• David Howells's avatar
    rxrpc: Rework local endpoint management · 4f95dd78
    David Howells authored
    Rework the local RxRPC endpoint management.
    
    Local endpoint objects are maintained in a flat list as before.  This
    should be okay as there shouldn't be more than one per open AF_RXRPC socket
    (there can be fewer as local endpoints can be shared if their local service
    ID is 0 and they share the same local transport parameters).
    
    Changes:
    
     (1) Local endpoints may now only be shared if they have local service ID 0
         (ie. they're not being used for listening).
    
         This prevents a scenario where process A is listening of the Cache
         Manager port and process B contacts a fileserver - which may then
         attempt to send CM requests back to B.  But if A and B are sharing a
         local endpoint, A will get the CM requests meant for B.
    
     (2) We use a mutex to handle lookups and don't provide RCU-only lookups
         since we only expect to access the list when opening a socket or
         destroying an endpoint.
    
         The local endpoint object is pointed to by the transport socket's
         sk_user_data for the life of the transport socket - allowing us to
         refer to it directly from the sk_data_ready and sk_error_report
         callbacks.
    
     (3) atomic_inc_not_zero() now exists and can be used to only share a local
         endpoint if the last reference hasn't yet gone.
    
     (4) We can remove rxrpc_local_lock - a spinlock that had to be taken with
         BH processing disabled given that we assume sk_user_data won't change
         under us.
    
     (5) The transport socket is shut down before we clear the sk_user_data
         pointer so that we can be sure that the transport socket's callbacks
         won't be invoked once the RCU destruction is scheduled.
    
     (6) Local endpoints have a work item that handles both destruction and
         event processing.  The means that destruction doesn't then need to
         wait for event processing.  The event queues can then be cleared after
         the transport socket is shut down.
    
     (7) Local endpoints are no longer available for resurrection beyond the
         life of the sockets that had them open.  As soon as their last ref
         goes, they are scheduled for destruction and may not have their usage
         count moved from 0.
    Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
    4f95dd78
ar-internal.h 29.6 KB