linux-kernel - Re: [BUGFIX PATCH][RESEND] kexec & iosapic: kexec oops when iosapic was removed

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Date:	Mon, 20 Aug 2012 15:46:46 +0800
From:	Hanjun Guo <guohanjun@...wei.com>
To:	Toshi Kani <toshi.kani@...com>
CC:	"Luck, Tony" <tony.luck@...el.com>,
	"Yu, Fenghua" <fenghua.yu@...el.com>,
	"linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	Eric Biederman <ebiederm@...ssion.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Haren Myneni <hbabu@...ibm.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Taku Izumi <izumi.taku@...fujitsu.com>,
	Wen Congyang <wency@...fujitsu.com>,
	Tang Chen <tangchen@...fujitsu.com>,
	Jianguo Wu <wujianguo@...wei.com>
Subject: Re: [BUGFIX PATCH][RESEND] kexec & iosapic: kexec oops when iosapic
 was removed

On 2012/8/17 3:33, Toshi Kani wrote:
> On Thu, 2012-08-16 at 18:28 +0800, Hanjun Guo wrote:
>> On 2012/8/13 10:54, Luck, Tony wrote:
>>>> 		vec = irq_to_vector(irq);
>>>> 		list_for_each_entry(rte, &info->rtes,
>>>> 				rte_list) {
>>>> +			if (rte->refcnt == NO_REF_RTE)
>>>> +				continue;
>>>> +
>>>> 			iosapic_write(rte->iosapic,
>>>> 					IOSAPIC_RTE_LOW(rte->rte_index),
>>>> 					IOSAPIC_MASK|vec);
>>>
>>> This will work - but is it papering over a problem when you removed the
>>> iosapic? Should we really have removed this "rte" from rte_list when the
>>> iosapic was removed?
>>>
>>> -Tony
>>>
>>
>> Hi Tony,
>>     Thanks for your comments, and sorry for the late reply.
>>
>> We only set rte->refcnt to NO_REF_RTE if no device attach to this RTE when
>> unregister a GSI, and increase the rte->refcnt if the RTE is already existing
>> when register a GSI, so "rte" will not removed from rte_list when the
>> iosapic is removed.
> 
> Hi Hanjun,
> 
> I think updating rte->refcnt makes sense as long as rte->iosapic points
> to a valid iosapic entry.  It looks odd to me that rte->iosapic is left
> pointing an invalid iosapic entry after this iosapic is removed.  So, I
> agree with Tony's concern.

Hi Toshi,

I agree with you and Tony.
I will find a better solution and do some clean up, and then send another patch.

Thanks
Hanjun Guo




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