rts/umlrt/umlrtmutex.cc

// umlrtmutex.cc

/*******************************************************************************
* Copyright (c) 2014-2015 Zeligsoft (2009) Limited  and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*******************************************************************************/


#include <errno.h>
#include <time.h>
#include "basefatal.hh"
#include "umlrtmutex.hh"
#include "umlrttimespec.hh"

// UMLRTMutex is platform-independent mutual-exclusion.

// Bug 32 tracks the move of this implementation to +/os/linux/osmutex.cc

UMLRTMutex::UMLRTMutex() : guard(), condition(), locked(false)
{
    pthread_mutex_init(&guard, NULL);
    pthread_cond_init(&condition, NULL);
}

UMLRTMutex::~UMLRTMutex()
{
    pthread_mutex_destroy(&guard);
    pthread_cond_destroy(&condition);
}

// Wait forever for mutex.
void UMLRTMutex::take()
{
    UMLRTMutexGuard g(guard);

    while (locked)
    {
        pthread_cond_wait(&condition, &guard);
    }
    locked = true;
}

// Timed - returns non-zero for success, zero for timeout.
#if (((__GNUC__ * 100) + __GNUC_MINOR__) >= 406)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
#endif

bool UMLRTMutex::take( uint32_t msec )
{
    struct timespec timeout;
    UMLRTTimespec::timespecAbsAddMsec( &timeout, msec );

    UMLRTMutexGuard g(guard);

    while (locked)
    {
        if (pthread_cond_timedwait(&condition, &guard, &timeout) != 0)
        {
            int errno_ = errno;
            if (errno_ != ETIMEDOUT)
            {
                FATAL_ERRNO("pthread_cond_timedwait");
            }
            return false; // Timed out - return error indication.
        }
    }
    locked = true;
    return true; // Obtained lock within timeout.
}

#if (((__GNUC__ * 100) + __GNUC_MINOR__) >= 406)
#pragma GCC diagnostic pop
#endif

// Give mutex back.
void UMLRTMutex::give()
{
    UMLRTMutexGuard g(guard);
    locked = false;
    pthread_cond_signal(&condition);
}