2 Bacula® - The Network Backup Solution
4 Copyright (C) 2001-2007 Free Software Foundation Europe e.V.
6 The main author of Bacula is Kern Sibbald, with contributions from
7 many others, a complete list can be found in the file AUTHORS.
8 This program is Free Software; you can redistribute it and/or
9 modify it under the terms of version two of the GNU General Public
10 License as published by the Free Software Foundation and included
13 This program is distributed in the hope that it will be useful, but
14 WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with this program; if not, write to the Free Software
20 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
23 Bacula® is a registered trademark of John Walker.
24 The licensor of Bacula is the Free Software Foundation Europe
25 (FSFE), Fiduciary Program, Sumatrastrasse 25, 8006 Zürich,
26 Switzerland, email:ftf@fsfeurope.org.
29 * Bacula Thread Read/Write locking code. It permits
30 * multiple readers but only one writer. Note, however,
31 * that the writer thread is permitted to make multiple
32 * nested write lock calls.
34 * Kern Sibbald, January MMI
38 * This code adapted from "Programming with POSIX Threads", by
46 * Initialize a read/write lock
48 * Returns: 0 on success
51 int rwl_init(brwlock_t *rwl)
55 rwl->r_active = rwl->w_active = 0;
56 rwl->r_wait = rwl->w_wait = 0;
57 if ((stat = pthread_mutex_init(&rwl->mutex, NULL)) != 0) {
60 if ((stat = pthread_cond_init(&rwl->read, NULL)) != 0) {
61 pthread_mutex_destroy(&rwl->mutex);
64 if ((stat = pthread_cond_init(&rwl->write, NULL)) != 0) {
65 pthread_cond_destroy(&rwl->read);
66 pthread_mutex_destroy(&rwl->mutex);
69 rwl->valid = RWLOCK_VALID;
74 * Destroy a read/write lock
76 * Returns: 0 on success
79 int rwl_destroy(brwlock_t *rwl)
81 int stat, stat1, stat2;
83 if (rwl->valid != RWLOCK_VALID) {
86 if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
91 * If any threads are active, report EBUSY
93 if (rwl->r_active > 0 || rwl->w_active) {
94 pthread_mutex_unlock(&rwl->mutex);
99 * If any threads are waiting, report EBUSY
101 if (rwl->r_wait > 0 || rwl->w_wait > 0) {
102 pthread_mutex_unlock(&rwl->mutex);
107 if ((stat = pthread_mutex_unlock(&rwl->mutex)) != 0) {
110 stat = pthread_mutex_destroy(&rwl->mutex);
111 stat1 = pthread_cond_destroy(&rwl->read);
112 stat2 = pthread_cond_destroy(&rwl->write);
113 return (stat != 0 ? stat : (stat1 != 0 ? stat1 : stat2));
117 * Handle cleanup when the read lock condition variable
120 static void rwl_read_release(void *arg)
122 brwlock_t *rwl = (brwlock_t *)arg;
125 pthread_mutex_unlock(&rwl->mutex);
129 * Handle cleanup when the write lock condition variable wait
132 static void rwl_write_release(void *arg)
134 brwlock_t *rwl = (brwlock_t *)arg;
137 pthread_mutex_unlock(&rwl->mutex);
141 * Lock for read access, wait until locked (or error).
143 int rwl_readlock(brwlock_t *rwl)
147 if (rwl->valid != RWLOCK_VALID) {
150 if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
154 rwl->r_wait++; /* indicate that we are waiting */
155 pthread_cleanup_push(rwl_read_release, (void *)rwl);
156 while (rwl->w_active) {
157 stat = pthread_cond_wait(&rwl->read, &rwl->mutex);
159 break; /* error, bail out */
162 pthread_cleanup_pop(0);
163 rwl->r_wait--; /* we are no longer waiting */
166 rwl->r_active++; /* we are running */
168 pthread_mutex_unlock(&rwl->mutex);
173 * Attempt to lock for read access, don't wait
175 int rwl_readtrylock(brwlock_t *rwl)
179 if (rwl->valid != RWLOCK_VALID) {
182 if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
188 rwl->r_active++; /* we are running */
190 stat2 = pthread_mutex_unlock(&rwl->mutex);
191 return (stat == 0 ? stat2 : stat);
197 int rwl_readunlock(brwlock_t *rwl)
201 if (rwl->valid != RWLOCK_VALID) {
204 if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
208 if (rwl->r_active == 0 && rwl->w_wait > 0) { /* if writers waiting */
209 stat = pthread_cond_broadcast(&rwl->write);
211 stat2 = pthread_mutex_unlock(&rwl->mutex);
212 return (stat == 0 ? stat2 : stat);
217 * Lock for write access, wait until locked (or error).
218 * Multiple nested write locking is permitted.
