2 * Copyright 2000, International Business Machines Corporation and others.
5 * This software has been released under the terms of the IBM Public
6 * License. For details, see the LICENSE file in the top-level source
7 * directory or online at http://www.openafs.org/dl/license10.html
10 #ifndef __AFSLOCK_INCLUDE__
11 #define __AFSLOCK_INCLUDE__ 1
13 #if !defined(KERNEL) && !defined(KDUMP_KERNEL)
14 #error Do not include afs/lock.h except for kernel code.
18 * (C) COPYRIGHT IBM CORPORATION 1987
19 * LICENSED MATERIALS - PROPERTY OF IBM
22 #define INSTRUMENT_LOCKS
23 /* This is the max lock number in use. Please update it if you add any new
26 #define MAX_LOCK_NUMBER 780
28 #define AFS_RWLOCK_INIT(lock, nm) Lock_Init(lock)
30 #define LOCK_INIT(lock, nm) Lock_Init(lock)
32 /* The following macros allow multi statement macros to be defined safely, i.e.
33 - the multi statement macro can be the object of an if statement;
34 - the call to the multi statement macro may be legally followed by a semi-colon.
35 BEGINMAC and ENDMAC have been tested with both the portable C compiler and
36 Hi-C. Both compilers were from the Palo Alto 4.2BSD software releases, and
37 both optimized out the constant loop code. For an example of the use
38 of BEGINMAC and ENDMAC, see the definition for ReleaseWriteLock, below.
39 An alternative to this, using "if(1)" for BEGINMAC is not used because it
40 may generate worse code with pcc, and may generate warning messages with hi-C.
44 #define ENDMAC } while (0)
47 typedef unsigned int afs_lock_tracker_t;
48 # define MyPidxx (get_user_struct()->u_procp->p_pid )
49 # define MyPidxx2Pid(x) (x)
50 #elif defined(AFS_SUN5_ENV)
51 typedef kthread_t * afs_lock_tracker_t;
52 # define MyPidxx (curthread)
53 # define MyPidxx2Pid(x) (x ? ttoproc(x)->p_pid : 0)
54 #elif defined(AFS_SUN5_ENV) || defined(AFS_OBSD_ENV)
55 typedef unsigned int afs_lock_tracker_t;
56 # define MyPidxx (curproc->p_pid)
57 # define MyPidxx2Pid(x) (x)
58 #elif defined(AFS_AIX41_ENV)
59 typedef tid_t afs_lock_tracker_t;
60 extern tid_t thread_self();
61 # define MyPidxx (thread_self())
62 # define MyPidxx2Pid(x) ((afs_int32)(x))
63 #elif defined(AFS_HPUX101_ENV)
64 # if defined(AFS_HPUX1111_ENV)
65 typedef struct kthread * afs_lock_tracker_t;
66 # define MyPidxx (u.u_kthreadp)
67 # define MyPidxx2Pid(x) (x ? kt_tid(x) : 0)
69 typedef afs_proc_t * afs_lock_tracker_t;
70 # define MyPidxx (u.u_procp)
71 # define MyPidxx2Pid(x) (x ? (afs_int32)p_pid(x) : 0)
73 #elif defined(AFS_SGI64_ENV)
74 # if defined(AFS_SGI65_ENV)
75 typedef unsigned int afs_lock_tracker_t;
76 # define MyPidxx proc_pid(curproc())
77 # define MyPidxx2Pid(x) (x)
79 typedef unsigned int afs_lock_tracker_t;
80 # define MyPidxx current_pid()
81 # define MyPidxx2Pid(x) (x)
83 #elif defined(AFS_LINUX20_ENV)
84 typedef struct task_struct * afs_lock_tracker_t;
85 # define MyPidxx (current)
86 # define MyPidxx2Pid(x) (x? (x)->pid : 0)
87 #elif defined(AFS_DARWIN_ENV)
88 # if defined(AFS_DARWIN80_ENV)
89 typedef unsigned int afs_lock_tracker_t;
90 # define MyPidxx (proc_selfpid())
91 # define MyPidxx2Pid(x) (x)
93 typedef unsigned int afs_lock_tracker_t;
94 # define MyPidxx (current_proc()->p_pid )
95 # define MyPidxx2Pid(x) (x)
97 #elif defined(AFS_FBSD_ENV)
98 typedef unsigned int afs_lock_tracker_t;
99 # define MyPidxx (curproc->p_pid )
100 # define MyPidxx2Pid(x) (x)
101 #elif defined(AFS_NBSD40_ENV)
102 typedef unsigned int afs_lock_tracker_t;
103 #define MyPidxx osi_getpid() /* XXX could generalize this (above) */
104 #define MyPidxx2Pid(x) (x)
106 typedef unsigned int afs_lock_tracker_t;
107 # define MyPidxx (u.u_procp->p_pid )
108 # define MyPidxx2Pid(x) (x)
