[ovs-dev] [PATCH] dpif-netdev: Make datapath port mutex recursive.

Ilya Maximets i.maximets at ovn.org
Wed Jan 15 17:29:19 UTC 2020


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
acquired:

  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>
---

Ideas for better solution are welcome.

 lib/dpif-netdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index 079bd1bdf..d4b1ebbff 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -1547,7 +1547,7 @@ create_dp_netdev(const char *name, const struct dpif_class *class,
     ovs_refcount_init(&dp->ref_cnt);
     atomic_flag_clear(&dp->destroyed);
 
-    ovs_mutex_init(&dp->port_mutex);
+    ovs_mutex_init_recursive(&dp->port_mutex);
     hmap_init(&dp->ports);
     dp->port_seq = seq_create();
     fat_rwlock_init(&dp->upcall_rwlock);
-- 
2.17.1



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