//Enqueue d into the FIFO, blocking until the FIFO has room to accept it.
void fifo_wr(struct fifo *f,unsigned long d){
sem_wait(&f->wr_sem); //wait for an available slot to write
sem_wait(&f->mutex); //obtain the mutex
f->buf[f->next_write++]=d; //perform the write
f->next_write%=MYFIFO_BUFSIZ;
sem_inc(&f->mutex); //release the mutex
sem_inc(&f->rd_sem); //increment the number of available reading slots
}
void fifo_wr(struct fifo *f, unsigned long d) {
sem_wait(&f->s_wk);
sem_wait(&f->s_w);
f->queue[*f->end % MYFIFO_BUFSIZ] = d;
(*f->end)++;
sem_inc(&f->s_wk);
sem_inc(&f->s_r);
}
unsigned long fifo_rd(struct fifo *f) {
sem_wait(&f->s_rk);
sem_wait(&f->s_r);
unsigned long result = f->queue[*(f->start) % MYFIFO_BUFSIZ];
(*f->start)++;
sem_inc(&f->s_rk);
sem_inc(&f->s_w);
return result;
}
//Dequeue and return the next data word, blocking until there are available words.
unsigned long fifo_rd(struct fifo *f){
unsigned long d;
sem_wait(&f->rd_sem); //wait for an available slot to read
sem_wait(&f->mutex); //obtain the mutex
d=f->buf[f->next_read++]; //perform the read
f->next_read%=MYFIFO_BUFSIZ;
sem_inc(&f->mutex); //release the mutex
sem_inc(&f->wr_sem); //increment the number of available writing slots
return d;
}
void fifo_wr(struct fifo *f, unsigned long d) {
while(1) {
sem_wait(&f->wr_sem);
if (mutex_trylock(&f->wr_lock)) {
f->arr[f->wr_pos] = d;
f->wr_pos = (f->wr_pos + 1)%MYFIFO_BUFSIZ;
mutex_unlock(&f->wr_lock);
sem_inc(&f->rd_sem);
return;
}
else
sem_inc(&f->wr_sem);
}
}
unsigned long fifo_rd(struct fifo *f) {
unsigned long retval;
while(1) {
sem_wait(&f->rd_sem);
if (mutex_trylock(&f->rd_lock)) {
retval = f->arr[f->rd_pos];
f->rd_pos = (f->rd_pos + 1)%MYFIFO_BUFSIZ;
mutex_unlock(&f->rd_lock);
sem_inc(&f->wr_sem);
return retval;
}
else
sem_inc(&f->rd_sem);
}
}
int main(int argc, char** argv) {
int procs[NUMPROC];
int *mapped;
s = mmap(0,(sizeof (struct sem)),PROT_READ|PROT_WRITE,MAP_SHARED|MAP_ANONYMOUS,-1,0);
sem_init(s, 1);
mapped = mmap(0,(sizeof (int)),PROT_READ|PROT_WRITE,MAP_SHARED|MAP_ANONYMOUS,-1,0);
mapped[0] = 0;
int curr_proc;
int i;
for (i = 1; i < NUMPROC; i++) {
curr_proc = fork();
procs[i] = curr_proc;
if (curr_proc == 0)
break;
else if (curr_proc == -1){
perror("couldn't fork\n");
exit(1);
}
my_procnum = i;
}
int initial;
int end;
int j;
for (j = 0; j < 1e6; j++){
sem_wait(s);
fprintf(stderr," locked for process %d\n",my_procnum);
initial = mapped[0];
end = ++mapped[0];
if (end != initial+1){
fprintf(stderr,"size mismatch! process %d started with %d and ended with %d\n",i,initial,end);
for(j = 0; j < NUMPROC; j++) {
if (j != my_procnum && s->pids[j]) {
kill(s->pids[j], SIGINT);
}
}
exit (1);
}
else{
fprintf(stderr,"process %d started with %d and ended with %d\n",my_procnum,initial,end);
}
fprintf(stderr,"unlocked for process %d\n",my_procnum);
sem_inc(s);
}
return 0;
}