linux-kernel - [PATCH rcu 02/12] rcu/torture: Change order of warning and trace dump

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Date:   Mon, 20 Jun 2022 15:58:07 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com,
        rostedt@...dmis.org, Anna-Maria Behnsen <anna-maria@...utronix.de>,
        Benedikt Spranger <b.spranger@...utronix.de>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH rcu 02/12] rcu/torture: Change order of warning and trace dump

From: Anna-Maria Behnsen <anna-maria@...utronix.de>

Dumping a big ftrace buffer could lead to a RCU stall. So there is the
ftrace buffer and the stall information which needs to be printed. When
there is additionaly a WARN_ON() which describes the reason for the ftrace
buffer dump and the WARN_ON() is executed _after_ ftrace buffer dump, the
information get lost in the middle of the RCU stall information.

Therefore print WARN_ON() message before dumping the ftrace buffer in
rcu_torture_writer().

[ paulmck: Add tracing_off() to avoid cruft from WARN(). ]

Signed-off-by: Anna-Maria Behnsen <anna-maria@...utronix.de>
Reviewed-by: Benedikt Spranger <b.spranger@...utronix.de>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/rcutorture.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 7120165a93426..3032dd7c7ad35 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1321,8 +1321,9 @@ rcu_torture_writer(void *arg)
 				if (list_empty(&rcu_tortures[i].rtort_free) &&
 				    rcu_access_pointer(rcu_torture_current) !=
 				    &rcu_tortures[i]) {
-					rcu_ftrace_dump(DUMP_ALL);
+					tracing_off();
 					WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
+					rcu_ftrace_dump(DUMP_ALL);
 				}
 		if (stutter_waited)
 			sched_set_normal(current, oldnice);
-- 
2.31.1.189.g2e36527f23