psm2_am.h

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/* Copyright (c) 2003-2014 Intel Corporation. All rights reserved. */

#ifndef PSM2_AM_H
#define PSM2_AM_H

#include <stddef.h>
#include <stdint.h>
#include <psm2.h>

#ifdef __cplusplus
extern "C" {
#endif

/*!
 * @file psm2_am.h
 * @brief PSM2 Active Message.
 *
 * @page psm2_am Active Message Interface
 *
 * PSM2 implements an Active Message (AM) component that lives alongside the
 * Matched Queues (MQ) component. The active message interface essentially
 * provides a remote procedure call mechanism. A PSM2 process can generate a
 * request to run an active message handler on a remote PSM2 process
 * identified by its end-point address (epaddr). End-point address values
 * are returned by PSM2 when connecting end-points using the psm2_ep_connect()
 * function.
 *
 * An AM handler may make local state updates, and may generate at most
 * one reply to be returned to the original requestor. This reply will cause
 * a handler to be run on that requestor. The requestor handler may make
 * local state updates but is not allowed to reply nor request in that handler
 * context. A request or reply can convey a small number of in-line arguments
 * plus a short amount of data. A tight bound is placed on the number of
 * in-line arguments to allow them to be packed into a header. A bound is
 * placed on the size of the data payload so that the request or reply can
 * be sent as a single packet within the MTU of the underlying communication
 * transport. Longer payloads must be synthesized on top of the provided
 * short request/reply mechanism by fragmentation and reassembly, or
 * transported by some other means.
 *
 * Handlers are run in the process context of the targeted PSM2 process,
 * either in its main thread of execution or in a progress thread. A handler
 * may therefore be executed concurrently with the main thread of execution
 * of the PSM2 process. PSM2 ensures that its own state is protected against this
 * concurrent execution. However, a handler must make its own arrangements to
 * protect its own state. Alternatively, the PSM2 progress thread can be
 * disabled using the PSM_RCVTHREAD environment variable if this is too
 * onerous for the handler.
 *
 * PSM2 has an active progress model and requires that the PSM2 library is
 * called in order to make progress. This can be achieved using the psm2_poll()
 * function. A PSM2 implementatation may provide passive progress through some
 * other mechanism (e.g. a receive thread), but a PSM2 consumer must not assume
 * this and must arrange to make active progress through calls into the PSM
 * library. Note that the PSM2 AM interface is not MTsafe, same as the other PSM
 * interfaces, and that MTsafety must be provided by the consumer if required.
 *
 * The order in which AM requests are issued by an initiator to a particular
 * target defines the order in which those AM requests will be executed on
 * that target. Therefore the AM implementation will maintain the order
 * of handler executions on a flow, and this also applies when progress
 * threads are used. For multiple initiators issuing requests to a particular
 * target, the handler executions will be interleaved in some sequentially
 * consistent ordering.
 */

/*! @defgroup am PSM2 Active Message
 *
 * @{
 */

/** @brief Datatype for an index representing an active message handler */
typedef uint32_t psm2_handler_t;

/** @brief Datatype for a token for an active message handler.*/
typedef void *psm2_am_token_t;

/* PSM2 AM flags
 * These flags may be combined using bitwise-or.
 */
#define PSM2_AM_FLAG_NONE    0 /**< No other PSM2 AM flags are needed. */
#define PSM2_AM_FLAG_ASYNC   1 /**< No need to copy source data. */
#define PSM2_AM_FLAG_NOREPLY 2 /**< The handler for this AM request is
				   guaranteed not to generate a reply. */

/** @brief The psm2_amarg type represents the type of an AM argument. This is
 *  a 64-bit type and is broken down into four 16-bit fields, two 32-bit
 *  fields or one 64-bit field for the convenience of code using the PSM2 AM
 *  interface.
 */
typedef
struct psm2_amarg {
	union {
		struct {
			uint16_t u16w3;
			uint16_t u16w2;
			uint16_t u16w1;
			uint16_t u16w0;
		};
		struct {
			uint32_t u32w1;
			uint32_t u32w0;
		};
		uint64_t u64w0;
		uint64_t u64;
	};
} psm2_amarg_t;

/** @brief The AM handler function type
 *
 * psm2_am_handler_fm_t is the datatype for an AM handler. PSM2 AM will call-back
 * into an AM handler using this function prototype. The parameters and result
 * of these handler functions are described here.
 *
 * @param[in] token This is an opaque token value passed into a handler.
 *                  A request handler may send at most one reply back to the
 *                  original requestor, and must pass this value as the token
 *                  parameter to the psm2_am_reply_short() function. A reply
 *                  handler is also passed a token value, but must not attempt
 *                  to reply.
 * @param[in] args A pointer to the arguments provided to this handler.
 * @param[in] nargs The number of arguments.
 * @param[in] src A pointer to the data payload provided to this handler.
 * @param[in] len The length of the data payload in bytes.
 *
 * @returns 0 The handler should always return a result of 0.
 */
typedef
int (*psm2_am_handler_fn_t) (psm2_am_token_t token,
			    psm2_amarg_t *args, int nargs,
			    void *src, uint32_t len);