111 /* all locks wait on excl_locked except for READ_LOCK, which waits on readers_reading */
113 unsigned char wait_states; /* type of lockers waiting */
114 unsigned char excl_locked; /* anyone have boosted, shared or write lock? */
115 unsigned short readers_reading; /* # readers actually with read locks */
116 unsigned short num_waiting; /* probably need this soon */
117 unsigned short spare; /* not used now */
118 osi_timeval_t time_waiting; /* for statistics gathering */
119 #if defined(INSTRUMENT_LOCKS)
120 /* the following are useful for debugging
121 ** the field 'src_indicator' is updated only by ObtainLock() and
122 ** only for writes/shared locks. Hence, it indictes where in the
123 ** source code the shared/write lock was set.
125 afs_lock_tracker_t pid_last_reader; /* proceess id of last reader */
126 afs_lock_tracker_t pid_writer; /* process id of writer, else 0 */
127 unsigned int src_indicator; /* third param to ObtainLock() */
128 #endif /* INSTRUMENT_LOCKS */
130 typedef struct afs_lock afs_lock_t;
131 typedef struct afs_lock afs_rwlock_t;
135 #define SHARED_LOCK 4
136 /* this next is not a flag, but rather a parameter to Afs_Lock_Obtain */
137 #define BOOSTED_LOCK 6
139 /* next defines wait_states for which we wait on excl_locked */
140 #define EXCL_LOCKS (WRITE_LOCK|SHARED_LOCK)
145 extern int afs_trclock;
147 #define AFS_LOCK_TRACE_ENABLE 0
148 #if AFS_LOCK_TRACE_ENABLE
149 #define AFS_LOCK_TRACE(op, lock, type) \
150 if (afs_trclock) Afs_Lock_Trace(op, lock, type, __FILE__, __LINE__);
152 #define AFS_LOCK_TRACE(op, lock, type)
155 #if defined(INSTRUMENT_LOCKS)
157 #define ObtainReadLock(lock)\
159 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, READ_LOCK);\
160 if (!((lock)->excl_locked & WRITE_LOCK)) \
161 ((lock)->readers_reading)++; \
163 Afs_Lock_Obtain(lock, READ_LOCK); \
164 (lock)->pid_last_reader = MyPidxx; \
167 #define NBObtainReadLock(lock) \
168 (((lock)->excl_locked & WRITE_LOCK) ? EWOULDBLOCK : (((lock)->readers_reading++), ((lock)->pid_last_reader = MyPidxx), 0))
170 #define ObtainWriteLock(lock, src)\
172 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, WRITE_LOCK);\
173 if (!(lock)->excl_locked && !(lock)->readers_reading)\
174 (lock) -> excl_locked = WRITE_LOCK;\
176 Afs_Lock_Obtain(lock, WRITE_LOCK); \
177 (lock)->pid_writer = MyPidxx; \
178 (lock)->src_indicator = src;\
181 #define NBObtainWriteLock(lock, src) (((lock)->excl_locked || (lock)->readers_reading) ? EWOULDBLOCK : (((lock) -> excl_locked = WRITE_LOCK), ((lock)->pid_writer = MyPidxx), ((lock)->src_indicator = src), 0))
183 #define ObtainSharedLock(lock, src)\
185 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, SHARED_LOCK);\
186 if (!(lock)->excl_locked)\
187 (lock) -> excl_locked = SHARED_LOCK;\
189 Afs_Lock_Obtain(lock, SHARED_LOCK); \
190 (lock)->pid_writer = MyPidxx; \
191 (lock)->src_indicator = src;\
194 #define NBObtainSharedLock(lock, src) (((lock)->excl_locked) ? EWOULDBLOCK : (((lock) -> excl_locked = SHARED_LOCK), ((lock)->pid_writer = MyPidxx), ((lock)->src_indicator = src), 0))
196 #define UpgradeSToWLock(lock, src)\
198 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, BOOSTED_LOCK);\
199 if (!(lock)->readers_reading)\
200 (lock)->excl_locked = WRITE_LOCK;\
202 Afs_Lock_Obtain(lock, BOOSTED_LOCK); \
203 (lock)->pid_writer = MyPidxx; \
204 (lock)->src_indicator = src;\
207 /* this must only be called with a WRITE or boosted SHARED lock! */
208 #define ConvertWToSLock(lock)\
210 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, SHARED_LOCK);\
211 (lock)->excl_locked = SHARED_LOCK; \
212 if((lock)->wait_states) \
213 Afs_Lock_ReleaseR(lock); \
216 #define ConvertWToRLock(lock) \
218 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
