linux-kernel - Re: [PATCH] PM / runtime: Fixup reference counting of device link suppliers at probe

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Message-ID: <CAJZ5v0ikXsWdXq-h8rWLd-vfzi-gFmxyHmOGvRvDUoJHC3L2XA@mail.gmail.com>
Date:   Fri, 18 May 2018 10:58:20 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] PM / runtime: Fixup reference counting of device link
 suppliers at probe

On Fri, May 18, 2018 at 10:48 AM, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> In the driver core, before it invokes really_probe() it runtime resumes the
> suppliers for the device via calling pm_runtime_get_suppliers(), which also
> increases the runtime PM usage count for each of the available supplier.
>
> This makes sense, as to be able to allow the consumer device to be probed
> by its driver. However, if the driver decides to add a new supplier link
> during ->probe(), hence updating the list of suppliers,

Do any of the existing drivers do that?

> the following call to pm_runtime_put_suppliers(), invoked after really_probe()
> in the driver core, we get into trouble.