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#include <assert.h>
#include <pthread.h>
#include <stdlib.h>
#include "fb.h"
#include "rototiller.h"
#include "threads.h"
#include "util.h"
/* This is a very simple/naive implementation, there's certainly room for improvement.
* Some things to explore:
* - switch to a single condition variable and broadcast to wake up the threads?
* - use lock-free algorithms?
*/
typedef struct fragment_node_t fragment_node_t;
struct fragment_node_t {
fragment_node_t *next;
fb_fragment_t *fragment;
};
typedef struct thread_t {
pthread_t thread;
pthread_mutex_t mutex;
pthread_cond_t cond;
void (*render_fragment_func)(fb_fragment_t *fragment);
fragment_node_t *fragments;
} thread_t;
typedef struct threads_t {
unsigned n_threads;
fragment_node_t fragment_nodes[ROTOTILLER_FRAME_MAX_FRAGMENTS];
thread_t threads[];
} threads_t;
/* render submitted fragments using the supplied render function */
static void * thread_func(void *_thread)
{
thread_t *thread = _thread;
for (;;) {
pthread_mutex_lock(&thread->mutex);
while (!thread->fragments)
pthread_cond_wait(&thread->cond, &thread->mutex);
do {
thread->render_fragment_func(thread->fragments->fragment);
thread->fragments = thread->fragments->next;
} while (thread->fragments);
pthread_mutex_unlock(&thread->mutex);
pthread_cond_signal(&thread->cond);
}
return NULL;
}
/* submit a list of fragments to render using the specified thread and render_fragment_func */
static void thread_fragments_submit(thread_t *thread, void (*render_fragment_func)(fb_fragment_t *fragment), fragment_node_t *fragments)
{
pthread_mutex_lock(&thread->mutex);
while (thread->fragments != NULL) /* XXX: never true due to thread_wait_idle() */
pthread_cond_wait(&thread->cond, &thread->mutex);
thread->render_fragment_func = render_fragment_func;
thread->fragments = fragments;
pthread_mutex_unlock(&thread->mutex);
pthread_cond_signal(&thread->cond);
}
/* wait for a thread to be idle */
static void thread_wait_idle(thread_t *thread)
{
pthread_mutex_lock(&thread->mutex);
while (thread->fragments)
pthread_cond_wait(&thread->cond, &thread->mutex);
pthread_mutex_unlock(&thread->mutex);
}
/* submit a frame's fragments to the threads */
void threads_frame_submit(threads_t *threads, rototiller_frame_t *frame, void (*render_fragment_func)(fb_fragment_t *fragment))
{
unsigned i, t;
fragment_node_t *lists[threads->n_threads];
assert(frame->n_fragments <= ROTOTILLER_FRAME_MAX_FRAGMENTS);
for (i = 0; i < threads->n_threads; i++)
lists[i] = NULL;
for (i = 0; i < frame->n_fragments;) {
for (t = 0; i < frame->n_fragments && t < threads->n_threads; t++, i++) {
threads->fragment_nodes[i].next = lists[t];
lists[t] = &threads->fragment_nodes[i];
lists[t]->fragment = &frame->fragments[i];
}
}
for (i = 0; i < threads->n_threads; i++)
thread_fragments_submit(&threads->threads[i], render_fragment_func, lists[i]);
}
/* wait for all threads to drain their fragments list and become idle */
void threads_wait_idle(threads_t *threads)
{
unsigned i;
for (i = 0; i < threads->n_threads; i++)
thread_wait_idle(&threads->threads[i]);
}
/* create threads instance, a thread per cpu is created */
threads_t * threads_create(void)
{
threads_t *threads;
unsigned i, num = get_ncpus();
threads = calloc(1, sizeof(threads_t) + sizeof(thread_t) * num);
if (!threads)
return NULL;
for (i = 0; i < num; i++) {
pthread_mutex_init(&threads->threads[i].mutex, NULL);
pthread_cond_init(&threads->threads[i].cond, NULL);
pthread_create(&threads->threads[i].thread, NULL, thread_func, &threads->threads[i]);
}
threads->n_threads = num;
return threads;
}
/* destroy a threads instance */
void threads_destroy(threads_t *threads)
{
unsigned i;
for (i = 0; i < threads->n_threads; i++)
pthread_cancel(threads->threads[i].thread);
for (i = 0; i < threads->n_threads; i++)
pthread_join(threads->threads[i].thread, NULL);
free(threads);
}
/* return the number of threads */
unsigned threads_num_threads(threads_t *threads)
{
return threads->n_threads;
}
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