semmutex-linux.cpp revision 227e0e8b2a8cbb5c51ad3b245cd9f7df81f8ec59
/* $Id$ */
/** @file
* IPRT - Mutex 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.
*/
/*******************************************************************************
* Header Files *
*******************************************************************************/
#include <iprt/semaphore.h>
#include <iprt/assert.h>
#include <iprt/alloc.h>
#include <iprt/thread.h>
#include <iprt/asm.h>
#include <iprt/err.h>
#include "internal/magics.h"
#include "internal/strict.h"
#include <errno.h>
#include <limits.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/syscall.h>
#if 0 /* With 2.6.17 futex.h has become C++ unfriendly. */
# include <linux/futex.h>
#else
# define FUTEX_WAIT 0
# define FUTEX_WAKE 1
#endif
/*******************************************************************************
* Structures and Typedefs *
*******************************************************************************/
/**
* Linux internal representation of a Mutex semaphore.
*/
struct RTSEMMUTEXINTERNAL
{
/** The futex state variable.
* 0 means unlocked.
* 1 means locked, no waiters.
* 2 means locked, one or more waiters.
*/
int32_t volatile iState;
/** Nesting count. */
uint32_t volatile cNesting;
/** The owner of the mutex. */
pthread_t volatile Owner;
/** Magic value. */
intptr_t volatile iMagic;
};
/**
* Wrapper for the futex syscall.
*/
static long sys_futex(int32_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) RTSemMutexCreate(PRTSEMMUTEX pMutexSem)
{
/*
* Allocate semaphore handle.
*/
struct RTSEMMUTEXINTERNAL *pThis = (struct RTSEMMUTEXINTERNAL *)RTMemAlloc(sizeof(struct RTSEMMUTEXINTERNAL));
if (pThis)
{
pThis->iMagic = RTSEMMUTEX_MAGIC;
pThis->iState = 0;
pThis->Owner = (pthread_t)~0;
pThis->cNesting = 0;
*pMutexSem = pThis;
return VINF_SUCCESS;
}
return VERR_NO_MEMORY;
}
RTDECL(int) RTSemMutexDestroy(RTSEMMUTEX MutexSem)
{
/*
* Validate input.
*/
if (MutexSem == NIL_RTSEMMUTEX)
return VERR_INVALID_HANDLE;
struct RTSEMMUTEXINTERNAL *pThis = MutexSem;
AssertPtrReturn(pThis, VERR_INVALID_HANDLE);
AssertMsgReturn(pThis->iMagic == RTSEMMUTEX_MAGIC,
("MutexSem=%p iMagic=%#x\n", pThis, pThis->iMagic),
VERR_INVALID_HANDLE);
/*
* Invalidate the semaphore and wake up anyone waiting on it.
*/
ASMAtomicXchgSize(&pThis->iMagic, RTSEMMUTEX_MAGIC + 1);
if (ASMAtomicXchgS32(&pThis->iState, 0) > 0)
{
sys_futex(&pThis->iState, FUTEX_WAKE, INT_MAX, NULL, NULL, 0);
usleep(1000);
}
pThis->Owner = (pthread_t)~0;
pThis->cNesting = 0;
/*
* Free the semaphore memory and be gone.
*/
RTMemFree(pThis);
return VINF_SUCCESS;
}
static int rtsemMutexRequest(RTSEMMUTEX MutexSem, unsigned cMillies, bool fAutoResume)
{
/*
* Validate input.
*/
struct RTSEMMUTEXINTERNAL *pThis = MutexSem;
AssertReturn(VALID_PTR(pThis) && pThis->iMagic == RTSEMMUTEX_MAGIC,
VERR_INVALID_HANDLE);
/*
* Check if nested request.
*/
pthread_t Self = pthread_self();
if ( pThis->Owner == Self
&& pThis->cNesting > 0)
{
pThis->cNesting++;
return VINF_SUCCESS;
}
/*
* Convert timeout value.
*/
struct timespec ts;
struct timespec *pTimeout = NULL;
if (cMillies != RT_INDEFINITE_WAIT)
{
ts.tv_sec = cMillies / 1000;
ts.tv_nsec = (cMillies % 1000) * 1000000;
pTimeout = &ts;
}
/*
* Lock the mutex.
