On Wed, Nov 16, 2016 at 10:14:10AM -0800, Florian Fainelli wrote:
> 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 <jo...@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.
I'll cook something up for -next, but how about using
put_device(&phydev->mdio.dev)
for the reference taken by of_phy_find_device() (as some driver
already do) to fix the immediate leaks?
Then deregistration would look like:
phydev = of_phy_find_device(port_dn);
if (phydev) {
- phy_device_free(phydev);
fixed_phy_unregister(phydev);
+ put_device(&phydev->mdio.dev)
+ phy_device_free(phydev);
Thanks,
Johan
