From: Florian Fainelli <f.fainelli@gmail.com>
To: Johan Hovold <johan@kernel.org>
Cc: Andrew Lunn <andrew@lunn.ch>,
Vivien Didelot <vivien.didelot@savoirfairelinux.com>,
"David S. Miller" <davem@davemloft.net>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: dsa: fix fixed-link-phy device leaks
Date: Wed, 16 Nov 2016 10:14:10 -0800 [thread overview]
Message-ID: <8387696c-813a-4c88-5f10-7d2e5fdae6b8@gmail.com> (raw)
In-Reply-To: <20161116171145.GE4864@localhost>
On 11/16/2016 09:11 AM, Johan Hovold wrote:
> On Wed, Nov 16, 2016 at 09:06:26AM -0800, Florian Fainelli wrote:
>> On 11/16/2016 06:47 AM, Johan Hovold wrote:
>>> Make sure to drop the reference taken by of_phy_find_device() when
>>> registering and deregistering the fixed-link PHY-device.
>>>
>>> Note that we need to put both references held at deregistration.
>>>
>>> Fixes: 39b0c705195e ("net: dsa: Allow configuration of CPU & DSA port
>>> speeds/duplex")
>>> Signed-off-by: Johan Hovold <johan@kernel.org>
>>> ---
>>>
>>> Hi,
>>>
>>> This is one has been compile tested only, but fixes a couple of leaks
>>> similar to one that was found in the cpsw driver for which I just posted
>>> a patch.
>>>
>>> It turns out all drivers but DSA fail to deregister the fixed-link PHYs
>>> registered by of_phy_register_fixed_link(). Due to the way this
>>> interface was designed, deregistering such a PHY is a bit cumbersome and
>>> looks like it would benefit from a common helper.
>>>
>>> However, perhaps the interface should instead be changed so that the PHY
>>> device is returned so that drivers do not need to use
>>> of_phy_find_device() when they need to access properties of the fixed
>>> link (e.g. as in dsu_cpu_dsa_setup below).
>>>
>>> Thoughts?
>>>
>>> Thanks,
>>> Johan
>>>
>>>
>>> net/dsa/dsa.c | 8 +++++++-
>>> 1 file changed, 7 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
>>> index a6902c1e2f28..798a6a776a5f 100644
>>> --- a/net/dsa/dsa.c
>>> +++ b/net/dsa/dsa.c
>>> @@ -233,6 +233,8 @@ int dsa_cpu_dsa_setup(struct dsa_switch *ds, struct device *dev,
>>> genphy_read_status(phydev);
>>> if (ds->ops->adjust_link)
>>> ds->ops->adjust_link(ds, port, phydev);
>>> +
>>> + phy_device_free(phydev); /* of_phy_find_device */
>>> }
>>>
>>> return 0;
>>> @@ -509,8 +511,12 @@ void dsa_cpu_dsa_destroy(struct device_node *port_dn)
>>> if (of_phy_is_fixed_link(port_dn)) {
>>> phydev = of_phy_find_device(port_dn);
>>> if (phydev) {
>>> - phy_device_free(phydev);
>>> fixed_phy_unregister(phydev);
>>> + /* Put references taken by of_phy_find_device() and
>>> + * of_phy_register_fixed_link().
>>> + */
>>> + phy_device_free(phydev);
>>> + phy_device_free(phydev);
>>
>> Double free, this looks bogus here. Actually would not this mean a
>> triple free since you already free in dsa_cpu_dsa_setup() which is
>> paired with dsa_cpu_dsa_destroy()?
>
> The naming of phy_device_free() is unfortunate when it's really a put():
>
> void phy_device_free(struct phy_device *phydev)
> {
> put_device(&phydev->mdio.dev);
> }
Indeed, should have looked a little harder.
>
> which may need to be called multiple times, specifically after a call to
> of_phy_find_device() which takes another reference.
>
> With this patch the refcounts are properly balanced.
The intent of your patch is good, but it still feels like having to
double imbalance the refcount is symptomatic of a larger issue here, it
does not seem like having several refcounts are necessary, so we may
really want to rework the API.
--
Florian
next prev parent reply other threads:[~2016-11-16 18:14 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-16 14:47 [PATCH] net: dsa: fix fixed-link-phy device leaks Johan Hovold
2016-11-16 17:06 ` Florian Fainelli
2016-11-16 17:11 ` Johan Hovold
2016-11-16 18:14 ` Florian Fainelli [this message]
2016-11-17 9:52 ` Johan Hovold
2016-11-17 16:47 ` Johan Hovold
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=8387696c-813a-4c88-5f10-7d2e5fdae6b8@gmail.com \
--to=f.fainelli@gmail.com \
--cc=andrew@lunn.ch \
--cc=davem@davemloft.net \
--cc=johan@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=vivien.didelot@savoirfairelinux.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).