/* $Id: semevent-linux.cpp 22959 2009-09-11 13:45:44Z vboxsync $ */ /** @file * IPRT - Event Semaphore, Linux (2.6.x+). */ /* * Copyright (C) 2006-2007 Sun Microsystems, Inc. * * This file is part of VirtualBox Open Source Edition (OSE), as * available from http://www.virtualbox.org. This file is free software; * you can redistribute it and/or modify it under the terms of the GNU * General Public License (GPL) as published by the Free Software * Foundation, in version 2 as it comes in the "COPYING" file of the * VirtualBox OSE distribution. VirtualBox OSE is distributed in the * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind. * * The contents of this file may alternatively be used under the terms * of the Common Development and Distribution License Version 1.0 * (CDDL) only, as it comes in the "COPYING.CDDL" file of the * VirtualBox OSE 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. * * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa * Clara, CA 95054 USA or visit http://www.sun.com if you need * additional information or have any questions. */ #include #if __GLIBC_PREREQ(2,6) && !defined(IPRT_WITH_FUTEX_BASED_SEMS) /* * glibc 2.6 fixed a serious bug in the mutex implementation. We wrote this * linux specific event semaphores code in order to work around the bug. We * will fall back on the pthread-based implementation if glibc is known to * contain the bug fix. * * The external refernce to epoll_pwait is a hack which prevents that we link * against glibc < 2.6. */ #include "../posix/semevent-posix.cpp" asm volatile (".global epoll_pwait"); #else /* glibc < 2.6 */ /******************************************************************************* * Header Files * *******************************************************************************/ #include #include #include #include #include #include #include "internal/magics.h" #include #include #include #include #include #include #if 0 /* With 2.6.17 futex.h has become C++ unfriendly. */ # include #else # define FUTEX_WAIT 0 # define FUTEX_WAKE 1 #endif /******************************************************************************* * Structures and Typedefs * *******************************************************************************/ /** * Linux (single wakup) event semaphore. */ struct RTSEMEVENTINTERNAL { /** Magic value. */ intptr_t volatile iMagic; /** The futex state variable. * 0 means not signalled. 1 means signalled. */ uint32_t volatile fSignalled; /** The number of waiting threads */ int32_t volatile cWaiters; }; /** * Wrapper for the futex syscall. */ static long sys_futex(uint32_t volatile *uaddr, int op, int val, struct timespec *utime, int32_t *uaddr2, int val3) { errno = 0; long rc = syscall(__NR_futex, uaddr, op, val, utime, uaddr2, val3); if (rc < 0) { Assert(rc == -1); rc = -errno; } return rc; } RTDECL(int) RTSemEventCreate(PRTSEMEVENT pEventSem) { /* * Allocate semaphore handle. */ struct RTSEMEVENTINTERNAL *pThis = (struct RTSEMEVENTINTERNAL *)RTMemAlloc(sizeof(struct RTSEMEVENTINTERNAL)); if (pThis) { pThis->iMagic = RTSEMEVENT_MAGIC; pThis->cWaiters = 0; pThis->fSignalled = 0; *pEventSem = pThis; return VINF_SUCCESS; } return VERR_NO_MEMORY; } RTDECL(int) RTSemEventDestroy(RTSEMEVENT EventSem) { /* * Validate input. */ if (EventSem == NIL_RTSEMEVENT) /* don't bitch */ return VERR_INVALID_HANDLE; struct RTSEMEVENTINTERNAL *pThis = EventSem; AssertPtrReturn(pThis, VERR_INVALID_HANDLE); AssertReturn(pThis->iMagic == RTSEMEVENT_MAGIC, VERR_INVALID_HANDLE); /* * Invalidate the semaphore and wake up anyone waiting on it. */ ASMAtomicXchgSize(&pThis->iMagic, RTSEMEVENT_MAGIC | UINT32_C(0x80000000)); if (ASMAtomicXchgS32(&pThis->cWaiters, INT32_MIN / 2) > 0) { sys_futex(&pThis->fSignalled, FUTEX_WAKE, INT_MAX, NULL, NULL, 0); usleep(1000); } /* * Free the semaphore memory and be gone. */ RTMemFree(pThis); return VINF_SUCCESS; } RTDECL(int) RTSemEventSignal(RTSEMEVENT EventSem) { /* * Validate input. */ struct RTSEMEVENTINTERNAL *pThis = EventSem; AssertReturn(VALID_PTR(pThis) && pThis->iMagic == RTSEMEVENT_MAGIC, VERR_INVALID_HANDLE); ASMAtomicWriteU32(&pThis->fSignalled, 1); if (ASMAtomicReadS32(&pThis->cWaiters) < 1) return VINF_SUCCESS; /* somebody is waiting, try wake up one of them. */ long cWoken = sys_futex(&pThis->fSignalled, FUTEX_WAKE, 1, NULL, NULL, 0); if (RT_LIKELY(cWoken >= 0)) return VINF_SUCCESS; if (RT_UNLIKELY(pThis->iMagic != RTSEMEVENT_MAGIC)) return VERR_SEM_DESTROYED; return VERR_INVALID_PARAMETER; } static int rtSemEventWait(RTSEMEVENT EventSem, unsigned cMillies, bool fAutoResume) { /* * Validate input. */ struct RTSEMEVENTINTERNAL *pThis = EventSem; AssertReturn(VALID_PTR(pThis) && pThis->iMagic == RTSEMEVENT_MAGIC, VERR_INVALID_HANDLE); /* * Quickly check whether it's signaled. */ if (ASMAtomicCmpXchgU32(&pThis->fSignalled, 0, 1)) return VINF_SUCCESS; /* * Convert the timeout value. */ struct timespec ts; struct timespec *pTimeout = NULL; uint64_t u64End = 0; /* shut up gcc */ if (cMillies != RT_INDEFINITE_WAIT) { if (!cMillies) return VERR_TIMEOUT; ts.tv_sec = cMillies / 1000; ts.tv_nsec = (cMillies % 1000) * 1000000; u64End = RTTimeSystemNanoTS() + cMillies * 1000000; pTimeout = &ts; } ASMAtomicIncS32(&pThis->cWaiters); /* * The wait loop. */ int rc = VINF_SUCCESS; for (;;) { long lrc = sys_futex(&pThis->fSignalled, FUTEX_WAIT, 0, pTimeout, NULL, 0); if (RT_UNLIKELY(pThis->iMagic != RTSEMEVENT_MAGIC)) { rc = VERR_SEM_DESTROYED; break; } if (RT_LIKELY(lrc == 0 || lrc == -EWOULDBLOCK)) { /* successful wakeup or fSignalled > 0 in the meantime */ if (ASMAtomicCmpXchgU32(&pThis->fSignalled, 0, 1)) break; } else if (lrc == -ETIMEDOUT) { rc = VERR_TIMEOUT; break; } else if (lrc == -EINTR) { if (!fAutoResume) { rc = VERR_INTERRUPTED; break; } } else { /* this shouldn't happen! */ AssertMsgFailed(("rc=%ld errno=%d\n", lrc, errno)); rc = RTErrConvertFromErrno(lrc); break; } /* adjust the relative timeout */ if (pTimeout) { int64_t i64Diff = u64End - RTTimeSystemNanoTS(); if (i64Diff < 1000) { rc = VERR_TIMEOUT; break; } ts.tv_sec = i64Diff / 1000000000; ts.tv_nsec = i64Diff % 1000000000; } } ASMAtomicDecS32(&pThis->cWaiters); return rc; } RTDECL(int) RTSemEventWait(RTSEMEVENT EventSem, unsigned cMillies) { int rc = rtSemEventWait(EventSem, cMillies, true); Assert(rc != VERR_INTERRUPTED); Assert(rc != VERR_TIMEOUT || cMillies != RT_INDEFINITE_WAIT); return rc; } RTDECL(int) RTSemEventWaitNoResume(RTSEMEVENT EventSem, unsigned cMillies) { return rtSemEventWait(EventSem, cMillies, false); } #endif /* glibc < 2.6 || IPRT_WITH_FUTEX_BASED_SEMS */