linux-kernel - Re: [PATCH v3] PM / sleep: don't suspend parent when async child suspend

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Message-ID: <20161110020028.GA141513@google.com>
Date:   Wed, 9 Nov 2016 18:00:29 -0800
From:   Brian Norris <briannorris@...omium.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Doug Anderson <dianders@...omium.org>,
        Brian Norris <computersforpeace@...il.com>,
        Jeffy Chen <jeffy.chen@...k-chips.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Chuansheng Liu <chuansheng.liu@...el.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
Subject: Re: [PATCH v3] PM / sleep: don't suspend parent when async child
 suspend_{noirq,late} fails

On Thu, Nov 10, 2016 at 02:53:20AM +0100, Rafael J. Wysocki wrote:
> On Thu, Nov 10, 2016 at 2:21 AM, Brian Norris <briannorris@...omium.org> wrote:
> > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> > index c58563581345..57a8ca4bc8ab 100644
> > --- a/drivers/base/power/main.c
> > +++ b/drivers/base/power/main.c
> > @@ -1027,6 +1027,8 @@ static int __device_suspend_noirq(struct device *dev, pm_message_t state, bool a
> >         TRACE_DEVICE(dev);
> >         TRACE_SUSPEND(0);
> >
> > +       dpm_wait_for_children(dev, async);
> > +
> 
> On a second thought. I'd move the
> 
> if (dev->power.syscore || dev->power.direct_complete)
> 
> along with this (and put it in front), because those flags won't
> change while children are being waited on anyway.

I can do that, but is it really necessary? It's also not the order we do
it for __device_suspend(). I don't like arbitrarily making optimizations
in this code differently to the non-{noirq,late} versions.

Also, would it cause any problem to have a parent return success before
its children have suspended? I haven't reasoned through all the cases
there, but I wouldn't do that without reason.

Brian