* reimplementation using mutexes and condition variables.

Originally committed as revision 3138 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/pthread.c

 /*
- * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
+ * Copyright (c) 2004 Roman Shaposhnik.
+ * 
+ * Many thanks to Steven M. Schultz for providing clever ideas and
+ * to Michael Niedermayer <michaelni@gmx.at> for writing initial
+ * implementation.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -16,186 +20,149 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  *
  */
-#include <semaphore.h>
 #include <pthread.h>
 
-//#define DEBUG
-
 #include "avcodec.h"
 #include "common.h"
 
-typedef struct JobContext{
-    sem_t available_sem;
-    int assigned;
-    int (*func)(AVCodecContext *c, void *arg);
-    void *arg;
-    int ret;
-}JobContext;
-
-typedef struct WorkerContext{
-    AVCodecContext *avctx;
-    pthread_t thread;
-    int start_index;
-    sem_t work_sem;
-    sem_t done_sem;
-}WorkerContext;
+typedef int (action_t)(AVCodecContext *c, void *arg);
 
-typedef struct ThreadContext{
-    WorkerContext *worker;
-    JobContext *job;
+typedef struct ThreadContext {
+    pthread_t *workers;
+    action_t *func;
+    void **args;
+    int *rets;
+    int rets_count;
     int job_count;
-    int allocated_job_count;
-}ThreadContext;
-
-static void * thread_func(void *v){
-    WorkerContext *w= v;
-    ThreadContext *c= w->avctx->thread_opaque;
-    int i;
-
-    for(;;){
-//av_log(w->avctx, AV_LOG_DEBUG, "thread_func %X enter wait\n", (int)v);
-        sem_wait(&w->work_sem);
-//av_log(w->avctx, AV_LOG_DEBUG, "thread_func %X after wait\n", (int)v);
-        if(c->job_count == 0)
-           break;
-        
-        for(i=0; i<c->job_count; i++){
-            int index= (i + w->start_index) % c->job_count;
-            JobContext *j= &c->job[index];
-        
-//av_log(w->avctx, AV_LOG_DEBUG, "thread_func %X first check of %d\n", (int)v, index);
-            if(j->assigned) continue; //unsynced check, if != 0 it is already given to another worker, it never becomes available before the next execute() call so this should be safe
+    
+    pthread_cond_t last_job_cond;
+    pthread_cond_t current_job_cond;
+    pthread_mutex_t current_job_lock;
+    int current_job;
+    int done;
+} ThreadContext;
+
+static void* worker(void *v) 
+{
+    AVCodecContext *avctx = v;
+    ThreadContext *c = avctx->thread_opaque;
+    int our_job = c->job_count;
+    int thread_count = avctx->thread_count;
+    int self_id;
+
+    pthread_mutex_lock(&c->current_job_lock);
+    self_id = c->current_job++;
+    for (;;){ 
+	while (our_job >= c->job_count) {
+	    if (c->current_job == thread_count + c->job_count)
+	        pthread_cond_signal(&c->last_job_cond);
             
-//av_log(w->avctx, AV_LOG_DEBUG, "thread_func %X second check of %d\n", (int)v, index);
-            if(sem_trywait(&j->available_sem) == 0){
-                j->assigned=1;
-                j->ret= j->func(w->avctx, j->arg);
-//av_log(w->avctx, AV_LOG_DEBUG, "thread_func %X done %d\n", (int)v, index);
-            }
-        }
-//av_log(w->avctx, AV_LOG_DEBUG, "thread_func %X complete\n", (int)v);
-        sem_post(&w->done_sem);
+	    pthread_cond_wait(&c->current_job_cond, &c->current_job_lock);
+            our_job = self_id;
+	    
+	    if (c->done) {
+	        pthread_mutex_unlock(&c->current_job_lock);
+		return NULL;
+	    }
+	}
+	pthread_mutex_unlock(&c->current_job_lock);
+	
+	c->rets[our_job%c->rets_count] = c->func(avctx, c->args[our_job]);
+	
+	pthread_mutex_lock(&c->current_job_lock);
+	our_job = c->current_job++;
     }
-    
-    return NULL;
 }
 
