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Date:   Fri, 20 Jan 2023 08:05:22 +0100
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc:     linux-kernel@vger.kernel.org,
        Frederic Weisbecker <frederic@kernel.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Zhouyi Zhou <zhouzhouyi@gmail.com>,
        Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
        rcu <rcu@vger.kernel.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Ingo Molnar <mingo@kernel.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] tick/nohz: Fix cpu_is_hotpluggable() by checking with
 nohz subsystem
Message-ID: <Y8o9Mh1ktK0jdQy9@kroah.com>
References: <20230119204434.4017605-1-joel@joelfernandes.org>
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On Thu, Jan 19, 2023 at 08:44:35PM +0000, Joel Fernandes (Google) wrote:
> For CONFIG_NO_HZ_FULL systems, the tick_do_timer_cpu cannot be offlined.
> However, cpu_is_hotpluggable() still returns true for those CPUs. This causes
> torture tests that do offlining to end up trying to offline this CPU causing
> test failures. Such failure happens on all architectures.
> 
> Fix it by asking the opinion of the nohz subsystem on whether the CPU can
> be hotplugged.
> 
> [ Apply Frederic Weisbecker feedback on refactoring tick_nohz_cpu_down(). ]
> 
> Cc: Frederic Weisbecker <frederic@kernel.org>
> Cc: "Paul E. McKenney" <paulmck@kernel.org>
> Cc: Zhouyi Zhou <zhouzhouyi@gmail.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: rcu <rcu@vger.kernel.org>
> Fixes: 2987557f52b9 ("driver-core/cpu: Expose hotpluggability to the rest of the kernel")
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>

Also want to cc: stable on the patch?

Anyway, for the driver core portion:

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>