RDMA/ocrdma: Depend on async link events from CNA
authorDevesh Sharma <devesh.sharma@avagotech.com>
Thu, 24 Dec 2015 18:14:07 +0000 (13:14 -0500)
committerDoug Ledford <dledford@redhat.com>
Tue, 19 Jan 2016 19:00:47 +0000 (14:00 -0500)
commit3b1ea43009f2aca9f8ff0dd6540f6701e0871baf
treec3d915f0e9381614b3dc12c2f1f765ed5088ab89
parentd310a344e18c1d9a6a2ab11ef15f2954418c493d
RDMA/ocrdma: Depend on async link events from CNA

Recently Dough Ledford reported a deadlock happening
between ocrdma-load sequence and NetworkManager service
issuing "open" on be2net interface.

The deadlock happens when any be2net hook (e.g. open/close) is called
in parallel to insmod ocrdma.ko.

A. be2net is sending administrative open/close event to ocrdma holding
   device_list_mutex. It does this from ndo_open/ndo_stop hooks of be2net.
   So sequence of locks is rtnl_lock---> device_list lock

B.  When new ocrdma roce device gets registered, infiniband stack now
    takes rtnl_lock in ib_register_device() in GID initialization routines.
    So sequence of locks in this path is device_list lock ---> rtnl_lock.

This improper locking sequence causes deadlock.

With this patch we stop using administrative open and close events
injected by be2net driver. These events were used to dispatch PORT_ACTIVE
and PORT_ERROR events to the IB-stack. This patch implements a logic
to receive async-link-events generated from CNA whenever link-state-change
is detected. Now on, these async-events will be used to dispatch
PORT_ACTIVE and PORT_ERROR events to IB-stack.

Depending on async-events from CNA removes the need to hold device-list-mutex
and thus breaks the busy-wait scenario.

Reported-by: Doug Ledford <dledford@redhat.com>
CC: Sathya Perla <sathya.perla@avagotech.com>
Signed-off-by: Padmanabh Ratnakar <padmanabh.ratnakar@avagotech.com>
Signed-off-by: Selvin Xavier <selvin.xavier@avagotech.com>
Signed-off-by: Devesh Sharma <devesh.sharma@avagotech.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
drivers/infiniband/hw/ocrdma/ocrdma.h
drivers/infiniband/hw/ocrdma/ocrdma_hw.c
drivers/infiniband/hw/ocrdma/ocrdma_hw.h
drivers/infiniband/hw/ocrdma/ocrdma_main.c
drivers/infiniband/hw/ocrdma/ocrdma_sli.h
drivers/infiniband/hw/ocrdma/ocrdma_verbs.c