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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:17:27 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:17:27 +0000
commitf215e02bf85f68d3a6106c2a1f4f7f063f819064 (patch)
tree6bb5b92c046312c4e95ac2620b10ddf482d3fa8b /include/iprt/req.h
parentInitial commit. (diff)
downloadvirtualbox-f215e02bf85f68d3a6106c2a1f4f7f063f819064.tar.xz
virtualbox-f215e02bf85f68d3a6106c2a1f4f7f063f819064.zip
Adding upstream version 7.0.14-dfsg.upstream/7.0.14-dfsg
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'include/iprt/req.h')
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+/** @file
+ * IPRT - Request Queue & Pool.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * The contents of this file may alternatively be used under the terms
+ * of the Common Development and Distribution License Version 1.0
+ * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
+ * in the VirtualBox distribution, in which case the provisions of the
+ * CDDL are applicable instead of those of the GPL.
+ *
+ * You may elect to license modified versions of this file under the
+ * terms and conditions of either the GPL or the CDDL or both.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
+ */
+
+#ifndef IPRT_INCLUDED_req_h
+#define IPRT_INCLUDED_req_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include <iprt/cdefs.h>
+#include <iprt/types.h>
+
+#include <iprt/stdarg.h>
+
+RT_C_DECLS_BEGIN
+
+/** @defgroup grp_rt_req RTReq - Request Queue & Pool.
+ * @ingroup grp_rt
+ * @{
+ */
+
+/** Request queue handle. */
+typedef struct RTREQQUEUEINT *RTREQQUEUE;
+/** Pointer to a request queue handle. */
+typedef RTREQQUEUE *PRTREQQUEUE;
+/** NIL request queue handle. */
+#define NIL_RTREQQUEUE ((RTREQQUEUE)0)
+
+/** Request thread pool handle. */
+typedef struct RTREQPOOLINT *RTREQPOOL;
+/** Poiner to a request thread pool handle. */
+typedef RTREQPOOL *PRTREQPOOL;
+/** NIL request pool handle. */
+#define NIL_RTREQPOOL ((RTREQPOOL)0)
+
+
+/**
+ * Request type.
+ */
+typedef enum RTREQTYPE
+{
+ /** Invalid request. */
+ RTREQTYPE_INVALID = 0,
+ /** RT: Internal. */
+ RTREQTYPE_INTERNAL,
+ /** Maximum request type (exclusive). Used for validation. */
+ RTREQTYPE_MAX
+} RTREQTYPE;
+
+/**
+ * Request flags.
+ */
+typedef enum RTREQFLAGS
+{
+ /** The request returns a IPRT status code. */
+ RTREQFLAGS_IPRT_STATUS = 0,
+ /** The request is a void request and have no status code. */
+ RTREQFLAGS_VOID = 1,
+ /** Return type mask. */
+ RTREQFLAGS_RETURN_MASK = 1,
+ /** Caller does not wait on the packet. */
+ RTREQFLAGS_NO_WAIT = 2
+} RTREQFLAGS;
+
+
+/** A request packet. */
+typedef struct RTREQ RTREQ;
+/** Pointer to an RT request packet. */
+typedef RTREQ *PRTREQ;
+/** Nil request handle. */
+#define NIL_RTREQ ((PRTREQ)0)
+
+
+#ifdef IN_RING3
+
+/**
+ * Create a request packet queue
+ *
+ * @returns IPRT status code.
+ * @param phQueue Where to store the request queue handle.
+ */
+RTDECL(int) RTReqQueueCreate(PRTREQQUEUE phQueue);
+
+/**
+ * Destroy a request packet queue
+ *
+ * @returns IPRT status code.
+ * @param hQueue The request queue.
+ */
+RTDECL(int) RTReqQueueDestroy(RTREQQUEUE hQueue);
+
+/**
+ * Process one or more request packets
+ *
+ * @returns IPRT status code. Any non-VINF_SUCCESS returns from request
+ * processing is immediately propagated to the caller.
