linux-kernel - Re: WARNING: CPU: 0 PID: 0 at drivers/irqchip/irq-gic-v3-its.c

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Date:   Fri, 9 Nov 2018 17:28:04 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     cai@....us, open list <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        ard.biesheuvel@...aro.org, Jason Cooper <jason@...edaemon.net>,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: WARNING: CPU: 0 PID: 0 at drivers/irqchip/irq-gic-v3-its.c

On Fri, Nov 9, 2018 at 4:10 PM Marc Zyngier <marc.zyngier@....com> wrote:
>
[...]

>
> See bb42ca474010 and d003d029cea8 for details.
>
> Now, activating this workaround leads to lockdep being really angry,
> most likely because the cpus_read_lock is not taken, which is a change
> in behaviour...
>
> I'm trying to dig into this now.
>

Yes we found similar issue in kernel/sched/core.c sched_init_smp
There's a fix with detailed description in -next
(Commit 40fa3780bac2 ("sched/core: Take the hotplug lock in sched_init_smp()")

The behaviour changed since  commit cb538267ea1e ("jump_label/lockdep:
Assert we hold the hotplug lock for _cpuslocked() operations")

--
Regards,
Sudeep