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Message-ID: <c567c622-1ee1-4828-8730-62bf6bfc2ecc@nokia.com>
Date: Fri, 8 Mar 2024 11:20:58 +0100
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH] arm: smp: Avoid false positive CPU hotplug Lockdep-RCU
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Content-Language: en-US
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Russell King <linux@armlinux.org.uk>,
 "Paul E. McKenney" <paulmck@kernel.org>,
 Joel Fernandes <joel@joelfernandes.org>,
 Josh Triplett <josh@joshtriplett.org>, Steven Rostedt <rostedt@goodmis.org>,
 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
 Lai Jiangshan <jiangshanlai@gmail.com>, Zqiang <qiang.zhang1211@gmail.com>,
 linux-arm-kernel@lists.infradead.org, rcu@vger.kernel.org,
 linux-kernel@vger.kernel.org, Frederic Weisbecker <frederic@kernel.org>
References: <20240307160951.3607374-1-stefan.wiehler@nokia.com>
 <ZeoMRfy9ISBOVMsV@boqun-archlinux>
From: Stefan Wiehler <stefan.wiehler@nokia.com>
Organization: Nokia
In-Reply-To: <ZeoMRfy9ISBOVMsV@boqun-archlinux>
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> I'm not sure this is a false-positive: if you traverse an RCU-list
> without RCU watching the CPU, then a grace period may pass, the next
> list can be garbage and you can go anywhere from the list. Or am I
> missing something that a CPU hotplug can block a grace period?
Thanks for the feedback! Yes, calling it a false positive is probably not
correct, I will remove that. However, as Russell has explained in a previous
email, the spinlock is fundamental for ASID handling and cannot be removed.

@Russell, I will submit to the patch tracking system then.