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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
41 #ifndef _SYS_LOCKMGR_H_
42 #define _SYS_LOCKMGR_H_
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 const 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;
67 const char *lk_sfilename;
68 const char *lk_slockername;
74 * LK_SHARED - get one of many possible shared locks. If a process
75 * holding an exclusive lock requests a shared lock, the exclusive
76 * lock(s) will be downgraded to shared locks.
77 * LK_EXCLUSIVE - stop further shared locks, when they are cleared,
78 * grant a pending upgrade if it exists, then grant an exclusive
79 * lock. Only one exclusive lock may exist at a time, except that
80 * a process holding an exclusive lock may get additional exclusive
81 * locks if it explicitly sets the LK_CANRECURSE flag in the lock
82 * request, or if the LK_CANRECUSE flag was set when the lock was
84 * LK_UPGRADE - the process must hold a shared lock that it wants to
85 * have upgraded to an exclusive lock. Other processes may get
86 * exclusive access to the resource between the time that the upgrade
87 * is requested and the time that it is granted.
88 * LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
89 * have upgraded to an exclusive lock. If the request succeeds, no
90 * other processes will have gotten exclusive access to the resource
91 * between the time that the upgrade is requested and the time that
92 * it is granted. However, if another process has already requested
93 * an upgrade, the request will fail (see error returns below).
94 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants
95 * to have downgraded to a shared lock. If the process holds multiple
96 * (recursive) exclusive locks, they will all be downgraded to shared
98 * LK_RELEASE - release one instance of a lock.
99 * LK_DRAIN - wait for all activity on the lock to end, then mark it
100 * decommissioned. This feature is used before freeing a lock that
101 * is part of a piece of memory that is about to be freed.
102 * LK_EXCLOTHER - return for lockstatus(). Used when another process
103 * holds the lock exclusively.
105 * These are flags that are passed to the lockmgr routine.
107 #define LK_TYPE_MASK 0x0000000f /* type of lock sought */
108 #define LK_SHARED 0x00000001 /* shared lock */
109 #define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
110 #define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
111 #define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */
112 #define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
113 #define LK_RELEASE 0x00000006 /* release any type of lock */
114 #define LK_DRAIN 0x00000007 /* wait for all lock activity to end */
115 #define LK_EXCLOTHER 0x00000008 /* other process holds lock */
117 * External lock flags.
119 * The first three flags may be set in lock_init to set their mode permanently,
120 * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
121 * set only at the release of a lock obtained by drain.
123 #define LK_EXTFLG_MASK 0x03000070 /* mask of external flags */
124 #define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
125 #define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
126 #define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
127 #define LK_REENABLE 0x00000080 /* lock is be reenabled after drain */
128 #define LK_NOPAUSE 0x01000000 /* no spinloop */
129 #define LK_TIMELOCK 0x02000000 /* use lk_timo, else no timeout */
131 * Internal lock flags.
133 * These flags are used internally to the lock manager.
135 #define LK_WANT_UPGRADE 0x00000100 /* waiting for share-to-excl upgrade */
136 #define LK_WANT_EXCL 0x00000200 /* exclusive lock sought */
137 #define LK_HAVE_EXCL 0x00000400 /* exclusive lock obtained */
138 #define LK_WAITDRAIN 0x00000800 /* process waiting for lock to drain */
139 #define LK_DRAINING 0x00004000 /* lock is being drained */
143 * Non-persistent external flags.
145 #define LK_INTERLOCK 0x00010000 /*
146 * unlock passed mutex after getting
149 #define LK_RETRY 0x00020000 /* vn_lock: retry until locked */
150 #define LK_NOOBJ 0x00040000 /* vget: don't create object */
151 #define LK_THISLAYER 0x00080000 /* vn_lock: lock/unlock only current layer */
154 * Internal state flags corresponding to lk_sharecount, and lk_waitcount
156 #define LK_SHARE_NONZERO 0x00100000
157 #define LK_WAIT_NONZERO 0x00200000
160 * Lock return status.
162 * Successfully obtained locks return 0. Locks will always succeed
163 * unless one of the following is true:
164 * LK_FORCEUPGRADE is requested and some other process has already
165 * requested a lock upgrade (returns EBUSY).
166 * LK_WAIT is set and a sleep would be required (returns EBUSY).
167 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
168 * PCATCH is set in lock priority and a signal arrives (returns
169 * either EINTR or ERESTART if system calls is to be restarted).
170 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
171 * A failed lock attempt always returns a non-zero error value. No lock
172 * is held after an error return (in particular, a failed LK_UPGRADE
173 * or LK_FORCEUPGRADE will have released its shared access lock).
177 * Indicator that no process holds exclusive lock
179 #define LK_KERNPROC ((pid_t) -2)
180 #define LK_NOPROC ((pid_t) -1)
183 #define LOCKMGR_ASSERT(lkp, what, p) do { \
186 if (lockstatus((lkp), (p)) == LK_SHARED) \
188 /* fall into exclusive */ \
190 if (lockstatus((lkp), (p)) != LK_EXCLUSIVE) \
191 panic("lock %s %s not held at %s:%d", \
192 (lkp)->lk_wmesg, #what, __FILE__, \
196 panic("unknown LOCKMGR_ASSERT at %s:%d", __FILE__, \
200 #else /* INVARIANTS */
201 #define LOCKMGR_ASSERT(lkp, p, what)
202 #endif /* INVARIANTS */
204 void dumplockinfo(struct lock *lkp);
207 void lockinit(struct lock *, int prio, const char *wmesg,
208 int timo, int flags);
209 void lockdestroy(struct lock *);
212 int debuglockmgr(struct lock *, u_int flags,
213 struct mtx *, struct thread *p,
217 #define lockmgr(lockp, flags, slockp, proc) \
218 debuglockmgr((lockp), (flags), (slockp), (proc), \
219 "lockmgr", __FILE__, __LINE__)
221 int lockmgr(struct lock *, u_int flags,
222 struct mtx *, struct thread *p);
224 void lockmgr_printinfo(struct lock *);
225 int lockstatus(struct lock *, struct thread *);
226 int lockcount(struct lock *);
228 #endif /* !_SYS_LOCKMGR_H_ */