Re: [dpdk-dev] [PATCH v2] ixgbe: Fix disable interrupt twice

["Zhang, Helin" <helin.zhang@intel.com>]

> -----Original Message-----
> From: Qiu, Michael
> Sent: Tuesday, February 2, 2016 10:07 AM
> To: Lu, Wenzhuo; dev@dpdk.org
> Cc: Zhou, Danny; Liu, Yong; Liang, Cunming; Zhang, Helin
> Subject: Re: [PATCH v2] ixgbe: Fix disable interrupt twice
> 
> [+cc helin]
> 
> On 2/2/2016 9:03 AM, Lu, Wenzhuo wrote:
> > Hi Michael,
> >
> >> -----Original Message-----
> >> From: Qiu, Michael
> >> Sent: Monday, February 1, 2016 4:05 PM
> >> To: Lu, Wenzhuo; dev@dpdk.org
> >> Cc: Zhou, Danny; Liu, Yong; Liang, Cunming
> >> Subject: Re: [PATCH v2] ixgbe: Fix disable interrupt twice
> >>
> >> On 1/29/2016 4:07 PM, Lu, Wenzhuo wrote:
> >>> Hi Michael,
> >>>
> >>>> -----Original Message-----
> >>>> From: Qiu, Michael
> >>>> Sent: Friday, January 29, 2016 1:58 PM
> >>>> To: dev@dpdk.org
> >>>> Cc: Zhou, Danny; Liu, Yong; Liang, Cunming; Lu, Wenzhuo; Qiu,
> >>>> Michael
> >>>> Subject: [PATCH v2] ixgbe: Fix disable interrupt twice
> >>>>
> >>>> Currently, ixgbe vf and pf will disable interrupt twice in stop
> >>>> stage and uninit stage. It will cause an error:
> >>>>
> >>>>     testpmd> quit
> >>>>
> >>>>     Shutting down port 0...
> >>>>     Stopping ports...
> >>>>     Done
> >>>>     Closing ports...
> >>>>     EAL: Error disabling MSI-X interrupts for fd 26
> >>>>     Done
> >>>>
> >>>> Becasue the interrupt already been disabled in stop stage.
> >>>> Since it is enabled in init stage, better remove from stop stage.
> >>> I'm afraid it's not a good idea to just remove the intr_disable from
> dev_stop.
> >>> I think dev_stop have the chance to be used independently with
> >>> dev_unint. In
> >> this scenario, we still need intr_disable, right?
> >>> Maybe what we need is some check before we disable the intr:)
> >> Yes, indeed we need some check in disable intr, but it need
> >> additional fields in "struct rte_intr_handle",  and it's much saft to
> >> do so, but as I check i40e/fm10k code, only ixgbe disable it in dev_stop().
> > I found fm10k doesn't enable intr in dev_start. So, I think it's OK. But i40e
> enables intr in dev_start.
> > To my opinion, it's more like i40e misses the intr_disable in dev_stop.
> 
> I don't think i40e miss it, because it not the right please to disable interrupt.
> because all interrupts are enabled in init stage.
> 
> Actually, ixgbe enable the interrupt in init stage, but in dev_start, it disable it
> first and re-enable, so it just the same with doing nothing about interrupt.
> 
> Just think below:
> 
> 1. start the port.(interrupt already enabled in init stage, disable -->
> re-enable)
> 2. stop the port.(disable interrupt)
> 3. start port again(Try to disable, but failed, already disabled)
> 
> Would you think the code has issue?
[Zhang, Helin] in ixgbe PMD, it can be seen that uninit() calls dev_close(),
which calls dev_stop(). So I think the disabling can be done only in dev_stop().
All others can make use of dev_stop to disable the interrupt.

Regards,
Helin

> 
> Thanks,
> Michael
> 
> > Maybe we can follow fm10k's style.
> >
> >> On other hand, if we remove it in dev_stop, any side effect? In ixgbe
> >> start, it will always disable it first and then re-enable it, so it's safe.
> > I think you mean we can disable intr anyway even if it has been disabled.
> 
> Actually, we couldn't, DPDK call VFIO ioctl to kernel to disable interrupts, and
> if we try disable twice, it will return and error.
> That's why I mean we need a flag to show the interrupts stats. If it already
> disabled, we do not need call in to kernel. just return and give a warning
> message.
> 
> Thanks,
> Michael
> 
> >  Sounds more like why we don't
> > need this patch :)
> >
> >> Thanks,
> >> Michael
> >