219 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
220 ((lock)->readers_reading)++;\
221 (lock)->pid_last_reader = MyPidxx ; \
222 (lock)->pid_writer = 0;\
223 Afs_Lock_ReleaseR(lock);\
226 #define ConvertSToRLock(lock) \
228 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
229 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
230 ((lock)->readers_reading)++;\
231 (lock)->pid_last_reader = MyPidxx ; \
232 (lock)->pid_writer = 0;\
233 Afs_Lock_ReleaseR(lock);\
236 #define ReleaseReadLock(lock)\
238 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, READ_LOCK);\
239 if (!(--((lock)->readers_reading)) && (lock)->wait_states)\
240 Afs_Lock_ReleaseW(lock) ; \
241 if ( (lock)->pid_last_reader == MyPidxx ) \
242 (lock)->pid_last_reader =0;\
245 #define ReleaseWriteLock(lock)\
247 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, WRITE_LOCK);\
248 (lock)->excl_locked &= ~WRITE_LOCK;\
249 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
250 (lock)->pid_writer=0; \
253 /* can be used on shared or boosted (write) locks */
254 #define ReleaseSharedLock(lock)\
256 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, SHARED_LOCK);\
257 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
258 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
259 (lock)->pid_writer=0; \
262 #else /* INSTRUMENT_LOCKS */
264 #define ObtainReadLock(lock)\
266 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, READ_LOCK);\
267 if (!((lock)->excl_locked & WRITE_LOCK)) \
268 ((lock)->readers_reading)++; \
270 Afs_Lock_Obtain(lock, READ_LOCK); \
273 #define NBObtainReadLock(lock) \
274 (((lock)->excl_locked & WRITE_LOCK) ? EWOULDBLOCK : (((lock)->readers_reading++), 0))
276 #define ObtainWriteLock(lock, src)\
278 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, WRITE_LOCK);\
279 if (!(lock)->excl_locked && !(lock)->readers_reading)\
280 (lock) -> excl_locked = WRITE_LOCK;\
282 Afs_Lock_Obtain(lock, WRITE_LOCK); \
285 #define NBObtainWriteLock(lock, src) (((lock)->excl_locked || (lock)->readers_reading) ? EWOULDBLOCK : (((lock) -> excl_locked = WRITE_LOCK), 0))
287 #define ObtainSharedLock(lock, src)\
289 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, SHARED_LOCK);\
290 if (!(lock)->excl_locked)\
291 (lock) -> excl_locked = SHARED_LOCK;\
293 Afs_Lock_Obtain(lock, SHARED_LOCK); \
296 #define NBObtainSharedLock(lock, src) (((lock)->excl_locked) ? EWOULDBLOCK : (((lock) -> excl_locked = SHARED_LOCK), 0))
298 #define UpgradeSToWLock(lock, src)\
300 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, BOOSTED_LOCK);\
301 if (!(lock)->readers_reading)\
302 (lock)->excl_locked = WRITE_LOCK;\
304 Afs_Lock_Obtain(lock, BOOSTED_LOCK); \
307 /* this must only be called with a WRITE or boosted SHARED lock! */
308 #define ConvertWToSLock(lock)\
310 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, SHARED_LOCK);\
311 (lock)->excl_locked = SHARED_LOCK; \
312 if((lock)->wait_states) \
313 Afs_Lock_ReleaseR(lock); \
316 #define ConvertWToRLock(lock) \
318 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
319 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
320 ((lock)->readers_reading)++;\
321 Afs_Lock_ReleaseR(lock);\
324 #define ConvertSToRLock(lock) \
326 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
327 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
328 ((lock)->readers_reading)++;\
329 Afs_Lock_ReleaseR(lock);\
332 #define ReleaseReadLock(lock)\
334 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, READ_LOCK);\
335 if (!(--((lock)->readers_reading)) && (lock)->wait_states)\
336 Afs_Lock_ReleaseW(lock) ; \
339 #define ReleaseWriteLock(lock)\
341 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, WRITE_LOCK);\
