Re: [PATCH 2/2] selftests/seccomp: Ensure that notifications come in FIFO order

On Wed, Apr 27, 2022 at 06:54:47PM -0700, Sargun Dhillon wrote:

• /* Start children, and them generate notifications */

^^ - they maybe?

• for (i = 0; i < ARRAY_SIZE(pids); i++) {

• pid = fork();
  

• if (pid == 0) {
  

• 	ret = syscall(__NR_getppid);
  

• 	exit(ret != USER_NOTIF_MAGIC);
  

• }
  

• pids[i] = pid;
  

• }
• /* This spins until all of the children are sleeping */

+restart_wait:

• for (i = 0; i < ARRAY_SIZE(pids); i++) {

• if (get_proc_stat(pids[i]) != 'S') {
  

• 	nanosleep(&delay, NULL);
  

• 	goto restart_wait;
  

• }
  

• }

I wonder if we should/can combine this loop with the previous one, and wait for the child to sleep in getppid() before we fork the next one. Otherwise isn't racy in the case that your loop continues to the next iteration before the child processes are scheduled, so things might be out of order? Maybe I'm missing something.

In any case, this change seems reasonable to me.

Tycho