[PATCH] pidns: reboot_pid_ns: use SEND_SIG_FORCED instead of force_sig()

[Oleg Nesterov <oleg@redhat.com>]

cf3f8921 "pidns: add reboot_pid_ns() to handle the reboot syscall"
uses force_sig() to kill the SIGNAL_UNKILLABLE cinit, this was the
only choice.

After 629d362b we can use SEND_SIG_FORCED instead, force_sig() has
the special semantics and should be avoided if possible.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 57bc1fd..ef35e20 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -241,7 +241,7 @@ int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
 	}
 
 	read_lock(&tasklist_lock);
-	force_sig(SIGKILL, pid_ns->child_reaper);
+	do_send_sig_info(SIGKILL, SEND_SIG_FORCED, pid_ns->child_reaper, true);
 	read_unlock(&tasklist_lock);
 
 	do_exit(0);