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

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Date:	Fri, 6 Mar 2015 12:58:00 -0500
From:	Murali Karicheri <m-karicheri2@...com>
To:	Guenter Roeck <linux@...ck-us.net>
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 03/06/2015 11:55 AM, Guenter Roeck wrote:
> 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.
>
Fixed and attached.

Murali
> 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
>>
>


-- 
Murali Karicheri
Linux Kernel, Texas Instruments

View attachment "0001-pci-of-fix-kernel-crash.patch" of type "text/x-diff" (1642 bytes)