Fork-join_none not working

SystemVerilog
, ,
1

I need help with the code below. What is wrong in the code below?


task test_code();
  int i=15;
  do begin
  fork
      begin
        #5;
        $display("%t: val=%d", $time(), i);
        i--;
      end
      begin
        if(i>0) begin
            #5;
            $display("%t: val=%d", $time(), i);
        end
      end    
  join_none
  end while (i>0);
endtask
2

In reply to hk123:

Please use code tags. I have added them for you.

You will need to provide more context regarding your issue. Does the code not compile? Does it not function as you expect it to? What do you expect the results to be?

One significant issue is that you have an infinite loop. A join_none statement is non-blocking, hence your do loop will run forever since i is never decremented.

3

In reply to cgales:

Thanks cgles for fixing the code format.
The code doesn’t compile. I’m trying to run two threads where thread#1 is decrementing the value of i which is initialized to 15 and thread#2 is running till i is >0.

4

In reply to hk123:

So something like:


task test_code();
  automatic int i=15;

  fork
    while (i>0) begin
      #5;
      $display("%t: val=%d", $time(), i);
      i--;
    end
    while (i>0) begin
      #5;
      $display("%t: val=%d", $time(), i);
    end
  join
endtask

module top();
  initial begin
    test_code();
  end
endmodule
5

In reply to cgales:

Behavior is correct but I want to use join_none instead of join. Thread#2 should run independently of thread#1.

6

In reply to hk123:

I’m not sure what you mean as the join_none has no effect on the threads running independently of each other.

If you want to keep the second thread running forever, you can use:


task test_code();
  automatic int i=15;

  fork
    while (i>0) begin
      #5;
      $display("Decrement thread: %t: val=%d", $time(), i);
      i--;
    end
    forever begin
      #5;
      $display("Monitor thread: %t: val=%d", $time(), i);
    end
  join_none
endtask

module top();
  initial begin
    test_code();
    #500;
    $finish;
  end
endmodule