+ * @retval VERR_TIMEOUT if @a cMillies was reached without the packet being
+ * added.
+ * @retval VERR_INVALID_HANDLE if @a hQueue not a valid queue handle.
+ *
+ * @param hQueue The request queue.
+ * @param cMillies Max number of milliseconds to wait for a pending
+ * request. This is not adjusted down before another
+ * wait, so the function may end up waiting for much
+ * longer than the given amount if there are requests
+ * trickling in at a rate slightly higher than the
+ * timeout.
+ *
+ * Use RT_INDEFINITE_WAIT to process requests until a
+ * non-VINF_SUCCESS return code is encountered.
+ *
+ * @remarks The function may repeatedly try wait for @a cMillies on new
+ * requests if requests arrive before it times out.
+ */
+RTDECL(int) RTReqQueueProcess(RTREQQUEUE hQueue, RTMSINTERVAL cMillies);
+
+/**
+ * Allocate and queue a call request.
+ *
+ * If it's desired to poll on the completion of the request set cMillies
+ * to 0 and use RTReqWait() to check for completion. In the other case
+ * use RT_INDEFINITE_WAIT.
+ * The returned request packet must be freed using RTReqRelease().
+ *
+ * @returns iprt statuscode.
+ * Will not return VERR_INTERRUPTED.
+ * @returns VERR_TIMEOUT if cMillies was reached without the packet being completed.
+ *
+ * @param hQueue The request queue.
+ * @param ppReq Where to store the pointer to the request.
+ * This will be NULL or a valid request pointer no matter what happens.
+ * @param cMillies Number of milliseconds to wait for the request to
+ * be completed. Use RT_INDEFINITE_WAIT to only
+ * wait till it's completed.
+ * @param pfnFunction Pointer to the function to call.
+ * @param cArgs Number of arguments following in the ellipsis.
+ * @param ... Function arguments.
+ *
+ * @remarks See remarks on RTReqQueueCallV.
+ */
+RTDECL(int) RTReqQueueCall(RTREQQUEUE hQueue, PRTREQ *ppReq, RTMSINTERVAL cMillies, PFNRT pfnFunction, unsigned cArgs, ...);
+
+/**
+ * Allocate and queue a call request to a void function.
+ *
+ * If it's desired to poll on the completion of the request set cMillies
+ * to 0 and use RTReqWait() to check for completion. In the other case
+ * use RT_INDEFINITE_WAIT.
+ * The returned request packet must be freed using RTReqRelease().
+ *
+ * @returns IPRT status code.
+ * Will not return VERR_INTERRUPTED.
+ * @returns VERR_TIMEOUT if cMillies was reached without the packet being completed.
+ *
+ * @param hQueue The request queue.
+ * @param ppReq Where to store the pointer to the request.
+ * This will be NULL or a valid request pointer no matter what happens.
+ * @param cMillies Number of milliseconds to wait for the request to
+ * be completed. Use RT_INDEFINITE_WAIT to only
+ * wait till it's completed.
+ * @param pfnFunction Pointer to the function to call.
+ * @param cArgs Number of arguments following in the ellipsis.
+ * @param ... Function arguments.
+ *
+ * @remarks See remarks on RTReqQueueCallV.
+ */
+RTDECL(int) RTReqQueueCallVoid(RTREQQUEUE hQueue, PRTREQ *ppReq, RTMSINTERVAL cMillies, PFNRT pfnFunction, unsigned cArgs, ...);
+
+/**
+ * Allocate and queue a call request to a void function.
+ *
+ * If it's desired to poll on the completion of the request set cMillies
+ * to 0 and use RTReqWait() to check for completion. In the other case
+ * use RT_INDEFINITE_WAIT.
+ * The returned request packet must be freed using RTReqRelease().
+ *
+ * @returns IPRT status code.
