dat_srq_post_recv(3DAT) 			     Direct Access Transport Library Functions				   dat_srq_post_recv(3DAT)

NAME

       dat_srq_post_recv - add receive buffers to shared receive queue

SYNOPSIS

       cc [ flag... ] file... -ldat [ library... ]
       #include <dat/udat.h>

       DAT_RETURN
	   dat_srq_post_recv (
	   IN	   DAT_SRQ_HANDLE      srq_handle,
	   IN	   DAT_COUNT	       num_segments,
	   IN	   DAT_LMR_TRIPLET     *local_iov,
	   IN	   DAT_DTO_COOKIE      user_cookie
	   )

PARAMETERS

       srq_handle      A handle for an instance of the SRQ.

       num_segments    The number of lmr_triplets in local_iov. Can be 0 for receiving a zero-size message.

       local_iov       An I/O Vector that specifies the local buffer to be filled.  Can be NULL for receiving a zero-size message.

       user_cookie     A user-provided cookie that is returned to the Consumer at the completion of the Receive DTO. Can be NULL.

DESCRIPTION

       The  dat_srq_post_recv() function posts the receive buffer that can be used for the incoming message into the local_iov by any connected EP
       that uses SRQ.

       The num_segments argument specifies the number of segments in the local_iov. The local_iov segments are filled  in  the	I/O  Vector  order
       until  the  whole message is received. This ensures that all the front segments of the local_iov I/O Vector are completely filled, only one
       segment is partially filled, if needed, and all segments that follow it are not filled at all. The actual order of segment fillings is left
       to the implementation.

       The  user_cookie argument allows Consumers to have unique identifiers for each DTO. These identifiers are completely under user control and
       are opaque to the Provider. There is no requirement on the Consumer that  the  value  user_cookie  should  be  unique  for  each  DTO.  The
       user_cookie is returned to the Consumer in the Completion event for the posted Receive.

       The  completion	of the posted Receive is reported to the Consumer asynchronously through a DTO Completion event based on the configuration
       of the EP that dequeues the posted buffer and the specified completion_flags value for Solicited Wait for the matching  Send.  If  EP  Recv
       Completion  Flag is DAT_COMPLETION_UNSIGNALLED_FLAG, which is the default value for SRQ EP, then all posted Recvs will generate completions
       with Signal Notifications.

       A Consumer should not modify the local_iov or its content until the DTO is completed. When a Consumer does not adhere  to  this	rule,  the
       behavior  of the Provider and the underlying Transport is not defined. Providers that allow Consumers to get ownership of the local_iov but
       not the memory it specified back after the dat_srq_post_recv() returns should document this  behavior  and  also  specify  its  support	in
       Provider  attributes.  This  behavior allows Consumer full control of the local_iov content after dat_srq_post_recv() returns. Because this
       behavior is not guaranteed by all Providers, portable Consumers shall not rely on this behavior. Consumers shall not rely on  the  Provider
       copying local_iov information.

       The  DAT_SUCCESS  return of the dat_srq_post_recv() is at least the equivalent of posting a Receive operation directly by native Transport.
       Providers shall avoid resource allocation as part of dat_srq_post_recv() to ensure that this operation is nonblocking.

       The completion of the Receive posted to the SRQ is equivalent to what happened to the Receive posted to the Endpoint for the Endpoint  that
       dequeued the Receive buffer from the Shared Receive queue.

       The  posted  Recv  DTO  will complete with signal, equivalently to the completion of Recv posted directly to the Endpoint that dequeued the
       Recv buffer from SRQ with DAT_COMPLETION_UNSIGNALLED_FLAG value not set for it.

       The posted Recv DTOs will complete in the order of Send postings to the other endpoint of each connection whose local EP uses SRQ. There is
       no ordering among different connections regardless if they share SRQ and recv_evd or not.

       If  the	reported  status  of the Completion DTO event corresponding to the posted RDMA Read DTO is not DAT_DTO_SUCCESS, the content of the
       local_iov is not defined and the transfered_length in the DTO Completion event is not defined.

       The operation is valid for all states of the Shared Receive Queue.

       The dat_srq_post_recv() function is asynchronous, nonblocking, and its thread safety is Provider-dependent.

RETURN VALUES

       DAT_SUCCESS

	   The operation was successful.

       DAT_INVALID_HANDLE

	   The srq_handle argument is an invalid DAT handle.

       DAT_INSUFFICIENT_RESOURCES

	   The operation failed due to resource limitations.

       DAT_INVALID_PARAMETER

	   Invalid parameter. For example, one of the IOV segments pointed to a memory outside its LMR.

       DAT_PROTECTION_VIOLATION

	   Protection violation for local or remote memory access.

	   Protection Zone mismatch between an LMR of one of the local_iov segments and the SRQ.

       DAT_PRIVILEGES_VIOLATION

	   Privileges violation for local or remote memory access.  One of the LMRs used in local_iov was either invalid or did not have the local
	   write privileges.

USAGE

       For  the  best  Recv  operation	performance,  the  Consumer  should align each buffer segment of local_iov to the Optimal Buffer Alignment
       attribute of the Provider. For portable applications, the Consumer should align each buffer segment of local_iov to the	DAT_OPTIMAL_ALIGN-
       MENT.

       Since  any  of the Endpoints that use the SRQ can dequeue the posted buffer from SRQ, Consumers should post a buffer large enough to handle
       incoming message on any of these Endpoint connections.

       The buffer posted to SRQ does not have a DTO completion flag value.  Posting Recv buffer to SRQ is semantically equivalent to posting to EP
       with DAT_COMPLETION_UNSIGNALLED_FLAG is not set. The configuration of the Recv Completion flag of an Endpoint that dequeues the posted buf-
       fer defines how DTO completion is generated. If the Endpoint Recv Completion flag is DAT_COMPLETION_SOLICITED_WAIT_FLAG then matching  Send
       DTO completion flag value for Solicited Wait determines if the completion will be Signalled or not. If the Endpoint Recv Completion flag is
       not DAT_COMPLETION_SOLICITED_WAIT_FLAG, the posted Recv completion will be generated with Signal. If the Endpoint Recv Completion  flag	is
       DAT_COMPLETION_EVD_THRESHOLD_FLAG,  the	posted	Recv completion will be generated with Signal and dat_evd_wait threshold value controls if
       the waiter will be unblocked or not.

       Only the Endpoint that is in Connected or Disconnect Pending states can dequeue buffers from SRQ. When an  Endpoint  is	transitioned  into
       Disconnected  state,  all  the buffers that it dequeued from SRQ are queued on the Endpoint recv_evd. All the buffers that the Endpoint has
       not completed by the time of transition into Disconnected state and that have not completed message reception will be flushed.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard: uDAPL, 1.2	   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Unsafe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       dat_srq_create(3DAT), dat_srq_free(3DAT), dat_srq_query(3DAT), dat_srq_resize(3DAT), dat_srq_set_lw(3DAT), libdat(3LIB), attributes(5)

SunOS 5.10							    16 Jul 2004 					   dat_srq_post_recv(3DAT)