How does "prctl(PR_SET_PDEATHSIG, SIGKILL)" do

Question

Hi i was reading a C code that creates a child process via clone(), and in the child process/function there is a line that i don't clearly understand :

prctl(PR_SET_PDEATHSIG, SIGKILL)

i searched for a while about prctl() and about this particular line, and what i understood is that it will kill the child process if the parent thread dies.

i know that if the parent thread exits/dies a PR_SET_PDEATHSIG signal will be sent to the child (if my 1st guess is true), and i know what SIGKILL means, but i don't understand what pctrl() does with them both, does it mean :

• if the parent thread dies then the child process receives a PR_SET_PDEATHSIG signal then he will send a SIGKILL to itself. OR :
• PR_SET_PDEATHSIG is not even a signal and it is used to refer to the parent thread death, and what the line means is if the parent thread exits/dies then the child process will receive SIGKILL signal. OR:
• something else, kindly clarify

The C code is something like this:

#INCLUDES

static int child_function( ... ) {

   if( prctl(PR_SET_PDEATHSIG, SIGKILL) )
       printf("ERROR");

   //CHILD CODE
}

int main( ... ) {
  //PARENT CODE

  int child_pid = clone(child_function, ...);

  //PARENT CODE
}