342 (lock)->excl_locked &= ~WRITE_LOCK;\
343 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
346 /* can be used on shared or boosted (write) locks */
347 #define ReleaseSharedLock(lock)\
349 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, SHARED_LOCK);\
350 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
351 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
354 #endif /* INSTRUMENT_LOCKS */
356 /* I added this next macro to make sure it is safe to nuke a lock -- Mike K. */
357 #define LockWaiters(lock)\
358 ((int) ((lock)->num_waiting))
360 #define CheckLock(lock)\
361 ((lock)->excl_locked? (int) -1 : (int) (lock)->readers_reading)
363 #define WriteLocked(lock)\
364 ((lock)->excl_locked & WRITE_LOCK)
369 You can also use the lock package for handling parent locks for independently-lockable sets of
370 small objects. The concept here is that the parent lock is at the same level in the
371 locking hierarchy as the little locks, but certain restrictions apply.
373 The general usage pattern is as follows. You have a set of entries to search. When searching it, you
374 have a "scan" lock on the table. If you find what you're looking for, you drop the lock down
375 to a "hold" lock, lock the entry, and release the parent lock. If you don't find what
376 you're looking for, you create the entry, downgrade the "scan" lock to a "hold" lock,
377 lock the entry and unlock the parent.
379 To delete an item from the table, you initially obtain a "purge" lock on the parent. Unlike all
380 of the other parent lock modes described herein, in order to obtain a "purge" lock mode, you
381 must have released all locks on any items in the table. Once you have obtained the parent
382 lock in "purge" mode, you should check to see if the entry is locked. If its not locked, you
383 are free to delete the entry, knowing that no one else can attempt to obtain a lock
384 on the entry while you have the purge lock held on the parent. Unfortunately, if it *is* locked,
385 you can not lock it yourself and wait for the other dude to release it, since the entry's locker
386 may need to lock another entry before unlocking the entry you want (which would result in
387 deadlock). Instead, then, you must release the parent lock, and try again "later" (see Lock_Wait
388 for assistance in waiting until later). Unfortunately, this is the best locking paradigm I've yet
391 What are the advantages to this scheme? First, the use of the parent lock ensures that
392 two people don't try to add the same entry at the same time or delete an entry while someone
393 else is adding it. It also ensures that when one process is deleting an entry, no one else is
394 preparing to lock the entry. Furthermore, when obtaining a lock on a little entry, you
395 are only holding a "hold" lock on the parent lock, so that others may come in and search
396 the table during this time. Thus it will not hold up the system if a little entry takes
397 a great deal of time to free up.
399 Here's how to compute the compatibility matrix:
403 add no deletions, additions allowed, additions will be performed, will obtain little locks
404 hold no deletions, additions allowed, no additions will be performed, will obtain little locks
405 purge no deletions or additions allowed, deletions will be performed, don't obtain little locks
407 When we compute the locking matrix, we note that hold is compatible with hold and add.
408 Add is compatible only with hold. purge is not compatible with anything. This is the same
409 matrix as obtained by mapping add->S, hold->read and purge->write locks. Thus we
410 can use the locks above to solve this problem, and we do.
414 #endif /* __AFSLOCK_INCLUDE__ */