* Optimize for the uncontended case (makes 1-2 ns difference).
*/
if (RT_UNLIKELY(!ASMAtomicCmpXchgS32(&pThis->iState, 1, 0)))
{
for (;;)
{
int32_t iOld = ASMAtomicXchgS32(&pThis->iState, 2);
/*
* Was the lock released in the meantime? This is unlikely (but possible)
*/
if (RT_UNLIKELY(iOld == 0))
break;
/*
* Go to sleep.
*/
long rc = sys_futex(&pThis->iState, FUTEX_WAIT, 2, pTimeout, NULL, 0);
if (RT_UNLIKELY(pThis->iMagic != RTSEMMUTEX_MAGIC))
return VERR_SEM_DESTROYED;
/*
* Act on the wakup code.
*/
if (rc == -ETIMEDOUT)
{
Assert(pTimeout);
return VERR_TIMEOUT;
}
if (rc == 0)
/* we'll leave the loop now unless another thread is faster */;
else if (rc == -EWOULDBLOCK)
/* retry with new value. */;
else if (rc == -EINTR)
{
if (!fAutoResume)
return VERR_INTERRUPTED;
}
else
{
/* this shouldn't happen! */
AssertMsgFailed(("rc=%ld errno=%d\n", rc, errno));
return RTErrConvertFromErrno(rc);
}
}
/*
* When leaving this loop, iState is set to 2. This means that we gained the
* lock and there are _possibly_ some waiters. We don't know exactly as another
* thread might entered this loop at nearly the same time. Therefore we will
* call futex_wakeup once too often (if _no_ other thread entered this loop).
* The key problem is the simple futex_wait test for x != y (iState != 2) in
* our case).
*/
}
/*
* Set the owner and nesting.
*/
pThis->Owner = Self;
ASMAtomicXchgU32(&pThis->cNesting, 1);
#ifdef RTSEMMUTEX_STRICT
RTTHREAD Thread = RTThreadSelf();
if (Thread != NIL_RTTHREAD)
RTThreadWriteLockInc(Thread);
#endif
return VINF_SUCCESS;
}
RTDECL(int) RTSemMutexRequest(RTSEMMUTEX MutexSem, unsigned cMillies)
{
int rc = rtsemMutexRequest(MutexSem, cMillies, true);
Assert(rc != VERR_INTERRUPTED);
return rc;
}
RTDECL(int) RTSemMutexRequestNoResume(RTSEMMUTEX MutexSem, unsigned cMillies)
{
return rtsemMutexRequest(MutexSem, cMillies, false);
}
RTDECL(int) RTSemMutexRelease(RTSEMMUTEX MutexSem)
{
/*
* Validate input.
*/
struct RTSEMMUTEXINTERNAL *pThis = MutexSem;
AssertReturn(VALID_PTR(pThis) && pThis->iMagic == RTSEMMUTEX_MAGIC,
VERR_INVALID_HANDLE);
/*
* Check if nested.
*/
pthread_t Self = pthread_self();
if (RT_UNLIKELY( pThis->Owner != Self
|| pThis->cNesting == 0))
{
AssertMsgFailed(("Not owner of mutex %p!! Self=%08x Owner=%08x cNesting=%d\n",
pThis, Self, pThis->Owner, pThis->cNesting));
return VERR_NOT_OWNER;
}
/*
* If nested we'll just pop a nesting.
*/
if (pThis->cNesting > 1)
{
pThis->cNesting--;
return VINF_SUCCESS;
}
/*
* Clear the state. (cNesting == 1)
*/
#ifdef RTSEMMUTEX_STRICT
RTTHREAD Thread = RTThreadSelf();
if (Thread != NIL_RTTHREAD)
RTThreadWriteLockDec(Thread);
#endif
pThis->Owner = (pthread_t)~0;
ASMAtomicXchgU32(&pThis->cNesting, 0);
/*
* Release the mutex.
*/
int32_t iNew = ASMAtomicDecS32(&pThis->iState);
if (RT_UNLIKELY(iNew != 0))
{
/* somebody is waiting, try wake up one of them. */
ASMAtomicXchgS32(&pThis->iState, 0);
(void)sys_futex(&pThis->iState, FUTEX_WAKE, 1, NULL, NULL, 0);
}
return VINF_SUCCESS;
}