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)
74 typedef unsigned int afs_lock_tracker_t;
75 # define MyPidxx (get_user_struct()->u_procp->p_pid )
76 # define MyPidxx2Pid(x) (x)
77 #elif defined(AFS_SUN57_ENV)
78 typedef kthread_t * afs_lock_tracker_t;
79 # define MyPidxx (curthread)
80 # define MyPidxx2Pid(x) (x ? ttoproc(x)->p_pid : 0)
81 #elif defined(AFS_SUN5_ENV) || defined(AFS_OBSD_ENV)
82 typedef unsigned int afs_lock_tracker_t;
83 # define MyPidxx (curproc->p_pid)
84 # define MyPidxx2Pid(x) (x)
85 #elif defined(AFS_AIX41_ENV)
86 typedef tid_t afs_lock_tracker_t;
87 extern tid_t thread_self();
88 # define MyPidxx (thread_self())
89 # define MyPidxx2Pid(x) ((afs_int32)(x))
90 #elif defined(AFS_HPUX101_ENV)
91 # if defined(AFS_HPUX1111_ENV)
92 typedef struct kthread * afs_lock_tracker_t;
93 # define MyPidxx (u.u_kthreadp)
94 # define MyPidxx2Pid(x) (x ? kt_tid(x) : 0)
96 typedef afs_proc_t * afs_lock_tracker_t;
97 # define MyPidxx (u.u_procp)
98 # define MyPidxx2Pid(x) (x ? (afs_int32)p_pid(x) : 0)
100 #elif defined(AFS_SGI64_ENV)
101 # if defined(AFS_SGI65_ENV)
102 typedef unsigned int afs_lock_tracker_t;
103 # define MyPidxx proc_pid(curproc())
104 # define MyPidxx2Pid(x) (x)
106 typedef unsigned int afs_lock_tracker_t;
107 # define MyPidxx current_pid()
108 # define MyPidxx2Pid(x) (x)
110 #elif defined(AFS_LINUX20_ENV)
111 typedef struct task_struct * afs_lock_tracker_t;
112 # define MyPidxx (current)
113 # define MyPidxx2Pid(x) (x? (x)->pid : 0)
114 #elif defined(AFS_DARWIN_ENV)
115 # if defined(AFS_DARWIN80_ENV)
116 typedef unsigned int afs_lock_tracker_t;
117 # define MyPidxx (proc_selfpid())
118 # define MyPidxx2Pid(x) (x)
120 typedef unsigned int afs_lock_tracker_t;
121 # define MyPidxx (current_proc()->p_pid )
122 # define MyPidxx2Pid(x) (x)
124 #elif defined(AFS_FBSD_ENV)
125 typedef unsigned int afs_lock_tracker_t;
126 # define MyPidxx (curproc->p_pid )
127 # define MyPidxx2Pid(x) (x)
128 #elif defined(AFS_NBSD40_ENV)
129 typedef unsigned int afs_lock_tracker_t;
130 #define MyPidxx osi_getpid() /* XXX could generalize this (above) */
131 #define MyPidxx2Pid(x) (x)
133 typedef unsigned int afs_lock_tracker_t;
134 # define MyPidxx (u.u_procp->p_pid )
135 # define MyPidxx2Pid(x) (x)
138 /* all locks wait on excl_locked except for READ_LOCK, which waits on readers_reading */
140 unsigned char wait_states; /* type of lockers waiting */
141 unsigned char excl_locked; /* anyone have boosted, shared or write lock? */
142 unsigned short readers_reading; /* # readers actually with read locks */
143 unsigned short num_waiting; /* probably need this soon */
144 unsigned short spare; /* not used now */
145 osi_timeval_t time_waiting; /* for statistics gathering */
146 #if defined(INSTRUMENT_LOCKS)
147 /* the following are useful for debugging
148 ** the field 'src_indicator' is updated only by ObtainLock() and
149 ** only for writes/shared locks. Hence, it indictes where in the
150 ** source code the shared/write lock was set.
