Commit 73a860cd authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

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: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 2aa792e6

kernel/rcu/tree.c

+2 −2
Original line number Diff line number Diff line
@@ -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"));

kernel/rcu/tree_plugin.h

+3 −3
Original line number Diff line number Diff line
@@ -2237,7 +2237,7 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp) 
			(d = ULONG_CMP_GE(ACCESS_ONCE(rnp->completed), c)));

		if (likely(d))

			break;

		flush_signals(current);

		WARN_ON(signal_pending(current));

		trace_rcu_future_gp(rnp, rdp, c, TPS("ResumeWait"));

	}

	trace_rcu_future_gp(rnp, rdp, c, TPS("EndWait"));
@@ -2296,7 +2296,7 @@ wait_again: 
		if (!rcu_nocb_poll)

			trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu,

					    "WokeEmpty");

		flush_signals(current);

		WARN_ON(signal_pending(current));

		schedule_timeout_interruptible(1);



		/* Rescan in case we were a victim of memory ordering. */
@@ -2375,7 +2375,7 @@ static void nocb_follower_wait(struct rcu_data *rdp) 
		if (!rcu_nocb_poll)

			trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,

					    "WokeEmpty");

		flush_signals(current);

		WARN_ON(signal_pending(current));

		schedule_timeout_interruptible(1);

	}

}

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