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)
81 #elif defined(AFS_AIX41_ENV)
82 typedef tid_t afs_lock_tracker_t;
83 extern tid_t thread_self();
84 # define MyPidxx (thread_self())
85 # define MyPidxx2Pid(x) ((afs_int32)(x))
86 #elif defined(AFS_HPUX101_ENV)
87 # if defined(AFS_HPUX1111_ENV)
88 typedef struct kthread * afs_lock_tracker_t;
89 # define MyPidxx (u.u_kthreadp)
90 # define MyPidxx2Pid(x) (x ? kt_tid(x) : 0)
92 typedef afs_proc_t * afs_lock_tracker_t;
93 # define MyPidxx (u.u_procp)
94 # define MyPidxx2Pid(x) (x ? (afs_int32)p_pid(x) : 0)
96 #elif defined(AFS_SGI64_ENV)
97 # if defined(AFS_SGI65_ENV)
98 typedef unsigned int afs_lock_tracker_t;
99 # define MyPidxx proc_pid(curproc())
100 # define MyPidxx2Pid(x) (x)
102 typedef unsigned int afs_lock_tracker_t;
103 # define MyPidxx current_pid()
104 # define MyPidxx2Pid(x) (x)
106 #elif defined(AFS_LINUX20_ENV)
107 typedef struct task_struct * afs_lock_tracker_t;
108 # define MyPidxx (current)
109 # define MyPidxx2Pid(x) (x? (x)->pid : 0)
110 #elif defined(AFS_DARWIN_ENV)
111 # if defined(AFS_DARWIN80_ENV)
112 typedef unsigned int afs_lock_tracker_t;
113 # define MyPidxx (proc_selfpid())
114 # define MyPidxx2Pid(x) (x)
116 typedef unsigned int afs_lock_tracker_t;
117 # define MyPidxx (current_proc()->p_pid )
118 # define MyPidxx2Pid(x) (x)
120 #elif defined(AFS_FBSD_ENV)
121 typedef unsigned int afs_lock_tracker_t;
122 # define MyPidxx (curproc->p_pid )
123 # define MyPidxx2Pid(x) (x)
125 typedef unsigned int afs_lock_tracker_t;
126 # define MyPidxx (u.u_procp->p_pid )
127 # define MyPidxx2Pid(x) (x)
130 /* all locks wait on excl_locked except for READ_LOCK, which waits on readers_reading */
132 unsigned char wait_states; /* type of lockers waiting */
133 unsigned char excl_locked; /* anyone have boosted, shared or write lock? */
134 unsigned short readers_reading; /* # readers actually with read locks */
135 unsigned short num_waiting; /* probably need this soon */
136 unsigned short spare; /* not used now */
137 osi_timeval_t time_waiting; /* for statistics gathering */
138 #if defined(INSTRUMENT_LOCKS)
139 /* the following are useful for debugging
140 ** the field 'src_indicator' is updated only by ObtainLock() and
141 ** only for writes/shared locks. Hence, it indictes where in the
142 ** source code the shared/write lock was set.
144 afs_lock_tracker_t pid_last_reader; /* proceess id of last reader */
145 afs_lock_tracker_t pid_writer; /* process id of writer, else 0 */
146 unsigned int src_indicator; /* third param to ObtainLock() */
147 #endif /* INSTRUMENT_LOCKS */
149 typedef struct afs_lock afs_lock_t;
150 typedef struct afs_lock afs_rwlock_t;
154 #define SHARED_LOCK 4
155 /* this next is not a flag, but rather a parameter to Afs_Lock_Obtain */
156 #define BOOSTED_LOCK 6
158 /* next defines wait_states for which we wait on excl_locked */
159 #define EXCL_LOCKS (WRITE_LOCK|SHARED_LOCK)
164 extern int afs_trclock;
166 #define AFS_LOCK_TRACE_ENABLE 0
167 #if AFS_LOCK_TRACE_ENABLE
168 #define AFS_LOCK_TRACE(op, lock, type) \
169 if (afs_trclock) Afs_Lock_Trace(op, lock, type, __FILE__, __LINE__);
171 #define AFS_LOCK_TRACE(op, lock, type)
174 #if defined(INSTRUMENT_LOCKS)
176 #define ObtainReadLock(lock)\
178 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, READ_LOCK);\
179 if (!((lock)->excl_locked & WRITE_LOCK)) \
180 ((lock)->readers_reading)++; \
182 Afs_Lock_Obtain(lock, READ_LOCK); \
183 (lock)->pid_last_reader = MyPidxx; \
186 #define NBObtainReadLock(lock) \
187 (((lock)->excl_locked & WRITE_LOCK) ? EWOULDBLOCK : (((lock)->readers_reading++), ((lock)->pid_last_reader = MyPidxx), 0))
189 #define ObtainWriteLock(lock, src)\
191 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, WRITE_LOCK);\
192 if (!(lock)->excl_locked && !(lock)->readers_reading)\
193 (lock) -> excl_locked = WRITE_LOCK;\
195 Afs_Lock_Obtain(lock, WRITE_LOCK); \
196 (lock)->pid_writer = MyPidxx; \
197 (lock)->src_indicator = src;\
200 #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))
202 #define ObtainSharedLock(lock, src)\
204 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, SHARED_LOCK);\
