wait_for_helper: remove unneeded do_sigaction()

allow_signal(SIGCHLD) does all necessary job, no need to call do_sigaction()
prior to.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/kmod.c

@@ -185,14 +185,9 @@ static int wait_for_helper(void *data)
 {
 	struct subprocess_info *sub_info = data;
 	pid_t pid;
-	struct k_sigaction sa;
 
 	/* Install a handler: if SIGCLD isn't handled sys_wait4 won't
 	 * populate the status, but will return -ECHILD. */
-	sa.sa.sa_handler = SIG_IGN;
-	sa.sa.sa_flags = 0;
-	siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
-	do_sigaction(SIGCHLD, &sa, NULL);
 	allow_signal(SIGCHLD);
 
 	pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);