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 #if (defined(AFS_SUN5_ENV)) || defined(AFS_OSF_ENV)
23 #define AFS_NOBOZO_LOCK
26 #if !defined(AFS_OSF20_ENV) || defined(AFS_OSF30_ENV) || defined(AFS_OSF32_ENV)
27 /* We do not instrument locks on osf20 because the vcache structure
28 ** exceeds the maximim possible limit for a vnode.
30 #define INSTRUMENT_LOCKS
31 /* This is the max lock number in use. Please update it if you add any new
34 #define MAX_LOCK_NUMBER 700
38 short count; /* count of excl locks */
39 char flags; /* bit 1: is anyone waiting? */
40 char spare; /* for later */
41 char *proc; /* process holding the lock, really a struct proc * */
43 #ifndef AFS_NOBOZO_LOCK
44 typedef struct afs_bozoLock afs_bozoLock_t;
47 typedef kmutex_t afs_bozoLock_t;
49 typedef struct afs_bozoLock afs_bozoLock_t;
51 #define afs_BozonLock(lock, avc)
52 #define afs_BozonUnlock(lock, avc)
53 #define afs_BozonInit(lock, nm)
54 #define afs_CheckBozonLock(lock) 0
55 #define afs_CheckBozonLockBlocking(lock) 0
58 #define AFS_BOZONWAITING 1 /* someone is waiting for this lock */
60 #undef MObtainWriteLock /* Defined also in ../rx/rx_machdep.h" */
61 #undef MReleaseWriteLock
62 #define MObtainReadLock(lock) ObtainReadLock(lock)
63 #define MObtainWriteLock(lock,src) ObtainWriteLock(lock,src)
64 #define MObtainSharedLock(lock,src) ObtainSharedLock(lock,src)
65 #define MUpgradeSToWLock(lock,src) UpgradeSToWLock(lock,src)
66 #define MConvertWToSLock(lock) ConvertWToSLock(lock)
67 #define MReleaseReadLock(lock) ReleaseReadLock(lock)
68 #define MReleaseWriteLock(lock) ReleaseWriteLock(lock)
69 #define MReleaseSharedLock(lock) ReleaseSharedLock(lock)
71 #define RWLOCK_INIT(lock, nm) Lock_Init(lock)
73 #define LOCK_INIT(lock, nm) Lock_Init(lock)
75 /* The following macros allow multi statement macros to be defined safely, i.e.
76 - the multi statement macro can be the object of an if statement;
77 - the call to the multi statement macro may be legally followed by a semi-colon.
78 BEGINMAC and ENDMAC have been tested with both the portable C compiler and
79 Hi-C. Both compilers were from the Palo Alto 4.2BSD software releases, and
80 both optimized out the constant loop code. For an example of the use
81 of BEGINMAC and ENDMAC, see the definition for ReleaseWriteLock, below.
82 An alternative to this, using "if(1)" for BEGINMAC is not used because it
83 may generate worse code with pcc, and may generate warning messages with hi-C.
