[ovs-dev] [PATCH] dpif-netdev: Make datapath port mutex recursive.
i.maximets at ovn.org
Thu Jan 16 13:32:06 UTC 2020
On 16.01.2020 13:13, Stokes, Ian wrote:
> On 1/15/2020 5:29 PM, Ilya Maximets wrote:
>> Upcoming HW offloading will request flow statistics from the dpdk
>> offloading module. This operation requires holding datapath port
>> mutex. However, there is a possible scenarion in which flow deletion
>> happens during datapath reconfiguration process and the mutex already
>> 0 raise () from /lib64/libc.so.6
>> 1 abort () from /lib64/libc.so.6
>> 2 ovs_abort_valist ()
>> 3 ovs_abort ()
>> 4 ovs_mutex_lock_at ()
>> 5 dpif_netdev_get_flow_offload_status ()
>> 6 get_dpif_flow_status ()
>> 7 flow_del_on_pmd ()
>> 8 dpif_netdev_flow_del ()
>> 9 dpif_netdev_operate ()
>> 10 dpif_operate ()
>> 11 push_dp_ops ()
>> 12 push_ukey_ops ()
>> 13 dp_purge_cb ()
>> 14 dp_netdev_del_pmd ()
>> 15 reconfigure_pmd_threads ()
>> 16 reconfigure_datapath ()
>> 17 do_del_port ()
>> 18 dpif_netdev_port_del ()
>> 19 dpif_port_del ()
>> 20 port_del ()
>> 21 ofproto_port_del ()
>> 22 bridge_delete_or_reconfigure_ports ()
>> 23 bridge_reconfigure ()
>> 24 bridge_run ()
>> 25 main ()
>> This happens while removing the last port of a particular PMD thread.
>> Reconfiguration process decides that we need to remove current PMD
>> thread and calls datapath purge callback in order to clean up resources
>> assigned to it. This turns into flow removal and flow_del() tries to
>> request statistics.
>> Turning the dp->mutex into recursive version as a quick fix for this
>> issue. Better solutions might be to avoid statistics request somehow,
>> or fully disassociate offloaded flows from the datapath flows.
>> Signed-off-by: Ilya Maximets <i.maximets at ovn.org>
> Thanks for the patch Ilya, makes snse to me as a workaround for the moment. Tested in my own deployment and didnt see any issues.
Thanks. I don't really like this solution. Recursive mutexes usually
indicates architectural issues (which we definitely have) and should be
avoided as possible. Hope, we'll find a way to revert this change in
the future. For now, applied to master.
Best regards, Ilya Maximets.
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