linux-kernel - Re: [patch 00/47] Sparse irq rework

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Date:	Sat, 09 Oct 2010 00:03:39 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Grant Likely <grant.likely@...retlab.ca>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	LKML <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org,
	Linus Torvalds <torvalds@...l.org>,
	Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mundt <lethal@...ux-sh.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [patch 00/47] Sparse irq rework

On 10/08/2010 11:10 PM, Thomas Gleixner wrote:
> On Fri, 8 Oct 2010, Yinghai Lu wrote:
> 
>> On 10/08/2010 02:54 PM, Thomas Gleixner wrote:
>>> On Fri, 8 Oct 2010, Thomas Gleixner wrote:
>>>
>>>> On Wed, 6 Oct 2010, Yinghai Lu wrote:
>>>>> On 10/06/2010 09:01 PM, Thomas Gleixner wrote:
>>>>>> Well, I'm not too happy about this preallocated stuff anyway, which is
>>>>>> the reason for the warning below.
>>>>>>  
>>>>>>> [   80.726176] WARNING: at drivers/pci/intr_remapping.c:67 irq_2_iommu_alloc+0x52/0xdc()
>>>>>>> [   80.745935] Hardware name: Sun Fire X4800
>>>>>>> [   80.746179] irq_2_iommu!=NULL irq 8
>>>>>>
>>>>>
>>>>> no, irq_2_iommu are all dynamically allocated even for irq < 16.
>>>>
>>>> I know. I was talking about the preallocated irq descriptors and the
>>>> handling of it in general.
>>>>
>>>> Nevertheless, that irq_2_iommu stuff does not need it's own allocation
>>>> function. It's bound to a specific irq_cfg anyway, so the next logical
>>>> step is to move irq_2_iommu into struct irq_cfg and get rid of the
>>>> extra allocation/free in intr_remapping.c.
>>>
>>> Forgot to say, that I updated the git tree with all the fallout
>>> fixes.
>>>
>>> git://git.kernel.org/pub/scm/linux/kernel/git/tglx/linux-2.6-sparse-irq.git master
>>>
>>> Can you please retest ?
>>>
>>
>> one warning and two panics
>>
>> [   37.369332] ------------[ cut here ]------------
>> [   37.383782] WARNING: at drivers/pci/intr_remapping.c:67 irq_2_iommu_alloc+0x52/0xdc()
>> [   37.384463] Hardware name: Sun Fire X4800
>> [   37.403803] irq_2_iommu!=NULL irq 9
>> [   37.404054] Modules linked in:
>> [   37.404311] Pid: 1, comm: swapper Not tainted 2.6.36-rc7-tip-yh-01944-ge8a4c5f-dirty #171
> 
> Hmm, so that interrupt is already set up in the iommmu.
>  
>> [   59.429741] BUG: unable to handle kernel NULL pointer dereference at (null)
>> [   59.449366] IP: [<ffffffff8147d715>] acpi_pci_irq_find_prt_entry+0x85/0xb1
> 
> I can hardly see how this is related to the irq work.
> 
>> [   71.076886] Pid: 1, comm: swapper Tainted: G        W   2.6.36-rc7-tip-yh-01944-ge8a4c5f-dirty #171      /Sun Fire x4800
>> [   71.096947] RIP: 0010:[<ffffffff8141e232>]  [<ffffffff8141e232>] strcmp+0x4/0x21
> 
> Ditto.

don't know.

but without merging your branch, those problems don't come out.

only thing i can think about that you real free irq code could stress or expose other subsystem's bug etc.

Yinghai
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