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))
23 #define AFS_NOBOZO_LOCK
26 #define INSTRUMENT_LOCKS
27 /* This is the max lock number in use. Please update it if you add any new
30 #define MAX_LOCK_NUMBER 780
33 short count; /* count of excl locks */
34 char flags; /* bit 1: is anyone waiting? */
35 char spare; /* for later */
36 char *proc; /* process holding the lock, really an afs_proc_t * */
38 #ifndef AFS_NOBOZO_LOCK
39 typedef struct afs_bozoLock afs_bozoLock_t;
42 typedef kmutex_t afs_bozoLock_t;
44 typedef struct afs_bozoLock afs_bozoLock_t;
46 #define afs_BozonLock(lock, avc)
47 #define afs_BozonUnlock(lock, avc)
48 #define afs_BozonInit(lock, nm)
49 #define afs_CheckBozonLock(lock) 0
50 #define afs_CheckBozonLockBlocking(lock) 0
53 #define AFS_BOZONWAITING 1 /* someone is waiting for this lock */
55 #define AFS_RWLOCK_INIT(lock, nm) Lock_Init(lock)
57 #define LOCK_INIT(lock, nm) Lock_Init(lock)
59 /* The following macros allow multi statement macros to be defined safely, i.e.
60 - the multi statement macro can be the object of an if statement;
61 - the call to the multi statement macro may be legally followed by a semi-colon.
62 BEGINMAC and ENDMAC have been tested with both the portable C compiler and
63 Hi-C. Both compilers were from the Palo Alto 4.2BSD software releases, and
64 both optimized out the constant loop code. For an example of the use
65 of BEGINMAC and ENDMAC, see the definition for ReleaseWriteLock, below.
66 An alternative to this, using "if(1)" for BEGINMAC is not used because it
67 may generate worse code with pcc, and may generate warning messages with hi-C.
71 #define ENDMAC } while (0)
73 #if defined(AFS_SUN57_ENV)
74 typedef kthread_t * afs_lock_tracker_t;
75 #define MyPidxx (curthread)
76 #define MyPidxx2Pid(x) (x ? ttoproc(x)->p_pid : 0)
77 #elif defined(AFS_SUN5_ENV) || defined(AFS_OBSD_ENV)
78 typedef unsigned int afs_lock_tracker_t;
79 #define MyPidxx (curproc->p_pid)
80 #define MyPidxx2Pid(x) (x)
82 #if defined(AFS_AIX41_ENV)
83 typedef tid_t afs_lock_tracker_t;
84 extern tid_t thread_self();
85 #define MyPidxx (thread_self())
86 #define MyPidxx2Pid(x) ((afs_int32)(x))
87 #else /* AFS_AIX41_ENV */
88 #if defined(AFS_HPUX101_ENV)
89 #if defined(AFS_HPUX1111_ENV)
90 typedef struct kthread * afs_lock_tracker_t;
91 #define MyPidxx (u.u_kthreadp)
92 #define MyPidxx2Pid(x) (x ? kt_tid(x) : 0)
94 typedef afs_proc_t * afs_lock_tracker_t;
95 #define MyPidxx (u.u_procp)
96 #define MyPidxx2Pid(x) (x ? (afs_int32)p_pid(x) : 0)
99 #if defined(AFS_SGI64_ENV)
100 #if defined(AFS_SGI65_ENV)
101 typedef unsigned int afs_lock_tracker_t;
102 #define MyPidxx proc_pid(curproc())
103 #define MyPidxx2Pid(x) (x)
105 typedef unsigned int afs_lock_tracker_t;
106 #define MyPidxx current_pid()
107 #define MyPidxx2Pid(x) (x)
109 #else /* AFS_SGI64_ENV */
110 #ifdef AFS_LINUX20_ENV
111 typedef struct task_struct * afs_lock_tracker_t;
112 #define MyPidxx (current)
113 #define MyPidxx2Pid(x) (x? (x)->pid : 0)
115 #if defined(AFS_DARWIN_ENV)
116 #if defined(AFS_DARWIN80_ENV)
117 typedef unsigned int afs_lock_tracker_t;
118 #define MyPidxx (proc_selfpid())
119 #define MyPidxx2Pid(x) (x)
121 typedef unsigned int afs_lock_tracker_t;
122 #define MyPidxx (current_proc()->p_pid )
123 #define MyPidxx2Pid(x) (x)
126 #if defined(AFS_FBSD_ENV)
127 typedef unsigned int afs_lock_tracker_t;
128 #define MyPidxx (curproc->p_pid )
129 #define MyPidxx2Pid(x) (x)
131 typedef unsigned int afs_lock_tracker_t;
132 #define MyPidxx (u.u_procp->p_pid )
133 #define MyPidxx2Pid(x) (x)
134 #endif /* AFS_FBSD_ENV */
135 #endif /* AFS_DARWIN_ENV */
136 #endif /* AFS_LINUX20_ENV */
137 #endif /* AFS_SGI64_ENV */
138 #endif /* AFS_HPUX101_ENV */
