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)
129 typedef unsigned int afs_lock_tracker_t;
130 # define MyPidxx (u.u_procp->p_pid )
131 # define MyPidxx2Pid(x) (x)
134 /* all locks wait on excl_locked except for READ_LOCK, which waits on readers_reading */
136 unsigned char wait_states; /* type of lockers waiting */
137 unsigned char excl_locked; /* anyone have boosted, shared or write lock? */
138 unsigned short readers_reading; /* # readers actually with read locks */
139 unsigned short num_waiting; /* probably need this soon */
140 unsigned short spare; /* not used now */
141 osi_timeval_t time_waiting; /* for statistics gathering */
142 #if defined(INSTRUMENT_LOCKS)
143 /* the following are useful for debugging
144 ** the field 'src_indicator' is updated only by ObtainLock() and
145 ** only for writes/shared locks. Hence, it indictes where in the
146 ** source code the shared/write lock was set.
148 afs_lock_tracker_t pid_last_reader; /* proceess id of last reader */
149 afs_lock_tracker_t pid_writer; /* process id of writer, else 0 */
150 unsigned int src_indicator; /* third param to ObtainLock() */
151 #endif /* INSTRUMENT_LOCKS */
153 typedef struct afs_lock afs_lock_t;
154 typedef struct afs_lock afs_rwlock_t;
158 #define SHARED_LOCK 4
159 /* this next is not a flag, but rather a parameter to Afs_Lock_Obtain */
160 #define BOOSTED_LOCK 6
162 /* next defines wait_states for which we wait on excl_locked */
163 #define EXCL_LOCKS (WRITE_LOCK|SHARED_LOCK)
168 extern int afs_trclock;
170 #define AFS_LOCK_TRACE_ENABLE 0
171 #if AFS_LOCK_TRACE_ENABLE
172 #define AFS_LOCK_TRACE(op, lock, type) \
173 if (afs_trclock) Afs_Lock_Trace(op, lock, type, __FILE__, __LINE__);
175 #define AFS_LOCK_TRACE(op, lock, type)
178 #if defined(INSTRUMENT_LOCKS)
180 #define ObtainReadLock(lock)\
182 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, READ_LOCK);\
183 if (!((lock)->excl_locked & WRITE_LOCK)) \
184 ((lock)->readers_reading)++; \
186 Afs_Lock_Obtain(lock, READ_LOCK); \
187 (lock)->pid_last_reader = MyPidxx; \
190 #define NBObtainReadLock(lock) \
191 (((lock)->excl_locked & WRITE_LOCK) ? EWOULDBLOCK : (((lock)->readers_reading++), ((lock)->pid_last_reader = MyPidxx), 0))
193 #define ObtainWriteLock(lock, src)\
195 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, WRITE_LOCK);\
196 if (!(lock)->excl_locked && !(lock)->readers_reading)\
197 (lock) -> excl_locked = WRITE_LOCK;\
199 Afs_Lock_Obtain(lock, WRITE_LOCK); \
200 (lock)->pid_writer = MyPidxx; \
201 (lock)->src_indicator = src;\
204 #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))
206 #define ObtainSharedLock(lock, src)\
208 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, SHARED_LOCK);\
209 if (!(lock)->excl_locked)\
210 (lock) -> excl_locked = SHARED_LOCK;\
212 Afs_Lock_Obtain(lock, SHARED_LOCK); \
213 (lock)->pid_writer = MyPidxx; \
214 (lock)->src_indicator = src;\
217 #define NBObtainSharedLock(lock, src) (((lock)->excl_locked) ? EWOULDBLOCK : (((lock) -> excl_locked = SHARED_LOCK), ((lock)->pid_writer = MyPidxx), ((lock)->src_indicator = src), 0))
219 #define UpgradeSToWLock(lock, src)\
221 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, BOOSTED_LOCK);\
222 if (!(lock)->readers_reading)\
223 (lock)->excl_locked = WRITE_LOCK;\
225 Afs_Lock_Obtain(lock, BOOSTED_LOCK); \
226 (lock)->pid_writer = MyPidxx; \
227 (lock)->src_indicator = src;\
230 /* this must only be called with a WRITE or boosted SHARED lock! */
231 #define ConvertWToSLock(lock)\
233 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, SHARED_LOCK);\
234 (lock)->excl_locked = SHARED_LOCK; \
235 if((lock)->wait_states) \
236 Afs_Lock_ReleaseR(lock); \
239 #define ConvertWToRLock(lock) \
241 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
242 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
243 ((lock)->readers_reading)++;\
244 (lock)->pid_last_reader = MyPidxx ; \
245 (lock)->pid_writer = 0;\
246 Afs_Lock_ReleaseR(lock);\
249 #define ConvertSToRLock(lock) \
251 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
252 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
253 ((lock)->readers_reading)++;\
254 (lock)->pid_last_reader = MyPidxx ; \
255 (lock)->pid_writer = 0;\
256 Afs_Lock_ReleaseR(lock);\
259 #define ReleaseReadLock(lock)\
261 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, READ_LOCK);\
262 if (!(--((lock)->readers_reading)) && (lock)->wait_states)\
263 Afs_Lock_ReleaseW(lock) ; \
264 if ( (lock)->pid_last_reader == MyPidxx ) \
265 (lock)->pid_last_reader =0;\
268 #define ReleaseWriteLock(lock)\
270 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, WRITE_LOCK);\
271 (lock)->excl_locked &= ~WRITE_LOCK;\
272 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
273 (lock)->pid_writer=0; \
276 /* can be used on shared or boosted (write) locks */
277 #define ReleaseSharedLock(lock)\
279 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, SHARED_LOCK);\
280 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
281 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
282 (lock)->pid_writer=0; \
285 #else /* INSTRUMENT_LOCKS */
287 #define ObtainReadLock(lock)\
289 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, READ_LOCK);\
290 if (!((lock)->excl_locked & WRITE_LOCK)) \
291 ((lock)->readers_reading)++; \
293 Afs_Lock_Obtain(lock, READ_LOCK); \
296 #define NBObtainReadLock(lock) \
297 (((lock)->excl_locked & WRITE_LOCK) ? EWOULDBLOCK : (((lock)->readers_reading++), 0))
