linux-kernel - Re: [PATCH 2/6] PCI: vmd: Fix deadlock when enabling ASPM

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Message-ID: <20231117102829.GK250770@thinkpad>
Date:   Fri, 17 Nov 2023 15:58:29 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Johan Hovold <johan+linaro@...nel.org>
Cc:     Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh@...nel.org>,
        Nirmal Patel <nirmal.patel@...ux.intel.com>,
        Jonathan Derrick <jonathan.derrick@...ux.dev>,
        linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Michael Bottini <michael.a.bottini@...ux.intel.com>,
        "David E . Box" <david.e.box@...ux.intel.com>
Subject: Re: [PATCH 2/6] PCI: vmd: Fix deadlock when enabling ASPM

On Tue, Nov 14, 2023 at 02:55:49PM +0100, Johan Hovold wrote:
> The vmd_pm_enable_quirk() helper is called from pci_walk_bus() during
> probe to enable ASPM for controllers with VMD_FEAT_BIOS_PM_QUIRK set.
> 
> Since pci_walk_bus() already holds a pci_bus_sem read lock, use the new
> locked helper to enable link states in order to avoid a potential
> deadlock (e.g. in case someone takes a write lock before reacquiring
> the read lock).
> 
> Fixes: f492edb40b54 ("PCI: vmd: Add quirk to configure PCIe ASPM and LTR")
> Cc: stable@...r.kernel.org      # 6.3
> Cc: Michael Bottini <michael.a.bottini@...ux.intel.com>
> Cc: David E. Box <david.e.box@...ux.intel.com>
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

- Mani

> ---
>  drivers/pci/controller/vmd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index 94ba61fe1c44..0452cbc362ee 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -751,7 +751,7 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
>  	if (!(features & VMD_FEAT_BIOS_PM_QUIRK))
>  		return 0;
>  
> -	pci_enable_link_state(pdev, PCIE_LINK_STATE_ALL);
> +	pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL);
>  
>  	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_LTR);
>  	if (!pos)
> -- 
> 2.41.0
> 

-- 
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