[rds-devel] RDS - resource leakage - recv_ring counters - looks buggy

[Viral Mehta]

Hi,

I am, somehow, not able to forward this to netdev list.

When we run any rds-ping test, it creates a connection. It sets up QP. And then it posts (1024 or whatever mentioned through sysctl) recvs. 
Basically these are pre-post recvs. Extra recvs will be posted again if it goes below low-watermark.

By design,
Connection and all RDMA resources are destroyed only when module is unloaded. 
Now in unloading process, before destroying RDMA resources, it  waits till all send_ring/recv_ring becomes empty.
===========
iw_cm.c:600:            wait_event(rds_iw_ring_empty_wait,
iw_cm.c-601-                  rds_iw_ring_empty(&ic->i_send_ring) &&
iw_cm.c-602-                  rds_iw_ring_empty(&ic->i_recv_ring));
===========

Ring empty means diff (i.e., ring->w_alloc_ctr - ring->free_ctr) should be zero. 
w_alloc_ctr are number of posted recvs and free_ctr is number of recvs consumed. 
Ideally, this can never be zero as we always want some pre-posted recvs and thus recv_ring will never be empty.

Thanks,
Viral