rcu: Replace flush_signals() with WARN_ON(signal_pending())

Currently, when RCU awakens from a wait_event_interruptible() that
might have awakened prematurely, it does a flush_signals(). This is
done on the off-chance that someone figured out how to deliver a signal
to a kthread, which is supposed to be impossible.  Given that this
is supposed to be impossible, this commit changes the flush_signals()
calls into WARN_ON(signal_pending()).

Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 9e83cd9a32f1..3e002c1cb441 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1796,7 +1796,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
                         if (rcu_gp_init(rsp))
                                 break;
                         cond_resched();
-                        flush_signals(current);
+                        WARN_ON(signal_pending(current));
                         trace_rcu_grace_period(rsp->name,
                                                ACCESS_ONCE(rsp->gpnum),
                                                TPS("reqwaitsig"));
@@ -1842,7 +1842,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
                         } else {
                                 /* Deal with stray signal. */
                                 cond_resched();
-                                flush_signals(current);
+                                WARN_ON(signal_pending(current));
                                 trace_rcu_grace_period(rsp->name,
                                                        ACCESS_ONCE(rsp->gpnum),
                                                        TPS("fqswaitsig"));