+ * Will not return VERR_INTERRUPTED.
+ * @returns VERR_TIMEOUT if cMillies was reached without the packet being completed.
+ *
+ * @param hQueue The request queue.
+ * @param ppReq Where to store the pointer to the request. Optional
+ * when RTREQFLAGS_NO_WAIT is used.
+ * This variable will be set to NIL or a valid request
+ * handle no matter what happens.
+ * @param cMillies Number of milliseconds to wait for the request to
+ * be completed. Use RT_INDEFINITE_WAIT to only
+ * wait till it's completed.
+ * @param fFlags A combination of the RTREQFLAGS values.
+ * @param pfnFunction Pointer to the function to call.
+ * @param cArgs Number of arguments following in the ellipsis.
+ * @param ... Function arguments.
+ *
+ * @remarks See remarks on RTReqQueueCallV.
+ */
+RTDECL(int) RTReqQueueCallEx(RTREQQUEUE hQueue, PRTREQ *ppReq, RTMSINTERVAL cMillies, unsigned fFlags, PFNRT pfnFunction, unsigned cArgs, ...);
+
+/**
+ * Allocate and queue a call request.
+ *
+ * If it's desired to poll on the completion of the request set cMillies
+ * to 0 and use RTReqWait() to check for completion. In the other case
+ * use RT_INDEFINITE_WAIT.
+ * The returned request packet must be freed using RTReqRelease().
+ *
+ * @returns IPRT status code.
+ * Will not return VERR_INTERRUPTED.
+ * @returns VERR_TIMEOUT if cMillies was reached without the packet being completed.
+ *
+ * @param hQueue The request queue.
+ * @param ppReq Where to store the pointer to the request. Optional
+ * when RTREQFLAGS_NO_WAIT is used.
+ * This variable will be set to NIL or a valid request
+ * handle no matter what happens.
+ * @param cMillies Number of milliseconds to wait for the request to
+ * be completed. Use RT_INDEFINITE_WAIT to only
+ * wait till it's completed.
+ * @param fFlags A combination of the RTREQFLAGS values.
+ * @param pfnFunction Pointer to the function to call.
+ * @param cArgs Number of arguments following in the ellipsis.
+ * @param Args Variable argument vector.
+ *
+ * @remarks Caveats:
+ * - Do not pass anything which is larger than an uintptr_t.
+ * - 64-bit integers are larger than uintptr_t on 32-bit hosts.
+ * Pass integers > 32-bit by reference (pointers).
+ * - Don't use NULL since it should be the integer 0 in C++ and may
+ * therefore end up with garbage in the bits 63:32 on 64-bit
+ * hosts because 'int' is 32-bit.
+ * Use (void *)NULL or (uintptr_t)0 instead of NULL.
+ */
+RTDECL(int) RTReqQueueCallV(RTREQQUEUE hQueue, PRTREQ *ppReq, RTMSINTERVAL cMillies, unsigned fFlags, PFNRT pfnFunction, unsigned cArgs, va_list Args);
+
+/**
+ * Checks if the queue is busy or not.
+ *
+ * The caller is responsible for dealing with any concurrent submitts.
+ *
+ * @returns true if busy, false if idle.
+ * @param hQueue The queue.
+ */
+RTDECL(bool) RTReqQueueIsBusy(RTREQQUEUE hQueue);
+
+/**
+ * Allocates a request packet.
+ *
+ * The caller allocates a request packet, fills in the request data
+ * union and queues the request.
+ *
+ * @returns IPRT status code.
+ *
+ * @param hQueue The request queue.
+ * @param enmType Package type.
+ * @param phReq Where to store the handle to the new request.
+ */
+RTDECL(int) RTReqQueueAlloc(RTREQQUEUE hQueue, RTREQTYPE enmType, PRTREQ *phReq);
+
+
+/**
+ * Creates a request thread pool.