139 #endif /* AFS_AIX41_ENV */
142 /* all locks wait on excl_locked except for READ_LOCK, which waits on readers_reading */
144 unsigned char wait_states; /* type of lockers waiting */
145 unsigned char excl_locked; /* anyone have boosted, shared or write lock? */
146 unsigned short readers_reading; /* # readers actually with read locks */
147 unsigned short num_waiting; /* probably need this soon */
148 unsigned short spare; /* not used now */
149 osi_timeval_t time_waiting; /* for statistics gathering */
150 #if defined(INSTRUMENT_LOCKS)
151 /* the following are useful for debugging
152 ** the field 'src_indicator' is updated only by ObtainLock() and
153 ** only for writes/shared locks. Hence, it indictes where in the
154 ** source code the shared/write lock was set.
156 afs_lock_tracker_t pid_last_reader; /* proceess id of last reader */
157 afs_lock_tracker_t pid_writer; /* process id of writer, else 0 */
158 unsigned int src_indicator; /* third param to ObtainLock() */
159 #endif /* INSTRUMENT_LOCKS */
161 typedef struct afs_lock afs_lock_t;
162 typedef struct afs_lock afs_rwlock_t;
166 #define SHARED_LOCK 4
167 /* this next is not a flag, but rather a parameter to Afs_Lock_Obtain */
168 #define BOOSTED_LOCK 6
170 /* next defines wait_states for which we wait on excl_locked */
171 #define EXCL_LOCKS (WRITE_LOCK|SHARED_LOCK)
176 extern int afs_trclock;
178 #define AFS_LOCK_TRACE_ENABLE 0
179 #if AFS_LOCK_TRACE_ENABLE
180 #define AFS_LOCK_TRACE(op, lock, type) \
181 if (afs_trclock) Afs_Lock_Trace(op, lock, type, __FILE__, __LINE__);
183 #define AFS_LOCK_TRACE(op, lock, type)
186 #if defined(INSTRUMENT_LOCKS)
188 #define ObtainReadLock(lock)\
190 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, READ_LOCK);\
191 if (!((lock)->excl_locked & WRITE_LOCK)) \
192 ((lock)->readers_reading)++; \
194 Afs_Lock_Obtain(lock, READ_LOCK); \
195 (lock)->pid_last_reader = MyPidxx; \
198 #define NBObtainReadLock(lock) \
199 (((lock)->excl_locked & WRITE_LOCK) ? EWOULDBLOCK : (((lock)->readers_reading++), ((lock)->pid_last_reader = MyPidxx), 0))
201 #define ObtainWriteLock(lock, src)\
203 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, WRITE_LOCK);\
204 if (!(lock)->excl_locked && !(lock)->readers_reading)\
205 (lock) -> excl_locked = WRITE_LOCK;\
207 Afs_Lock_Obtain(lock, WRITE_LOCK); \
208 (lock)->pid_writer = MyPidxx; \
209 (lock)->src_indicator = src;\
212 #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))
214 #define ObtainSharedLock(lock, src)\
216 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, SHARED_LOCK);\
217 if (!(lock)->excl_locked)\
218 (lock) -> excl_locked = SHARED_LOCK;\
220 Afs_Lock_Obtain(lock, SHARED_LOCK); \
221 (lock)->pid_writer = MyPidxx; \
222 (lock)->src_indicator = src;\
225 #define NBObtainSharedLock(lock, src) (((lock)->excl_locked) ? EWOULDBLOCK : (((lock) -> excl_locked = SHARED_LOCK), ((lock)->pid_writer = MyPidxx), ((lock)->src_indicator = src), 0))
227 #define UpgradeSToWLock(lock, src)\
229 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, BOOSTED_LOCK);\
230 if (!(lock)->readers_reading)\
231 (lock)->excl_locked = WRITE_LOCK;\
233 Afs_Lock_Obtain(lock, BOOSTED_LOCK); \
234 (lock)->pid_writer = MyPidxx; \
235 (lock)->src_indicator = src;\
238 /* this must only be called with a WRITE or boosted SHARED lock! */
239 #define ConvertWToSLock(lock)\
241 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, SHARED_LOCK);\
242 (lock)->excl_locked = SHARED_LOCK; \
243 if((lock)->wait_states) \
244 Afs_Lock_ReleaseR(lock); \
247 #define ConvertWToRLock(lock) \
249 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
250 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
