2 /* This work is part of OpenLDAP Software <http://www.openldap.org/>.
4 * Copyright 1998-2003 The OpenLDAP Foundation.
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted only as authorized by the OpenLDAP
11 * A copy of this license is available in file LICENSE in the
12 * top-level directory of the distribution or, alternatively, at
13 * <http://www.OpenLDAP.org/license.html>.
15 /* This work was initially developed by Kurt D. Zeilenga for inclusion
16 * in OpenLDAP Software. Additional significant contributors include:
21 * This is an improved implementation of Reader/Writer locks does
22 * not protect writers from starvation. That is, if a writer is
23 * currently waiting on a reader, any new reader will get
24 * the lock before the writer.
26 * Does not support cancellation nor does any status checking.
28 /* Adapted from publically available examples for:
29 * "Programming with Posix Threads"
30 * by David R Butenhof, Addison-Wesley
31 * http://cseng.aw.com/bookpage.taf?ISBN=0-201-63392-2
36 #include <ac/stdlib.h>
39 #include <ac/string.h>
43 #include "ldap_pvt_thread.h"
46 * implementations that provide their own compatible
47 * reader/writer locks define LDAP_THREAD_HAVE_RDWR
48 * in ldap_pvt_thread.h
50 #ifndef LDAP_THREAD_HAVE_RDWR
52 struct ldap_int_thread_rdwr_s {
53 ldap_pvt_thread_mutex_t ltrw_mutex;
54 ldap_pvt_thread_cond_t ltrw_read; /* wait for read */
55 ldap_pvt_thread_cond_t ltrw_write; /* wait for write */
57 #define LDAP_PVT_THREAD_RDWR_VALID 0x0bad
65 ldap_pvt_thread_rdwr_init( ldap_pvt_thread_rdwr_t *rwlock )
67 struct ldap_int_thread_rdwr_s *rw;
69 assert( rwlock != NULL );
71 rw = (struct ldap_int_thread_rdwr_s *) LDAP_CALLOC( 1,
72 sizeof( struct ldap_int_thread_rdwr_s ) );
74 /* we should check return results */
75 ldap_pvt_thread_mutex_init( &rw->ltrw_mutex );
76 ldap_pvt_thread_cond_init( &rw->ltrw_read );
77 ldap_pvt_thread_cond_init( &rw->ltrw_write );
79 rw->ltrw_valid = LDAP_PVT_THREAD_RDWR_VALID;
86 ldap_pvt_thread_rdwr_destroy( ldap_pvt_thread_rdwr_t *rwlock )
88 struct ldap_int_thread_rdwr_s *rw;
90 assert( rwlock != NULL );
94 assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
96 if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
97 return LDAP_PVT_THREAD_EINVAL;
99 ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
101 assert( rw->ltrw_w_active >= 0 );
102 assert( rw->ltrw_w_wait >= 0 );
103 assert( rw->ltrw_r_active >= 0 );
104 assert( rw->ltrw_r_wait >= 0 );
106 /* active threads? */
107 if( rw->ltrw_r_active > 0 || rw->ltrw_w_active > 0) {
108 ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
109 return LDAP_PVT_THREAD_EBUSY;
112 /* waiting threads? */
113 if( rw->ltrw_r_wait > 0 || rw->ltrw_w_wait > 0) {
114 ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
115 return LDAP_PVT_THREAD_EBUSY;
120 ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
122 ldap_pvt_thread_mutex_destroy( &rw->ltrw_mutex );
123 ldap_pvt_thread_cond_destroy( &rw->ltrw_read );
124 ldap_pvt_thread_cond_destroy( &rw->ltrw_write );
131 int ldap_pvt_thread_rdwr_rlock( ldap_pvt_thread_rdwr_t *rwlock )
133 struct ldap_int_thread_rdwr_s *rw;
135 assert( rwlock != NULL );
138 assert( rw != NULL );
139 assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
141 if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
142 return LDAP_PVT_THREAD_EINVAL;
144 ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
146 assert( rw->ltrw_w_active >= 0 );
147 assert( rw->ltrw_w_wait >= 0 );
148 assert( rw->ltrw_r_active >= 0 );
149 assert( rw->ltrw_r_wait >= 0 );
151 if( rw->ltrw_w_active > 0 ) {
152 /* writer is active */
157 ldap_pvt_thread_cond_wait(
158 &rw->ltrw_read, &rw->ltrw_mutex );
159 } while( rw->ltrw_w_active > 0 );
162 assert( rw->ltrw_r_wait >= 0 );
167 ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
172 int ldap_pvt_thread_rdwr_rtrylock( ldap_pvt_thread_rdwr_t *rwlock )
174 struct ldap_int_thread_rdwr_s *rw;
176 assert( rwlock != NULL );
179 assert( rw != NULL );
180 assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
182 if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
183 return LDAP_PVT_THREAD_EINVAL;
185 ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
187 assert( rw->ltrw_w_active >= 0 );
188 assert( rw->ltrw_w_wait >= 0 );
189 assert( rw->ltrw_r_active >= 0 );
190 assert( rw->ltrw_r_wait >= 0 );
192 if( rw->ltrw_w_active > 0) {
193 ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
194 return LDAP_PVT_THREAD_EBUSY;
199 ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
204 int ldap_pvt_thread_rdwr_runlock( ldap_pvt_thread_rdwr_t *rwlock )
