linux-kernel - Re: [4.5-rc4 Regression] qla2xxx: Add irq affinity notification

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Date:	Mon, 11 Apr 2016 21:28:30 +0000
From:	Quinn Tran <quinn.tran@...gic.com>
To:	Joseph Salisbury <joseph.salisbury@...onical.com>
CC:	Dept-Eng QLA2xxx Upstream <qla2xxx-upstream@...gic.com>,
	"jejb@...ux.vnet.ibm.com" <jejb@...ux.vnet.ibm.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"hch@....de" <hch@....de>,
	"bart.vanassche@...disk.com" <bart.vanassche@...disk.com>,
	Himanshu Madhani <himanshu.madhani@...gic.com>,
	"nab@...ux-iscsi.org" <nab@...ux-iscsi.org>
Subject: Re: [4.5-rc4 Regression] qla2xxx: Add irq affinity notification

Joe,

I see the crash point.  We’re accessing Null pointer.  The adapter in use is an older 4G adapter, where it does not have MSIX support.  We’re tripping over the same shared code segment.  The following is the propose fix.  Let me know if it works.  I’ll will follow up with a patch for upstream submission.

Thanks.

diff --git a/drivers/scsi/qla2xxx/qla_isr.c b/drivers/scsi/qla2xxx/qla_isr.c
index 4af9547..79469de 100644
--- a/drivers/scsi/qla2xxx/qla_isr.c
+++ b/drivers/scsi/qla2xxx/qla_isr.c
@@ -2552,7 +2552,7 @@ void qla24xx_process_response_queue(struct scsi_qla_host *vha,
        if (!vha->flags.online)
                return;
 
-       if (rsp->msix->cpuid != smp_processor_id()) {
+       if (rsp->msix && (rsp->msix->cpuid != smp_processor_id())) {
                /* if kernel does not notify qla of IRQ's CPU change,
                 * then set it here.
                 */




Regards,
Quinn Tran






-----Original Message-----
From: Joseph Salisbury <joseph.salisbury@...onical.com>
Date: Monday, April 11, 2016 at 11:41 AM
To: Quinn Tran <quinn.tran@...gic.com>
Cc: Dept-Eng QLA2xxx Upstream <qla2xxx-upstream@...gic.com>, "jejb@...ux.vnet.ibm.com" <jejb@...ux.vnet.ibm.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, linux-scsi <linux-scsi@...r.kernel.org>, linux-kernel <linux-kernel@...r.kernel.org>, "hch@....de" <hch@....de>, "bart.vanassche@...disk.com" <bart.vanassche@...disk.com>, Himanshu Madhani <himanshu.madhani@...gic.com>, Nicholas Bellinger <nab@...ux-iscsi.org>
Subject: Re: [4.5-rc4 Regression] qla2xxx: Add irq affinity notification

>On 04/11/2016 01:48 PM, Quinn Tran wrote:
>> Joe,
>>
>> How do I get access to this specific Ubuntu kernel where the bug is found?  Is there stack trace/bug report that you could share?  Any data would be helpful.  Thanks.
>The git tree for the specific Ubuntu kernel that exhibits this bug can
>be found here:
>git://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/xenial
>
>The bug can be found here, and has screen shots of the panic as well as
>dmesg under the "Attachments" header:
>http://pad.lv/1554003
>
>Just let me know if additional debug information is needed.
>
>
>>
>> In the mean time, I will download 4.5 rc4 to re-verify.
>>
>> Regards,
>> Quinn Tran
>>
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: Joseph Salisbury <joseph.salisbury@...onical.com>
>> Date: Monday, April 11, 2016 at 10:26 AM
>> To: Quinn Tran <quinn.tran@...gic.com>
>> Cc: Dept-Eng QLA2xxx Upstream <qla2xxx-upstream@...gic.com>, "jejb@...ux.vnet.ibm.com" <jejb@...ux.vnet.ibm.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, linux-scsi <linux-scsi@...r.kernel.org>, linux-kernel <linux-kernel@...r.kernel.org>, "hch@....de" <hch@....de>, "bart.vanassche@...disk.com" <bart.vanassche@...disk.com>, Himanshu Madhani <himanshu.madhani@...gic.com>, Nicholas Bellinger <nab@...ux-iscsi.org>
>> Subject: [4.5-rc4 Regression] qla2xxx: Add irq affinity notification
>>
>>> Hello Quinn,
>>>
>>> A kernel bug report was opened against Ubuntu [0].  After a kernel
>>> bisect, it was found that reverting the following commit resolved this bug:
>>>
>>> commit cdb898c52d1dfad4b4800b83a58b3fe5d352edde
>>> Author: Quinn Tran <quinn.tran@...gic.com>
>>> Date: Thu Dec 17 14:57:05 2015 -0500
>>>   
>>>    qla2xxx: Add irq affinity notification
>>>
>>>
>>> However, the prior commit also required the following three commits to
>>> also be reverted:
>>>
>>> commit 5327c7dbd1a7fd980608f44789076a636e5ee5fc
>>> Author: Quinn Tran <quinn.tran@...gic.com>
>>> Date: Wed Feb 10 18:59:14 2016 -0500
>>>
>>>    qla2xxx: use TARGET_SCF_USE_CPUID flag to indiate CPU Affinity
>>>
>>> commit 9095adaab8c1d82707e4e9961b6ad79b62f3361b
>>> Author: Quinn Tran <quinn.tran@...gic.com>
>>> Date: Wed Feb 10 18:59:13 2016 -0500
>>>   
>>>    target/transport: add flag to indicate CPU Affinity is observed
>>>
>>> commit fb3269baf4ecc2ce6d17d4eb537080035bdf6d5b
>>> Author: Quinn Tran <quinn.tran@...gic.com>
>>> Date: Thu Dec 17 14:57:06 2015 -0500
>>>   
>>>    qla2xxx: Add selective command queuing
>>>
>>>
>>>
>>> The regression was introduced as of v4.5-rc4.
>>>    
>>> I was hoping to get your feedback, since you are the patch author. The
>>> dependant reverts all look like they are improving cpu affinity, which
>>> would likely impact performance.  Do you thing there is a way forward
>>> instead of the reverts, or would it be best to submit a revert request?
>>>    
>>>    
>>> Thanks,
>>>    
>>> Joe
>>>
>>>
>>> [0] http://pad.lv/1554003
>>>
>>>
>