87 #define ENDMAC } while (0)
89 #if defined(AFS_SUN57_ENV)
90 #define MyPidxx (curthread->t_tid)
92 #if defined(AFS_OBSD_ENV) || defined(AFS_SUN5_ENV)
93 #define MyPidxx (curproc->p_pid)
95 #if defined(AFS_AIX41_ENV)
96 extern tid_t thread_self();
97 #define MyPidxx thread_self()
98 #else /* AFS_AIX41_ENV */
99 #if defined(AFS_HPUX101_ENV)
100 #define MyPidxx ((int)p_pid(u.u_procp))
102 #if defined(AFS_SGI64_ENV)
103 #if defined(AFS_SGI65_ENV)
104 #define MyPidxx proc_pid(curproc())
106 #define MyPidxx current_pid()
108 #else /* AFS_SGI64_ENV */
109 #ifdef AFS_LINUX20_ENV
110 #define MyPidxx current->pid
112 #if defined(AFS_DARWIN_ENV)
113 #if defined(AFS_DARWIN80_ENV)
114 #define MyPidxx (proc_selfpid())
116 #define MyPidxx (current_proc()->p_pid )
119 #if defined(AFS_FBSD_ENV)
120 #define MyPidxx (curproc->p_pid )
122 #define MyPidxx (u.u_procp->p_pid )
123 #endif /* AFS_FBSD_ENV */
124 #endif /* AFS_DARWIN_ENV */
125 #endif /* AFS_LINUX20_ENV */
126 #endif /* AFS_SGI64_ENV */
127 #endif /* AFS_HPUX101_ENV */
128 #endif /* AFS_AIX41_ENV */
132 /* all locks wait on excl_locked except for READ_LOCK, which waits on readers_reading */
134 unsigned char wait_states; /* type of lockers waiting */
135 unsigned char excl_locked; /* anyone have boosted, shared or write lock? */
136 unsigned short readers_reading; /* # readers actually with read locks */
137 unsigned short num_waiting; /* probably need this soon */
138 unsigned short spare; /* not used now */
139 osi_timeval_t time_waiting; /* for statistics gathering */
140 #if defined(INSTRUMENT_LOCKS)
141 /* the following are useful for debugging
142 ** the field 'src_indicator' is updated only by ObtainLock() and
143 ** only for writes/shared locks. Hence, it indictes where in the
144 ** source code the shared/write lock was set.
146 unsigned int pid_last_reader; /* proceess id of last reader */
147 unsigned int pid_writer; /* process id of writer, else 0 */
148 unsigned int src_indicator; /* third param to ObtainLock() */
149 #endif /* INSTRUMENT_LOCKS */
151 typedef struct afs_lock afs_lock_t;
152 typedef struct afs_lock afs_rwlock_t;
156 #define SHARED_LOCK 4
157 /* this next is not a flag, but rather a parameter to Afs_Lock_Obtain */
158 #define BOOSTED_LOCK 6
160 /* next defines wait_states for which we wait on excl_locked */
161 #define EXCL_LOCKS (WRITE_LOCK|SHARED_LOCK)
166 extern int afs_trclock;
168 #define AFS_LOCK_TRACE_ENABLE 0
169 #if AFS_LOCK_TRACE_ENABLE
170 #define AFS_LOCK_TRACE(op, lock, type) \
171 if (afs_trclock) Afs_Lock_Trace(op, lock, type, __FILE__, __LINE__);
173 #define AFS_LOCK_TRACE(op, lock, type)
176 #if defined(INSTRUMENT_LOCKS)
178 #define ObtainReadLock(lock)\
180 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, READ_LOCK);\
181 if (!((lock)->excl_locked & WRITE_LOCK)) \
182 ((lock)->readers_reading)++; \
184 Afs_Lock_Obtain(lock, READ_LOCK); \
185 (lock)->pid_last_reader = MyPidxx; \
188 #define ObtainWriteLock(lock, src)\
190 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, WRITE_LOCK);\
191 if (!(lock)->excl_locked && !(lock)->readers_reading)\
192 (lock) -> excl_locked = WRITE_LOCK;\
194 Afs_Lock_Obtain(lock, WRITE_LOCK); \
195 (lock)->pid_writer = MyPidxx; \
196 (lock)->src_indicator = src;\
199 #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))
201 #define ObtainSharedLock(lock, src)\
203 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, SHARED_LOCK);\
204 if (!(lock)->excl_locked)\
205 (lock) -> excl_locked = SHARED_LOCK;\
207 Afs_Lock_Obtain(lock, SHARED_LOCK); \
208 (lock)->pid_writer = MyPidxx; \
209 (lock)->src_indicator = src;\
212 #define NBObtainSharedLock(lock, src) (((lock)->excl_locked) ? EWOULDBLOCK : (((lock) -> excl_locked = SHARED_LOCK), ((lock)->pid_writer = MyPidxx), ((lock)->src_indicator = src), 0))
214 #define UpgradeSToWLock(lock, src)\
216 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, BOOSTED_LOCK);\
