source: Sophya/trunk/SophyaExt/JThreadsC++/JTCSrc/Cond.cpp@ 1224

// **********************************************************************
//
// Copyright (c) 2000
// Object Oriented Concepts, Inc.
// Billerica, MA, USA
//
// All Rights Reserved
//
// **********************************************************************

#include <JTC/Types.h>
#include <JTC/Syscall.h>
#include <JTC/Mutex.h>
#include <JTC/Event.h>
#include <JTC/Cond.h>
#include <JTC/Handle.h>
#include <JTC/HandleI.h>
#include <JTC/Thread.h>
#include <JTC/Monitor.h>
#include <JTC/ThreadGroup.h>
#include <JTC/Runnable.h>
#include <JTC/Sync.h>

#include <errno.h>

#if defined(HAVE_POSIX_THREADS)
#include <unistd.h>
#include <sys/time.h>
#endif

#ifdef HAVE_STD_IOSTREAM
using namespace std;
#endif

#ifndef WIN32
//
// This helper class is used to re-acquire the the recursive mutex.
// It's in place to help with robustness in the event of
// pthread_cancel.
//
class JTCCondHelper
{
    JTCRecursiveMutex& mut_;
    int count_;

public:

    JTCCondHelper(JTCRecursiveMutex& m,
                  int c)
        : mut_(m), count_(c)
    {
    }

    ~JTCCondHelper()
    {
        //       
        // We need to acquire the mutex rationally... We unlock the
        // mutexes critical section, and lock the mutex.  Restore
        // saved information. NOTE: It's not correct to set the count
        // and the owner of the mutex, the lock API method MUST be
        // called.
        //
        pthread_mutex_unlock(&mut_.crit_);
        mut_.lock(count_);
    }
};
#endif

// ----------------------------------------------------------------------
// JTCCond private member implementation
// ----------------------------------------------------------------------

//
// Wait for the condition variable to be signalled. The posix threads
// and NT threads implementation are essentially the same, except that
// the NT threads implementation uses an NT semaphore instead of a
// native condition variable.
//
// A timeout value of -1 means wait forever. Otherwise, only wait for
// timeout milliseconds.
//
void
JTCCond::_wait(long timeout)
{
#if defined(HAVE_POSIX_THREADS) || defined(HAVE_DCE_THREADS)
    //
    // The mutex is locked at this point. We need to acquire internal,
    // save count. The cond_wait will unlock the mutexes critical
    // section.
    //
    // To see that this code is correct, consider the following cases:
    //
    // - If no thread is currently attempting to lock the mutex then code
    //   code is correct.
    //
    // - If another thread is attempting to unlock the mutex the
    //   application is in error, since the thread calling wait owns the
    //   mutex.
    //
    // - If thread B is attempting to lock the mutex, while thread A
    //   is calling wait then the following cases need to be considered:
    //
    //   - Thread B obtains lock on internal first. The mutex count
    //     will be 0, the owner will be nullThreadId. (set below)
    //     Thread B unlocks internal. Thread A can now obtain it's lock
    //     on internal. It locks internal, discovers count is 0,
    //     increments count, sets owner, and attempts to lock
    //     crit_. This lock cannot proceed until pthread_cond_wait below
    //     is called.
    //
    //   - Thread A obtains lock on internal first. Count is non-zero,
    //     and thread A does not own the mutex. Thread A attempts to
    //     lock crit_, which blocks until pthread_cond_wait below is
    //     called.
    //
    
    int count;
    {
        JTCSynchronized guard(mutex_.internal_);
        
        //
        // Save internal state information to be restored on method
        // exit.
        //
        count = mutex_.count_;
        mutex_.count_ = 0;
        mutex_.owner_ = JTCThreadId();
    }

    //
    // Calculate the timeout period.
    //
    struct timespec abstime;
    if(timeout >= 0)
    {
        struct timeval tv;
        gettimeofday(&tv, 0);
                               //123456789 - 10^9
        const long oneBillion = 1000000000;
        abstime.tv_sec = tv.tv_sec + (timeout/1000);
        abstime.tv_nsec = (tv.tv_usec * 1000) + ((timeout%1000) * 1000000);
        if(abstime.tv_nsec > oneBillion)
        {
            ++abstime.tv_sec;
            abstime.tv_nsec -= oneBillion;
        }
    }

    try
    {
        JTCCondHelper unlock(mutex_, count);
        
        if(timeout < 0)
        {
            JTC_SYSCALL_2(pthread_cond_wait, &cond_, &mutex_.crit_, < 0);
        }
        else
        {
                JTC_SYSCALL_3(pthread_cond_timedwait, &cond_, &mutex_.crit_,
                              &abstime, < 0);
        }
    }
    catch(const JTCSystemCallException& e)
    {
        //
        // EINTR is translated to InterruptedException.
        //
        if(e.getError() == EINTR)
            throw JTCInterruptedException();
        //
        // EAGAIN means that the wait time has passed.
        //
        else if (e.getError() == EAGAIN)
            return;
        
