Messages in this thread | | | Subject | Re: [PATCH v2 net] net: sch_generic: aviod concurrent reset and enqueue op for lockless qdisc | From | Vishwanath Pai <> | Date | Wed, 28 Oct 2020 16:04:52 -0400 |
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On 10/28/20 1:47 PM, Cong Wang wrote: > On Wed, Oct 28, 2020 at 8:37 AM Pai, Vishwanath <vpai@akamai.com> wrote: >> Hi, >> >> We noticed some problems when testing the latest 5.4 LTS kernel and traced it >> back to this commit using git bisect. When running our tests the machine stops >> responding to all traffic and the only way to recover is a reboot. I do not see >> a stack trace on the console. > > Do you mean the machine is still running fine just the network is down? > > If so, can you dump your tc config with stats when the problem is happening? > (You can use `tc -s -d qd show ...`.) > >> >> This can be reproduced using the packetdrill test below, it should be run a >> few times or in a loop. You should hit this issue within a few tries but >> sometimes might take up to 15-20 tries. > ... >> I can reproduce the issue easily on v5.4.68, and after reverting this commit it >> does not happen anymore. > > This is odd. The patch in this thread touches netdev reset path, if packetdrill > is the only thing you use to trigger the bug (that is netdev is always active), > I can not connect them. > > Thanks.
Hi Cong,
> Do you mean the machine is still running fine just the network is down?
I was able to access the machine via serial console, it looks like it is up and running, just that networking is down.
> If so, can you dump your tc config with stats when the problem is happening? > (You can use `tc -s -d qd show ...`.)
If I try running tc when the machine is in this state the command never returns. It doesn't print anything but doesn't exit either.
> This is odd. The patch in this thread touches netdev reset path, if packetdrill > is the only thing you use to trigger the bug (that is netdev is always active), > I can not connect them.
I think packetdrill creates a tun0 interface when it starts the test and tears it down at the end, so it might be hitting this code path during teardown.
P.S: My mail server is having connectivity issues with vger.kernel.org so messages aren't getting delivered to netdev. It'll hopefully get resolved soon.
Thanks, Vishwanath
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