+ *
+ * The core configuration is given as parameters, finer pool tuning can be
+ * achieved via RTReqPoolSetCfgVar.
+ *
+ * @returns IPRT status code.
+ * @param cMaxThreads The maximum number of worker threads.
+ * UINT32_MAX is an alias for the highest
+ * allowed thread count.
+ * @param cMsMinIdle The number of milliseconds a worker
+ * thread needs to be idle before it is
+ * considered for shutdown. The value
+ * RT_INDEFINITE_WAIT disables automatic
+ * idle thread shutdown.
+ * @param cThreadsPushBackThreshold At which worker thread count the push
+ * back should kick in.
+ * @param cMsMaxPushBack The max number of milliseconds to push
+ * back a submitter. UINT32_MAX is an
+ * alias for the highest allowed push back.
+ * @param pszName The pool name. Keep it short as it is
+ * used for naming worker threads.
+ * @param phPool Where to return the pool handle.
+ */
+RTDECL(int) RTReqPoolCreate(uint32_t cMaxThreads, RTMSINTERVAL cMsMinIdle,
+ uint32_t cThreadsPushBackThreshold, uint32_t cMsMaxPushBack,
+ const char *pszName, PRTREQPOOL phPool);
+
+/**
+ * Retains a reference to a request thread pool.
+ *
+ * @returns The new reference count, UINT32_MAX on invalid handle (asserted).
+ * @param hPool The request thread pool handle.
+ */
+RTDECL(uint32_t) RTReqPoolRetain(RTREQPOOL hPool);
+
+/**
+ * Releases a reference to the request thread pool.
+ *
+ * When the reference count reaches zero, the request will be pooled for reuse.
+ *
+ * @returns The new reference count, UINT32_MAX on invalid handle (asserted).
+ * @param hPool The request thread pool handle.
+ */
+RTDECL(uint32_t) RTReqPoolRelease(RTREQPOOL hPool);
+
+/**
+ * Request thread pool configuration variable.
+ */
+typedef enum RTREQPOOLCFGVAR
+{
+ /** Invalid zero value. */
+ RTREQPOOLCFGVAR_INVALID = 0,
+ /** The desired RTTHREADTYPE of the worker threads. */
+ RTREQPOOLCFGVAR_THREAD_TYPE,
+ /** The RTTHREADFLAGS mask for the worker threads (not waitable). */
+ RTREQPOOLCFGVAR_THREAD_FLAGS,
+ /** The minimum number of threads to keep handy once spawned. */
+ RTREQPOOLCFGVAR_MIN_THREADS,
+ /** The maximum number of thread to start. */
+ RTREQPOOLCFGVAR_MAX_THREADS,
+ /** The minimum number of milliseconds a worker thread needs to be idle
+ * before we consider shutting it down. The other shutdown criteria
+ * being set by RTREQPOOLCFGVAR_MIN_THREADS. The value
+ * RT_INDEFINITE_WAIT can be used to disable shutting down idle threads. */
+ RTREQPOOLCFGVAR_MS_MIN_IDLE,
+ /** The sleep period, in milliseoncds, to employ when idling. The value
+ * RT_INDEFINITE_WAIT can be used to disable shutting down idle threads. */
+ RTREQPOOLCFGVAR_MS_IDLE_SLEEP,
+ /** The number of threads at which to start pushing back. The value
+ * UINT64_MAX is an alias for the current upper thread count limit, i.e.
