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#include <sys/mman.h> // mmap()
#include <unistd.h> // fork()
#include <sys/wait.h> // wait()
#include <semaphore.h> // sem_init(), Link with -pthread
#include <errno.h> // errno
#include <stdint.h> // uint32_t
#include <stdio.h> // printf()
int do_fork1();
int do_fork2();
int parent();
int worker_gl();
int worker_sdl();
typedef struct {
sem_t worker_gl_can_render, worker_sdl_can_render, parent_can_read_result;
int scene;
uint32_t framebuf[256*256];
} shm_t;
shm_t *shm;
int main() {
shm = mmap(NULL, sizeof(shm_t), PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, 0, 0);
if (sem_init(&shm->worker_gl_can_render, 1, 0) < 0) return 1;
if (sem_init(&shm->worker_sdl_can_render, 1, 0) < 0) return 2;
if (sem_init(&shm->parent_can_read_result, 1, 0) < 0) return 3;
shm->scene = 0;
return do_fork1();
}
int do_fork1() {
switch (fork()) {
case -1: return 4; break;
case 0: return worker_gl(); break;
default: return do_fork2(); break;
}
}
int do_fork2() {
switch (fork()) {
case -1: return 5; break;
case 0: return worker_sdl(); break;
default: return parent(); break;
}
}
int parent() {
int i, child_status;
shm->scene++;
printf("parent1 %i\n", shm->scene);
for(i=0;i<4;i++) {
if ( sem_post(&shm->worker_sdl_can_render) == -1 ) {
return 6;
}
while ( sem_wait(&shm->parent_can_read_result) == -1 ) {
switch(errno) {
case EINTR:
case EAGAIN:
break;
default:
return 7;
}
}
printf("parent2 %i\n", shm->scene);
if ( sem_post(&shm->worker_gl_can_render) == -1 ) {
return 6;
}
while ( sem_wait(&shm->parent_can_read_result) == -1 ) {
switch(errno) {
case EINTR:
case EAGAIN:
break;
default:
return 8;
}
}
printf("parent3 %i\n", shm->scene);
}
if ( wait(&child_status) != -1 ) {
if ( child_status > 0 ) return child_status;
}
if ( wait(&child_status) != -1 ) {
if ( child_status > 0 ) return child_status;
}
return 0;
}
int worker_gl() {
int done=0;
while ( !done ) {
while ( sem_wait(&shm->worker_gl_can_render) == -1 ) {
switch(errno) {
case EINTR:
case EAGAIN:
break;
default:
return 10;
}
}
printf("worker_gl %i\n", shm->scene);
shm->scene++;
if ( sem_post(&shm->parent_can_read_result) == -1 ) {
return 11;
}
}
return 0;
}
int worker_sdl() {
int done=0;
while ( !done ) {
while ( sem_wait(&shm->worker_sdl_can_render) == -1 ) {
switch(errno) {
case EINTR:
case EAGAIN:
break;
default:
return 20;
}
}
printf("worker_sdl %i\n", shm->scene);
shm->scene++;
if ( sem_post(&shm->parent_can_read_result) == -1 ) {
return 21;
}
}
return 0;
}
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