251 ((lock)->readers_reading)++;\
252 (lock)->pid_last_reader = MyPidxx ; \
253 (lock)->pid_writer = 0;\
254 Afs_Lock_ReleaseR(lock);\
257 #define ConvertSToRLock(lock) \
259 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
260 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
261 ((lock)->readers_reading)++;\
262 (lock)->pid_last_reader = MyPidxx ; \
263 (lock)->pid_writer = 0;\
264 Afs_Lock_ReleaseR(lock);\
267 #define ReleaseReadLock(lock)\
269 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, READ_LOCK);\
270 if (!(--((lock)->readers_reading)) && (lock)->wait_states)\
271 Afs_Lock_ReleaseW(lock) ; \
272 if ( (lock)->pid_last_reader == MyPidxx ) \
273 (lock)->pid_last_reader =0;\
276 #define ReleaseWriteLock(lock)\
278 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, WRITE_LOCK);\
279 (lock)->excl_locked &= ~WRITE_LOCK;\
280 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
281 (lock)->pid_writer=0; \
284 /* can be used on shared or boosted (write) locks */
285 #define ReleaseSharedLock(lock)\
287 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, SHARED_LOCK);\
288 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
289 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
290 (lock)->pid_writer=0; \
293 #else /* INSTRUMENT_LOCKS */
295 #define ObtainReadLock(lock)\
297 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, READ_LOCK);\
298 if (!((lock)->excl_locked & WRITE_LOCK)) \
299 ((lock)->readers_reading)++; \
301 Afs_Lock_Obtain(lock, READ_LOCK); \
304 #define NBObtainReadLock(lock) \
305 (((lock)->excl_locked & WRITE_LOCK) ? EWOULDBLOCK : (((lock)->readers_reading++), 0))
307 #define ObtainWriteLock(lock, src)\
309 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, WRITE_LOCK);\
310 if (!(lock)->excl_locked && !(lock)->readers_reading)\
311 (lock) -> excl_locked = WRITE_LOCK;\
313 Afs_Lock_Obtain(lock, WRITE_LOCK); \
316 #define NBObtainWriteLock(lock, src) (((lock)->excl_locked || (lock)->readers_reading) ? EWOULDBLOCK : (((lock) -> excl_locked = WRITE_LOCK), 0))
318 #define ObtainSharedLock(lock, src)\
320 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, SHARED_LOCK);\
321 if (!(lock)->excl_locked)\
322 (lock) -> excl_locked = SHARED_LOCK;\
324 Afs_Lock_Obtain(lock, SHARED_LOCK); \
327 #define NBObtainSharedLock(lock, src) (((lock)->excl_locked) ? EWOULDBLOCK : (((lock) -> excl_locked = SHARED_LOCK), 0))
329 #define UpgradeSToWLock(lock, src)\
331 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, BOOSTED_LOCK);\
332 if (!(lock)->readers_reading)\
333 (lock)->excl_locked = WRITE_LOCK;\
335 Afs_Lock_Obtain(lock, BOOSTED_LOCK); \
338 /* this must only be called with a WRITE or boosted SHARED lock! */
339 #define ConvertWToSLock(lock)\
341 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, SHARED_LOCK);\
342 (lock)->excl_locked = SHARED_LOCK; \
343 if((lock)->wait_states) \
344 Afs_Lock_ReleaseR(lock); \
347 #define ConvertWToRLock(lock) \
349 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
350 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
351 ((lock)->readers_reading)++;\
352 Afs_Lock_ReleaseR(lock);\
355 #define ConvertSToRLock(lock) \
357 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
358 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
359 ((lock)->readers_reading)++;\
360 Afs_Lock_ReleaseR(lock);\
363 #define ReleaseReadLock(lock)\
365 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, READ_LOCK);\
366 if (!(--((lock)->readers_reading)) && (lock)->wait_states)\
367 Afs_Lock_ReleaseW(lock) ; \
370 #define ReleaseWriteLock(lock)\
372 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, WRITE_LOCK);\
