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From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com,
	rostedt@goodmis.org, "Paul E. McKenney" <paulmck@kernel.org>,
	Chris Mason <clm@meta.com>,
	Joel Fernandes <joelagnelf@nvidia.com>
Subject: [PATCH v4 2/2] rcutorture: Correctly compute probability to invoke ->exp_current()
Date: Mon, 29 Dec 2025 11:16:16 -0800	[thread overview]
Message-ID: <20251229191616.693898-2-paulmck@kernel.org> (raw)
In-Reply-To: <2ca142cc-0487-45e2-830e-8ece0fcd72cb@paulmck-laptop>

Lack of parentheses causes the ->exp_current() function, for example,
srcu_expedite_current(), to be called only once in four billion times
instead of the intended once in 256 times.  This commit therefore adds
the needed parentheses.

Reported-by: Chris Mason <clm@meta.com>
Reported-by: Joel Fernandes <joelagnelf@nvidia.com>
Fixes: 950063c6e897 ("rcutorture: Test srcu_expedite_current()")
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 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 63053031ade21..47ce7f49b52c6 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);
-- 
2.40.1


      parent reply	other threads:[~2025-12-29 19:16 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-12-29 19:16 [PATCH 0/2] Miscellaneous fixes for post-v4.19 Paul E. McKenney
2025-12-29 19:16 ` [PATCH v4 1/2] rcu: Make expedited RCU CPU stall warnings detect stall-end races Paul E. McKenney
2025-12-31 17:13   ` Borislav Petkov
2025-12-29 19:16 ` Paul E. McKenney [this message]

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