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cthread_pool.c
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cthread_pool.c
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#include "cthread.h"
typedef enum {
immediate_shutdown = 1,
graceful_shutdown,
terminate_shutdown
} pool_shutdown_t;
/* The work struct */
typedef struct {
/* Pointer to the function that will perform the task. */
void (*function)(void *);
/* Argument to be passed to the function. */
void *argument;
} pool_task_t;
/* The pool struct */
struct pool_s {
mtx_t lock;
/* Condition variable to notify worker threads. */
cnd_t notify;
/* threads currently working*/
int num_working;
/* used for thread count etc */
mtx_t count_lock;
/* signal to thrd_wait */
cnd_t all_idle;
/* Array containing worker threads ID. */
thrd_t *threads;
/* Array containing the task queue. */
pool_task_t *queue;
/* Number of threads*/
int thread_count;
/* Size of the task queue.*/
int queue_size;
/* Index of the first element. */
int head;
/* Index of the next element. */
int tail;
/* Number of pending tasks */
int count;
/* Flag indicating if the pool is shutting down*/
int shutdown;
/* Number of started threads */
int started;
};
/**
* @brief the worker thread
* @param pool the pool which own the thread
*/
static void *pool_thread(void *args);
int thrd_free(thrd_pool_t *pool);
thrd_pool_t *thrd_pool(int thread_count, int queue_size) {
thrd_pool_t *pool;
int i;
if ((pool = (thrd_pool_t *)ZE_MALLOC(sizeof(thrd_pool_t))) == NULL) {
goto err;
}
/* Initialize */
pool->thread_count = 0;
pool->queue_size = queue_size;
pool->head = pool->tail = pool->count = 0;
pool->shutdown = pool->started = 0;
pool->num_working = 0;
/* Allocate thread and task queue */
pool->threads = (thrd_t *)ZE_MALLOC(sizeof(thrd_t) * thread_count);
pool->queue = (pool_task_t *)ZE_MALLOC
(sizeof(pool_task_t) * queue_size);
/* Initialize mutex and conditional variable first */
if ((mtx_init(&(pool->lock), mtx_plain) != thrd_success) ||
(cnd_init(&(pool->notify)) != thrd_success) ||
(mtx_init(&(pool->count_lock), mtx_plain) != thrd_success) ||
(cnd_init(&(pool->all_idle)) != thrd_success) ||
(pool->threads == NULL) ||
(pool->queue == NULL)) {
goto err;
}
/* Start worker threads */
for (i = 0; i < thread_count; i++) {
if (thrd_create(&(pool->threads[i]), (thrd_start_t)pool_thread, (void *)pool) != thrd_success) {
thrd_destroy(pool, 0);
return NULL;
}
pool->thread_count++;
pool->started++;
}
return pool;
err:
if (pool) {
thrd_free(pool);
}
return NULL;
}
int thrd_add(thrd_pool_t *pool, void (*function)(void *),
void *argument) {
int err = 0;
int next;
if (pool == NULL || function == NULL) {
return pool_invalid;
}
if (mtx_lock(&(pool->lock)) != thrd_success) {
return pool_lock_failure;
}
next = (pool->tail + 1) % pool->queue_size;
do {
/* Are we full ? */
if (pool->count == pool->queue_size) {
err = pool_queue_full;
break;
}
/* Are we shutting down ? */
if (pool->shutdown) {
err = pool_shutdown;
break;
}
/* Add task to queue */
pool->queue[pool->tail].function = function;
pool->queue[pool->tail].argument = argument;
pool->tail = next;
pool->count += 1;
/* pthread_cond_broadcast */
if (cnd_signal(&(pool->notify)) != thrd_success) {
err = pool_lock_failure;
break;
}
} while (0);
if (mtx_unlock(&pool->lock) != thrd_success) {
err = pool_lock_failure;
}
return err;
}
int thrd_destroy(thrd_pool_t *pool, int flags) {
int i, err = 0, kill_flag = flags;
if (pool == NULL) {
return pool_invalid;
}
if (mtx_lock(&(pool->lock)) != thrd_success) {
return pool_lock_failure;
}
do {
/* Already shutting down */
if (pool->shutdown) {
err = pool_shutdown;
break;
}
flags = kill_flag == pool_kill ? 0 : flags;
pool->shutdown = (flags & pool_graceful) ?
graceful_shutdown : immediate_shutdown;
/* Wake up all worker threads */
if ((cnd_broadcast(&(pool->notify)) != thrd_success) ||
(mtx_unlock(&(pool->lock)) != thrd_success)) {
err = pool_lock_failure;
break;
}
/* Join all worker thread */
for (i = 0; i < pool->thread_count; i++) {
if (kill_flag == pool_kill)
err = pthread_cancel(pool->threads[i]);
else if (thrd_join(pool->threads[i], NULL) != thrd_success) {
err = pool_thread_failure;
}
}
} while (0);
/* Only if everything went well do we deallocate the pool */
if (!err) {
thrd_free(pool);
}
return err;
}
int thrd_free(thrd_pool_t *pool) {
if (pool == NULL || pool->started > 0) {
return -1;
}
/* Did we manage to allocate ? */
if (pool->threads) {
ZE_FREE(pool->threads);
ZE_FREE(pool->queue);
mtx_destroy(&(pool->lock));
cnd_destroy(&(pool->notify));
mtx_destroy(&(pool->count_lock));
cnd_destroy(&(pool->all_idle));
}
ZE_FREE(pool);
return 0;
}
static void *pool_thread(void *args) {
thrd_pool_t *pool = (thrd_pool_t *)args;
pool_task_t task;
for (;;) {
/* Lock must be taken to wait on conditional variable */
mtx_lock(&(pool->lock));
/* Wait on condition variable, check for spurious wakeups.
When returning from cnd_wait(), we own the lock. */
while ((pool->count == 0) && (!pool->shutdown)) {
cnd_wait(&(pool->notify), &(pool->lock));
}
if ((pool->shutdown == immediate_shutdown) ||
((pool->shutdown == graceful_shutdown) &&
(pool->count == 0))) {
break;
}
/* Grab our task */
task.function = pool->queue[pool->head].function;
task.argument = pool->queue[pool->head].argument;
pool->head = (pool->head + 1) % pool->queue_size;
pool->count -= 1;
/* Unlock */
mtx_unlock(&(pool->lock));
/* Get to work */
mtx_lock(&pool->count_lock);
pool->num_working++;
mtx_unlock(&pool->count_lock);
(*(task.function))(task.argument);
mtx_lock(&pool->count_lock);
pool->num_working--;
if (!pool->num_working)
cnd_signal(&pool->all_idle);
mtx_unlock(&pool->count_lock);
}
pool->started--;
mtx_unlock(&(pool->lock));
thrd_exit(0);
return(NULL);
}
void thrd_wait(thrd_pool_t *pool) {
mtx_lock(&pool->count_lock);
while (pool->count || pool->num_working) {
cnd_wait(&pool->all_idle, &pool->count_lock);
}
mtx_unlock(&pool->count_lock);
}