linux-kernel - Re: [PCI] BUG: unable to handle kernel

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Message-ID: <20150306165504.GA30094@roeck-us.net>
Date:	Fri, 6 Mar 2015 08:55:04 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Murali Karicheri <m-karicheri2@...com>
Cc:	Fengguang Wu <fengguang.wu@...el.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, LKP <lkp@...org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PCI] BUG: unable to handle kernel

On Fri, Mar 06, 2015 at 10:48:59AM -0500, Murali Karicheri wrote:
[ ... ]

> >From 098b4f5e4ab9407fbdbfcca3a91785c17e25cf03 Mon Sep 17 00:00:00 2001
> From: Murali Karicheri <m-karicheri2@...com>
> Date: Fri, 6 Mar 2015 10:23:08 -0500
> Subject: [PATCH] pci: of : fix kernel crash
> 
> This is a debug patch to root cause the kernel crash
> 
> 	commit 0b2af171520e5d5e7d5b5f479b90a6a5014d9df6
> 
> 	PCI: Update DMA configuration from DT
> 
> Signed-off-by: Murali Karicheri <m-karicheri2@...com>
> ---
>  drivers/of/of_pci.c       |    8 ++++++++
>  drivers/pci/host-bridge.c |    5 +++++
>  2 files changed, 13 insertions(+)
> 
> diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
> index 86d3c38..5a59fb8 100644
> --- a/drivers/of/of_pci.c
> +++ b/drivers/of/of_pci.c
> @@ -129,6 +129,14 @@ void of_pci_dma_configure(struct pci_dev *pci_dev)
>  	struct device *dev = &pci_dev->dev;
>  	struct device *bridge = pci_get_host_bridge_device(pci_dev);
>  
> +	if (!bridge || !bridge->parent) {
> +		if (!bridge)
> +			pr_err("PCI bridge not found\n");
> +		if (!bridge->parent)
> +			pr_err("PCI bridge parent not found\n");

You'll see a crash here if bridge is NULL. Maybe add an else before the second
if statement ? Also, dev_err might be a bit more useful and would be available.

Thanks,
Guenter

> +		return;
> +	}
> +
>  	of_dma_configure(dev, bridge->parent->of_node);
>  	pci_put_host_bridge_device(bridge);
>  }
> diff --git a/drivers/pci/host-bridge.c b/drivers/pci/host-bridge.c
> index 3e5bbf9..ef2ab51 100644
> --- a/drivers/pci/host-bridge.c
> +++ b/drivers/pci/host-bridge.c
> @@ -28,6 +28,11 @@ struct device *pci_get_host_bridge_device(struct pci_dev *dev)
>  	struct pci_bus *root_bus = find_pci_root_bus(dev->bus);
>  	struct device *bridge = root_bus->bridge;
>  
> +	if (!bridge) {
> +		pr_err("PCI: bridge not found\n");
> +		return NULL;
> +	}
> +
>  	kobject_get(&bridge->kobj);
>  	return bridge;
>  }
> -- 
> 1.7.9.5
> 

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