From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
To: linux-kernel@vger.kernel.org
Cc: "Joel Fernandes (Google)" <joel@joelfernandes.org>,
Frederic Weisbecker <frederic@kernel.org>,
Josh Triplett <josh@joshtriplett.org>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Neeraj Upadhyay <quic_neeraju@quicinc.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
rcu@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>
Subject: [PATCH rcu/next 1/3] rcu/tree: Use READ_ONCE() for lockless read of rnp->qsmask
Date: Thu, 15 Sep 2022 00:14:17 +0000 [thread overview]
Message-ID: <20220915001419.55617-2-joel@joelfernandes.org> (raw)
In-Reply-To: <20220915001419.55617-1-joel@joelfernandes.org>
The rnp->qsmask is locklessly accessed from rcutree_dying_cpu(). This
may help avoid load tearing due to concurrent access, KCSAN
issues, and preserve sanity of people reading the mask in tracing.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
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 0ca21ac0f064..5ec97e3f7468 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2106,7 +2106,7 @@ int rcutree_dying_cpu(unsigned int cpu)
if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
return 0;
- blkd = !!(rnp->qsmask & rdp->grpmask);
+ blkd = !!(READ_ONCE(rnp->qsmask) & rdp->grpmask);
trace_rcu_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq),
blkd ? TPS("cpuofl-bgp") : TPS("cpuofl"));
return 0;
--
2.37.2.789.g6183377224-goog
next prev parent reply other threads:[~2022-09-15 0:14 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-15 0:14 [PATCH rcu/next 0/3] Preparatory patches borrowed from lazy rcu v5 Joel Fernandes (Google)
2022-09-15 0:14 ` Joel Fernandes (Google) [this message]
2022-09-16 10:55 ` [PATCH rcu/next 1/3] rcu/tree: Use READ_ONCE() for lockless read of rnp->qsmask Frederic Weisbecker
2022-09-15 0:14 ` [PATCH rcu/next 2/3] rcu: Move trace_rcu_callback() before bypassing Joel Fernandes (Google)
2022-09-16 11:09 ` Frederic Weisbecker
2022-09-16 14:10 ` Joel Fernandes
2022-09-16 14:14 ` Joel Fernandes
2022-09-16 22:19 ` Joel Fernandes
2022-09-16 22:21 ` Joel Fernandes
2022-09-15 0:14 ` [PATCH rcu/next 3/3] rcu: Fix late wakeup when flush of bypass cblist happens Joel Fernandes (Google)
2022-09-16 12:51 ` Frederic Weisbecker
2022-09-17 16:41 [PATCH rcu/next 0/3] Preparatory patches borrowed from lazy rcu v5 Joel Fernandes (Google)
2022-09-17 16:41 ` [PATCH rcu/next 1/3] rcu/tree: Use READ_ONCE() for lockless read of rnp->qsmask Joel Fernandes (Google)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220915001419.55617-2-joel@joelfernandes.org \
--to=joel@joelfernandes.org \
--cc=frederic@kernel.org \
--cc=jiangshanlai@gmail.com \
--cc=josh@joshtriplett.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=paulmck@kernel.org \
--cc=quic_neeraju@quicinc.com \
--cc=rcu@vger.kernel.org \
--cc=rostedt@goodmis.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®