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Mon, 04 Nov 2024 07:12:40 -0800 (PST) Received: from localhost.localdomain ([202.119.23.198]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-211057c7560sm61787095ad.237.2024.11.04.07.12.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Nov 2024 07:12:39 -0800 (PST) From: Zilin Guan To: paulmck@kernel.org Cc: frederic@kernel.org, neeraj.upadhyay@kernel.org, joel@joelfernandes.org, josh@joshtriplett.org, boqun.feng@gmail.com, urezki@gmail.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang.zhang1211@gmail.com, rcu@vger.kernel.org, linux-kernel@vger.kernel.org, Zilin Guan Subject: [PATCH] rcu: Use READ_ONCE() for rdp->gpwrap access in __note_gp_changes() Date: Mon, 4 Nov 2024 15:12:30 +0000 Message-Id: <20241104151230.3107133-1-zilinguan811@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In function __note_gp_changes(), rdp->gpwrap is read using READ_ONCE() in line 1307: 1307 if (IS_ENABLED(CONFIG_PROVE_RCU) && READ_ONCE(rdp->gpwrap)) 1308 WRITE_ONCE(rdp->last_sched_clock, jiffies); while read directly in line 1305: 1305 if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || rdp->gpwrap) 1306 WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed); In the same environment, reads in two places should have the same protection. Signed-off-by: Zilin Guan --- kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index b1f883fcd918..d3e2b420dce5 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1302,7 +1302,7 @@ static bool __note_gp_changes(struct rcu_node *rnp, s= truct rcu_data *rdp) zero_cpu_stall_ticks(rdp); } rdp->gp_seq =3D rnp->gp_seq; /* Remember new grace-period state. */ - if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || rdp->gpwrap) + if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || READ_ONCE(rdp= ->gpwrap)) WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed); if (IS_ENABLED(CONFIG_PROVE_RCU) && READ_ONCE(rdp->gpwrap)) WRITE_ONCE(rdp->last_sched_clock, jiffies); --=20 2.34.1