/*
* Bacula Thread Read/Write locking code. It permits
- * multiple readers but only one writer.
+ * 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
*
*
*/
/*
- Copyright (C) 2000, 2001, 2002 Kern Sibbald and John Walker
+ Copyright (C) 2000-2003 Kern Sibbald and John Walker
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
#include "bacula.h"
-#ifdef REALLY_IMPLEMENTED
-
/*
* Initialize a read/write lock
*
* Returns: 0 on success
* errno on failure
*/
-int rwl_init(rwlock_t *rwl)
+int rwl_init(brwlock_t *rwl)
{
int stat;
* Returns: 0 on success
* errno on failure
*/
-int rwl_destroy(rwlock_t *rwl)
+int rwl_destroy(brwlock_t *rwl)
{
int stat, stat1, stat2;
*/
static void rwl_read_release(void *arg)
{
- rwlock_t *rwl = (rwlock_t *)arg;
+ brwlock_t *rwl = (brwlock_t *)arg;
rwl->r_wait--;
pthread_mutex_unlock(&rwl->mutex);
*/
static void rwl_write_release(void *arg)
{
- rwlock_t *rwl = (rwlock_t *)arg;
+ brwlock_t *rwl = (brwlock_t *)arg;
rwl->w_wait--;
pthread_mutex_unlock(&rwl->mutex);
/*
* Lock for read access, wait until locked (or error).
*/
-int rwl_readlock(rwlock_t *rwl)
+int rwl_readlock(brwlock_t *rwl)
{
int stat;
/*
* Attempt to lock for read access, don't wait
*/
-int rwl_readtrylock(rwlock_t *rwl)
+int rwl_readtrylock(brwlock_t *rwl)
{
int stat, stat2;
/*
* Unlock read lock
*/
-int rwl_readunlock(rwlock_t *rwl)
+int rwl_readunlock(brwlock_t *rwl)
{
int stat, stat2;
/*
* Lock for write access, wait until locked (or error).
+ * Multiple nested write locking is permitted.
*/
-int rwl_writelock(rwlock_t *rwl)
+int rwl_writelock(brwlock_t *rwl)
{
int stat;
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) {
rwl->w_wait++; /* indicate that we are waiting */
pthread_cleanup_push(rwl_write_release, (void *)rwl);
while (rwl->w_active || rwl->r_active > 0) {
- stat = pthread_cond_wait(&rwl->write, &rwl->mutex);
- if (stat != 0) {
+ if ((stat = pthread_cond_wait(&rwl->write, &rwl->mutex)) != 0) {
break; /* error, bail out */
}
}
rwl->w_wait--; /* we are no longer waiting */
}
if (stat == 0) {
- rwl->w_active = 1; /* we are running */
+ rwl->w_active++; /* we are running */
+ rwl->writer_id = pthread_self(); /* save writer thread's id */
}
pthread_mutex_unlock(&rwl->mutex);
return stat;
/*
* Attempt to lock for write access, don't wait
*/
-int rwl_writetrylock(rwlock_t *rwl)
+int rwl_writetrylock(brwlock_t *rwl)
{
int stat, stat2;
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 */
}
stat2 = pthread_mutex_unlock(&rwl->mutex);
return (stat == 0 ? stat2 : stat);
* Unlock write lock
* Start any waiting writers in preference to waiting readers
*/
-int rwl_writeunlock(rwlock_t *rwl)
+int rwl_writeunlock(brwlock_t *rwl)
{
int stat, stat2;
if ((stat = pthread_mutex_lock(&rwl->mutex)) != 0) {
return stat;
}
- rwl->w_active = 0;
- if (rwl->w_wait > 0) { /* if writers waiting */
- stat = pthread_cond_signal(&rwl->write);
- } else if (rwl->r_wait > 0) {
- stat = pthread_cond_broadcast(&rwl->read);
+ if (rwl->w_active <= 0) {
+ Emsg0(M_ABORT, 0, "rwl_writeunlock called too many times.\n");
+ }
+ rwl->w_active--;
+ if (!pthread_equal(pthread_self(), rwl->writer_id)) {
+ Emsg0(M_ABORT, 0, "rwl_writeunlock by non-owner.\n");
+ }
+ if (rwl->w_active > 0) {
+ stat = 0; /* writers still active */
+ } else {
+ /* 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_signal(&rwl->write);
+ }
}
stat2 = pthread_mutex_unlock(&rwl->mutex);
return (stat == 0 ? stat2 : stat);
}
+#ifdef TEST_RWLOCK
+
+#define THREADS 5
+#define DATASIZE 15
+#define ITERATIONS 10000
+
+/*
+ * 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;
+
+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 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 = rwl_writelock(&data[element].lock);
+ if (status != 0) {
+ Emsg1(M_ABORT, 0, "Write lock failed. ERR=%s\n", strerror(status));
+ }
+ data[element].data = self->thread_num;
+ data[element].writes++;
+ self->writes++;
+ status = rwl_writeunlock(&data[element].lock);
+ if (status != 0) {
+ Emsg1(M_ABORT, 0, "Write unlock failed. ERR=%s\n", strerror(status));
+ }
+ } else {
+ /*
+ * Look at the current data element to see whether
+ * the current thread last updated it. Count the
+ * times to report later.
+ */
+ status = rwl_readlock(&data[element].lock);
+ if (status != 0) {
+ Emsg1(M_ABORT, 0, "Read lock failed. ERR=%s\n", strerror(status));
+ }
+ self->reads++;
+ if (data[element].data == self->thread_num)
+ repeats++;
+ status = rwl_readunlock(&data[element].lock);
+ if (status != 0) {
+ Emsg1(M_ABORT, 0, "Read unlock failed. ERR=%s\n", strerror(status));
+ }
+ }
+ 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) {
+ Emsg1(M_ABORT, 0, "Init rwlock failed. ERR=%s\n", strerror(status));
+ }
+ }
+
+ /*
+ * 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;
+ status = pthread_create (&threads[count].thread_id,
+ NULL, thread_routine, (void*)&threads[count]);
+ if (status != 0) {
+ Emsg1(M_ABORT, 0, "Create thread failed. ERR=%s\n", strerror(status));
+ }
+ }
+
+ /*
+ * 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) {
+ Emsg1(M_ABORT, 0, "Join thread failed. ERR=%s\n", strerror(status));
+ }
+ 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;
+
+ 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;
+ }
+ 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 / blobdiff