+ * disabling push back. The value 0 (zero) is an alias for the current
+ * lower thread count, a good value to start pushing back at. The value
+ * must otherwise be within */
+ RTREQPOOLCFGVAR_PUSH_BACK_THRESHOLD,
+ /** The minimum push back time in milliseconds. */
+ RTREQPOOLCFGVAR_PUSH_BACK_MIN_MS,
+ /** The maximum push back time in milliseconds. */
+ RTREQPOOLCFGVAR_PUSH_BACK_MAX_MS,
+ /** The maximum number of free requests to keep handy for recycling. */
+ RTREQPOOLCFGVAR_MAX_FREE_REQUESTS,
+ /** The end of the range of valid config variables. */
+ RTREQPOOLCFGVAR_END,
+ /** Blow the type up to 32-bits. */
+ RTREQPOOLCFGVAR_32BIT_HACK = 0x7fffffff
+} RTREQPOOLCFGVAR;
+
+
+/**
+ * Sets a config variable for a request thread pool.
+ *
+ * @returns IPRT status code.
+ * @param hPool The pool handle.
+ * @param enmVar The variable to set.
+ * @param uValue The new value.
+ */
+RTDECL(int) RTReqPoolSetCfgVar(RTREQPOOL hPool, RTREQPOOLCFGVAR enmVar, uint64_t uValue);
+
+/**
+ * Gets a config variable for a request thread pool.
+ *
+ * @returns The value, UINT64_MAX on invalid parameters.
+ * @param hPool The pool handle.
+ * @param enmVar The variable to query.
+ */
+RTDECL(uint64_t) RTReqPoolGetCfgVar(RTREQPOOL hPool, RTREQPOOLCFGVAR enmVar);
+
+/**
+ * Request thread pool statistics value names.
+ */
+typedef enum RTREQPOOLSTAT
+{
+ /** The invalid zero value, as per tradition. */
+ RTREQPOOLSTAT_INVALID = 0,
+ /** The current number of worker threads. */
+ RTREQPOOLSTAT_THREADS,
+ /** The number of threads that have been created. */
+ RTREQPOOLSTAT_THREADS_CREATED,
+ /** The total number of requests that have been processed. */
+ RTREQPOOLSTAT_REQUESTS_PROCESSED,
+ /** The total number of requests that have been submitted. */
+ RTREQPOOLSTAT_REQUESTS_SUBMITTED,
+ /** The total number of requests that have been cancelled. */
+ RTREQPOOLSTAT_REQUESTS_CANCELLED,
+ /** the current number of pending (waiting) requests. */
+ RTREQPOOLSTAT_REQUESTS_PENDING,
+ /** The current number of active (executing) requests. */
+ RTREQPOOLSTAT_REQUESTS_ACTIVE,
+ /** The current number of free (recycled) requests. */
+ RTREQPOOLSTAT_REQUESTS_FREE,
+ /** Total time the requests took to process. */
+ RTREQPOOLSTAT_NS_TOTAL_REQ_PROCESSING,
+ /** Total time the requests had to wait in the queue before being
+ * scheduled. */
+ RTREQPOOLSTAT_NS_TOTAL_REQ_QUEUED,
+ /** Average time the requests took to process. */
+ RTREQPOOLSTAT_NS_AVERAGE_REQ_PROCESSING,
+ /** Average time the requests had to wait in the queue before being
+ * scheduled. */
+ RTREQPOOLSTAT_NS_AVERAGE_REQ_QUEUED,
+ /** The end of the valid statistics value names. */
+ RTREQPOOLSTAT_END,
+ /** Blow the type up to 32-bit. */
+ RTREQPOOLSTAT_32BIT_HACK = 0x7fffffff
+} RTREQPOOLSTAT;
+
+/**
+ * Reads a statistics value from the request thread pool.
+ *
+ * @returns The value, UINT64_MAX if an invalid parameter was given.
+ * @param hPool The request thread pool handle.
+ * @param enmStat The statistics value to get.
+ */
+RTDECL(uint64_t) RTReqPoolGetStat(RTREQPOOL hPool, RTREQPOOLSTAT enmStat);
+
+/**
+ * Allocates a request packet.
+ *
+ * This is mostly for internal use, please use the convenience methods.
+ *
+ * @returns IPRT status code.
+ *
+ * @param hPool The request thread pool handle.
+ * @param enmType Package type.
