linux-kernel - Re: [PATCH V3 2/3] driver core: Add ability to delete device links of unregistered devices

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Message-ID: <CAJZ5v0gCiHucpwejmHEJFgzUCPvWMXfth1JEUiAvLR=U-c9DrA@mail.gmail.com>
Date:   Wed, 14 Jul 2021 20:26:14 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Saravana Kannan <saravanak@...gle.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        "James E . J . Bottomley" <jejb@...ux.ibm.com>,
        "open list:TARGET SUBSYSTEM" <linux-scsi@...r.kernel.org>,
        Avri Altman <avri.altman@....com>,
        Bean Huo <huobean@...il.com>, Can Guo <cang@...eaurora.org>,
        Asutosh Das <asutoshd@...eaurora.org>,
        Bart Van Assche <bvanassche@....org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 2/3] driver core: Add ability to delete device links of
 unregistered devices

On Sat, Jul 10, 2021 at 12:38 PM Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> Managed device links are deleted by device_del(). However it is possible to
> add a device link to a consumer before device_add(), and then discover an

I would say "discovering an error"

> error prevents the device from being used. In that case normally references
> to the device would be dropped and the device would be deleted. However the
> device link holds a reference to the device, so the device link and device
> remain indefinitely (unless the supplier is deleted).
>
> Amend device link removal to accept removal of a link with an
> unregistered consumer device.
>
> Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Fixes: b294ff3e34490 ("scsi: ufs: core: Enable power management for wlun")

This patch by itself doesn't fix the above one, so the tag doesn't
seem to be suitable here.

Frankly, I would consider folding it into the third patch in the
series in which case please feel free to add

Reviewed-by: Rafael J. Wysocki <rafael@...nel.org>

to the resulting combo patch.

> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>  drivers/base/core.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 2de8f7d8cf54..983e895d4ced 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -887,6 +887,8 @@ static void device_link_put_kref(struct device_link *link)
>  {
>         if (link->flags & DL_FLAG_STATELESS)
>                 kref_put(&link->kref, __device_link_del);
> +       else if (!device_is_registered(link->consumer))
> +               __device_link_del(&link->kref);
>         else
>                 WARN(1, "Unable to drop a managed device link reference\n");
>  }
> --
> 2.17.1
>