205 if (!(lock)->excl_locked)\
206 (lock) -> excl_locked = SHARED_LOCK;\
208 Afs_Lock_Obtain(lock, SHARED_LOCK); \
209 (lock)->pid_writer = MyPidxx; \
210 (lock)->src_indicator = src;\
213 #define NBObtainSharedLock(lock, src) (((lock)->excl_locked) ? EWOULDBLOCK : (((lock) -> excl_locked = SHARED_LOCK), ((lock)->pid_writer = MyPidxx), ((lock)->src_indicator = src), 0))
215 #define UpgradeSToWLock(lock, src)\
217 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, BOOSTED_LOCK);\
218 if (!(lock)->readers_reading)\
219 (lock)->excl_locked = WRITE_LOCK;\
221 Afs_Lock_Obtain(lock, BOOSTED_LOCK); \
222 (lock)->pid_writer = MyPidxx; \
223 (lock)->src_indicator = src;\
226 /* this must only be called with a WRITE or boosted SHARED lock! */
227 #define ConvertWToSLock(lock)\
229 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, SHARED_LOCK);\
230 (lock)->excl_locked = SHARED_LOCK; \
231 if((lock)->wait_states) \
232 Afs_Lock_ReleaseR(lock); \
235 #define ConvertWToRLock(lock) \
237 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
238 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
239 ((lock)->readers_reading)++;\
240 (lock)->pid_last_reader = MyPidxx ; \
241 (lock)->pid_writer = 0;\
242 Afs_Lock_ReleaseR(lock);\
245 #define ConvertSToRLock(lock) \
247 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
248 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
249 ((lock)->readers_reading)++;\
250 (lock)->pid_last_reader = MyPidxx ; \
251 (lock)->pid_writer = 0;\
252 Afs_Lock_ReleaseR(lock);\
255 #define ReleaseReadLock(lock)\
257 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, READ_LOCK);\
258 if (!(--((lock)->readers_reading)) && (lock)->wait_states)\
259 Afs_Lock_ReleaseW(lock) ; \
260 if ( (lock)->pid_last_reader == MyPidxx ) \
261 (lock)->pid_last_reader =0;\
264 #define ReleaseWriteLock(lock)\
266 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, WRITE_LOCK);\
267 (lock)->excl_locked &= ~WRITE_LOCK;\
268 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
269 (lock)->pid_writer=0; \
272 /* can be used on shared or boosted (write) locks */
273 #define ReleaseSharedLock(lock)\
275 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, SHARED_LOCK);\
276 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
277 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
278 (lock)->pid_writer=0; \
281 #else /* INSTRUMENT_LOCKS */
283 #define ObtainReadLock(lock)\
285 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, READ_LOCK);\
286 if (!((lock)->excl_locked & WRITE_LOCK)) \
287 ((lock)->readers_reading)++; \
289 Afs_Lock_Obtain(lock, READ_LOCK); \
292 #define NBObtainReadLock(lock) \
293 (((lock)->excl_locked & WRITE_LOCK) ? EWOULDBLOCK : (((lock)->readers_reading++), 0))
295 #define ObtainWriteLock(lock, src)\
297 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, WRITE_LOCK);\
298 if (!(lock)->excl_locked && !(lock)->readers_reading)\
299 (lock) -> excl_locked = WRITE_LOCK;\
301 Afs_Lock_Obtain(lock, WRITE_LOCK); \
304 #define NBObtainWriteLock(lock, src) (((lock)->excl_locked || (lock)->readers_reading) ? EWOULDBLOCK : (((lock) -> excl_locked = WRITE_LOCK), 0))
306 #define ObtainSharedLock(lock, src)\
308 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, SHARED_LOCK);\
309 if (!(lock)->excl_locked)\
310 (lock) -> excl_locked = SHARED_LOCK;\
312 Afs_Lock_Obtain(lock, SHARED_LOCK); \
315 #define NBObtainSharedLock(lock, src) (((lock)->excl_locked) ? EWOULDBLOCK : (((lock) -> excl_locked = SHARED_LOCK), 0))
317 #define UpgradeSToWLock(lock, src)\
319 AFS_LOCK_TRACE(CM_TRACE_LOCKOBTAIN, lock, BOOSTED_LOCK);\
320 if (!(lock)->readers_reading)\
321 (lock)->excl_locked = WRITE_LOCK;\
323 Afs_Lock_Obtain(lock, BOOSTED_LOCK); \
326 /* this must only be called with a WRITE or boosted SHARED lock! */
327 #define ConvertWToSLock(lock)\
329 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, SHARED_LOCK);\
330 (lock)->excl_locked = SHARED_LOCK; \
331 if((lock)->wait_states) \
332 Afs_Lock_ReleaseR(lock); \
335 #define ConvertWToRLock(lock) \
337 AFS_LOCK_TRACE(CM_TRACE_LOCKDOWN, lock, READ_LOCK);\
338 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
