linux-kernel - Re: [PATCH 3/3] PM: runtime: Resume the device earlier in __device_release

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Date:   Thu, 22 Oct 2020 16:16:25 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     "chenxiang (M)" <chenxiang66@...ilicon.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Lukas Wunner <lukas@...ner.de>,
        Saravana Kannan <saravanak@...gle.com>
Subject: Re: [PATCH 3/3] PM: runtime: Resume the device earlier in __device_release_driver()

On Thu, Oct 22, 2020 at 3:40 PM chenxiang (M) <chenxiang66@...ilicon.com> wrote:
>
> Hi Rafael,
>
> 在 2020/10/22 3:14, Rafael J. Wysocki 写道:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > Since the device is resumed from runtime-suspend in
> > __device_release_driver() anyway, it is better to do that before
> > looking for busy managed device links from it to consumers, because
> > if there are any, device_links_unbind_consumers() will be called
> > and it will cause the consumer devices' drivers to unbind, so the
> > consumer devices will be runtime-resumed.  In turn, resuming each
> > consumer device will cause the supplier to be resumed and when the
> > runtime PM references from the given consumer to it are dropped, it
> > may be suspended.  Then, the runtime-resume of the next consumer
> > will cause the supplier to resume again and so on.
> >
> > Update the code accordingly.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Fixes: 9ed9895370ae ("driver core: Functional dependencies tracking support")
> > Cc: All applicable <stable@...r.kernel.org> # All applicable
> > ---
> >   drivers/base/dd.c |    4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > Index: linux-pm/drivers/base/dd.c
> > ===================================================================
> > --- linux-pm.orig/drivers/base/dd.c
> > +++ linux-pm/drivers/base/dd.c
> > @@ -1117,6 +1117,8 @@ static void __device_release_driver(stru
> >
> >       drv = dev->driver;
> >       if (drv) {
> > +             pm_runtime_get_sync(dev);
> > +
> >               while (device_links_busy(dev)) {
> >                       __device_driver_unlock(dev, parent);
> >
> > @@ -1132,8 +1134,6 @@ static void __device_release_driver(stru
>
> pm_runtime_put_sync() is required to be called if existed from here.
>
> >                               return;

Right, I overlooked this, thanks!

> >               }
> >
> > -             pm_runtime_get_sync(dev);
> > -
> >               driver_sysfs_remove(dev);
> >
> >               if (dev->bus)