Direct Access Transport Library Functions
                                    datlmrsyncrdmawrite(3DAT)



NAME
     datlmrsyncrdmawrite - synchronize local memory with RDMA
     write on non-coherent memory

SYNOPSIS
     cc [ flag... ] file... -ldat [ library... ]
     #include 

     DATRETURN
         datlmrsyncrdmawrite (
         IN DATIAHANDLE iahandle,
         IN const DATLMRTRIPLET *localsegments,
         IN DATVLEN numsegments
         )


PARAMETERS
     iahandle         A handle for an open instance of the IA.


     localsegments    An array of buffer segments.


     numsegments      The   number   of    segments    in    the
                       localsegments argument.


DESCRIPTION
     The datlmrsyncrdmawrite() function makes effects  of  an
     incoming  RDMA Write operation visible to the Consumer. This
     operation guarantees consistency by locally invalidating the
     non-coherent cache whose buffer has been populated by remote
     peer RDMA write operations.


     The datlmrsyncrdmawrite() function is needed if and only
     if  the  Provider attribute specifies that this operation is
     needed after an incoming RDMA Write operation. The  Consumer
     must call datlmrsyncrdmawrite() before reading data from
     a memory range in this region that  was  the  target  of  an
     incoming RDMA Write operation. The datlmrsyncrdmawrite()
     function must be called after the RDMA Write operation  com-
     pletes,  and  the memory range that was modified by the RDMA
     Write must be supplied by the caller in the local  segments
     array.  After this call returns, the Consumer may safely see
     the modified contents of the memory range. It is permissible
     to  batch synchronizations of multiple RDMA Write operations
     in a single call by  passing  a  localsegments  array  that
     includes  all  modified  memory  ranges.  The localsegments
     entries need not contain the same LMR and need not be in the
     same Protection Zone.



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Direct Access Transport Library Functions
                                    datlmrsyncrdmawrite(3DAT)



     The Consumer must also  use  datlmrsyncrdmawrite()  when
     performing  local  writes to a memory range that was or will
     be the target of incoming RDMA writes. After performing  the
     local      write,      the      Consumer      must      call
     datlmrsyncrdmawrite() before  the  RDMA  Write  is  ini-
     tiated.  Conversely, after an RDMA Write completes, the Con-
     sumer must call datlmrsyncrdmawrite() before  performing
     a local write to the same range.


     If the Provider attribute specifies that this  operation  is
     needed and the Consumer attempts to read from a memory range
     in   an   LMR   without   properly    synchronizing    using
     datlmrsyncrdmawrite(),  the  returned contents are unde-
     fined. If the Consumer attempts to write to a  memory  range
     without  properly  synchronizing, the contents of the memory
     range become undefined.

RETURN VALUES
     DATSUCES              The operation was successful.


     DATINVALIDHANDLE       The DAT handle is invalid.


     DATINVALIDPARAMETER    One of the parameters  is  invalid.
                              For  example, the address range for
                              a local segment  fell  outside  the
                              boundaries   of  the  corresponding
                              Local Memory Region or the LMR han-
                              dle was invalid.


USAGE
     Determining when an RDMA  Write  completes  and  determining
     which  memory range was modified is the Consumer's responsi-
     bility. One possibility is for the RDMA Write  initiator  to
     post  a  Send DTO message after each RDMA Write that identi-
     fies the range in the body of the Send. The Consumer at  the
     target  of  the  RDMA Write can receive the message and know
     when and how to call datlmrsyncrdmawrite().


     This call ensures that the Provider receives a coherent view
     of  the buffer contents after a subsequent remote RDMA Write
     operation. After the call completes,  the  Consumer  can  be
     assured  that all platform-specific buffer and cache updates
     have been performed, and that the LMR range has  consistency
     with  the Provider hardware. Any subsequent read by the Con-
     sumer  can  void  this  consistency.  The  Provider  is  not
     required to detect such access.



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Direct Access Transport Library Functions
                                    datlmrsyncrdmawrite(3DAT)



     The action performed on the  cache  before  the  RDMA  Write
     depends on the cache type:

         o    I/O noncoherent cache will be flushed.

         o    CPU noncoherent cache will be invalidated.

ATRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     
           ATRIBUTE TYPE               ATRIBUTE VALUE       
    
     Interface Stability          Standard: uDAPL, 1.2        
    
     MT-Level                     Unsafe                      
    


SEE ALSO
     datlmrsyncrdmaread(3DAT), libdat(3LIB), attributes(5)






























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Direct Access Transport Library Functions
                                    datlmrsyncrdmawrite(3DAT)






















































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