152 afs_lock_tracker_t pid_last_reader; /* proceess id of last reader */
153 afs_lock_tracker_t pid_writer; /* process id of writer, else 0 */
154 unsigned int src_indicator; /* third param to ObtainLock() */
155 #endif /* INSTRUMENT_LOCKS */
157 typedef struct afs_lock afs_lock_t;
158 typedef struct afs_lock afs_rwlock_t;
162 #define SHARED_LOCK 4
163 /* this next is not a flag, but rather a parameter to Afs_Lock_Obtain */
164 #define BOOSTED_LOCK 6
166 /* next defines wait_states for which we wait on excl_locked */
167 #define EXCL_LOCKS (WRITE_LOCK|SHARED_LOCK)
172 extern int afs_trclock;
174 #define AFS_LOCK_TRACE_ENABLE 0
175 #if AFS_LOCK_TRACE_ENABLE
176 #define AFS_LOCK_TRACE(op, lock, type) \
177 if (afs_trclock) Afs_Lock_Trace(op, lock, type, __FILE__, __LINE__);
179 #define AFS_LOCK_TRACE(op, lock, type)
182 #if defined(INSTRUMENT_LOCKS)
184 #define ObtainReadLock(lock)\
186 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, READ_LOCK);\
187 if (!((lock)->excl_locked & WRITE_LOCK)) \
188 ((lock)->readers_reading)++; \
190 Afs_Lock_Obtain(lock, READ_LOCK); \
191 (lock)->pid_last_reader = MyPidxx; \
194 #define NBObtainReadLock(lock) \
195 (((lock)->excl_locked & WRITE_LOCK) ? EWOULDBLOCK : (((lock)->readers_reading++), ((lock)->pid_last_reader = MyPidxx), 0))
197 #define ObtainWriteLock(lock, src)\
199 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, WRITE_LOCK);\
200 if (!(lock)->excl_locked && !(lock)->readers_reading)\
201 (lock) -> excl_locked = WRITE_LOCK;\
203 Afs_Lock_Obtain(lock, WRITE_LOCK); \
204 (lock)->pid_writer = MyPidxx; \
205 (lock)->src_indicator = src;\
208 #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))
210 #define ObtainSharedLock(lock, src)\
212 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, SHARED_LOCK);\
213 if (!(lock)->excl_locked)\
214 (lock) -> excl_locked = SHARED_LOCK;\
216 Afs_Lock_Obtain(lock, SHARED_LOCK); \
217 (lock)->pid_writer = MyPidxx; \
218 (lock)->src_indicator = src;\
221 #define NBObtainSharedLock(lock, src) (((lock)->excl_locked) ? EWOULDBLOCK : (((lock) -> excl_locked = SHARED_LOCK), ((lock)->pid_writer = MyPidxx), ((lock)->src_indicator = src), 0))
223 #define UpgradeSToWLock(lock, src)\
225 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, BOOSTED_LOCK);\
226 if (!(lock)->readers_reading)\
227 (lock)->excl_locked = WRITE_LOCK;\
229 Afs_Lock_Obtain(lock, BOOSTED_LOCK); \
230 (lock)->pid_writer = MyPidxx; \
231 (lock)->src_indicator = src;\
234 /* this must only be called with a WRITE or boosted SHARED lock! */
235 #define ConvertWToSLock(lock)\
237 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, SHARED_LOCK);\
238 (lock)->excl_locked = SHARED_LOCK; \
239 if((lock)->wait_states) \
240 Afs_Lock_ReleaseR(lock); \
243 #define ConvertWToRLock(lock) \
245 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
246 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
247 ((lock)->readers_reading)++;\
248 (lock)->pid_last_reader = MyPidxx ; \
249 (lock)->pid_writer = 0;\
250 Afs_Lock_ReleaseR(lock);\
253 #define ConvertSToRLock(lock) \
255 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
256 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
257 ((lock)->readers_reading)++;\
258 (lock)->pid_last_reader = MyPidxx ; \
259 (lock)->pid_writer = 0;\
260 Afs_Lock_ReleaseR(lock);\
263 #define ReleaseReadLock(lock)\
265 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, READ_LOCK);\
266 if (!(--((lock)->readers_reading)) && (lock)->wait_states)\
267 Afs_Lock_ReleaseW(lock) ; \
268 if ( (lock)->pid_last_reader == MyPidxx ) \
269 (lock)->pid_last_reader =0;\
272 #define ReleaseWriteLock(lock)\
274 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, WRITE_LOCK);\
275 (lock)->excl_locked &= ~WRITE_LOCK;\
276 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
277 (lock)->pid_writer=0; \
280 /* can be used on shared or boosted (write) locks */
281 #define ReleaseSharedLock(lock)\
283 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, SHARED_LOCK);\
284 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
285 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
286 (lock)->pid_writer=0; \
289 #else /* INSTRUMENT_LOCKS */
291 #define ObtainReadLock(lock)\
293 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, READ_LOCK);\
294 if (!((lock)->excl_locked & WRITE_LOCK)) \
295 ((lock)->readers_reading)++; \
297 Afs_Lock_Obtain(lock, READ_LOCK); \
300 #define NBObtainReadLock(lock) \
301 (((lock)->excl_locked & WRITE_LOCK) ? EWOULDBLOCK : (((lock)->readers_reading++), 0))
303 #define ObtainWriteLock(lock, src)\
305 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, WRITE_LOCK);\
306 if (!(lock)->excl_locked && !(lock)->readers_reading)\
307 (lock) -> excl_locked = WRITE_LOCK;\
309 Afs_Lock_Obtain(lock, WRITE_LOCK); \
312 #define NBObtainWriteLock(lock, src) (((lock)->excl_locked || (lock)->readers_reading) ? EWOULDBLOCK : (((lock) -> excl_locked = WRITE_LOCK), 0))
314 #define ObtainSharedLock(lock, src)\
316 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, SHARED_LOCK);\
317 if (!(lock)->excl_locked)\
318 (lock) -> excl_locked = SHARED_LOCK;\
