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37 * @(#)lock.h 8.12 (Berkeley) 5/19/95
44 #include <machine/lock.h>
49 * The general lock structure. Provides for multiple shared locks,
50 * upgrading from shared to exclusive, and sleeping until the lock
54 struct mtx *lk_interlock; /* lock on remaining fields */
55 u_int lk_flags; /* see below */
56 int lk_sharecount; /* # of accepted shared locks */
57 int lk_waitcount; /* # of processes sleeping for lock */
58 short lk_exclusivecount; /* # of recursive exclusive locks */
59 short lk_prio; /* priority at which to sleep */
60 char *lk_wmesg; /* resource sleeping (for tsleep) */
61 int lk_timo; /* maximum sleep time (for tsleep) */
62 pid_t lk_lockholder; /* pid of exclusive lock holder */
64 const char *lk_filename;
65 const char *lk_lockername;
71 * LK_SHARED - get one of many possible shared locks. If a process
72 * holding an exclusive lock requests a shared lock, the exclusive
73 * lock(s) will be downgraded to shared locks.
74 * LK_EXCLUSIVE - stop further shared locks, when they are cleared,
75 * grant a pending upgrade if it exists, then grant an exclusive
76 * lock. Only one exclusive lock may exist at a time, except that
77 * a process holding an exclusive lock may get additional exclusive
78 * locks if it explicitly sets the LK_CANRECURSE flag in the lock
79 * request, or if the LK_CANRECUSE flag was set when the lock was
81 * LK_UPGRADE - the process must hold a shared lock that it wants to
82 * have upgraded to an exclusive lock. Other processes may get
83 * exclusive access to the resource between the time that the upgrade
84 * is requested and the time that it is granted.
85 * LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
86 * have upgraded to an exclusive lock. If the request succeeds, no
87 * other processes will have gotten exclusive access to the resource
88 * between the time that the upgrade is requested and the time that
89 * it is granted. However, if another process has already requested
90 * an upgrade, the request will fail (see error returns below).
91 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants
92 * to have downgraded to a shared lock. If the process holds multiple
93 * (recursive) exclusive locks, they will all be downgraded to shared
95 * LK_RELEASE - release one instance of a lock.
96 * LK_DRAIN - wait for all activity on the lock to end, then mark it
97 * decommissioned. This feature is used before freeing a lock that
98 * is part of a piece of memory that is about to be freed.
99 * LK_EXCLOTHER - return for lockstatus(). Used when another process
100 * holds the lock exclusively.
102 * These are flags that are passed to the lockmgr routine.
104 #define LK_TYPE_MASK 0x0000000f /* type of lock sought */
105 #define LK_SHARED 0x00000001 /* shared lock */
106 #define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
107 #define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
108 #define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */
109 #define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
110 #define LK_RELEASE 0x00000006 /* release any type of lock */
111 #define LK_DRAIN 0x00000007 /* wait for all lock activity to end */
112 #define LK_EXCLOTHER 0x00000008 /* other process holds lock */
114 * External lock flags.
116 * The first three flags may be set in lock_init to set their mode permanently,
117 * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
118 * set only at the release of a lock obtained by drain.
120 #define LK_EXTFLG_MASK 0x01000070 /* mask of external flags */
121 #define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
122 #define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
123 #define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
124 #define LK_REENABLE 0x00000080 /* lock is be reenabled after drain */
125 #define LK_NOPAUSE 0x01000000 /* no spinloop */
127 * Internal lock flags.
129 * These flags are used internally to the lock manager.
131 #define LK_WANT_UPGRADE 0x00000100 /* waiting for share-to-excl upgrade */
132 #define LK_WANT_EXCL 0x00000200 /* exclusive lock sought */
133 #define LK_HAVE_EXCL 0x00000400 /* exclusive lock obtained */
134 #define LK_WAITDRAIN 0x00000800 /* process waiting for lock to drain */
135 #define LK_DRAINING 0x00004000 /* lock is being drained */
139 * Non-persistent external flags.
141 #define LK_INTERLOCK 0x00010000 /*
142 * unlock passed mutex after getting
145 #define LK_RETRY 0x00020000 /* vn_lock: retry until locked */
146 #define LK_NOOBJ 0x00040000 /* vget: don't create object */
147 #define LK_THISLAYER 0x00080000 /* vn_lock: lock/unlock only current layer */
150 * Internal state flags corresponding to lk_sharecount, and lk_waitcount
152 #define LK_SHARE_NONZERO 0x00100000
153 #define LK_WAIT_NONZERO 0x00200000
156 * Lock return status.
158 * Successfully obtained locks return 0. Locks will always succeed
159 * unless one of the following is true:
160 * LK_FORCEUPGRADE is requested and some other process has already
161 * requested a lock upgrade (returns EBUSY).
162 * LK_WAIT is set and a sleep would be required (returns EBUSY).
163 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
164 * PCATCH is set in lock priority and a signal arrives (returns
165 * either EINTR or ERESTART if system calls is to be restarted).
166 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
167 * A failed lock attempt always returns a non-zero error value. No lock
168 * is held after an error return (in particular, a failed LK_UPGRADE
169 * or LK_FORCEUPGRADE will have released its shared access lock).
173 * Indicator that no process holds exclusive lock
175 #define LK_KERNPROC ((pid_t) -2)
176 #define LK_NOPROC ((pid_t) -1)
179 #define LOCKMGR_ASSERT(lkp, what, p) do { \
182 if (lockstatus((lkp), (p)) == LK_SHARED) \
184 /* fall into exclusive */ \
186 if (lockstatus((lkp), (p)) != LK_EXCLUSIVE) \
187 panic("lock %s %s not held at %s:%d", \
188 (lkp)->lk_wmesg, #what, __FILE__, \
192 panic("unknown LOCKMGR_ASSERT at %s:%d", __FILE__, \
196 #else /* INVARIANTS */
197 #define LOCKMGR_ASSERT(lkp, p, what)
198 #endif /* INVARIANTS */
200 void dumplockinfo(struct lock *lkp);
203 void lockinit __P((struct lock *, int prio, char *wmesg, int timo,
205 void lockdestroy __P((struct lock *));
208 int debuglockmgr __P((struct lock *, u_int flags,
209 struct mtx *, struct proc *p,
213 #define lockmgr(lockp, flags, slockp, proc) \
214 debuglockmgr((lockp), (flags), (slockp), (proc), \
215 "lockmgr", __FILE__, __LINE__)
217 int lockmgr __P((struct lock *, u_int flags,
218 struct mtx *, struct proc *p));
220 void lockmgr_printinfo __P((struct lock *));
221 int lockstatus __P((struct lock *, struct proc *));
222 int lockcount __P((struct lock *));
224 #endif /* !_LOCK_H_ */