linux-kernel - Re: [PATCH v1] PM / sleep: make pm notifier called symmetrically

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Message-ID: <CAJFUiJiuzDL9Cu5rNBXbTo9CH2hS9VuNpuV3uqZC6rkqfQMzZg@mail.gmail.com>
Date:	Wed, 18 May 2016 23:06:49 -0700
From:	Lianwei Wang <lianwei.wang@...il.com>
To:	"Rafael J. Wysocki" <rafael@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v1] PM / sleep: make pm notifier called symmetrically

On Wed, May 18, 2016 at 1:34 PM, Rafael J. Wysocki <rafael@...nel.org> wrote:
> On Wed, May 18, 2016 at 8:07 AM, Lianwei Wang <lianwei.wang@...il.com> wrote:
>> This makes pm notifier PREPARE/POST symmetrical: if PREPARE
>> fails, we will only undo what ever happened on PREPARE.
>>
>> It fixes the unbalanced cpu hotplug enable in cpu pm notifier.
>
> Can you please describe the problem you're trying to address in a bit
> more detail?

It is described in another patch, and it is a common issue. I fixed
the similar issue several times, all because that the CPU_POST_SUSPEND
notifier callback is called without call CPU_SUSPEND_PREPARE notifier
callback before. Something is DO in PM_XXX_PREPARE and UNDO in
POST_XXX. If we don't DO it in XXX_PREPARE then we don't need to UNDO
it in  PM_POST_XXX.

Here is the link for the unbalanced cpu hotplug enable case:
https://lkml.org/lkml/2016/5/6/61 .

Thanks,
Lianwei