+ * @param phReq Where to store the handle to the new request.
+ */
+RTDECL(int) RTReqPoolAlloc(RTREQPOOL hPool, RTREQTYPE enmType, PRTREQ *phReq);
+
+/**
+ * Calls a function on a worker thread.
+ *
+ * @returns IPRT status code.
+ * @param hPool The request thread pool handle.
+ * @param cMillies The number of milliseconds to wait for the request
+ * to be processed.
+ * @param phReq Where to store the pointer to the request. Optional
+ * when RTREQFLAGS_NO_WAIT is used.
+ * This variable will be set to NIL or a valid request
+ * handle no matter what happens.
+ * @param fFlags A combination of RTREQFLAGS values.
+ * @param pfnFunction The function to be called. Must be declared by a
+ * DECL macro because of calling conventions.
+ * @param cArgs The number of arguments in the ellipsis.
+ * @param ... Arguments.
+ *
+ * @remarks The function better avoid taking uint64_t and structs as part of the
+ * arguments (use pointers to these instead). In general anything
+ * that's larger than an uintptr_t is problematic.
+ */
+RTDECL(int) RTReqPoolCallEx(RTREQPOOL hPool, RTMSINTERVAL cMillies, PRTREQ *phReq, uint32_t fFlags, PFNRT pfnFunction, unsigned cArgs, ...);
+
+
+/**
+ * Calls a function on a worker thread.
+ *
+ * @returns IPRT status code.
+ * @param hPool The request thread pool handle.
+ * @param cMillies The number of milliseconds to wait for the request
+ * to be processed.
+ * @param phReq Where to store the pointer to the request. Optional
+ * when RTREQFLAGS_NO_WAIT is used.
+ * This variable will be set to NIL or a valid request
+ * handle no matter what happens.
+ * @param fFlags A combination of RTREQFLAGS values.
+ * @param pfnFunction The function to be called. Must be declared by a
+ * DECL macro because of calling conventions.
+ * @param cArgs The number of arguments in the variable argument
+ * list.
+ * @param va Arguments.
+ * @remarks See remarks on RTReqPoolCallEx.
+ */
+RTDECL(int) RTReqPoolCallExV(RTREQPOOL hPool, RTMSINTERVAL cMillies, PRTREQ *phReq, uint32_t fFlags, PFNRT pfnFunction, unsigned cArgs, va_list va);
+
+/**
+ * Calls a function on a worker thread, wait for it to return.
+ *
+ * @returns IPRT status code returned by @a pfnFunction or request pool error.
+ * @param hPool The request thread pool handle.
+ * @param pfnFunction The function to be called. Must be declared by a
+ * DECL macro because of calling conventions. The
+ * function must return an int value compatible with
+ * the IPRT status code convention.
+ * @param cArgs The number of arguments in the elipsis.
+ * @param ... Arguments.
+ * @remarks See remarks on RTReqPoolCallEx.
+ */
+RTDECL(int) RTReqPoolCallWait(RTREQPOOL hPool, PFNRT pfnFunction, unsigned cArgs, ...);
+
+/**
+ * Calls a function on a worker thread, don't wait for it to return.
+ *
+ * @returns IPRT status code.
+ * @param hPool The request thread pool handle.
+ * @param pfnFunction The function to be called. Must be declared by a
+ * DECL macro because of calling conventions. The
+ * function should return an int value compatible with
+ * the IPRT status code convention, thought it's not
+ * all that important as it's thrown away.
+ * @param cArgs The number of arguments in the elipsis.
+ * @param ... Arguments.
+ * @remarks See remarks on RTReqPoolCallEx.
+ */
+RTDECL(int) RTReqPoolCallNoWait(RTREQPOOL hPool, PFNRT pfnFunction, unsigned cArgs, ...);
+
+/**
+ * Calls a void function on a worker thread.
+ *
+ * @returns IPRT status code.