-/**
- * free what has been allocated by avcodec_thread_init().
- * must be called after decoding has finished, especially dont call while avcodec_thread_execute() is running
- */
-void avcodec_thread_free(AVCodecContext *s){
-    ThreadContext *c= s->thread_opaque;
-    int i, val;
-    
-    for(i=0; i<c->allocated_job_count; i++){
-        sem_getvalue(&c->job[i].available_sem, &val); assert(val == 0);
-        sem_destroy(&c->job[i].available_sem);
-    }
-
-    c->job_count= 0;
-    for(i=0; i<s->thread_count; i++){
-        sem_getvalue(&c->worker[i].work_sem, &val); assert(val == 0);
-        sem_getvalue(&c->worker[i].done_sem, &val); assert(val == 0);
-
-        sem_post(&c->worker[i].work_sem);
-        pthread_join(c->worker[i].thread, NULL);
-        sem_destroy(&c->worker[i].work_sem);
-        sem_destroy(&c->worker[i].done_sem);
-    }
-
-    av_freep(&c->job);
-    av_freep(&c->worker);
-    av_freep(&s->thread_opaque);
+static always_inline void avcodec_thread_park_workers(ThreadContext *c, int thread_count)
+{
+    pthread_cond_wait(&c->last_job_cond, &c->current_job_lock);
+    pthread_mutex_unlock(&c->current_job_lock);
 }
 
-int avcodec_thread_execute(AVCodecContext *s, int (*func)(AVCodecContext *c2, void *arg2),void **arg, int *ret, int job_count){
-    ThreadContext *c= s->thread_opaque;
-    int i, val;
+void avcodec_thread_free(AVCodecContext *avctx) 
+{
+    ThreadContext *c = avctx->thread_opaque;
+    int i;
     
-    assert(s == c->avctx);
-    if(job_count > c->allocated_job_count){
-        c->job= av_realloc(c->job, job_count*sizeof(JobContext));
-
-        for(i=c->allocated_job_count; i<job_count; i++){
-            memset(&c->job[i], 0, sizeof(JobContext));
-            c->allocated_job_count++;
+    pthread_mutex_lock(&c->current_job_lock);
+    c->done = 1;
+    pthread_cond_signal(&c->current_job_cond);
+    pthread_mutex_unlock(&c->current_job_lock);
+
+    for (i=0; i<avctx->thread_count; i++)
+         pthread_join(c->workers[i], NULL);
+
+    pthread_mutex_destroy(&c->current_job_lock);
+    pthread_cond_destroy(&c->current_job_cond);
+    pthread_cond_destroy(&c->last_job_cond);
+    av_free(c->workers);
+    av_freep(c);
+}
 
-            if(sem_init(&c->job[i].available_sem, 0, 0))
-                return -1;
-        }
-    }
-    c->job_count= job_count;
+int avcodec_thread_execute(AVCodecContext *avctx, action_t* func, void **arg, int *ret, int job_count) 
+{
+    ThreadContext *c= avctx->thread_opaque;
+    int dummy_ret;
+   
+    if (job_count <= 0)
+        return 0;
     