        //
        // Rethrow caught exception.
        //
        throw;
    }

#endif
#if defined(HAVE_WIN32_THREADS)

    {
        JTCSynchronized guard(waitersMutex_);
        //
        // mutex_ is locked on entry.
        //
        ++waiters_;
    }

    int count;

    if(timeout < 0)
        timeout = INFINITE;

    //
    // Save state information.
    //
    {
        JTCSynchronized guard(mutex_.internal_);

        count = mutex_.count_;
        mutex_.count_ = 0;
        mutex_.owner_ = JTCThreadId();
        LeaveCriticalSection(&mutex_.crit_);
    }

    try
    {
        JTC_SYSCALL_2(WaitForSingleObject, sema_, timeout, == WAIT_ABANDONED);
    }
    catch(const JTCSystemCallException&)
    {
        //
        // Restore the mutex lock count times.
        //
        {
            JTCSynchronized guard(waitersMutex_);
            --waiters_;
        }
        mutex_.lock(count);
        throw;
    }

    //
    // Restore the mutex lock count times.
    //
    {
        JTCSynchronized guard(waitersMutex_);
        --waiters_;
        if (waiters_ == 0 && haveBroadcast_)
            broadcastEvent_.post();
    }
    mutex_.lock(count);
#endif
}


// ----------------------------------------------------------------------
// JTCCond constructor and destructor
// ----------------------------------------------------------------------

JTCCond::JTCCond(JTCRecursiveMutex& mut)
    : mutex_(mut)
{
#if defined(HAVE_POSIX_THREADS)
    JTC_SYSCALL_2(pthread_cond_init, &cond_, 0, != 0)
#endif
#if defined(HAVE_DCE_THREADS)
    JTC_SYSCALL_2(pthread_cond_init, &cond_, pthread_condattr_default, != 0)
#endif
#if defined(HAVE_WIN32_THREADS)
    haveBroadcast_ = false; 
    waiters_ = 0;
    JTC_SYSCALL_4(sema_ = CreateSemaphore, 0, 0, 0x7fffffff, 0, == INVALID_HANDLE_VALUE)
#endif
}

JTCCond::~JTCCond()
{
#if defined(HAVE_POSIX_THREADS) || defined(HAVE_DCE_THREADS)
    pthread_cond_destroy(&cond_);
#endif
#if defined(HAVE_WIN32_THREADS)
    CloseHandle(sema_);
#endif
}

// ----------------------------------------------------------------------
// JTCMonitor public member implementation
// ----------------------------------------------------------------------

//
// Wait to be signalled for timeout milliseconds.
//
void
JTCCond::wait(long timeout)
{
    if(timeout < 0)
        throw JTCIllegalArgumentException("timeout value is negative");
    _wait(timeout);
}

//
// Wait to be signalled.
//
void
JTCCond::wait()
{
    _wait(-1);
}

//
// Wake one waiting thread.
//
void
JTCCond::signal()
{
#if defined(HAVE_POSIX_THREADS) || defined(HAVE_DCE_THREADS)
    JTC_SYSCALL_1(pthread_cond_signal,&cond_, != 0)
#endif
#if defined(HAVE_WIN32_THREADS)
    bool haveWaiters;
    {
        JTCSynchronized guard(waitersMutex_);
        haveWaiters = (waiters_ > 0);
    }
    if (haveWaiters)
    {
        JTC_SYSCALL_3(ReleaseSemaphore, sema_, 1, 0, == 0)
    }
#endif
}

//
// Wake all waiting threads.
//
void
JTCCond::broadcast()
{
#if defined(HAVE_POSIX_THREADS) || defined(HAVE_DCE_THREADS)
    JTC_SYSCALL_1(pthread_cond_broadcast,&cond_, != 0)
#endif
#if defined(HAVE_WIN32_THREADS)
    bool haveWaiters;
    int numWaiters;
    {
        JTCSynchronized guard(waitersMutex_);
        haveWaiters = (waiters_ > 0);
        numWaiters = waiters_;
    }
    if (haveWaiters)
    {
        //
        // This is a broadcast event, so set the flag and reset
        // the Event synchronization object.
        //
        haveBroadcast_ = true;
        broadcastEvent_.reset();

        //
        // Release the semaphore waiters_ times.
        //
        JTC_SYSCALL_3(ReleaseSemaphore, sema_, numWaiters, 0, == 0)

        //
        // Wait for each thread to wake.
        // After reset the haveBroadcast_ flag.
        //
        broadcastEvent_.wait();
        haveBroadcast_ = false;
    }
#endif
}