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Date: Wed, 12 Apr 2017 12:21:00 +0530
From: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
To: gowrishankar muthukrishnan <gowrishankar.m@linux.vnet.ibm.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>, Kumar A S <kumaras@chelsio.com>,
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Subject: Re: [dpdk-dev] Segfault seen in netmap_compat app on Power8
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On Thursday, April 04/06/17, 2017 at 15:06:03 +0530, gowrishankar muthukrishnan wrote:
>    With gcc 6.3.0, I find this app functioning w/o crash.
> 
>    Did disabling gcc optimization help ? (set EXTRA_CFLAGS='-O0' before
>    compile).
> 

Yes, with optimization disabled, the app is not hitting the segfault.

Thanks,
Rahul

>    Regards,
>    Gowrishankar
>    On Thursday 06 April 2017 02:34 PM, Rahul Lakkireddy wrote:
>    > Hi,
>    >
>    > For netmap_compat bridge application on Power8, in netmap_regif
>    > function, the assignment to nmif->ring_ofs[i] is not getting reflected
>    > immediately.
>    >
>    > As a result, the subsequent call to netmap_ring_setup ends up writing
>    > data at wrong offset. This causes segfault in the app.
>    >
>    > If we print the nmif->ring_ofs[i] after assignment, then, we see the
>    > correct offset and application starts fine.
>    >
>    > So, probably, some kind of barrier or mechanism to flush write is
>    > required on Power8?
>    >
>    > BTW, this was tried with ToT dpdk git tree on RHEL 7.3 having below
>    > gcc version:
>    >
>    > gcc version 4.8.5 20150623 (Red Hat 4.8.5-11) (GCC)
>    >
>    > Thanks,
>    > Rahul
>    >
>    >