once.cpp revision 96ae2df030763cee874d3f5ac0be07cd1f793281
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * IPRT - Execute Once.
e64031e20c39650a7bc902a3e1aba613b9415deevboxsync * Copyright (C) 2007 Oracle Corporation
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * This file is part of VirtualBox Open Source Edition (OSE), as
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * available from http://www.virtualbox.org. This file is free software;
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * you can redistribute it and/or modify it under the terms of the GNU
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * General Public License (GPL) as published by the Free Software
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * Foundation, in version 2 as it comes in the "COPYING" file of the
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * The contents of this file may alternatively be used under the terms
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * of the Common Development and Distribution License Version 1.0
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * VirtualBox OSE distribution, in which case the provisions of the
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * CDDL are applicable instead of those of the GPL.
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * You may elect to license modified versions of this file under the
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * terms and conditions of either the GPL or the CDDL or both.
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync/*******************************************************************************
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync* Header Files *
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync*******************************************************************************/
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * The state loop of the other threads.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * @returns VINF_SUCCESS when everything went smoothly. IPRT status code if we
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * encountered trouble.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * @param pOnce The execute once structure.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * @param phEvtM Where to store the semaphore handle so the caller
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * can do the cleaning up for us.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsyncstatic int rtOnceOtherThread(PRTONCE pOnce, PRTSEMEVENTMULTI phEvtM)
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * No semaphore, try create one.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync if (ASMAtomicCmpXchgS32(&pOnce->iState, RTONCESTATE_BUSY_CREATING_SEM, RTONCESTATE_BUSY_NO_SEM))
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync ASMAtomicWriteHandle(&pOnce->hEventMulti, *phEvtM);
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync int32_t cRefs = ASMAtomicIncS32(&pOnce->cEventRefs); Assert(cRefs == 1); NOREF(cRefs);
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync if (!ASMAtomicCmpXchgS32(&pOnce->iState, RTONCESTATE_BUSY_HAVE_SEM, RTONCESTATE_BUSY_CREATING_SEM))
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync /* Too slow. */
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync AssertReturn(ASMAtomicCmpXchgS32(&pOnce->iState, RTONCESTATE_DONE, RTONCESTATE_DONE_CREATING_SEM)
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync ASMAtomicWriteHandle(&pOnce->hEventMulti, NIL_RTSEMEVENTMULTI);
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync cRefs = ASMAtomicDecS32(&pOnce->cEventRefs); Assert(cRefs == 0);
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync AssertReturn( ASMAtomicCmpXchgS32(&pOnce->iState, RTONCESTATE_BUSY_SPIN, RTONCESTATE_BUSY_CREATING_SEM)
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync || ASMAtomicCmpXchgS32(&pOnce->iState, RTONCESTATE_DONE, RTONCESTATE_DONE_CREATING_SEM)
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * This isn't nice, but it's the easy way out.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * There is a semaphore, try wait on it.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * We continue waiting after reaching DONE_HAVE_SEM if we
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * already got the semaphore to avoid racing the first thread.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync /* fall thru */
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * Grab the semaphore if we haven't got it yet.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * We must take care not to increment the counter if it
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * is 0. This may happen if we're racing a state change.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync int32_t cEventRefs = ASMAtomicUoReadS32(&pOnce->cEventRefs);
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync && ASMAtomicUoReadS32(&pOnce->iState) == RTONCESTATE_BUSY_HAVE_SEM)
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync if (ASMAtomicCmpXchgExS32(&pOnce->cEventRefs, cEventRefs + 1, cEventRefs, &cEventRefs))
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync AssertReturn(*phEvtM != NIL_RTSEMEVENTMULTI, VERR_INTERNAL_ERROR_2);
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * We've got a sempahore, do the actual waiting.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync RTSemEventMultiWaitNoResume(*phEvtM, RT_INDEFINITE_WAIT);
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync while (ASMAtomicReadS32(&pOnce->iState) == RTONCESTATE_BUSY_HAVE_SEM);
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync AssertMsgFailedReturn(("%d\n", iState), VERR_INTERNAL_ERROR_3);
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsyncRTDECL(int) RTOnce(PRTONCE pOnce, PFNRTONCE pfnOnce, void *pvUser1, void *pvUser2)
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * Validate input (strict builds only).
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * Deal with the 'initialized' case first
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync int32_t iState = ASMAtomicUoReadS32(&pOnce->iState);
33b0e5fd502b10034575ffa7c8a30c6816222ce2vboxsync * Do we initialize it?
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync && ASMAtomicCmpXchgS32(&pOnce->iState, RTONCESTATE_BUSY_NO_SEM, RTONCESTATE_UNINITIALIZED))
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * Yes, so do the execute once stuff.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * If there is a sempahore to signal, we're in for some extra work here.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync if ( !ASMAtomicCmpXchgS32(&pOnce->iState, RTONCESTATE_DONE, RTONCESTATE_BUSY_NO_SEM)
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync && !ASMAtomicCmpXchgS32(&pOnce->iState, RTONCESTATE_DONE, RTONCESTATE_BUSY_SPIN)
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync && !ASMAtomicCmpXchgS32(&pOnce->iState, RTONCESTATE_DONE_CREATING_SEM, RTONCESTATE_BUSY_CREATING_SEM)
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync /* Grab the sempahore by switching to 'DONE_HAVE_SEM' before reaching 'DONE'. */
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync AssertReturn(ASMAtomicCmpXchgS32(&pOnce->iState, RTONCESTATE_DONE_HAVE_SEM, RTONCESTATE_BUSY_HAVE_SEM),
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync int32_t cRefs = ASMAtomicIncS32(&pOnce->cEventRefs);
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync ASMAtomicWriteS32(&pOnce->iState, RTONCESTATE_DONE);
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync /* Signal it and return. */
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * Wait for the first thread to complete. Delegate this to a helper
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync * function to simplify cleanup and keep things a bit shorter.
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync ASMAtomicCmpXchgHandle(&pOnce->hEventMulti, NIL_RTSEMEVENTMULTI, hEvtM, fRc); Assert(fRc);
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync fRc = ASMAtomicCmpXchgS32(&pOnce->iState, RTONCESTATE_DONE, RTONCESTATE_DONE_HAVE_SEM); Assert(fRc);
6e59cff536e8de93f15fa1fb6b46d0ee01e06829vboxsync /* Cannot be done while busy! */
96ae2df030763cee874d3f5ac0be07cd1f793281vboxsync int32_t iState = ASMAtomicUoReadS32(&pOnce->iState);
6e59cff536e8de93f15fa1fb6b46d0ee01e06829vboxsync /* Do the same as RTONCE_INITIALIZER does. */
6e59cff536e8de93f15fa1fb6b46d0ee01e06829vboxsync ASMAtomicWriteS32(&pOnce->rc, VERR_INTERNAL_ERROR);