--- /dev/null
+/*
+ Bacula® - The Network Backup Solution
+
+ Copyright (C) 2001-2010 Free Software Foundation Europe e.V.
+
+ The main author of Bacula is Kern Sibbald, with contributions from
+ many others, a complete list can be found in the file AUTHORS.
+ This program is Free Software; you can redistribute it and/or
+ modify it under the terms of version two of the GNU General Public
+ License as published by the Free Software Foundation and included
+ in the file LICENSE.
+
+ This program is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ 02110-1301, USA.
+
+ Bacula® is a registered trademark of Kern Sibbald.
+ The licensor of Bacula is the Free Software Foundation Europe
+ (FSFE), Fiduciary Program, Sumatrastrasse 25, 8006 Zürich,
+ Switzerland, email:ftf@fsfeurope.org.
+*/
+/*
+ * Bacula Thread Read/Write locking code. It permits
+ * multiple readers but only one writer. Note, however,
+ * that the writer thread is permitted to make multiple
+ * nested write lock calls.
+ *
+ * Kern Sibbald, January MMI
+ *
+ * This code adapted from "Programming with POSIX Threads", by
+ * David R. Butenhof
+ *
+ */
+
+#define _LOCKMGR_COMPLIANT
+#include "bacula.h"
+#include "devlock.h"
+
+/*
+ * Initialize a read/write lock
+ *
+ * Returns: 0 on success
+ * errno on failure
+ */
+
+devlock *new_devlock()
+{
+ devlock *lock;
+ lock = (devlock *)malloc(sizeof (devlock));
+ memset(lock, 0, sizeof(devlock));
+ return lock;
+}
+
+int devlock::init(int priority)
+{
+ int stat;
+ devlock *rwl = this;
+
+ rwl->r_active = rwl->w_active = 0;
+ rwl->r_wait = rwl->w_wait = 0;
+ rwl->priority = priority;
+ if ((stat = pthread_mutex_init(&rwl->mutex, NULL)) != 0) {
+ return stat;
+ }
+ if ((stat = pthread_cond_init(&rwl->read, NULL)) != 0) {
+ pthread_mutex_destroy(&rwl->mutex);
+ return stat;
+ }
+ if ((stat = pthread_cond_init(&rwl->write, NULL)) != 0) {
+ pthread_cond_destroy(&rwl->read);
+ pthread_mutex_destroy(&rwl->mutex);
+ return stat;
+ }
+ rwl->valid = DEVLOCK_VALID;
+ return 0;
+}
+
+/*
+ * Destroy a read/write lock
+ *
+ * Returns: 0 on success
+ * errno on failure
+ */
+int devlock::destroy()
+{
+ devlock *rwl = this;
+ int stat, stat1, stat2;
+
+ if (rwl->valid != DEVLOCK_VALID) {
+ return EINVAL;
+ }
+ if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
+ return stat;
+ }
+
+ /*
+ * If any threads are active, report EBUSY
+ */
+ if (rwl->r_active > 0 || rwl->w_active) {
+ pthread_mutex_unlock(&rwl->mutex);
+ return EBUSY;
+ }
+
+ /*
+ * If any threads are waiting, report EBUSY
+ */
+ if (rwl->r_wait > 0 || rwl->w_wait > 0) {
+ pthread_mutex_unlock(&rwl->mutex);
+ return EBUSY;
+ }
+
+ rwl->valid = 0;
+ if ((stat = pthread_mutex_unlock(&rwl->mutex)) != 0) {
+ return stat;
+ }
+ stat = pthread_mutex_destroy(&rwl->mutex);
+ stat1 = pthread_cond_destroy(&rwl->read);
+ stat2 = pthread_cond_destroy(&rwl->write);
+ return (stat != 0 ? stat : (stat1 != 0 ? stat1 : stat2));
+}
+
+/*
+ * Handle cleanup when the read lock condition variable
+ * wait is released.
+ */
+static void devlock_read_release(void *arg)
+{
+ devlock *rwl = (devlock *)arg;
+ rwl->read_release();
+}
+
+void devlock::read_release()
+{
+ r_wait--;
+ pthread_mutex_unlock(&mutex);
+}
+
+/*
+ * Handle cleanup when the write lock condition variable wait
+ * is released.