217 if (!(lock)->readers_reading)\
218 (lock)->excl_locked = WRITE_LOCK;\
220 Afs_Lock_Obtain(lock, BOOSTED_LOCK); \
221 (lock)->pid_writer = MyPidxx; \
222 (lock)->src_indicator = src;\
225 /* this must only be called with a WRITE or boosted SHARED lock! */
226 #define ConvertWToSLock(lock)\
228 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, SHARED_LOCK);\
229 (lock)->excl_locked = SHARED_LOCK; \
230 if((lock)->wait_states) \
231 Afs_Lock_ReleaseR(lock); \
234 #define ConvertWToRLock(lock) \
236 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
237 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
238 ((lock)->readers_reading)++;\
239 (lock)->pid_last_reader = MyPidxx ; \
240 (lock)->pid_writer = 0;\
241 Afs_Lock_ReleaseR(lock);\
244 #define ConvertSToRLock(lock) \
246 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
247 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
248 ((lock)->readers_reading)++;\
249 (lock)->pid_last_reader = MyPidxx ; \
250 (lock)->pid_writer = 0;\
251 Afs_Lock_ReleaseR(lock);\
254 #define ReleaseReadLock(lock)\
256 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, READ_LOCK);\
257 if (!(--((lock)->readers_reading)) && (lock)->wait_states)\
258 Afs_Lock_ReleaseW(lock) ; \
259 if ( (lock)->pid_last_reader == MyPidxx ) \
260 (lock)->pid_last_reader =0;\
263 #define ReleaseWriteLock(lock)\
265 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, WRITE_LOCK);\
266 (lock)->excl_locked &= ~WRITE_LOCK;\
267 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
268 (lock)->pid_writer=0; \
271 /* can be used on shared or boosted (write) locks */
272 #define ReleaseSharedLock(lock)\
274 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, SHARED_LOCK);\
275 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
276 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
277 (lock)->pid_writer=0; \
280 #else /* INSTRUMENT_LOCKS */
282 #define ObtainReadLock(lock)\
284 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, READ_LOCK);\
285 if (!((lock)->excl_locked & WRITE_LOCK)) \
286 ((lock)->readers_reading)++; \
288 Afs_Lock_Obtain(lock, READ_LOCK); \
291 #define ObtainWriteLock(lock, src)\
293 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, WRITE_LOCK);\
294 if (!(lock)->excl_locked && !(lock)->readers_reading)\
295 (lock) -> excl_locked = WRITE_LOCK;\
297 Afs_Lock_Obtain(lock, WRITE_LOCK); \
300 #define NBObtainWriteLock(lock, src) (((lock)->excl_locked || (lock)->readers_reading) ? EWOULDBLOCK : (((lock) -> excl_locked = WRITE_LOCK), 0))
302 #define ObtainSharedLock(lock, src)\
304 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, SHARED_LOCK);\
305 if (!(lock)->excl_locked)\
306 (lock) -> excl_locked = SHARED_LOCK;\
308 Afs_Lock_Obtain(lock, SHARED_LOCK); \
311 #define NBObtainSharedLock(lock, src) (((lock)->excl_locked) ? EWOULDBLOCK : (((lock) -> excl_locked = SHARED_LOCK), 0))
313 #define UpgradeSToWLock(lock, src)\
315 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, BOOSTED_LOCK);\
316 if (!(lock)->readers_reading)\
317 (lock)->excl_locked = WRITE_LOCK;\
319 Afs_Lock_Obtain(lock, BOOSTED_LOCK); \
322 /* this must only be called with a WRITE or boosted SHARED lock! */
323 #define ConvertWToSLock(lock)\
325 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, SHARED_LOCK);\
326 (lock)->excl_locked = SHARED_LOCK; \
327 if((lock)->wait_states) \
328 Afs_Lock_ReleaseR(lock); \
331 #define ConvertWToRLock(lock) \
333 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
334 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
335 ((lock)->readers_reading)++;\
336 Afs_Lock_ReleaseR(lock);\
339 #define ConvertSToRLock(lock) \
341 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
342 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
343 ((lock)->readers_reading)++;\
344 Afs_Lock_ReleaseR(lock);\
347 #define ReleaseReadLock(lock)\
349 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, READ_LOCK);\
