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5 * The DragonFly Project. All rights reserved.
7 * This code contains ideas from software contributed to Berkeley by
8 * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
9 * System project at Carnegie-Mellon University.
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32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
40 * A number of third party programs #include <sys/lock.h> for no good
41 * reason. Don't actually include anything unless we are the kernel.
43 #if defined(_KERNEL) || defined(_KERNEL_STRUCTURES)
45 #include <machine/lock.h>
46 #ifndef _SYS_THREAD_H_
47 #include <sys/thread.h> /* lwkt_token */
49 #ifndef _SYS_SPINLOCK_H_
50 #include <sys/spinlock.h>
54 * The general lock structure. Provides for multiple shared locks,
55 * upgrading from shared to exclusive, and sleeping until the lock
61 u_int lk_flags; /* see below */
62 int lk_count; /* -shared, +exclusive */
63 int lk_timo; /* maximum sleep time (for tsleep) */
64 const char *lk_wmesg; /* resource sleeping (for tsleep) */
65 struct thread *lk_lockholder; /* thread of excl lock holder */
72 * Get one of many possible shared locks. If a process holding an
73 * exclusive lock requests a shared lock, the exclusive lock(s) will
74 * be downgraded to shared locks.
77 * Stop further shared locks, when they are cleared, grant a pending
78 * upgrade if it exists, then grant an exclusive lock. Only one exclusive
79 * lock may exist at a time, except that a process holding an exclusive
80 * lock may get additional exclusive locks if it explicitly sets the
81 * LK_CANRECURSE flag in the lock request, or if the LK_CANRECURSE flag
82 * was set when the lock was initialized.
85 * The process must hold a shared lock that it wants to have upgraded
86 * to an exclusive lock. Other processes may get exclusive access to
87 * the resource between the time that the upgrade is requested and the
88 * time that it is granted.
91 * the process must hold a shared lock that it wants to have upgraded
92 * to an exclusive lock. If the request succeeds, no other processes
93 * will have gotten exclusive access to the resource between the time
94 * that the upgrade is requested and the time that it is granted.
95 * However, if another process has already requested an upgrade, the
96 * request will fail (see error returns below).
99 * The process must hold an exclusive lock that it wants to have
100 * downgraded to a shared lock. If the process holds multiple (recursive)
101 * exclusive locks, they will all be downgraded to shared locks.
104 * Release one instance of a lock.
107 * The current exclusive lock holder can cancel any blocked lock requests,
108 * or any new requests, whos callers specified LK_CANCELABLE. They will
109 * receive a ENOLCK error code. Cancel beg/end does not stack.
111 * The cancel command stays in effect until the exclusive lock holder
112 * releases the last count on the lock or issues a LK_CANCEL_END command.
115 * The current exclusive lock holder can stop canceling new requests
116 * whos callers specify LK_CANCELABLE. The exclusive lock is maintained.
118 * Note that the last release of the exclusive lock will also
119 * automatically end cancel mode.
124 * LK_EXCLOTHER - return for lockstatus(). Used when another process
125 * holds the lock exclusively.
127 * These are flags that are passed to the lockmgr routine.
129 #define LK_TYPE_MASK 0x0000000f /* type of lock sought */
130 #define LK_SHARED 0x00000001 /* shared lock */
131 #define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
132 #define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
133 #define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */
134 #define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
135 #define LK_RELEASE 0x00000006 /* release any type of lock */
136 #define LK_WAITUPGRADE 0x00000007
137 #define LK_EXCLOTHER 0x00000008 /* other process holds lock */
138 #define LK_CANCEL_BEG 0x00000009 /* cancel other requests */
139 #define LK_CANCEL_END 0x0000000a /* stop canceling other requests */
142 * lk_count bit fields.
144 * Positive count is exclusive, negative count is shared. The count field
145 * must be large enough to accomodate all possible threads.
147 #define LKC_EXREQ 0x80000000 /* waiting for exclusive lock */
148 #define LKC_SHREQ 0x40000000 /* waiting for shared lock */
149 #define LKC_UPREQ 0x20000000 /* waiting for upgrade */
150 #define LKC_EXCL 0x10000000 /* exclusive (else shr or unlocked) */
151 #define LKC_UPGRANT 0x08000000 /* upgrade granted */
152 #define LKC_CANCEL 0x04000000 /* cancel in effect */
153 #define LKC_MASK 0x03FFFFFF
156 * External lock flags.
