Does Semaphore PUT with TRY_GET add more keys to bucket?

SystemVerilog
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1

I tried the below sample program to understand semaphores better.
At time 45 both process-1 and process-2 get the keys at the same time.
Is this because the PUT corresponding to try_get added a key to the pool even though it did not get a key ?


  semaphore sema; //declaring semaphore sema
  initial begin
    sema=new(1); //creating sema with '1' key
    fork
      display(1); //process-1
      display(2); //process-2
      // display(3); //process-2
    join
  end
  
  //display method
  task automatic display(int id);
    bit success = 0; 
    success = sema.try_get(); //getting '1' key from sema
    $display($time,"\tTRY_GET KEY for ID = %0d, success = %0d, Simulation Time", id, success);
    #30;
    sema.put(); //putting '1' key to sema
    $display($time,"\tPUT KEY TRY for ID = %0d, Simulation Time", id);
    sema.get();
    $display($time,"\tGET KEY for ID = %0d, Simulation Time", id);
    #15; 
    sema.put(); 
    $display($time,"\tPUT KEY for ID = %0d, Simulation Time", id);
  endtask
endmodule

Output:
0 TRY_GET KEY for ID = 1, success = 1, Simulation Time
0 TRY_GET KEY for ID = 2, success = 0, Simulation Time
30 PUT KEY TRY for ID = 1, Simulation Time
30 GET KEY for ID = 1, Simulation Time
30 PUT KEY TRY for ID = 2, Simulation Time
30 GET KEY for ID = 2, Simulation Time
45 PUT KEY for ID = 1, Simulation Time
45 PUT KEY for ID = 2, Simulation Time

2

In reply to dyn_verif:

Putting and getting are independent operations—a semaphore maintains a storage space for keys, only tracks which processes are waiting in a FIFO queue to get an available key. And keys are just blank tokens so its up to the user not to do a put() unless they have successful get().