320 Afs_Lock_Obtain(lock, SHARED_LOCK); \
323 #define NBObtainSharedLock(lock, src) (((lock)->excl_locked) ? EWOULDBLOCK : (((lock) -> excl_locked = SHARED_LOCK), 0))
325 #define UpgradeSToWLock(lock, src)\
327 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, BOOSTED_LOCK);\
328 if (!(lock)->readers_reading)\
329 (lock)->excl_locked = WRITE_LOCK;\
331 Afs_Lock_Obtain(lock, BOOSTED_LOCK); \
334 /* this must only be called with a WRITE or boosted SHARED lock! */
335 #define ConvertWToSLock(lock)\
337 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, SHARED_LOCK);\
338 (lock)->excl_locked = SHARED_LOCK; \
339 if((lock)->wait_states) \
340 Afs_Lock_ReleaseR(lock); \
343 #define ConvertWToRLock(lock) \
345 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
346 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
347 ((lock)->readers_reading)++;\
348 Afs_Lock_ReleaseR(lock);\
351 #define ConvertSToRLock(lock) \
353 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
354 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
355 ((lock)->readers_reading)++;\
356 Afs_Lock_ReleaseR(lock);\
359 #define ReleaseReadLock(lock)\
361 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, READ_LOCK);\
362 if (!(--((lock)->readers_reading)) && (lock)->wait_states)\
363 Afs_Lock_ReleaseW(lock) ; \
366 #define ReleaseWriteLock(lock)\
368 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, WRITE_LOCK);\
369 (lock)->excl_locked &= ~WRITE_LOCK;\
370 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
373 /* can be used on shared or boosted (write) locks */
374 #define ReleaseSharedLock(lock)\
376 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, SHARED_LOCK);\
377 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
378 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
381 #endif /* INSTRUMENT_LOCKS */
383 /* I added this next macro to make sure it is safe to nuke a lock -- Mike K. */
384 #define LockWaiters(lock)\
385 ((int) ((lock)->num_waiting))
387 #define CheckLock(lock)\
388 ((lock)->excl_locked? (int) -1 : (int) (lock)->readers_reading)
390 #define WriteLocked(lock)\
391 ((lock)->excl_locked & WRITE_LOCK)
396 You can also use the lock package for handling parent locks for independently-lockable sets of
397 small objects. The concept here is that the parent lock is at the same level in the
398 locking hierarchy as the little locks, but certain restrictions apply.
400 The general usage pattern is as follows. You have a set of entries to search. When searching it, you
401 have a "scan" lock on the table. If you find what you're looking for, you drop the lock down
402 to a "hold" lock, lock the entry, and release the parent lock. If you don't find what
403 you're looking for, you create the entry, downgrade the "scan" lock to a "hold" lock,
404 lock the entry and unlock the parent.
406 To delete an item from the table, you initially obtain a "purge" lock on the parent. Unlike all
407 of the other parent lock modes described herein, in order to obtain a "purge" lock mode, you
408 must have released all locks on any items in the table. Once you have obtained the parent
409 lock in "purge" mode, you should check to see if the entry is locked. If its not locked, you
410 are free to delete the entry, knowing that no one else can attempt to obtain a lock
411 on the entry while you have the purge lock held on the parent. Unfortunately, if it *is* locked,
412 you can not lock it yourself and wait for the other dude to release it, since the entry's locker
413 may need to lock another entry before unlocking the entry you want (which would result in
414 deadlock). Instead, then, you must release the parent lock, and try again "later" (see Lock_Wait
415 for assistance in waiting until later). Unfortunately, this is the best locking paradigm I've yet
418 What are the advantages to this scheme? First, the use of the parent lock ensures that
419 two people don't try to add the same entry at the same time or delete an entry while someone
420 else is adding it. It also ensures that when one process is deleting an entry, no one else is
421 preparing to lock the entry. Furthermore, when obtaining a lock on a little entry, you
422 are only holding a "hold" lock on the parent lock, so that others may come in and search
423 the table during this time. Thus it will not hold up the system if a little entry takes
424 a great deal of time to free up.
426 Here's how to compute the compatibility matrix:
430 add no deletions, additions allowed, additions will be performed, will obtain little locks
431 hold no deletions, additions allowed, no additions will be performed, will obtain little locks
432 purge no deletions or additions allowed, deletions will be performed, don't obtain little locks
434 When we compute the locking matrix, we note that hold is compatible with hold and add.
435 Add is compatible only with hold. purge is not compatible with anything. This is the same
436 matrix as obtained by mapping add->S, hold->read and purge->write locks. Thus we
437 can use the locks above to solve this problem, and we do.
441 #endif /* __AFSLOCK_INCLUDE__ */