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Subject: Re: [bug, bisected] pfifo_fast causes packet reordering
To:     John Fastabend <john.fastabend@gmail.com>,
        Dave Taht <dave.taht@gmail.com>
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        "David S. Miller" <davem@davemloft.net>,
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        Martin Elshuber <martin.elshuber@theobroma-systems.com>
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From:   Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>
Message-ID: <983427eb-2e25-f201-c953-4cff22569deb@theobroma-systems.com>
Date:   Wed, 21 Mar 2018 20:44:04 +0100
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On 21.03.18 19:43, John Fastabend wrote:
> Thats my theory at least. Are you able to test a patch if I generate
> one to fix this?

Yes, no problem.

I just tested with the flag change you suggested (see below, I had to 
keep TCQ_F_CPUSTATS to prevent a crash) and I have NOT seen OOO so far.

Thanks,
Jakob


diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 190570f21b20..51b68ef4977b 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -792,7 +792,7 @@ struct Qdisc_ops pfifo_fast_ops __read_mostly = {
         .dump           =       pfifo_fast_dump,
         .change_tx_queue_len =  pfifo_fast_change_tx_queue_len,
         .owner          =       THIS_MODULE,
-       .static_flags   =       TCQ_F_NOLOCK | TCQ_F_CPUSTATS,
+       .static_flags   =       TCQ_F_CPUSTATS,
  };
  EXPORT_SYMBOL(pfifo_fast_ops);