• Ying Xue's avatar
    tipc: convert topology server to use new server facility · 13a2e898
    Ying Xue authored
    As the new TIPC server infrastructure has been introduced, we can
    now convert the TIPC topology server to it.  We get two benefits
    from doing this:
    
    1) It simplifies the topology server locking policy.  In the
    original locking policy, we placed one spin lock pointer in the
    tipc_subscriber structure to reuse the lock of the subscriber's
    server port, controlling access to members of tipc_subscriber
    instance.  That is, we only used one lock to ensure both
    tipc_port and tipc_subscriber members were safely accessed.
    
    Now we introduce another spin lock for tipc_subscriber structure
    only protecting themselves, to get a finer granularity locking
    policy.  Moreover, the change will allow us to make the topology
    server code more readable and maintainable.
    
    2) It fixes a bug where sent subscription events may be lost when
    the topology port is congested.  Using the new service, the
    topology server now queues sent events into an outgoing buffer,
    and then wakes up a sender process which has been blocked in
    workqueue context.  The process will keep picking events from the
    buffer and send them to their respective subscribers, using the
    kernel socket interface, until the buffer is empty. Even if the
    socket is congested during transmission there is no risk that
    events may be dropped, since the sender process may block when
    needed.
    
    Some minor reordering of initialization is done, since we now
    have a scenario where the topology server must be started after
    socket initialization has taken place, as the former depends
    on the latter.  And overall, we see a simplification of the
    TIPC subscriber code in making this changeover.
    Signed-off-by: default avatarYing Xue <ying.xue@windriver.com>
    Signed-off-by: default avatarJon Maloy <jon.maloy@ericsson.com>
    Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    13a2e898
subscr.c 11.4 KB