/** @brief Type for a completion call-back handler.
 *
 * A completion handler can be specified to give a call-back on the initiation
 * side that an AM request or reply has completed on the target side. The
 * call-back has a context pointer which is provided along with the call-back
 * function pointer when the initiator generates the request or reply. This
 * approach will typically give higher performance than using an AM request or
 * reply to achieve the same effect, though note that no additional information
 * can be passed from the target side back to the initiator side with the
 * completion handler approach.
 *
 * @param[in] context A context pointer.
 * @returns void This handler has no return result.
 */
typedef
void (*psm2_am_completion_fn_t) (void *context);

/** @brief Register AM call-back handlers at the specified end-point.
 *
 * This function is used to register an array of handlers, and may be called
 * multiple times to register additonal handlers. The maximum number of
 * handlers that can be registered is limited to the max_handlers value
 * returned by psm2_am_get_parameters(). Handlers are associated with a PSM
 * end-point. The handlers are allocated index numbers in the the handler table
 * for that end-point.  The allocated index for the handler function in
 * handlers[i] is returned in handlers_idx[i] for i in (0, num_handlers]. These
 * handler index values are used in the psm2_am_request_short() and
 * psm2_am_reply_short() functions.
 *
 * @param[in] ep End-point value
 * @param[in] handlers Array of handler functions
 * @param[in] num_handlers Number of handlers (sizes the handlers and
 *                         handlers_idx arrays)
 * @param[out] handlers_idx Used to return handler index mapping table
 *
 * @returns PSM2_OK Indicates success
 * @returns PSM2_EP_NO_RESOURCES Insufficient slots in the AM handler table
 */
psm2_error_t psm2_am_register_handlers(psm2_ep_t ep,
				     const psm2_am_handler_fn_t *
				     handlers, int num_handlers,
				     int *handlers_idx);

/** @brief Generate an AM request.
 *
 * This function generates an AM request causing an AM handler function to be
 * called in the PSM2 process associated with the specified end-point address.
 * The number of arguments is limited to max_nargs and the payload length in
 * bytes to max_request_short returned by the psm2_am_get_parameters() function.
 * If arguments are not required, set the number of arguments to 0 and the
 * argument pointer will not be dereferenced. If payload is not required, set
 * the payload size to 0 and the payload pointer will not be dereferenced.
 *
 * Optionally a completion function and completion context pointer can be
 * provided, and a local call-back will be made to that function passing in
 * that context pointer once remote execution of the handler has completed. If
 * the completion call-back is not required, the handler should be specified as
 * NULL and the pointer value will not be used.
 *
 * The allowed flags are any combination of the following combined with
 * bitwise-or:
 *   PSM2_AM_FLAG_NONE    - No flags
 *   PSM2_AM_FLAG_ASYNC   - Indicates no need to copy source data
 *   PSM2_AM_FLAG_NOREPLY - The handler for this AM request is guaranteed not to
 *                         generate a reply
 *
 * The PSM2 AM implementation will not dereference the args pointer after return
 * from this function. If PSM2_AM_FLAG_ASYNC is not provided, the PSM2 AM
 * implementation will not dereference the src pointer after return from this
 * function. This may require the implementation to take a copy of the payload
 * if the request cannot be issued immediately.  However, if PSM2_AM_FLAG_ASYNC
 * is provided then a copy will not be taken and the PSM2 AM implementation
 * retains ownership of the payload src memory until the request is locally
 * complete. Local completion can be determined using the completion handler
 * call-back, or through an AM handler associated with an AM reply.
 *
 * The PSM2_AM_FLAG_NOREPLY flag indicates ahead of time to the AM handler that
 * a reply will not be generated. Use of this flag is optional, but it may
 * enable a performance optimization in this case by indicating that reply
 * state is not required.
 *
 * @param[in] epaddr End-point address to run handler on
 * @param[in] handler Index of handler to run
 * @param[in] args Array of arguments to be provided to the handler
 * @param[in] nargs Number of arguments to be provided to the handler
 * @param[in] src Pointer to the payload to be delivered to the handler
 * @param[in] len Length of the payload in bytes
 * @param[in] flags These are PSM2 AM flags and may be combined together with
 *                  bitwise-or
 * @param[in] completion_fn The completion function to called locally when
 *                          remote handler is complete
 * @param[in] completion_ctxt User-provided context pointer to be passed to the
 *                            completion handler
 *
 * @returns PSM2_OK indicates success.
 */
psm2_error_t
psm2_am_request_short(psm2_epaddr_t epaddr, psm2_handler_t handler,
		     psm2_amarg_t *args, int nargs, void *src,
		     size_t len, int flags,
		     psm2_am_completion_fn_t completion_fn,
		     void *completion_ctxt);

