netdev - Re: help on iproute2 hangs

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Message-ID: <CALDO+Sbnao8rERvOMbA6jycEGJ4wak4baREeoJY5we8hV08CeA@mail.gmail.com>
Date:   Thu, 1 Mar 2018 14:13:15 -0800
From:   William Tu <u9012063@...il.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        chrism@...lanox.com
Subject: Re: help on iproute2 hangs

On Thu, Mar 1, 2018 at 1:38 PM, David Ahern <dsahern@...il.com> wrote:
> On 3/1/18 11:51 AM, William Tu wrote:
>> root@osb:~/iproute2# ps aux | grep ip
>> root       3652  0.0  0.0  11532   884 pts/24   S+   10:43   0:00 ip
>> link add p0 type veth peer name ovs-p0
>>
>> root@osb:~/iproute2# cat /proc/3652/stack
>> [<0>] __skb_wait_for_more_packets+0x103/0x160
>> [<0>] __skb_recv_datagram+0x69/0xc0
>> [<0>] skb_recv_datagram+0x3f/0x60
>> [<0>] netlink_recvmsg+0x59/0x420
>> [<0>] ___sys_recvmsg+0xee/0x230
>> [<0>] __sys_recvmsg+0x4e/0x90
>> [<0>] entry_SYSCALL_64_fastpath+0x24/0x87
>> [<0>] 0xffffffffffffffff
>>
>> if I run strace on "ip link add p0 type veth peer name ovs-p0"
>> open("/usr/lib/ip/link_veth.so", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No
>> such file or directory)
>> sendmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0,
>> groups=00000000},
>> msg_iov(1)=[{"X\0\0\0\20\0\5\6\315J\230Z\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
>> 88}], msg_controllen=0, msg_flags=0}, 0) = 88
>> recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0,
>> groups=00000000}, msg_iov(1)=[{NULL, 0}], msg_controllen=0,
>> msg_flags=MSG_TRUNC}, MSG_PEEK|MSG_TRUNC) = 36
>> recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0,
>> groups=00000000},
>> msg_iov(1)=[{"$\0\0\0\2\0\0\1\315J\230Z1\24\0\0\0\0\0\0X\0\0\0\20\0\5\6\315J\230Z"...,
>> 36}], msg_controllen=0, msg_flags=0}, 0) = 36
>>
>> Thanks a lot
>> William
>>
>
> Can you send me the kernel config you use. I'll drop back to 4.15.0 and
> try with that.

Thanks a lot. Please see the attachment. However, I think it's hard
for you to reproduce.

On 4.15.0 kernel, if I put those commands in a script file (like what
you did), it will pass.
It hangs only when these commands are generated and run using our
testsuite generated by GNU autotest. [1]
And it's odd that before this rtnl_talk_iov commit, the same test
generated by GNU autotest passes.
So I guess something in GNU autotest plus the new change in this
commit cause the failure.

If you're interested:
[1] https://github.com/openvswitch/ovs/blob/master/tests/system-common-macros.at#L74

Regards,
William

Download attachment "config-4.15.0+" of type "application/octet-stream" (208255 bytes)