-    /* note, we can be certain that this is not called with the same AVCodecContext by different threads at the same time */
-
-    for(i=0; i<job_count; i++){
-        sem_getvalue(&c->job[i].available_sem, &val); assert(val == 0);
-        
-        c->job[i].arg= arg[i];
-        c->job[i].func= func;
-        c->job[i].ret= 12345;
-        c->job[i].assigned= 0;
-        sem_post(&c->job[i].available_sem);
-    }
-
-    for(i=0; i<s->thread_count && i<job_count; i++){
-        sem_getvalue(&c->worker[i].work_sem, &val); assert(val == 0);
-        sem_getvalue(&c->worker[i].done_sem, &val); assert(val == 0);
-
-        c->worker[i].start_index= (i + job_count/2)/job_count;
-//av_log(s, AV_LOG_DEBUG, "start worker %d\n", i);
-        sem_post(&c->worker[i].work_sem);
-    }
-
-    for(i=0; i<s->thread_count && i<job_count; i++){
-//av_log(s, AV_LOG_DEBUG, "wait for worker %d\n", i);
-        sem_wait(&c->worker[i].done_sem);
-
-        sem_getvalue(&c->worker[i].work_sem, &val); assert(val == 0);
-        sem_getvalue(&c->worker[i].done_sem, &val); assert(val == 0);
-    }
-
-    for(i=0; i<job_count; i++){
-        sem_getvalue(&c->job[i].available_sem, &val); assert(val == 0);
-        
-        c->job[i].func= NULL;
-        if(ret) ret[i]= c->job[i].ret;
+    pthread_mutex_lock(&c->current_job_lock);
+
+    c->current_job = avctx->thread_count;
+    c->job_count = job_count;
+    c->args = arg;
+    c->func = func;
+    if (ret) {
+        c->rets = ret;
+	c->rets_count = job_count;
+    } else { 
+        c->rets = &dummy_ret;
+	c->rets_count = 1;
     }
+    pthread_cond_broadcast(&c->current_job_cond);
 
+    avcodec_thread_park_workers(c, avctx->thread_count);
+    
     return 0;
 }
 
-int avcodec_thread_init(AVCodecContext *s, int thread_count){
+int avcodec_thread_init(AVCodecContext *avctx, int thread_count) 
+{
     int i;
     ThreadContext *c;
-    WorkerContext *worker;
 
-    s->thread_count= thread_count;
+    c = av_mallocz(sizeof(ThreadContext));
+    if (!c)
+        return -1;
+	
+    c->workers = av_mallocz(sizeof(pthread_t)*thread_count);
+    if (!c->workers) {
+        av_free(c);
+        return -1;
+    }
 
-    assert(!s->thread_opaque);
-    c= av_mallocz(sizeof(ThreadContext));
-    worker= av_mallocz(sizeof(WorkerContext)*thread_count);
-    s->thread_opaque= c;
-    c->worker= worker;
-        
-    for(i=0; i<thread_count; i++){
-//printf("init semaphors %d\n", i); fflush(stdout);
-        worker[i].avctx= s;
-        if(sem_init(&worker[i].work_sem, 0, 0))
-            goto fail;
-        if(sem_init(&worker[i].done_sem, 0, 0))
-            goto fail;
-//printf("create thread %d\n", i); fflush(stdout);
-        if(pthread_create(&worker[i].thread, NULL, thread_func, &worker[i]))
-            goto fail;
+    avctx->thread_opaque = c;
+    avctx->thread_count = thread_count;
+    c->current_job = 0;
+    c->job_count = 0;
+    c->done = 0;
+    pthread_cond_init(&c->current_job_cond, NULL); 
+    pthread_cond_init(&c->last_job_cond, NULL);
+    pthread_mutex_init(&c->current_job_lock, NULL);
+    pthread_mutex_lock(&c->current_job_lock);
+    for (i=0; i<thread_count; i++) { 
+        if(pthread_create(&c->workers[i], NULL, worker, avctx)) {
+	   avctx->thread_count = i;
+	   pthread_mutex_unlock(&c->current_job_lock);
+           avcodec_thread_free(avctx);
+           return -1;
+        }
     }
-//printf("init done\n"); fflush(stdout);
     
-    s->execute= avcodec_thread_execute;
-
+    avcodec_thread_park_workers(c, thread_count);
+    
+    avctx->execute = avcodec_thread_execute;
     return 0;
-fail:
-    avcodec_thread_free(s);
-    return -1;
 }