netdev - RE: [PATCH] net: fec: Fix reference count leak in fec series ops

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Date:   Mon, 9 Nov 2020 03:01:32 +0000
From:   Andy Duan <fugang.duan@....com>
To:     zhangqilong <zhangqilong3@...wei.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH] net: fec: Fix reference count leak in fec series ops

From: zhangqilong <zhangqilong3@...wei.com>ent: Monday, November 9, 2020 10:52 AM
> > From: Zhang Qilong <zhangqilong3@...wei.com> Sent: Sunday, November 8,
> > 2020 5:53 PM
> > > pm_runtime_get_sync() will increment pm usage at first and it will
> > > resume the device later. If runtime of the device has error or
> > > device is in inaccessible state(or other error state), resume
> > > operation will fail. If we do not call put operation to decrease the
> > > reference, it will result in
> > reference count leak.
> > > Moreover, this device cannot enter the idle state and always stay
> > > busy or other non-idle state later. So we fixed it through adding
> > pm_runtime_put_noidle.
> > >
> > > Fixes: 8fff755e9f8d0 ("net: fec: Ensure clocks are enabled while
> > > using mdio bus")
> > > Signed-off-by: Zhang Qilong <zhangqilong3@...wei.com>
> >
> > From early discussion for the topic, Wolfram Sang wonder if such
> > de-reference can be better handled by pm runtime core code.
> >
> I have read the discussion just now, They didn't give a definite result. I agreed
> with introducing a new or help function to replace the pm_runtime_get_sync
> gradually. How do you think so ?
> 
> Regards,
> Zhang

I also think so to avoid so much duplication code in function driver.
> 
> > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flkml
> > .org%2Flkml%2F2020%2F6%2F14%2F76&amp;data=04%7C01%7Cfugang.dua
> n%40nxp.
> >
> com%7Ceaef5020d1c143dfda5208d8845a6391%7C686ea1d3bc2b4c6fa92cd99
> c5c301
> >
> 635%7C0%7C0%7C637404871050135426%7CUnknown%7CTWFpbGZsb3d8eyJ
> WIjoiMC4wL
> >
> jAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;s
> data
> > =GLi34HRLzzTnTjT54dpNXkMdvuPuyVhcSuAGqc1rdvw%3D&amp;reserved=0
> >
> > Regards,
> > Andy
> > > ---
> > >  drivers/net/ethernet/freescale/fec_main.c | 22
> > > ++++++++++++++++------
> > >  1 file changed, 16 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/freescale/fec_main.c
> > > b/drivers/net/ethernet/freescale/fec_main.c
> > > index d7919555250d..6c02f885c67e 100644
> > > --- a/drivers/net/ethernet/freescale/fec_main.c
> > > +++ b/drivers/net/ethernet/freescale/fec_main.c
> > > @@ -1809,8 +1809,10 @@ static int fec_enet_mdio_read(struct mii_bus
> > > *bus, int mii_id, int regnum)
> > >  	bool is_c45 = !!(regnum & MII_ADDR_C45);
> > >
> > >  	ret = pm_runtime_get_sync(dev);
> > > -	if (ret < 0)
> > > +	if (ret < 0) {
> > > +		pm_runtime_put_noidle(dev);
> > >  		return ret;
> > > +	}
> > >
> > >  	if (is_c45) {
> > >  		frame_start = FEC_MMFR_ST_C45;
> > > @@ -1868,10 +1870,12 @@ static int fec_enet_mdio_write(struct
> > > mii_bus *bus, int mii_id, int regnum,
> > >  	bool is_c45 = !!(regnum & MII_ADDR_C45);
> > >
> > >  	ret = pm_runtime_get_sync(dev);
> > > -	if (ret < 0)
> > > +	if (ret < 0) {
> > > +		pm_runtime_put_noidle(dev);
> > >  		return ret;
> > > -	else
> > > +	} else {
> > >  		ret = 0;
> > > +	}
> > >
> > >  	if (is_c45) {
> > >  		frame_start = FEC_MMFR_ST_C45;
> > > @@ -2276,8 +2280,10 @@ static void fec_enet_get_regs(struct
> > > net_device *ndev,
> > >  	int ret;
> > >
> > >  	ret = pm_runtime_get_sync(dev);
> > > -	if (ret < 0)
> > > +	if (ret < 0) {
> > > +		pm_runtime_put_noidle(dev);
> > >  		return;
> > > +	}
> > >
> > >  	regs->version = fec_enet_register_version;
> > >
> > > @@ -2977,8 +2983,10 @@ fec_enet_open(struct net_device *ndev)
> > >  	bool reset_again;
> > >
> > >  	ret = pm_runtime_get_sync(&fep->pdev->dev);
> > > -	if (ret < 0)
> > > +	if (ret < 0) {
> > > +		pm_runtime_put_noidle(&fep->pdev->dev);
> > >  		return ret;
> > > +	}
> > >
> > >  	pinctrl_pm_select_default_state(&fep->pdev->dev);
> > >  	ret = fec_enet_clk_enable(ndev, true); @@ -3771,8 +3779,10 @@
> > > fec_drv_remove(struct platform_device *pdev)
> > >  	int ret;
> > >
> > >  	ret = pm_runtime_get_sync(&pdev->dev);
> > > -	if (ret < 0)
> > > +	if (ret < 0) {
> > > +		pm_runtime_put_noidle(&pdev->dev);
> > >  		return ret;
> > > +	}
> > >
> > >  	cancel_work_sync(&fep->tx_timeout_work);
> > >  	fec_ptp_stop(pdev);
> > > --
> > > 2.25.4