350 if (!(--((lock)->readers_reading)) && (lock)->wait_states)\
351 Afs_Lock_ReleaseW(lock) ; \
354 #define ReleaseWriteLock(lock)\
356 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, WRITE_LOCK);\
357 (lock)->excl_locked &= ~WRITE_LOCK;\
358 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
361 /* can be used on shared or boosted (write) locks */
362 #define ReleaseSharedLock(lock)\
364 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, SHARED_LOCK);\
365 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
366 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
369 #endif /* INSTRUMENT_LOCKS */
371 /* I added this next macro to make sure it is safe to nuke a lock -- Mike K. */
372 #define LockWaiters(lock)\
373 ((int) ((lock)->num_waiting))
375 #define CheckLock(lock)\
376 ((lock)->excl_locked? (int) -1 : (int) (lock)->readers_reading)
378 #define WriteLocked(lock)\
379 ((lock)->excl_locked & WRITE_LOCK)
384 You can also use the lock package for handling parent locks for independently-lockable sets of
385 small objects. The concept here is that the parent lock is at the same level in the
386 locking hierarchy as the little locks, but certain restrictions apply.
388 The general usage pattern is as follows. You have a set of entries to search. When searching it, you
389 have a "scan" lock on the table. If you find what you're looking for, you drop the lock down
390 to a "hold" lock, lock the entry, and release the parent lock. If you don't find what
391 you're looking for, you create the entry, downgrade the "scan" lock to a "hold" lock,
392 lock the entry and unlock the parent.
394 To delete an item from the table, you initially obtain a "purge" lock on the parent. Unlike all
395 of the other parent lock modes described herein, in order to obtain a "purge" lock mode, you
396 must have released all locks on any items in the table. Once you have obtained the parent
397 lock in "purge" mode, you should check to see if the entry is locked. If its not locked, you
398 are free to delete the entry, knowing that no one else can attempt to obtain a lock
399 on the entry while you have the purge lock held on the parent. Unfortunately, if it *is* locked,
400 you can not lock it yourself and wait for the other dude to release it, since the entry's locker
401 may need to lock another entry before unlocking the entry you want (which would result in
402 deadlock). Instead, then, you must release the parent lock, and try again "later" (see Lock_Wait
403 for assistance in waiting until later). Unfortunately, this is the best locking paradigm I've yet
406 What are the advantages to this scheme? First, the use of the parent lock ensures that
407 two people don't try to add the same entry at the same time or delete an entry while someone
408 else is adding it. It also ensures that when one process is deleting an entry, no one else is
409 preparing to lock the entry. Furthermore, when obtaining a lock on a little entry, you
410 are only holding a "hold" lock on the parent lock, so that others may come in and search
411 the table during this time. Thus it will not hold up the system if a little entry takes
412 a great deal of time to free up.
414 Here's how to compute the compatibility matrix:
418 add no deletions, additions allowed, additions will be performed, will obtain little locks
419 hold no deletions, additions allowed, no additions will be performed, will obtain little locks
420 purge no deletions or additions allowed, deletions will be performed, don't obtain little locks
422 When we compute the locking matrix, we note that hold is compatible with hold and add.
423 Add is compatible only with hold. purge is not compatible with anything. This is the same
424 matrix as obtained by mapping add->S, hold->read and purge->write locks. Thus we
425 can use the locks above to solve this problem, and we do.
429 #endif /* __AFSLOCK_INCLUDE__ */