linux-kernel - Re: [PATCH] cpu/hotplug: handle unbalanced hotplug enable/disable

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Message-ID: <CAJFUiJir_zvQDXub=1zwPKJoZm_AnWNpGXuSUiCeHAEwEEUCMQ@mail.gmail.com>
Date:	Wed, 27 Apr 2016 23:10:34 -0700
From:	Lianwei Wang <lianwei.wang@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Peter Zijlstra <peterz@...radead.org>, oleg@...hat.com,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [PATCH] cpu/hotplug: handle unbalanced hotplug enable/disable

On Wed, Apr 27, 2016 at 3:17 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Mon, 25 Apr 2016, Lianwei Wang wrote:
>> On Mon, Apr 25, 2016 at 1:22 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
>> >> Anyway, from a product perspective way, if we don't want to restore
>> >> the unbalanced counter to 0, then maybe a BUG_ON is more reasonable
>> >> than WARN_ON.
>> >
>> > Not at all. BUG_ON is the last resort if we have no other way to handle an
>> > issue.
>> Actually to the customer, you do nothing currently at all, and once it
>> happened then there is no way for the customer to recover it except do
>> a power cycle. A BUG_ON can trigger a power cycle and recover it.
>
> Do you have a single incident where this happened?
>
> Thanks,
>
>         tglx

Yes. In our project, there is a kernel driver which register a pm
notifier. On some conditions this pm notifier will return an error and
abort the suspend process. The counter will be unbalanced in case it
happened.