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5 * This code contains ideas from software contributed to Berkeley by
6 * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
7 * System project at Carnegie-Mellon University.
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33 * @(#)lock.h 8.12 (Berkeley) 5/19/95
37 #ifndef _SYS_LOCKMGR_H_
38 #define _SYS_LOCKMGR_H_
41 #include <sys/stack.h> /* XXX */
43 #include <sys/queue.h>
44 #include <sys/_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 lock_object lk_object; /* common lock properties */
55 struct mtx *lk_interlock; /* lock on remaining fields */
56 u_int lk_flags; /* see below */
57 int lk_sharecount; /* # of accepted shared locks */
58 int lk_waitcount; /* # of processes sleeping for lock */
59 short lk_exclusivecount; /* # of recursive exclusive locks */
60 short lk_prio; /* priority at which to sleep */
61 int lk_timo; /* maximum sleep time (for tsleep) */
62 struct thread *lk_lockholder; /* thread of exclusive lock holder */
63 struct lock *lk_newlock; /* lock taking over this lock */
66 struct stack lk_stack;
70 #define lk_wmesg lk_object.lo_name
73 * LK_SHARED - get one of many possible shared locks. If a process
74 * holding an exclusive lock requests a shared lock, the exclusive
75 * lock(s) will be downgraded to shared locks.
76 * LK_EXCLUSIVE - stop further shared locks, when they are cleared,
77 * grant a pending upgrade if it exists, then grant an exclusive
78 * lock. Only one exclusive lock may exist at a time, except that
79 * a process holding an exclusive lock may get additional exclusive
80 * locks if it explicitly sets the LK_CANRECURSE flag in the lock
81 * request, or if the LK_CANRECUSE flag was set when the lock was
83 * LK_UPGRADE - the process must hold a shared lock that it wants to
84 * have upgraded to an exclusive lock. Other processes may get
85 * exclusive access to the resource between the time that the upgrade
86 * is requested and the time that it is granted.
87 * LK_DOWNGRADE - the process must hold an exclusive lock that it wants
88 * to have downgraded to a shared lock. If the process holds multiple
89 * (recursive) exclusive locks, they will all be downgraded to shared
91 * LK_RELEASE - release one instance of a lock.
92 * LK_DRAIN - wait for all activity on the lock to end, then mark it
93 * decommissioned. This feature is used before freeing a lock that
94 * is part of a piece of memory that is about to be freed.
95 * LK_EXCLOTHER - return for lockstatus(). Used when another process
96 * holds the lock exclusively.
98 * These are flags that are passed to the lockmgr routine.
100 #define LK_TYPE_MASK 0x0000000f /* type of lock sought */
101 #define LK_SHARED 0x00000001 /* shared lock */
102 #define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
103 #define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
104 #define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
105 #define LK_RELEASE 0x00000006 /* release any type of lock */
106 #define LK_DRAIN 0x00000007 /* wait for all lock activity to end */
107 #define LK_EXCLOTHER 0x00000008 /* other process holds lock */
109 * External lock flags.
111 * These may be set in lock_init to set their mode permanently,
112 * or passed in as arguments to the lock manager.
114 #define LK_EXTFLG_MASK 0x00000ff0 /* mask of external flags */
115 #define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
116 #define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
117 #define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
118 #define LK_NOSHARE 0x00000080 /* Only allow exclusive locks */
119 #define LK_TIMELOCK 0x00000100 /* use lk_timo, else no timeout */
121 * Nonpersistent external flags.
123 #define LK_RETRY 0x00001000 /* vn_lock: retry until locked */
124 #define LK_INTERLOCK 0x00002000 /*
125 * unlock passed mutex after getting
129 * Internal lock flags.
131 * These flags are used internally to the lock manager.
133 #define LK_WANT_UPGRADE 0x00010000 /* waiting for share-to-excl upgrade */
134 #define LK_WANT_EXCL 0x00020000 /* exclusive lock sought */
135 #define LK_HAVE_EXCL 0x00040000 /* exclusive lock obtained */
136 #define LK_WAITDRAIN 0x00080000 /* process waiting for lock to drain */
137 #define LK_DRAINING 0x00100000 /* lock is being drained */
138 #define LK_INTERNAL 0x00200000/* The internal lock is already held */
140 * Internal state flags corresponding to lk_sharecount, and lk_waitcount
142 #define LK_SHARE_NONZERO 0x01000000
143 #define LK_WAIT_NONZERO 0x02000000
147 * Lock return status.
149 * Successfully obtained locks return 0. Locks will always succeed
150 * unless one of the following is true:
151 * LK_FORCEUPGRADE is requested and some other process has already
152 * requested a lock upgrade (returns EBUSY).
153 * LK_WAIT is set and a sleep would be required (returns EBUSY).
154 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
155 * PCATCH is set in lock priority and a signal arrives (returns
156 * either EINTR or ERESTART if system calls is to be restarted).
157 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
158 * A failed lock attempt always returns a non-zero error value. No lock
159 * is held after an error return (in particular, a failed LK_UPGRADE
160 * or LK_FORCEUPGRADE will have released its shared access lock).
164 * Indicator that no process holds exclusive lock
166 #define LK_KERNPROC ((struct thread *)-2)
167 #define LK_NOPROC ((struct thread *) -1)
171 void lockinit(struct lock *, int prio, const char *wmesg,
172 int timo, int flags);
173 void lockdestroy(struct lock *);
175 int _lockmgr(struct lock *, u_int flags, struct mtx *, char *file,
177 void lockmgr_disown(struct lock *);
178 void lockmgr_printinfo(struct lock *);
179 int lockstatus(struct lock *, struct thread *);
180 int lockwaiters(struct lock *);
182 #define lockmgr(lock, flags, mtx) \
183 _lockmgr((lock), (flags), (mtx), __FILE__, __LINE__)
184 #define lockmgr_recursed(lkp) \
185 ((lkp)->lk_exclusivecount > 1)
187 int lockmgr_chain(struct thread *td, struct thread **ownerp);
190 #endif /* !_SYS_LOCKMGR_H_ */