220 int rwl_writelock(brwlock_t *rwl)
224 if (rwl->valid != RWLOCK_VALID) {
227 if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
230 if (rwl->w_active && pthread_equal(rwl->writer_id, pthread_self())) {
232 pthread_mutex_unlock(&rwl->mutex);
235 if (rwl->w_active || rwl->r_active > 0) {
236 rwl->w_wait++; /* indicate that we are waiting */
237 pthread_cleanup_push(rwl_write_release, (void *)rwl);
238 while (rwl->w_active || rwl->r_active > 0) {
239 if ((stat = pthread_cond_wait(&rwl->write, &rwl->mutex)) != 0) {
240 break; /* error, bail out */
243 pthread_cleanup_pop(0);
244 rwl->w_wait--; /* we are no longer waiting */
247 rwl->w_active++; /* we are running */
248 rwl->writer_id = pthread_self(); /* save writer thread's id */
250 pthread_mutex_unlock(&rwl->mutex);
255 * Attempt to lock for write access, don't wait
257 int rwl_writetrylock(brwlock_t *rwl)
261 if (rwl->valid != RWLOCK_VALID) {
264 if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
267 if (rwl->w_active && pthread_equal(rwl->writer_id, pthread_self())) {
269 pthread_mutex_unlock(&rwl->mutex);
272 if (rwl->w_active || rwl->r_active > 0) {
275 rwl->w_active = 1; /* we are running */
276 rwl->writer_id = pthread_self(); /* save writer thread's id */
278 stat2 = pthread_mutex_unlock(&rwl->mutex);
279 return (stat == 0 ? stat2 : stat);
284 * Start any waiting writers in preference to waiting readers
286 int rwl_writeunlock(brwlock_t *rwl)
290 if (rwl->valid != RWLOCK_VALID) {
293 if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
296 if (rwl->w_active <= 0) {
297 Emsg0(M_ABORT, 0, _("rwl_writeunlock called too many times.\n"));
300 if (!pthread_equal(pthread_self(), rwl->writer_id)) {
301 Emsg0(M_ABORT, 0, _("rwl_writeunlock by non-owner.\n"));
303 if (rwl->w_active > 0) {
304 stat = 0; /* writers still active */
306 /* No more writers, awaken someone */
307 if (rwl->r_wait > 0) { /* if readers waiting */
308 stat = pthread_cond_broadcast(&rwl->read);
309 } else if (rwl->w_wait > 0) {
310 stat = pthread_cond_broadcast(&rwl->write);
313 stat2 = pthread_mutex_unlock(&rwl->mutex);
314 return (stat == 0 ? stat2 : stat);
321 #define ITERATIONS 10000
324 * Keep statics for each thread.
326 typedef struct thread_tag {
335 * Read/write lock and shared data.
337 typedef struct data_tag {
343 thread_t threads[THREADS];
344 data_t data[DATASIZE];
347 * Thread start routine that uses read/write locks.
349 void *thread_routine(void *arg)
351 thread_t *self = (thread_t *)arg;
357 for (iteration=0; iteration < ITERATIONS; iteration++) {
359 * Each "self->interval" iterations, perform an
360 * update operation (write lock instead of read
363 if ((iteration % self->interval) == 0) {
364 status = rwl_writelock(&data[element].lock);
367 Emsg1(M_ABORT, 0, _("Write lock failed. ERR=%s\n"), be.bstrerror(status));
369 data[element].data = self->thread_num;
370 data[element].writes++;
372 status = rwl_writeunlock(&data[element].lock);
375 Emsg1(M_ABORT, 0, _("Write unlock failed. ERR=%s\n"), be.bstrerror(status));
379 * Look at the current data element to see whether
380 * the current thread last updated it. Count the
381 * times to report later.
383 status = rwl_readlock(&data[element].lock);
386 Emsg1(M_ABORT, 0, _("Read lock failed. ERR=%s\n"), be.bstrerror(status));
389 if (data[element].data == self->thread_num)
391 status = rwl_readunlock(&data[element].lock);
394 Emsg1(M_ABORT, 0, _("Read unlock failed. ERR=%s\n"), be.bstrerror(status));
398 if (element >= DATASIZE) {
403 Pmsg2(000, _("Thread %d found unchanged elements %d times\n"),
404 self->thread_num, repeats);
409 int main (int argc, char *argv[])
414 unsigned int seed = 1;
415 int thread_writes = 0;
420 * On Solaris 2.5, threads are not timesliced. To ensure
421 * that our threads can run concurrently, we need to
422 * increase the concurrency level to THREADS.
424 thr_setconcurrency (THREADS);
428 * Initialize the shared data.
430 for (data_count = 0; data_count < DATASIZE; data_count++) {
431 data[data_count].data = 0;
432 data[data_count].writes = 0;
433 status = rwl_init (&data[data_count].lock);
436 Emsg1(M_ABORT, 0, _("Init rwlock failed. ERR=%s\n"), be.bstrerror(status));
441 * Create THREADS threads to access shared data.
