linux-kernel - Re: [PATCH v4 03/12] PCI: brcmstb: Use common error handling code in brcm_pcie

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Message-ID: <CA+-6iNzpfh7_rXUEXNjZLCLQKu-e_bYMAO6PdKaxqReJRKjuAQ@mail.gmail.com>
Date: Fri, 26 Jul 2024 14:34:54 -0400
From: Jim Quinlan <james.quinlan@...adcom.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: linux-pci@...r.kernel.org, Nicolas Saenz Julienne <nsaenz@...nel.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Lorenzo Pieralisi <lorenzo.pieralisi@....com>, 
	Cyril Brulebois <kibi@...ian.org>, Stanimir Varbanov <svarbanov@...e.de>, 
	Krzysztof Kozlowski <krzk@...nel.org>, bcm-kernel-feedback-list@...adcom.com, 
	jim2101024@...il.com, Florian Fainelli <florian.fainelli@...adcom.com>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Krzysztof Wilczyński <kw@...ux.com>, 
	Rob Herring <robh@...nel.org>, 
	"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" <linux-rpi-kernel@...ts.infradead.org>, 
	"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" <linux-arm-kernel@...ts.infradead.org>, 
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 03/12] PCI: brcmstb: Use common error handling code in brcm_pcie_probe()

On Fri, Jul 26, 2024 at 1:04 AM Manivannan Sadhasivam
<manivannan.sadhasivam@...aro.org> wrote:
>
> On Thu, Jul 25, 2024 at 03:45:59PM -0400, Jim Quinlan wrote:
> > On Thu, Jul 25, 2024 at 12:31 AM Manivannan Sadhasivam
> > <manivannan.sadhasivam@...aro.org> wrote:
> > >
> > > On Tue, Jul 16, 2024 at 05:31:18PM -0400, Jim Quinlan wrote:
> > > > o Move the clk_prepare_enable() below the resource allocations.
> > > > o Add a jump target (clk_out) so that a bit of exception handling can be
> > > >   better reused at the end of this function implementation.
> > > >
> > > > Signed-off-by: Jim Quinlan <james.quinlan@...adcom.com>
> > > > Reviewed-by: Stanimir Varbanov <svarbanov@...e.de>
> > > > Reviewed-by: Florian Fainelli <florian.fainelli@...adcom.com>
> > > > ---
> > > >  drivers/pci/controller/pcie-brcmstb.c | 29 +++++++++++++++------------
> > > >  1 file changed, 16 insertions(+), 13 deletions(-)
> > > >
> > > > diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> > > > index c08683febdd4..c257434edc08 100644
> > > > --- a/drivers/pci/controller/pcie-brcmstb.c
> > > > +++ b/drivers/pci/controller/pcie-brcmstb.c
> > > > @@ -1613,31 +1613,30 @@ static int brcm_pcie_probe(struct platform_device *pdev)
> > > >
> > > >       pcie->ssc = of_property_read_bool(np, "brcm,enable-ssc");
> > > >
> > > > -     ret = clk_prepare_enable(pcie->clk);
> > > > -     if (ret) {
> > > > -             dev_err(&pdev->dev, "could not enable clock\n");
> > > > -             return ret;
> > > > -     }
> > > >       pcie->rescal = devm_reset_control_get_optional_shared(&pdev->dev, "rescal");
> > > > -     if (IS_ERR(pcie->rescal)) {
> > > > -             clk_disable_unprepare(pcie->clk);
> > > > +     if (IS_ERR(pcie->rescal))
> > > >               return PTR_ERR(pcie->rescal);
> > > > -     }
> > > > +
> > > >       pcie->perst_reset = devm_reset_control_get_optional_exclusive(&pdev->dev, "perst");
> > > > -     if (IS_ERR(pcie->perst_reset)) {
> > > > -             clk_disable_unprepare(pcie->clk);
> > > > +     if (IS_ERR(pcie->perst_reset))
> > > >               return PTR_ERR(pcie->perst_reset);
> > > > +
> > > > +     ret = clk_prepare_enable(pcie->clk);
> > > > +     if (ret) {
> > > > +             dev_err(&pdev->dev, "could not enable clock\n");
> > > > +             return ret;
> > > >       }
> > > >
> > > >       ret = reset_control_reset(pcie->rescal);
> > > > -     if (ret)
> > > > +     if (ret) {
> > > >               dev_err(&pdev->dev, "failed to deassert 'rescal'\n");
> > > > +             goto clk_out;
> > >
> > > Please use a descriptive name for the err labels. Here this err path disables
> > > and unprepares the clk, so use 'clk_disable_unprepare'.
> > ack
> > >
> > > > +     }
> > > >
> > > >       ret = brcm_phy_start(pcie);
> > > >       if (ret) {
> > > >               reset_control_rearm(pcie->rescal);
> > > > -             clk_disable_unprepare(pcie->clk);
> > > > -             return ret;
> > > > +             goto clk_out;
> > > >       }
> > > >
> > > >       ret = brcm_pcie_setup(pcie);
> > > > @@ -1676,6 +1675,10 @@ static int brcm_pcie_probe(struct platform_device *pdev)
> > > >
> > > >       return 0;
> > > >
> > > > +clk_out:
> > > > +     clk_disable_unprepare(pcie->clk);
> > > > +     return ret;
> > > > +
> > >
> > > This is leaking the resources. Move this new label below 'fail'.
> > What resources is it leaking?  At "clk_out" the return value will be negative
> > and only managed resources have been allocated at that juncture.
> >
>
> Right, but what about the err path below this one? If that path is taken, then
> clks won't be released, right?
No, that is the same situation.  The clock is originally allocated
with "devm_clk_get_optional()", i.e. it is a managed resource.
 If the probe fails, and it does in both of these error paths,
Linux deallocates the newly formed device structure and all of its resources.
Perhaps I am missing something?

>
> It is not a good design to return from each err labels. There should be only one
> return for all err labels at the end and those labels need to be in reverse
> order w.r.t the actual code.

Agreed.

Regards,
Jim Quinlan
Broadcom STB/CM
>
> - Mani
>
> --
> மணிவண்ணன் சதாசிவம்

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