Re: [PATCH] tick/nohz: Fix cpu_is_hotpluggable() by checking with nohz subsystem

[Greg Kroah-Hartman]

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@xxxxxxxxxx>
> Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
> Cc: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Marc Zyngier <maz@xxxxxxxxxx>
> Cc: rcu <rcu@xxxxxxxxxxxxxxx>
> Fixes: 2987557f52b9 ("driver-core/cpu: Expose hotpluggability to the rest of the kernel")
> Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>

Also want to cc: stable on the patch?

Anyway, for the driver core portion:

Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>