Multi thread in DPI-C structure

SystemVerilog
, , ,
1

Hi,

I export a dynamic task to C++ test bench, but the task looks skip forever loop.
How can I resolve it?


export "DPI-C" task freq;

task automatic freq();  // global task
  bit a = xDUV.aa;
  bit b = xDUV.bb;
  $display($time,">>> a= %b, b=%b", a, b); // display OK
  fork
    forever begin: checking
         $display("forever start"); // No displaying
         @(negedge b)
            $display($time,"b enabled");
         @(posedge a);
         @(posedge a)
             if(!b)
                 $display($time,"ERROR");
         disable checking;
     end
  join_none
endtask

c++ code


extern "C" void freq(void);
void TEST()
{
  freq();

  sim_printf("[INFO] Mask Test\n");  // display OK
  ....
  ....
}
2

In reply to uvmbee:

The variables ‘a’ and ‘b’ are assigned values when the task is called. These values will never change, hence it appears that your forever loop never executes.

3

In reply to cgales:

Thx cgales,

the frever loop never executes if assigned value would not be chaged. But even though I think the first $diaplay(“forever start”) should be worked.
I re-tested your comment as below, but the first display works well in usual verilog task call, not by DPI-C.



//export "DPI-C" task freq;
//Call in verilog module
 
task automatic freq();  // global task
  bit a = 1;
  bit b = 1;
  $display($time,">>> a= %b, b=%b", a, b); // display OK
  fork
    forever begin: checking
         $display("forever start"); // diaplay OK
         @(negedge b)
            $display($time,"b enabled");
         @(posedge a);
         @(posedge a)
             if(!b)
                 $display($time,"ERROR");
         disable checking;
     end
  join_none
endtask