linux-kernel - Re: Reported regressions for 4.7 as of Sunday, 2016-06-19

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Date:	Thu, 23 Jun 2016 09:22:40 +0200
From:	Johannes Thumshirn <jthumshirn@...e.de>
To:	Quinn Tran <quinn.tran@...gic.com>
Cc:	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Josh Boyer <jwboyer@...oraproject.org>,
	Thorsten Leemhuis <regressions@...mhuis.info>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-scsi@...r.kernel.org
Subject: Re: Reported regressions for 4.7 as of Sunday, 2016-06-19

[+ Cc linux-scsi@...r.kernel.org ]

On Wed, Jun 22, 2016 at 03:57:35PM +0000, Quinn Tran wrote:
> Johannes,  Martin,
> 
> Based on the screen shot/call trace,  it looks like this adapter is not using MSIX.  It defaulted back to MSI or INTx interrupt.  The code made an assumption  of MSIX is available.  There is no point in go through that code segment.
> 
> Can you try this work around?  It’s untested.  Thanks.
> 
> 
> diff --git a/drivers/scsi/qla2xxx/qla_isr.c b/drivers/scsi/qla2xxx/qla_isr.c
> index 5649c20..e033ecb 100644
> --- a/drivers/scsi/qla2xxx/qla_isr.c
> +++ b/drivers/scsi/qla2xxx/qla_isr.c
> @@ -2548,7 +2548,7 @@ 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.
>                  */
> 

But this still does not fix the race which would be possible if the HBA is
using MSI-X but triggering IRQs early enough.

Have a look at this (I admit theoretical) path:
qla24xx_enable_msix(struct qla_hw_data *ha, struct rsp_que *rsp)
{
	[...]
	/* Enable MSI-X vectors for the base queue */
	for (i = 0; i < 2; i++) {
			qentry = &ha->msix_entries[i];
			if (IS_P3P_TYPE(ha))
				ret = request_irq(qentry->vector,
					qla82xx_msix_entries[i].handler,
					0, qla82xx_msix_entries[i].name, rsp);
			else
				ret = request_irq(qentry->vector,
					msix_entries[i].handler,
					0, msix_entries[i].name, rsp);
			if (ret)
				goto msix_register_fail;
							<--- IRQ arrives here
			qentry->have_irq = 1;
			qentry->rsp = rsp;
			rsp->msix = qentry;

			[...]


void qla24xx_process_response_queue(struct scsi_qla_host *vha,
        struct rsp_que *rsp)
{
[...]
	if (rsp->msix->cpuid != smp_processor_id()) {
                  ^
                  \--- rsp->msix == NULL

			/* if kernel does not notify qla of IRQ's CPU change,
			 * then set it here.
			 */
			rsp->msix->cpuid = smp_processor_id();
			ha->tgt.rspq_vector_cpuid = rsp->msix->cpuid;

-- 
Johannes Thumshirn                                          Storage
jthumshirn@...e.de                                +49 911 74053 689
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