373 (lock)->excl_locked &= ~WRITE_LOCK;\
374 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
377 /* can be used on shared or boosted (write) locks */
378 #define ReleaseSharedLock(lock)\
380 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, SHARED_LOCK);\
381 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
382 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
385 #endif /* INSTRUMENT_LOCKS */
387 /* I added this next macro to make sure it is safe to nuke a lock -- Mike K. */
388 #define LockWaiters(lock)\
389 ((int) ((lock)->num_waiting))
391 #define CheckLock(lock)\
392 ((lock)->excl_locked? (int) -1 : (int) (lock)->readers_reading)
394 #define WriteLocked(lock)\
395 ((lock)->excl_locked & WRITE_LOCK)
400 You can also use the lock package for handling parent locks for independently-lockable sets of
401 small objects. The concept here is that the parent lock is at the same level in the
402 locking hierarchy as the little locks, but certain restrictions apply.
404 The general usage pattern is as follows. You have a set of entries to search. When searching it, you
405 have a "scan" lock on the table. If you find what you're looking for, you drop the lock down
406 to a "hold" lock, lock the entry, and release the parent lock. If you don't find what
407 you're looking for, you create the entry, downgrade the "scan" lock to a "hold" lock,
408 lock the entry and unlock the parent.
410 To delete an item from the table, you initially obtain a "purge" lock on the parent. Unlike all
411 of the other parent lock modes described herein, in order to obtain a "purge" lock mode, you
412 must have released all locks on any items in the table. Once you have obtained the parent
413 lock in "purge" mode, you should check to see if the entry is locked. If its not locked, you
414 are free to delete the entry, knowing that no one else can attempt to obtain a lock
415 on the entry while you have the purge lock held on the parent. Unfortunately, if it *is* locked,
416 you can not lock it yourself and wait for the other dude to release it, since the entry's locker
417 may need to lock another entry before unlocking the entry you want (which would result in
418 deadlock). Instead, then, you must release the parent lock, and try again "later" (see Lock_Wait
419 for assistance in waiting until later). Unfortunately, this is the best locking paradigm I've yet
422 What are the advantages to this scheme? First, the use of the parent lock ensures that
423 two people don't try to add the same entry at the same time or delete an entry while someone
424 else is adding it. It also ensures that when one process is deleting an entry, no one else is
425 preparing to lock the entry. Furthermore, when obtaining a lock on a little entry, you
426 are only holding a "hold" lock on the parent lock, so that others may come in and search
427 the table during this time. Thus it will not hold up the system if a little entry takes
428 a great deal of time to free up.
430 Here's how to compute the compatibility matrix:
434 add no deletions, additions allowed, additions will be performed, will obtain little locks
435 hold no deletions, additions allowed, no additions will be performed, will obtain little locks
436 purge no deletions or additions allowed, deletions will be performed, don't obtain little locks
438 When we compute the locking matrix, we note that hold is compatible with hold and add.
439 Add is compatible only with hold. purge is not compatible with anything. This is the same
440 matrix as obtained by mapping add->S, hold->read and purge->write locks. Thus we
441 can use the locks above to solve this problem, and we do.
445 #endif /* __AFSLOCK_INCLUDE__ */