+ * @param hPool The request thread pool handle.
+ * @param pfnFunction The function to be called. Must be declared by a
+ * DECL macro because of calling conventions. The
+ * function is taken to return void.
+ * @param cArgs The number of arguments in the elipsis.
+ * @param ... Arguments.
+ * @remarks See remarks on RTReqPoolCallEx.
+ */
+RTDECL(int) RTReqPoolCallVoidWait(RTREQPOOL hPool, PFNRT pfnFunction, unsigned cArgs, ...);
+
+/**
+ * Call a void function on a worker thread, don't wait for it to return.
+ *
+ * @returns IPRT status code.
+ * @param hPool The request thread pool handle.
+ * @param pfnFunction The function to be called. Must be declared by a
+ * DECL macro because of calling conventions. The
+ * function is taken to return void.
+ * @param cArgs The number of arguments in the elipsis.
+ * @param ... Arguments.
+ * @remarks See remarks on RTReqPoolCallEx.
+ */
+RTDECL(int) RTReqPoolCallVoidNoWait(RTREQPOOL hPool, PFNRT pfnFunction, unsigned cArgs, ...);
+
+
+/**
+ * Retains a reference to a request.
+ *
+ * @returns The new reference count, UINT32_MAX on invalid handle (asserted).
+ * @param hReq The request handle.
+ */
+RTDECL(uint32_t) RTReqRetain(PRTREQ hReq);
+
+/**
+ * Releases a reference to the request.
+ *
+ * When the reference count reaches zero, the request will be pooled for reuse.
+ *
+ * @returns The new reference count, UINT32_MAX on invalid handle (asserted).
+ * @param hReq Package to release.
+ */
+RTDECL(uint32_t) RTReqRelease(PRTREQ hReq);
+
+/**
+ * Queues a request.
+ *
+ * The request must be allocated using RTReqQueueAlloc() or RTReqPoolAlloc() and
+ * contain all the required data.
+ *
+ * If it's desired to poll on the completion of the request set cMillies
+ * to 0 and use RTReqWait() to check for completion. In the other case
+ * use RT_INDEFINITE_WAIT.
+ *
+ * @returns IPRT status code.
+ * Will not return VERR_INTERRUPTED.
+ * @returns VERR_TIMEOUT if cMillies was reached without the packet being completed.
+ *
+ * @param pReq The request to queue.
+ * @param cMillies Number of milliseconds to wait for the request to
+ * be completed. Use RT_INDEFINITE_WAIT to only
+ * wait till it's completed.
+ */
+RTDECL(int) RTReqSubmit(PRTREQ pReq, RTMSINTERVAL cMillies);
+
+/**
+ * Cancels a pending request.
+ *
+ * @returns IPRT status code.
+ * @retval VERR_RT_REQUEST_STATE if the request is not cancellable.
+ *
+ * @param hReq The request to cancel.
+ */
+RTDECL(int) RTReqCancel(PRTREQ hReq);
+
+/**
+ * Waits for a request to be completed.
+ *
+ * @returns IPRT status code.
+ * Will not return VERR_INTERRUPTED.
+ * @returns VERR_TIMEOUT if cMillies was reached without the packet being completed.
+ *
+ * @param pReq The request to wait for.
+ * @param cMillies Number of milliseconds to wait.
+ * Use RT_INDEFINITE_WAIT to only wait till it's completed.
+ */
+RTDECL(int) RTReqWait(PRTREQ pReq, RTMSINTERVAL cMillies);
+
+/**
+ * Gets the status of the request.
+ *
+ * @returns IPRT status code.
+ *
+ * @param pReq The request to get the status for.
+ */
+RTDECL(int) RTReqGetStatus(PRTREQ pReq);
+
+#endif /* IN_RING3 */
+
+
+/** @} */
+
+RT_C_DECLS_END
+
+#endif /* !IPRT_INCLUDED_req_h */
+