lockimpl.cpp

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/* SPDX-License-Identifier: MIT */
#include "ajabase/system/linux/lockimpl.h"
#include "ajabase/system/debug.h"
#include <errno.h>
 
// For converting milliseconds to nanoseconds
static const int MIL_2_NSEC = 1000000;
 
// Number of nanoseconds in a second
static const int MAX_NSEC = 1000000000;
 
// class AJALockImpl
 
AJALockImpl::AJALockImpl(const char* pName) :
    mName(pName),
    mOwner(0),
    mRefCount(0)
{
    bool okSoFar = true;
    bool freeAttr = false;
 
    // Set up the thread attributes
    pthread_mutexattr_t attr;
    int rc = pthread_mutexattr_init(&attr);
    if (rc)
    {
        AJA_REPORT(0, AJA_DebugSeverity_Error, "AJALockImpl(%s) attr init reported error %d", mName, rc);
        okSoFar = false;
    }
    freeAttr = true;
 
    if (okSoFar)
    {
        rc = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
        if (rc)
        {
            AJA_REPORT(0, AJA_DebugSeverity_Error, "AJALockImpl(%s) attr settype reported error %d", mName, rc);
            okSoFar = false;
        }
    }
 
    if (okSoFar)
    {
        rc = pthread_mutex_init(&mMutex, &attr);
        if (rc)
        {
            AJA_REPORT(0, AJA_DebugSeverity_Error, "AJALockImpl(%s) mutex init reported error %d", mName, rc);
            okSoFar = false;
        }
    }
 
    // Clean up the attribute memory
    if (freeAttr)
    {
        rc = pthread_mutexattr_destroy(&attr);
        if (rc)
        {
            AJA_REPORT(0, AJA_DebugSeverity_Error, "AJALockImpl(%s) attr destroy reported error %d", mName, rc);
        }
    }
}
 
 
AJALockImpl::~AJALockImpl()
{
    int rc;
 
    rc = pthread_mutex_destroy(&mMutex);
    if (rc)
    {
        AJA_REPORT(0, AJA_DebugSeverity_Error, "~AJALockImpl(%s) mutex destroy reported error %d", mName, rc);
    }
}
 
 
AJAStatus
AJALockImpl::Lock(uint32_t timeout)
{
    int rc;
 
    // Allow multiple locks by the same thread
    if (mOwner && (mOwner == pthread_self()))
    {
        mRefCount++;
        return AJA_STATUS_SUCCESS;
    }
 
    // get the current time of day
    struct timespec ts;
    clock_gettime(CLOCK_REALTIME, &ts);
 
    // calculate how long to wait
    if (timeout == 0xffffffff)
    {
        ts.tv_sec  += 60 * 60 * 24 * 365;  // A year is infinite enough
        ts.tv_nsec = 0;
    }
    else
    {
        uint64_t bigtimeout = (uint64_t) timeout * MIL_2_NSEC;
        ts.tv_sec  += bigtimeout / MAX_NSEC;
        ts.tv_nsec += bigtimeout % MAX_NSEC;
        if (ts.tv_nsec >= MAX_NSEC)
        {
            ts.tv_sec++;
            ts.tv_nsec -= MAX_NSEC;
        }
    }
 
    // Wait for the lock
    rc = pthread_mutex_timedlock(&mMutex, &ts);
    if (rc)
    {
        if (rc == ETIMEDOUT)
            return AJA_STATUS_TIMEOUT;
        
        AJA_REPORT(0, AJA_DebugSeverity_Error, "AJALockImpl::Lock(%s) mutex lock reported error %d", mName, rc);
        return AJA_STATUS_FAIL;
    }
 
    mOwner = pthread_self();
    mRefCount = 1;
 
    return AJA_STATUS_SUCCESS;
}
 
 
AJAStatus
AJALockImpl::Unlock()
{
    if (mOwner != pthread_self())
    {
        return AJA_STATUS_FAIL;
    }
 
    // Allow multiple unlocks by the same thread
    mRefCount--;
    if (mRefCount)
    {
        return AJA_STATUS_SUCCESS;
    }
 
    mOwner = 0;
    mRefCount = 0;
    pthread_mutex_unlock(&mMutex);
 
    return AJA_STATUS_SUCCESS;
}