Recursive mpi spawns (spawn from spawn) - c

Question

The problem is quite simple: a manager spawns X workers. Each worker spawns 2 more workers if a condition is met. Everything works fine as long as the workers don't spawn anymore (so condition not met, or if only the first "original" worker spawns; hangs for the other workers).
Manager code:
int main(int argc, char *argv[]) {
int myrank, numworkers, tag = 3, sum = 0, K = 1;
MPI_Status status;
MPI_Comm workercomm;
numworkers = atoi(argv[1]);
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
MPI_Comm_spawn("Project_child",
MPI_ARGV_NULL, numworkers, MPI_INFO_NULL, 0, MPI_COMM_SELF,
&workercomm, MPI_ERRCODES_IGNORE);
for (int i = 0; i < numworkers; i++) { //sends 1,2,3... to workers
K=i+1;
MPI_Send(&K, 1, MPI_INT, i, tag, workercomm);
}
for (int i = 0; i < numworkers; i++) { //receives an int from worker
MPI_Recv(&K, 1, MPI_INT, i, tag, workercomm, &status);
sum += K;
}
printf("%d \n", sum);
MPI_Comm_free(&workercomm);
MPI_Finalize();
return 0;
}
Worker code:
int main(int argc, char *argv[]) {
int K, myrank, tag = 3;
MPI_Status status;
MPI_Comm parentcomm;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
MPI_Comm_get_parent(&parentcomm);
MPI_Recv(&K, 1, MPI_INT, 0, tag, parentcomm, &status); //recv K
printf("child %d: k=%d\n", myrank, K);
K++;
if (K<5) { // && myrank==0) {
MPI_Comm childParentComm;
MPI_Comm_spawn("Project_child",
MPI_ARGV_NULL, 2, MPI_INFO_NULL, 0, MPI_COMM_SELF,
&childParentComm, MPI_ERRCODES_IGNORE);
//problem might be here?^
//sends the K to first worker_child
MPI_Send(&K, 1, MPI_INT, 0, tag, childParentComm);
//!!!!!!! IT HANGS HERE if worker != 0
K++;
//sends K+1 to second worker_child
MPI_Send(&K, 1, MPI_INT, 1, tag, childParentComm);
int K1, K2;
MPI_Recv(&K1, 1, MPI_INT, 0, tag, childParentComm, &status);
MPI_Recv(&K2, 1, MPI_INT, 1, tag, childParentComm, &status);
K = K1 + K2;
MPI_Comm_free(&childParentComm);
}
MPI_Send(&K, 1, MPI_INT, 0, tag, parentcomm);
MPI_Comm_free(&parentcomm);
MPI_Finalize();
return 0;
}
OK, I changed the code to simplify it.
Tested the code, problem is the same: worker0 spawns additional children (even his child0 spawns additional children), the others don't and they hang at the second send. So if the condition would be (if (K<5) && myrank==0), it would work, but that's not what I need.