linux-kernel - [PATCH] rcutorture: Fix operator precedence bug in exp

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Message-Id: <20251223004407.61147-1-joelagnelf@nvidia.com>
Date: Mon, 22 Dec 2025 19:44:07 -0500
From: Joel Fernandes <joelagnelf@...dia.com>
To: linux-kernel@...r.kernel.org,
	Davidlohr Bueso <dave@...olabs.net>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Josh Triplett <josh@...htriplett.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Uladzislau Rezki <urezki@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang@...ux.dev>
Cc: rcu@...r.kernel.org
Subject: [PATCH] rcutorture: Fix operator precedence bug in exp_current() invocation

Fix incorrect operator precedence in the conditional that determines
when to call exp_current() during torture testing. The modulo
by 0xff appears to do nothing.

Fix by adding parentheses:

    !(torture_random(&rand) % 0xff)

Signed-off-by: Joel Fernandes <joelagnelf@...dia.com>
---
 kernel/rcu/rcutorture.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 82588ceed9da..9873a1d54c46 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1749,7 +1749,7 @@ rcu_torture_writer(void *arg)
 					ulo[i] = cur_ops->get_comp_state();
 				gp_snap = cur_ops->start_gp_poll();
 				rcu_torture_writer_state = RTWS_POLL_WAIT;
-				if (cur_ops->exp_current && !torture_random(&rand) % 0xff)
+				if (cur_ops->exp_current && !(torture_random(&rand) % 0xff))
 					cur_ops->exp_current();
 				while (!cur_ops->poll_gp_state(gp_snap)) {
 					gp_snap1 = cur_ops->get_gp_state();
@@ -1771,7 +1771,7 @@ rcu_torture_writer(void *arg)
 					cur_ops->get_comp_state_full(&rgo[i]);
 				cur_ops->start_gp_poll_full(&gp_snap_full);
 				rcu_torture_writer_state = RTWS_POLL_WAIT_FULL;
-				if (cur_ops->exp_current && !torture_random(&rand) % 0xff)
+				if (cur_ops->exp_current && !(torture_random(&rand) % 0xff))
 					cur_ops->exp_current();
 				while (!cur_ops->poll_gp_state_full(&gp_snap_full)) {
 					cur_ops->get_gp_state_full(&gp_snap1_full);
-- 
2.34.1