339 ((lock)->readers_reading)++;\
340 Afs_Lock_ReleaseR(lock);\
343 #define ConvertSToRLock(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 ReleaseReadLock(lock)\
353 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, READ_LOCK);\
354 if (!(--((lock)->readers_reading)) && (lock)->wait_states)\
355 Afs_Lock_ReleaseW(lock) ; \
358 #define ReleaseWriteLock(lock)\
360 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, WRITE_LOCK);\
361 (lock)->excl_locked &= ~WRITE_LOCK;\
362 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
365 /* can be used on shared or boosted (write) locks */
366 #define ReleaseSharedLock(lock)\
368 AFS_LOCK_TRACE(CM_TRACE_LOCKDONE, lock, SHARED_LOCK);\
369 (lock)->excl_locked &= ~(SHARED_LOCK | WRITE_LOCK);\
370 if ((lock)->wait_states) Afs_Lock_ReleaseR(lock);\
373 #endif /* INSTRUMENT_LOCKS */
375 /* I added this next macro to make sure it is safe to nuke a lock -- Mike K. */
376 #define LockWaiters(lock)\
377 ((int) ((lock)->num_waiting))
379 #define CheckLock(lock)\
380 ((lock)->excl_locked? (int) -1 : (int) (lock)->readers_reading)
382 #define WriteLocked(lock)\
383 ((lock)->excl_locked & WRITE_LOCK)
388 You can also use the lock package for handling parent locks for independently-lockable sets of
389 small objects. The concept here is that the parent lock is at the same level in the
390 locking hierarchy as the little locks, but certain restrictions apply.
392 The general usage pattern is as follows. You have a set of entries to search. When searching it, you
393 have a "scan" lock on the table. If you find what you're looking for, you drop the lock down
394 to a "hold" lock, lock the entry, and release the parent lock. If you don't find what
395 you're looking for, you create the entry, downgrade the "scan" lock to a "hold" lock,
396 lock the entry and unlock the parent.
398 To delete an item from the table, you initially obtain a "purge" lock on the parent. Unlike all
399 of the other parent lock modes described herein, in order to obtain a "purge" lock mode, you
400 must have released all locks on any items in the table. Once you have obtained the parent
401 lock in "purge" mode, you should check to see if the entry is locked. If its not locked, you
402 are free to delete the entry, knowing that no one else can attempt to obtain a lock
403 on the entry while you have the purge lock held on the parent. Unfortunately, if it *is* locked,
404 you can not lock it yourself and wait for the other dude to release it, since the entry's locker
405 may need to lock another entry before unlocking the entry you want (which would result in
406 deadlock). Instead, then, you must release the parent lock, and try again "later" (see Lock_Wait
407 for assistance in waiting until later). Unfortunately, this is the best locking paradigm I've yet
410 What are the advantages to this scheme? First, the use of the parent lock ensures that
411 two people don't try to add the same entry at the same time or delete an entry while someone
412 else is adding it. It also ensures that when one process is deleting an entry, no one else is
413 preparing to lock the entry. Furthermore, when obtaining a lock on a little entry, you
414 are only holding a "hold" lock on the parent lock, so that others may come in and search
415 the table during this time. Thus it will not hold up the system if a little entry takes
416 a great deal of time to free up.
418 Here's how to compute the compatibility matrix:
422 add no deletions, additions allowed, additions will be performed, will obtain little locks
423 hold no deletions, additions allowed, no additions will be performed, will obtain little locks
424 purge no deletions or additions allowed, deletions will be performed, don't obtain little locks
426 When we compute the locking matrix, we note that hold is compatible with hold and add.
427 Add is compatible only with hold. purge is not compatible with anything. This is the same
428 matrix as obtained by mapping add->S, hold->read and purge->write locks. Thus we
429 can use the locks above to solve this problem, and we do.
433 #endif /* __AFSLOCK_INCLUDE__ */