at %s:%d", __FILE__, \
194 #else /* INVARIANTS */
195 #define LOCKMGR_ASSERT(lkp, p, what)
196 #endif /* INVARIANTS */
198 void dumplockinfo(struct lock *lkp);
201 void lockinit __P((struct lock *, int prio, char *wmesg, int timo,
203 void lockdestroy __P((struct lock *));
206 int debuglockmgr __P((struct lock *, u_int flags,
207 struct mtx *, struct proc *p,
211 #define lockmgr(lockp, flags, slockp, proc) \
212 debuglockmgr((lockp), (flags), (slockp), (proc), \
213 "lockmgr", __FILE__, __LINE__)
215 int lockmgr __P((struct lock *, u_int flags,
216 struct mtx *, struct proc *p));
218 void lockmgr_printinfo __P((struct lock *));
219 int lockstatus __P((struct lock *, struct proc *));
220 int lockcount __P((struct lock *));
222 #endif /* !_LOCK_H_ */