/** @brief Generate an AM reply.
 *
 * This function may only be called from an AM handler called due to an AM
 * request.  If the AM request uses the PSM2_AM_FLAG_NOREPLY flag, the AM
 * handler must not call this function. Otherwise, the AM request handler may
 * call psm2_am_reply_short() at most once, and must pass in the token value
 * that it received in its own handler call-back.
 *
 * This function generates an AM reply causing an AM handler function to be
 * called in the PSM2 process associated with the specified end-point address.
 * The number of arguments is limited to max_nargs and the payload length in
 * bytes to max_reply_short returned by the psm2_am_get_parameters() function.
 * If arguments are not required, set the number of arguments to 0 and the
 * argument pointer will not be dereferenced. If payload is not required, set
 * the payload size to 0 and the payload pointer will not be dereferenced.
 *
 * Optionally a completion function and completion context pointer can be
 * provided, and a local call-back will be made to that function passing in
 * that context pointer once remote execution of the handler has completed. If
 * the completion call-back is not required, the handler should be specified as
 * NULL and the pointer value will not be used.
 *
 * The allowed flags are any combination of the following combined with
 * bitwise-or:
 *   PSM2_AM_FLAG_NONE    - No flags
 *   PSM2_AM_FLAG_ASYNC   - Indicates no need to copy source data
 *
 * The PSM2 AM implementation will not dereference the args pointer after return
 * from this function. If PSM2_AM_FLAG_ASYNC is not provided, the PSM2 AM
 * implementation will not dereference the src pointer after return from this
 * function. This may require the implementation to take a copy of the payload
 * if the reply cannot be issued immediately.  However, if PSM2_AM_FLAG_ASYNC is
 * provided then a copy will not be taken and the PSM2 AM implementation retains
 * ownership of the payload src memory until the reply is locally complete.
 * Local completion can be determined using the completion handler call-back.
 *
 * @param[in] token Token value provided to the AM handler that is generating
 *                  the reply.
 * @param[in] handler Index of handler to run
 * @param[in] args Array of arguments to be provided to the handler
 * @param[in] nargs Number of arguments to be provided to the handler
 * @param[in] src Pointer to the payload to be delivered to the handler
 * @param[in] len Length of the payload in bytes
 * @param[in] flags These are PSM2 AM flags and may be combined together with
 *                  bitwise-or
 * @param[in] completion_fn The completion function to called locally when
 *                          remote handler is complete
 * @param[in] completion_ctxt User-provided context pointer to be passed to the
 *                            completion handler
 *
 * @returns PSM2_OK indicates success.
 */
psm2_error_t
psm2_am_reply_short(psm2_am_token_t token, psm2_handler_t handler,
		   psm2_amarg_t *args, int nargs, void *src,
		   size_t len, int flags,
		   psm2_am_completion_fn_t completion_fn,
		   void *completion_ctxt);

/** @brief Return the source end-point address for a token.
 *
 * This function is used to obtain the epaddr object representing the message
 * initiator from a token passed by PSM2 to a message handler.
 *
 * @param[in] token Token value provided to the AM handler that is generating
 *                  the reply.
 * @param[out] epaddr_out Pointer to the where the epaddr should be returned.
 *
 * @returns PSM2_OK indicates success.
 * @returns PSM2_PARAM_ERR token is invalid or epaddr_out is NULL.
 */
psm2_error_t psm2_am_get_source(psm2_am_token_t token,
			      psm2_epaddr_t *epaddr_out);

/** @brief AM parameters
 *
 * This structure is used to return PSM2 AM implementation-specific parameter
 * values back to the caller of the psm2_am_get_parameters() function. This
 * API also specifies the minimum values for these parameters that an
 * implementation must at least provide:
 *   max_handlers >= 64,
 *   max_nargs >= 2,
 *   max_request_short >= 256 and
 *   max_reply_short >= 256.
 */
struct psm2_am_parameters {
	/** Maximum number of handlers that can be registered. */
	uint32_t max_handlers;
	/** Maximum number of arguments to an AM handler. */
	uint32_t max_nargs;
	/** Maximum number of bytes in a request payload. */
	uint32_t max_request_short;
	/** Maximum number of bytes in a reply payload. */
	uint32_t max_reply_short;
};

/** @brief Get the AM parameter values
 *
 * This function retrieves the implementation-specific AM parameter values for
 * the specified end-point.
 *
 * @param[in] ep The end-point value returned by psm2_ep_open().
 * @param[out] parameters Pointer to the struct where the parameters will be
 *                        returned.
 * @param[in] sizeof_parameters_in The size in bytes of the struct provided by
 *                                 the caller.
 * @param[out] sizeof_parameters_out The size in bytes of the struct returned
 *                                   by PSM.
 *
 * @returns PSM2_OK indicates success.
 */
psm2_error_t
psm2_am_get_parameters(psm2_ep_t ep,
		      struct psm2_am_parameters *parameters,
		      size_t sizeof_parameters_in,
		      size_t *sizeof_parameters_out);

/*! @} */

#ifdef __cplusplus
} /* extern "C" */
#endif
#endif