Cannot invalidate launchd kextcache from helper executable

Question

I've built an uninstaller that call helper executable with elevated permissions to remove my driver's launchd-plist, so that it won't come up again on the next boot cycle.

In order reflect the new stage of /Library/LaunchDaemons, I invalidate the kextcache using the following command touch /Library/Extensions/ showed in this question.

However, when I do so from the helper executable right after the plist file was removed, it wouldn't succeed, and my driver still go up after reboot. When I do it manually by typing the command touch /Library/Extensions right after the uninstaller helper finish, it does the trick.

here's how my code looks like in the first option (invalidate from the helper exec).

        remove(OSX_LAUNCHD_PLIST_PATH);
        pid_t pid = -1;
        char const * args[] = {"touch", "/Library/Extensions", NULL};
        posix_spawn(&pid, "/usr/bin/touch", NULL, NULL, (char **)args, NULL);
        waitpid(pid, &status, WNOHANG|WUNTRACED);

perhaps you could tell me why do I get different behaviour in each of the options.

UPDATE:

it seems like the cache invalidation requires to repeat this command more than once. This code worked to me, but i don't have a clue why ...

        for (int x=0 ; x < 2; x++ ) {
            char const * args[] = {"touch", "/Library/Extensions", NULL};
            posix_spawn(&pid, "/usr/bin/touch", NULL, NULL, (char **)args, NULL);
            waitpid(pid, &status, WNOHANG|WUNTRACED);
            char const * args2[] = {"touch", "/System/Library/Extensions", NULL};
            posix_spawn(&pid, "/usr/bin/touch", NULL, NULL, (char **)args2, NULL);
            waitpid(pid, &status, WNOHANG|WUNTRACED);
        }