+ */
+static void devlock_write_release(void *arg)
+{
+ devlock *rwl = (devlock *)arg;
+ rwl->write_release();
+}
+
+void devlock::write_release()
+{
+ w_wait--;
+ pthread_mutex_unlock(&mutex);
+}
+
+/*
+ * Lock for read access, wait until locked (or error).
+ */
+int devlock::readlock()
+{
+ devlock *rwl = this;
+ int stat;
+
+ if (rwl->valid != DEVLOCK_VALID) {
+ return EINVAL;
+ }
+ if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
+ return stat;
+ }
+ if (rwl->w_active) {
+ rwl->r_wait++; /* indicate that we are waiting */
+ pthread_cleanup_push(devlock_read_release, (void *)rwl);
+ while (rwl->w_active) {
+ stat = pthread_cond_wait(&rwl->read, &rwl->mutex);
+ if (stat != 0) {
+ break; /* error, bail out */
+ }
+ }
+ pthread_cleanup_pop(0);
+ rwl->r_wait--; /* we are no longer waiting */
+ }
+ if (stat == 0) {
+ rwl->r_active++; /* we are running */
+ }
+ pthread_mutex_unlock(&rwl->mutex);
+ return stat;
+}
+
+/*
+ * Attempt to lock for read access, don't wait
+ */
+int devlock::readtrylock()
+{
+ devlock *rwl = this;
+ int stat, stat2;
+
+ if (rwl->valid != DEVLOCK_VALID) {
+ return EINVAL;
+ }
+ if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
+ return stat;
+ }
+ if (rwl->w_active) {
+ stat = EBUSY;
+ } else {
+ rwl->r_active++; /* we are running */
+ }
+ stat2 = pthread_mutex_unlock(&rwl->mutex);
+ return (stat == 0 ? stat2 : stat);
+}
+
+/*
+ * Unlock read lock
+ */
+int devlock::readunlock()
+{
+ devlock *rwl = this;
+ int stat, stat2;
+
+ if (rwl->valid != DEVLOCK_VALID) {
+ return EINVAL;
+ }
+ if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
+ return stat;
+ }
+ rwl->r_active--;
+ if (rwl->r_active == 0 && rwl->w_wait > 0) { /* if writers waiting */
+ stat = pthread_cond_broadcast(&rwl->write);
+ }
+ stat2 = pthread_mutex_unlock(&rwl->mutex);
+ return (stat == 0 ? stat2 : stat);
+}
+
+
+/*
+ * Lock for write access, wait until locked (or error).
+ * Multiple nested write locking is permitted.
+ */
+int devlock::writelock(int areason, bool acan_steal)
+{
+ devlock *rwl = this;
+ int stat;
+
+ if (rwl->valid != DEVLOCK_VALID) {
+ return EINVAL;
+ }
+ if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
+ return stat;
+ }
+ if (rwl->w_active && pthread_equal(rwl->writer_id, pthread_self())) {
+ rwl->w_active++;
+ pthread_mutex_unlock(&rwl->mutex);
+ return 0;
+ }
+ lmgr_pre_lock(rwl, rwl->priority, __FILE__, __LINE__);
+ if (rwl->w_active || rwl->r_active > 0) {
+ rwl->w_wait++; /* indicate that we are waiting */
+ pthread_cleanup_push(devlock_write_release, (void *)rwl);
+ while (rwl->w_active || rwl->r_active > 0) {
+ if ((stat = pthread_cond_wait(&rwl->write, &rwl->mutex)) != 0) {
+ lmgr_do_unlock(rwl);
+ break; /* error, bail out */
+ }
+ }
+ pthread_cleanup_pop(0);
+ rwl->w_wait--; /* we are no longer waiting */
+ }
+ if (stat == 0) {
+ rwl->w_active++; /* we are running */
+ rwl->writer_id = pthread_self(); /* save writer thread's id */
+ lmgr_post_lock();
+ }
+ rwl->reason = areason;
+ rwl->can_steal = acan_steal;
+ pthread_mutex_unlock(&rwl->mutex);
+ return stat;
+}
+
+/*
+ * Attempt to lock for write access, don't wait
+ */
+int devlock::writetrylock()
+{
+ devlock *rwl = this;
+ int stat, stat2;
+
+ if (rwl->valid != DEVLOCK_VALID) {
+ return EINVAL;
+ }
+ if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
+ return stat;
+ }
