linux-kernel - Re: Panic when cpu hot-remove

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Message-ID: <20150617115238.GC27750@8bytes.org>
Date:	Wed, 17 Jun 2015 13:52:39 +0200
From:	Joerg Roedeljoro <joro@...tes.org>
To:	范冬冬 <fandd@...pur.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	"jiang.liu@...el.com" <jiang.liu@...el.com>,
	iommu <iommu@...ts.linux-foundation.org>,
	闫晓峰 <yanxiaofeng@...pur.com>,
	刘长生 <liuchangsheng@...pur.com>
Subject: Re: Panic when cpu hot-remove

On Wed, Jun 17, 2015 at 10:42:49AM +0000, 范冬冬 wrote:
> Hi maintainer,
> 
> We found a problem that a panic happen when cpu was hot-removed. We also trace the problem according to the calltrace information.
> An endless loop happen because value head is not equal to value tail forever in the function qi_check_fault( ).
> The location code is as follows:
> 
> 
> do {
>         if (qi->desc_status[head] == QI_IN_USE)
>         qi->desc_status[head] = QI_ABORT;
>         head = (head - 2 + QI_LENGTH) % QI_LENGTH;
>     } while (head != tail);

Hmm, this code interates only over every second QI descriptor, and tail
probably points to a descriptor that is not iterated over.

Jiang, can you please have a look?


	Joerg

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