299 #define ObtainWriteLock(lock, src)\
301 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, WRITE_LOCK);\
302 if (!(lock)->excl_locked && !(lock)->readers_reading)\
303 (lock) -> excl_locked = WRITE_LOCK;\
305 Afs_Lock_Obtain(lock, WRITE_LOCK); \
308 #define NBObtainWriteLock(lock, src) (((lock)->excl_locked || (lock)->readers_reading) ? EWOULDBLOCK : (((lock) -> excl_locked = WRITE_LOCK), 0))
310 #define ObtainSharedLock(lock, src)\
312 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, SHARED_LOCK);\
313 if (!(lock)->excl_locked)\
314 (lock) -> excl_locked = SHARED_LOCK;\
316 Afs_Lock_Obtain(lock, SHARED_LOCK); \
319 #define NBObtainSharedLock(lock, src) (((lock)->excl_locked) ? EWOULDBLOCK : (((lock) -> excl_locked = SHARED_LOCK), 0))
321 #define UpgradeSToWLock(lock, src)\
323 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, BOOSTED_LOCK);\
324 if (!(lock)->readers_reading)\
325 (lock)->excl_locked = WRITE_LOCK;\
327 Afs_Lock_Obtain(lock, BOOSTED_LOCK); \
330 /* this must only be called with a WRITE or boosted SHARED lock! */
331 #define ConvertWToSLock(lock)\
333 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, SHARED_LOCK);\
334 (lock)->excl_locked = SHARED_LOCK; \
335 if((lock)->wait_states) \
336 Afs_Lock_ReleaseR(lock); \
339 #define ConvertWToRLock(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 ConvertSToRLock(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 ReleaseReadLock(lock)\
357 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, READ_LOCK);\
358 if (!(--((lock)->readers_reading)) && (lock)->wait_states)\
359 Afs_Lock_ReleaseW(lock) ; \
362 #define ReleaseWriteLock(lock)\
364 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, WRITE_LOCK);\
365 (lock)->excl_locked &= ~WRITE_LOCK;\
366 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
369 /* can be used on shared or boosted (write) locks */
370 #define ReleaseSharedLock(lock)\
372 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, SHARED_LOCK);\
373 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
374 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
377 #endif /* INSTRUMENT_LOCKS */
379 /* I added this next macro to make sure it is safe to nuke a lock -- Mike K. */
380 #define LockWaiters(lock)\
381 ((int) ((lock)->num_waiting))
383 #define CheckLock(lock)\
384 ((lock)->excl_locked? (int) -1 : (int) (lock)->readers_reading)
386 #define WriteLocked(lock)\
387 ((lock)->excl_locked & WRITE_LOCK)
392 You can also use the lock package for handling parent locks for independently-lockable sets of
393 small objects. The concept here is that the parent lock is at the same level in the
394 locking hierarchy as the little locks, but certain restrictions apply.
396 The general usage pattern is as follows. You have a set of entries to search. When searching it, you
397 have a "scan" lock on the table. If you find what you're looking for, you drop the lock down
398 to a "hold" lock, lock the entry, and release the parent lock. If you don't find what
399 you're looking for, you create the entry, downgrade the "scan" lock to a "hold" lock,
400 lock the entry and unlock the parent.
402 To delete an item from the table, you initially obtain a "purge" lock on the parent. Unlike all
403 of the other parent lock modes described herein, in order to obtain a "purge" lock mode, you
404 must have released all locks on any items in the table. Once you have obtained the parent
405 lock in "purge" mode, you should check to see if the entry is locked. If its not locked, you
406 are free to delete the entry, knowing that no one else can attempt to obtain a lock
407 on the entry while you have the purge lock held on the parent. Unfortunately, if it *is* locked,
408 you can not lock it yourself and wait for the other dude to release it, since the entry's locker
409 may need to lock another entry before unlocking the entry you want (which would result in
410 deadlock). Instead, then, you must release the parent lock, and try again "later" (see Lock_Wait
411 for assistance in waiting until later). Unfortunately, this is the best locking paradigm I've yet
414 What are the advantages to this scheme? First, the use of the parent lock ensures that
415 two people don't try to add the same entry at the same time or delete an entry while someone
416 else is adding it. It also ensures that when one process is deleting an entry, no one else is
417 preparing to lock the entry. Furthermore, when obtaining a lock on a little entry, you
418 are only holding a "hold" lock on the parent lock, so that others may come in and search
419 the table during this time. Thus it will not hold up the system if a little entry takes
420 a great deal of time to free up.
422 Here's how to compute the compatibility matrix:
426 add no deletions, additions allowed, additions will be performed, will obtain little locks
427 hold no deletions, additions allowed, no additions will be performed, will obtain little locks
428 purge no deletions or additions allowed, deletions will be performed, don't obtain little locks
430 When we compute the locking matrix, we note that hold is compatible with hold and add.
431 Add is compatible only with hold. purge is not compatible with anything. This is the same
432 matrix as obtained by mapping add->S, hold->read and purge->write locks. Thus we
433 can use the locks above to solve this problem, and we do.
437 #endif /* __AFSLOCK_INCLUDE__ */