+ if (rwl->w_active && pthread_equal(rwl->writer_id, pthread_self())) {
+ rwl->w_active++;
+ pthread_mutex_unlock(&rwl->mutex);
+ return 0;
+ }
+ if (rwl->w_active || rwl->r_active > 0) {
+ stat = EBUSY;
+ } else {
+ rwl->w_active = 1; /* we are running */
+ rwl->writer_id = pthread_self(); /* save writer thread's id */
+ lmgr_do_lock(rwl, rwl->priority, __FILE__, __LINE__);
+ }
+ stat2 = pthread_mutex_unlock(&rwl->mutex);
+ return (stat == 0 ? stat2 : stat);
+}
+
+/*
+ * Unlock write lock
+ * Start any waiting writers in preference to waiting readers
+ */
+int devlock::writeunlock()
+{
+ devlock *rwl = this;
+ int stat, stat2;
+
+ if (rwl->valid != DEVLOCK_VALID) {
+ return EINVAL;
+ }
+ if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
+ return stat;
+ }
+ if (rwl->w_active <= 0) {
+ pthread_mutex_unlock(&rwl->mutex);
+ Jmsg0(NULL, M_ABORT, 0, _("writeunlock called too many times.\n"));
+ }
+ rwl->w_active--;
+ if (!pthread_equal(pthread_self(), rwl->writer_id)) {
+ pthread_mutex_unlock(&rwl->mutex);
+ Jmsg0(NULL, M_ABORT, 0, _("writeunlock by non-owner.\n"));
+ }
+ if (rwl->w_active > 0) {
+ stat = 0; /* writers still active */
+ } else {
+ lmgr_do_unlock(rwl);
+ /* No more writers, awaken someone */
+ if (rwl->r_wait > 0) { /* if readers waiting */
+ stat = pthread_cond_broadcast(&rwl->read);
+ } else if (rwl->w_wait > 0) {
+ stat = pthread_cond_broadcast(&rwl->write);
+ }
+ }
+ stat2 = pthread_mutex_unlock(&rwl->mutex);
+ return (stat == 0 ? stat2 : stat);
+}
+
+#ifdef TEST_RWLOCK
+
+#define THREADS 300
+#define DATASIZE 15
+#define ITERATIONS 1000000
+
+/*
+ * Keep statics for each thread.
+ */
+typedef struct thread_tag {
+ int thread_num;
+ pthread_t thread_id;
+ int writes;
+ int reads;
+ int interval;
+} thread_t;
+
+/*
+ * Read/write lock and shared data.
+ */
+typedef struct data_tag {
+ brwlock_t lock;
+ int data;
+ int writes;
+} data_t;
+
+static thread_t threads[THREADS];
+static data_t data[DATASIZE];
+
+/*
+ * Thread start routine that uses read/write locks.
+ */
+void *thread_routine(void *arg)
+{
+ thread_t *self = (thread_t *)arg;
+ int repeats = 0;
+ int iteration;
+ int element = 0;
+ int status;
+
+ for (iteration=0; iteration < ITERATIONS; iteration++) {
+ /*
+ * Each "self->interval" iterations, perform an
+ * update operation (write lock instead of read
+ * lock).
+ */
+// if ((iteration % self->interval) == 0) {
+ status = writelock(&data[element].lock);
+ if (status != 0) {
+ berrno be;
+ printf("Write lock failed. ERR=%s\n", be.bstrerror(status));
+ exit(1);
+ }
+ data[element].data = self->thread_num;
+ data[element].writes++;
+ self->writes++;
+ status = writelock(&data[element].lock);
+ if (status != 0) {
+ berrno be;
+ printf("Write lock failed. ERR=%s\n", be.bstrerror(status));
+ exit(1);
+ }
+ data[element].data = self->thread_num;
+ data[element].writes++;
+ self->writes++;
+ status = writeunlock(&data[element].lock);
+ if (status != 0) {
+ berrno be;
+ printf("Write unlock failed. ERR=%s\n", be.bstrerror(status));
+ exit(1);
+ }
+ status = writeunlock(&data[element].lock);
+ if (status != 0) {
+ berrno be;
+ printf("Write unlock failed. ERR=%s\n", be.bstrerror(status));
+ exit(1);
+ }
+
+#ifdef xxx
+ } else {
+ /*
+ * Look at the current data element to see whether
+ * the current thread last updated it. Count the
+ * times to report later.
