1. 18 6月, 2013 1 次提交
    • Y
      tipc: introduce new TIPC server infrastructure · c5fa7b3c
      Ying Xue 提交于
      TIPC has two internal servers, one providing a subscription
      service for topology events, and another providing the
      configuration interface. These servers have previously been running
      in BH context, accessing the TIPC-port (aka native) API directly.
      Apart from these servers, even the TIPC socket implementation is
      partially built on this API.
      
      As this API may simultaneously be called via different paths and in
      different contexts, a complex and costly lock policiy is required
      in order to protect TIPC internal resources.
      
      To eliminate the need for this complex lock policiy, we introduce
      a new, generic service API that uses kernel sockets for message
      passing instead of the native API. Once the toplogy and configuration
      servers are converted to use this new service, all code pertaining
      to the native API can be removed. This entails a significant
      reduction in code amount and complexity, and opens up for a complete
      rework of the locking policy in TIPC.
      
      The new service also solves another problem:
      
      As the current topology server works in BH context, it cannot easily
      be blocked when sending of events fails due to congestion. In such
      cases events may have to be silently dropped, something that is
      unacceptable. Therefore, the new service keeps a dedicated outbound
      queue receiving messages from BH context. Once messages are
      inserted into this queue, we will immediately schedule a work from a
      special workqueue. This way, messages/events from the topology server
      are in reality sent in process context, and the server can block
      if necessary.
      
      Analogously, there is a new workqueue for receiving messages. Once a
      notification about an arriving message is received in BH context, we
      schedule a work from the receive workqueue to do the job of
      receiving the message in process context.
      
      As both sending and receive messages are now finished in processes,
      subscribed events cannot be dropped any more.
      
      As of this commit, this new server infrastructure is built, but
      not actually yet called by the existing TIPC code, but since the
      conversion changes required in order to use it are significant,
      the addition is kept here as a separate commit.
      Signed-off-by: NYing Xue <ying.xue@windriver.com>
      Signed-off-by: NJon Maloy <jon.maloy@ericsson.com>
      Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      c5fa7b3c