158 * The first three flags may be set in lock_init to set their mode permanently,
159 * or passed in as arguments to the lock manager.
161 #define LK_EXTFLG_MASK 0x070000F0 /* mask of external flags */
162 #define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
163 #define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
164 #define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
165 #define LK_NOCOLLSTATS 0x00000080 /* v_lock_coll not applicable */
166 #define LK_CANCELABLE 0x01000000 /* blocked caller can be canceled */
167 #define LK_TIMELOCK 0x02000000
168 #define LK_PCATCH 0x04000000 /* timelocked with signal catching */
173 * Non-persistent external flags.
175 #define LK_FAILRECLAIM 0x00010000 /* vn_lock: allowed to fail on reclaim */
176 #define LK_RETRY 0x00020000 /* vn_lock: retry until locked */
177 #define LK_UNUSED40000 0x00040000
178 #define LK_UNUSED80000 0x00080000
181 * Lock return status.
183 * Successfully obtained locks return 0. Locks will always succeed
184 * unless one of the following is true:
185 * LK_FORCEUPGRADE is requested and some other process has already
186 * requested a lock upgrade (returns EBUSY).
187 * LK_WAIT is set and a sleep would be required (returns EBUSY).
188 * LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
189 * PCATCH is set in lock priority and a signal arrives (returns
190 * either EINTR or ERESTART if system calls is to be restarted).
191 * Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
192 * A failed lock attempt always returns a non-zero error value. No lock
193 * is held after an error return (in particular, a failed LK_UPGRADE
194 * or LK_FORCEUPGRADE will have released its shared access lock).
198 * Indicator that no process holds exclusive lock
200 #define LK_KERNTHREAD ((struct thread *)-2)
201 #define LK_NOTHREAD ((struct thread *)-1)
205 void dumplockinfo(struct lock *lkp);
209 struct lock *la_lock;
214 #define LOCK_INITIALIZER(wmesg, timo, flags) \
216 .lk_flags = ((flags) & LK_EXTFLG_MASK), \
220 .lk_lockholder = LK_NOTHREAD \
223 void lockinit (struct lock *, const char *wmesg, int timo, int flags);
224 void lockreinit (struct lock *, const char *wmesg, int timo, int flags);
225 void lockuninit(struct lock *);
226 void lock_sysinit(struct lock_args *);
227 int lockmgr_shared (struct lock *, u_int flags);
228 int lockmgr_exclusive (struct lock *, u_int flags);
229 int lockmgr_downgrade (struct lock *, u_int flags);
230 int lockmgr_upgrade (struct lock *, u_int flags);
231 int lockmgr_release (struct lock *, u_int flags);
232 int lockmgr_cancel_beg (struct lock *, u_int flags);
233 int lockmgr_cancel_end (struct lock *, u_int flags);
234 void lockmgr_kernproc (struct lock *);
235 void lockmgr_printinfo (struct lock *);
236 int lockstatus (struct lock *, struct thread *);
237 int lockowned (struct lock *);
238 int lockcount (struct lock *);
239 int lockcountnb (struct lock *);
241 #define LOCK_SYSINIT(name, lock, desc, flags) \
242 static struct lock_args name##_args = { \
247 SYSINIT(name##_lock_sysinit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, \
248 lock_sysinit, &name##_args); \
249 SYSUNINIT(name##_lock_sysuninit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, \
253 * Most lockmgr() calls pass a constant flags parameter which
254 * we can optimize-out with an inline.
258 lockmgr(struct lock *lkp, u_int flags)
260 switch(flags & LK_TYPE_MASK) {
262 return lockmgr_shared(lkp, flags);
264 return lockmgr_exclusive(lkp, flags);
266 return lockmgr_downgrade(lkp, flags);
269 return lockmgr_upgrade(lkp, flags);
271 return lockmgr_release(lkp, flags);
273 return lockmgr_cancel_beg(lkp, flags);
275 return lockmgr_cancel_end(lkp, flags);
277 panic("lockmgr: unknown locktype request %d",
278 flags & LK_TYPE_MASK);
279 return EINVAL; /* NOT REACHED */
284 #endif /* _KERNEL || _KERNEL_STRUCTURES */
285 #endif /* _SYS_LOCK_H_ */