+ */
+ status = readlock(&data[element].lock);
+ if (status != 0) {
+ berrno be;
+ printf("Read lock failed. ERR=%s\n", be.bstrerror(status));
+ exit(1);
+ }
+ self->reads++;
+ if (data[element].data == self->thread_num)
+ repeats++;
+ status = readunlock(&data[element].lock);
+ if (status != 0) {
+ berrno be;
+ printf("Read unlock failed. ERR=%s\n", be.bstrerror(status));
+ exit(1);
+ }
+ }
+#endif
+ element++;
+ if (element >= DATASIZE) {
+ element = 0;
+ }
+ }
+ if (repeats > 0) {
+ Pmsg2(000, _("Thread %d found unchanged elements %d times\n"),
+ self->thread_num, repeats);
+ }
+ return NULL;
+}
+
+int main (int argc, char *argv[])
+{
+ int count;
+ int data_count;
+ int status;
+ unsigned int seed = 1;
+ int thread_writes = 0;
+ int data_writes = 0;
+
+#ifdef sun
+ /*
+ * On Solaris 2.5, threads are not timesliced. To ensure
+ * that our threads can run concurrently, we need to
+ * increase the concurrency level to THREADS.
+ */
+ thr_setconcurrency (THREADS);
+#endif
+
+ /*
+ * Initialize the shared data.
+ */
+ for (data_count = 0; data_count < DATASIZE; data_count++) {
+ data[data_count].data = 0;
+ data[data_count].writes = 0;
+ status = rwl_init(&data[data_count].lock);
+ if (status != 0) {
+ berrno be;
+ printf("Init rwlock failed. ERR=%s\n", be.bstrerror(status));
+ exit(1);
+ }
+ }
+
+ /*
+ * Create THREADS threads to access shared data.
+ */
+ for (count = 0; count < THREADS; count++) {
+ threads[count].thread_num = count + 1;
+ threads[count].writes = 0;
+ threads[count].reads = 0;
+ threads[count].interval = rand_r(&seed) % 71;
+ if (threads[count].interval <= 0) {
+ threads[count].interval = 1;
+ }
+ status = pthread_create (&threads[count].thread_id,
+ NULL, thread_routine, (void*)&threads[count]);
+ if (status != 0 || (int)threads[count].thread_id == 0) {
+ berrno be;
+ printf("Create thread failed. ERR=%s\n", be.bstrerror(status));
+ exit(1);
+ }
+ }
+
+ /*
+ * Wait for all threads to complete, and collect
+ * statistics.
+ */
+ for (count = 0; count < THREADS; count++) {
+ status = pthread_join (threads[count].thread_id, NULL);
+ if (status != 0) {
+ berrno be;
+ printf("Join thread failed. ERR=%s\n", be.bstrerror(status));
+ exit(1);
+ }
+ thread_writes += threads[count].writes;
+ printf (_("%02d: interval %d, writes %d, reads %d\n"),
+ count, threads[count].interval,
+ threads[count].writes, threads[count].reads);
+ }
+
+ /*
+ * Collect statistics for the data.
+ */
+ for (data_count = 0; data_count < DATASIZE; data_count++) {
+ data_writes += data[data_count].writes;
+ printf (_("data %02d: value %d, %d writes\n"),
+ data_count, data[data_count].data, data[data_count].writes);
+ rwl_destroy (&data[data_count].lock);
+ }
+
+ printf (_("Total: %d thread writes, %d data writes\n"),
+ thread_writes, data_writes);
+ return 0;
+}
+
+#endif
+
+#ifdef TEST_RW_TRY_LOCK
+/*
+ * brwlock_try_main.c
+ *
+ * Demonstrate use of non-blocking read-write locks.
+ *
+ * Special notes: On a Solaris system, call thr_setconcurrency()
+ * to allow interleaved thread execution, since threads are not
+ * timesliced.
+ */
+#include <pthread.h>
+#include "rwlock.h"
+#include "errors.h"
+
+#define THREADS 5
+#define ITERATIONS 1000
+#define DATASIZE 15
+
+/*
+ * Keep statistics for each thread.