443 for (count = 0; count < THREADS; count++) {
444 threads[count].thread_num = count + 1;
445 threads[count].writes = 0;
446 threads[count].reads = 0;
447 threads[count].interval = rand_r (&seed) % 71;
448 status = pthread_create (&threads[count].thread_id,
449 NULL, thread_routine, (void*)&threads[count]);
452 Emsg1(M_ABORT, 0, _("Create thread failed. ERR=%s\n"), be.bstrerror(status));
457 * Wait for all threads to complete, and collect
460 for (count = 0; count < THREADS; count++) {
461 status = pthread_join (threads[count].thread_id, NULL);
464 Emsg1(M_ABORT, 0, _("Join thread failed. ERR=%s\n"), be.bstrerror(status));
466 thread_writes += threads[count].writes;
467 printf (_("%02d: interval %d, writes %d, reads %d\n"),
468 count, threads[count].interval,
469 threads[count].writes, threads[count].reads);
473 * Collect statistics for the data.
475 for (data_count = 0; data_count < DATASIZE; data_count++) {
476 data_writes += data[data_count].writes;
477 printf (_("data %02d: value %d, %d writes\n"),
478 data_count, data[data_count].data, data[data_count].writes);
479 rwl_destroy (&data[data_count].lock);
482 printf (_("Total: %d thread writes, %d data writes\n"),
483 thread_writes, data_writes);
489 #ifdef TEST_RW_TRY_LOCK
493 * Demonstrate use of non-blocking read-write locks.
495 * Special notes: On a Solaris system, call thr_setconcurrency()
496 * to allow interleaved thread execution, since threads are not
504 #define ITERATIONS 1000
508 * Keep statistics for each thread.
510 typedef struct thread_tag {
520 * Read-write lock and shared data
522 typedef struct data_tag {
528 thread_t threads[THREADS];
529 data_t data[DATASIZE];
532 * Thread start routine that uses read-write locks
534 void *thread_routine (void *arg)
536 thread_t *self = (thread_t*)arg;
541 element = 0; /* Current data element */
543 for (iteration = 0; iteration < ITERATIONS; iteration++) {
544 if ((iteration % self->interval) == 0) {
545 status = rwl_writetrylock (&data[element].lock);
547 self->w_collisions++;
548 else if (status == 0) {
549 data[element].data++;
550 data[element].updates++;
552 rwl_writeunlock (&data[element].lock);
554 err_abort (status, _("Try write lock"));
556 status = rwl_readtrylock (&data[element].lock);
558 self->r_collisions++;
559 else if (status != 0) {
560 err_abort (status, _("Try read lock"));
562 if (data[element].data != data[element].updates)
563 printf ("%d: data[%d] %d != %d\n",
564 self->thread_num, element,
565 data[element].data, data[element].updates);
566 rwl_readunlock (&data[element].lock);
571 if (element >= DATASIZE)
577 int main (int argc, char *argv[])
579 int count, data_count;
580 unsigned int seed = 1;
581 int thread_updates = 0, data_updates = 0;
586 * On Solaris 2.5, threads are not timesliced. To ensure
587 * that our threads can run concurrently, we need to
588 * increase the concurrency level to THREADS.
590 DPRINTF (("Setting concurrency level to %d\n", THREADS));
591 thr_setconcurrency (THREADS);
595 * Initialize the shared data.
597 for (data_count = 0; data_count < DATASIZE; data_count++) {
598 data[data_count].data = 0;
599 data[data_count].updates = 0;
600 rwl_init (&data[data_count].lock);
604 * Create THREADS threads to access shared data.
606 for (count = 0; count < THREADS; count++) {
607 threads[count].thread_num = count;
608 threads[count].r_collisions = 0;
609 threads[count].w_collisions = 0;
610 threads[count].updates = 0;
611 threads[count].interval = rand_r (&seed) % ITERATIONS;
612 status = pthread_create (&threads[count].thread_id,
613 NULL, thread_routine, (void*)&threads[count]);
615 err_abort (status, _("Create thread"));
619 * Wait for all threads to complete, and collect
622 for (count = 0; count < THREADS; count++) {
623 status = pthread_join (threads[count].thread_id, NULL);
625 err_abort (status, _("Join thread"));
626 thread_updates += threads[count].updates;
627 printf (_("%02d: interval %d, updates %d, "
628 "r_collisions %d, w_collisions %d\n"),
629 count, threads[count].interval,
630 threads[count].updates,
631 threads[count].r_collisions, threads[count].w_collisions);
635 * Collect statistics for the data.
637 for (data_count = 0; data_count < DATASIZE; data_count++) {
638 data_updates += data[data_count].updates;
639 printf (_("data %02d: value %d, %d updates\n"),
640 data_count, data[data_count].data, data[data_count].updates);
641 rwl_destroy (&data[data_count].lock);