206 struct ldap_int_thread_rdwr_s *rw;
208 assert( rwlock != NULL );
211 assert( rw != NULL );
212 assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
214 if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
215 return LDAP_PVT_THREAD_EINVAL;
217 ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
221 assert( rw->ltrw_w_active >= 0 );
222 assert( rw->ltrw_w_wait >= 0 );
223 assert( rw->ltrw_r_active >= 0 );
224 assert( rw->ltrw_r_wait >= 0 );
226 if (rw->ltrw_r_active == 0 && rw->ltrw_w_wait > 0 ) {
227 ldap_pvt_thread_cond_signal( &rw->ltrw_write );
230 ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
235 int ldap_pvt_thread_rdwr_wlock( ldap_pvt_thread_rdwr_t *rwlock )
237 struct ldap_int_thread_rdwr_s *rw;
239 assert( rwlock != NULL );
242 assert( rw != NULL );
243 assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
245 if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
246 return LDAP_PVT_THREAD_EINVAL;
248 ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
250 assert( rw->ltrw_w_active >= 0 );
251 assert( rw->ltrw_w_wait >= 0 );
252 assert( rw->ltrw_r_active >= 0 );
253 assert( rw->ltrw_r_wait >= 0 );
255 if ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 ) {
259 ldap_pvt_thread_cond_wait(
260 &rw->ltrw_write, &rw->ltrw_mutex );
261 } while ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 );
264 assert( rw->ltrw_w_wait >= 0 );
269 ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
274 int ldap_pvt_thread_rdwr_wtrylock( ldap_pvt_thread_rdwr_t *rwlock )
276 struct ldap_int_thread_rdwr_s *rw;
278 assert( rwlock != NULL );
281 assert( rw != NULL );
282 assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
284 if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
285 return LDAP_PVT_THREAD_EINVAL;
287 ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
289 assert( rw->ltrw_w_active >= 0 );
290 assert( rw->ltrw_w_wait >= 0 );
291 assert( rw->ltrw_r_active >= 0 );
292 assert( rw->ltrw_r_wait >= 0 );
294 if ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 ) {
295 ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
296 return LDAP_PVT_THREAD_EBUSY;
301 ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
306 int ldap_pvt_thread_rdwr_wunlock( ldap_pvt_thread_rdwr_t *rwlock )
308 struct ldap_int_thread_rdwr_s *rw;
310 assert( rwlock != NULL );
313 assert( rw != NULL );
314 assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
316 if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
317 return LDAP_PVT_THREAD_EINVAL;
319 ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
323 assert( rw->ltrw_w_active >= 0 );
324 assert( rw->ltrw_w_wait >= 0 );
325 assert( rw->ltrw_r_active >= 0 );
326 assert( rw->ltrw_r_wait >= 0 );
328 if (rw->ltrw_r_wait > 0) {
329 ldap_pvt_thread_cond_broadcast( &rw->ltrw_read );
331 } else if (rw->ltrw_w_wait > 0) {
332 ldap_pvt_thread_cond_signal( &rw->ltrw_write );
335 ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
340 #ifdef LDAP_RDWR_DEBUG
343 * return 0 if false, suitable for assert(ldap_pvt_thread_rdwr_Xchk(rdwr))
345 * Currently they don't check if the calling thread is the one
346 * that has the lock, just that there is a reader or writer.
348 * Basically sufficent for testing that places that should have
352 int ldap_pvt_thread_rdwr_readers(ldap_pvt_thread_rdwr_t *rwlock)
354 struct ldap_int_thread_rdwr_s *rw;
356 assert( rwlock != NULL );
359 assert( rw != NULL );
360 assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
361 assert( rw->ltrw_w_active >= 0 );
362 assert( rw->ltrw_w_wait >= 0 );
363 assert( rw->ltrw_r_active >= 0 );
364 assert( rw->ltrw_r_wait >= 0 );
366 return( rw->ltrw_r_active );
369 int ldap_pvt_thread_rdwr_writers(ldap_pvt_thread_rdwr_t *rwlock)
371 struct ldap_int_thread_rdwr_s *rw;
373 assert( rwlock != NULL );
376 assert( rw != NULL );
377 assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
378 assert( rw->ltrw_w_active >= 0 );
379 assert( rw->ltrw_w_wait >= 0 );
380 assert( rw->ltrw_r_active >= 0 );
381 assert( rw->ltrw_r_wait >= 0 );
383 return( rw->ltrw_w_active );
386 int ldap_pvt_thread_rdwr_active(ldap_pvt_thread_rdwr_t *rwlock)
388 struct ldap_int_thread_rdwr_s *rw;
390 assert( rwlock != NULL );
393 assert( rw != NULL );
394 assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
395 assert( rw->ltrw_w_active >= 0 );
396 assert( rw->ltrw_w_wait >= 0 );
397 assert( rw->ltrw_r_active >= 0 );
398 assert( rw->ltrw_r_wait >= 0 );
400 return(ldap_pvt_thread_rdwr_readers(rw) +
401 ldap_pvt_thread_rdwr_writers(rw));
404 #endif /* LDAP_DEBUG */
406 #endif /* LDAP_THREAD_HAVE_RDWR */