+ */
+typedef struct thread_tag {
+ int thread_num;
+ pthread_t thread_id;
+ int r_collisions;
+ int w_collisions;
+ int updates;
+ int interval;
+} thread_t;
+
+/*
+ * Read-write lock and shared data
+ */
+typedef struct data_tag {
+ brwlock_t lock;
+ int data;
+ int updates;
+} data_t;
+
+thread_t threads[THREADS];
+data_t data[DATASIZE];
+
+/*
+ * Thread start routine that uses read-write locks
+ */
+void *thread_routine (void *arg)
+{
+ thread_t *self = (thread_t*)arg;
+ int iteration;
+ int element;
+ int status;
+ lmgr_init_thread();
+ element = 0; /* Current data element */
+
+ for (iteration = 0; iteration < ITERATIONS; iteration++) {
+ if ((iteration % self->interval) == 0) {
+ status = rwl_writetrylock (&data[element].lock);
+ if (status == EBUSY)
+ self->w_collisions++;
+ else if (status == 0) {
+ data[element].data++;
+ data[element].updates++;
+ self->updates++;
+ rwl_writeunlock (&data[element].lock);
+ } else
+ err_abort (status, _("Try write lock"));
+ } else {
+ status = rwl_readtrylock (&data[element].lock);
+ if (status == EBUSY)
+ self->r_collisions++;
+ else if (status != 0) {
+ err_abort (status, _("Try read lock"));
+ } else {
+ if (data[element].data != data[element].updates)
+ printf ("%d: data[%d] %d != %d\n",
+ self->thread_num, element,
+ data[element].data, data[element].updates);
+ rwl_readunlock (&data[element].lock);
+ }
+ }
+
+ element++;
+ if (element >= DATASIZE)
+ element = 0;
+ }
+ lmgr_cleanup_thread();
+ return NULL;
+}
+
+int main (int argc, char *argv[])
+{
+ int count, data_count;
+ unsigned int seed = 1;
+ int thread_updates = 0, data_updates = 0;
+ int status;
+
+#ifdef sun
+ /*
+ * On Solaris 2.5, threads are not timesliced. To ensure
+ * that our threads can run concurrently, we need to
+ * increase the concurrency level to THREADS.
+ */
+ DPRINTF (("Setting concurrency level to %d\n", THREADS));
+ thr_setconcurrency (THREADS);
+#endif
+
+ /*
+ * Initialize the shared data.
+ */
+ for (data_count = 0; data_count < DATASIZE; data_count++) {
+ data[data_count].data = 0;
+ data[data_count].updates = 0;
+ rwl_init(&data[data_count].lock);
+ }
+
+ /*
+ * Create THREADS threads to access shared data.
+ */
+ for (count = 0; count < THREADS; count++) {
+ threads[count].thread_num = count;
+ threads[count].r_collisions = 0;
+ threads[count].w_collisions = 0;
+ threads[count].updates = 0;
+ threads[count].interval = rand_r (&seed) % ITERATIONS;
+ status = pthread_create (&threads[count].thread_id,
+ NULL, thread_routine, (void*)&threads[count]);
+ if (status != 0)
+ err_abort (status, _("Create thread"));
+ }
+
+ /*
+ * Wait for all threads to complete, and collect
+ * statistics.
+ */
+ for (count = 0; count < THREADS; count++) {
+ status = pthread_join (threads[count].thread_id, NULL);
+ if (status != 0)
+ err_abort (status, _("Join thread"));
+ thread_updates += threads[count].updates;
+ printf (_("%02d: interval %d, updates %d, "
+ "r_collisions %d, w_collisions %d\n"),
+ count, threads[count].interval,
+ threads[count].updates,
+ threads[count].r_collisions, threads[count].w_collisions);
+ }
+
+ /*
+ * Collect statistics for the data.
+ */
+ for (data_count = 0; data_count < DATASIZE; data_count++) {
+ data_updates += data[data_count].updates;
+ printf (_("data %02d: value %d, %d updates\n"),
+ data_count, data[data_count].data, data[data_count].updates);
+ rwl_destroy (&data[data_count].lock);
+ }
+
+ return 0;
+}
+
+#endif
projects / bacula / bacula / commitdiff