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//==========================================================================

//

//      sync/mutex.cxx

//

//      Mutex and condition variable implementation

//

//==========================================================================

//####ECOSGPLCOPYRIGHTBEGIN####

// -------------------------------------------

// This file is part of eCos, the Embedded Configurable Operating System.

// Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.

//

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//

// As a special exception, if other files instantiate templates or use macros

// or inline functions from this file, or you compile this file and link it

// with other works to produce a work based on this file, this file does not

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//####ECOSGPLCOPYRIGHTEND####

//==========================================================================

//#####DESCRIPTIONBEGIN####

//

// Author(s):    nickg

// Contributors: nickg, jlarmour

// Date:         1999-02-17

// Purpose:      Mutex implementation

// Description:  This file contains the implementations of the mutex

//               and condition variable classes.

//

//####DESCRIPTIONEND####

//

//==========================================================================

#include <pkgconf/kernel.h>

#include <cyg/kernel/ktypes.h>         // base kernel types

#include <cyg/infra/cyg_trac.h>        // tracing macros

#include <cyg/infra/cyg_ass.h>         // assertion macros

#include <cyg/kernel/instrmnt.h>       // instrumentation

#include <cyg/kernel/mutex.hxx>        // our header

#include <cyg/kernel/thread.inl>       // thread inlines

#include <cyg/kernel/sched.inl>        // scheduler inlines

#include <cyg/kernel/clock.inl>        // clock inlines

// -------------------------------------------------------------------------

// Mutex protocol test macros.

// If the dynamic protocol option is enabled, then these generate appropriate

// tests on the protocol field. If there is no dynamic choice then they simply

// result in empty statements.

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_DYNAMIC

#define IF_PROTOCOL_INHERIT if( protocol == INHERIT )

#define IF_PROTOCOL_CEILING if( protocol == CEILING )

#define IF_PROTOCOL_ACTIVE  if( protocol != NONE )

#else

#define IF_PROTOCOL_INHERIT

#define IF_PROTOCOL_CEILING

#define IF_PROTOCOL_ACTIVE

#endif

// -------------------------------------------------------------------------

// Constructor

Cyg_Mutex::Cyg_Mutex()

{

    CYG_REPORT_FUNCTION();

    locked      = false;

    owner       = NULL;

#if defined(CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_DEFAULT) && \

    defined(CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_DYNAMIC)

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_DEFAULT_INHERIT

    protocol    = INHERIT;

#endif    

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_DEFAULT_CEILING

    protocol    = CEILING;

    ceiling     = CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_DEFAULT_PRIORITY;

#endif    

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_DEFAULT_NONE

    protocol    = NONE;

#endif

#else // not (DYNAMIC and DEFAULT defined)

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_CEILING    

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_DEFAULT_PRIORITY

    // if there is a default priority ceiling defined, use that to initialize

    // the ceiling.

    ceiling = CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_DEFAULT_PRIORITY;

#else

    // Otherwise set it to zero.

    ceiling = 0;

#endif    

#endif

#endif // DYNAMIC and DEFAULT defined

    CYG_REPORT_RETURN();

}

// -------------------------------------------------------------------------

// Construct with defined protocol

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_DYNAMIC

Cyg_Mutex::Cyg_Mutex( cyg_protcol protocol_arg )

{

    CYG_REPORT_FUNCTION();

    locked      = false;

    owner       = NULL;

    protocol    = protocol_arg;

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_CEILING    

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_DEFAULT_PRIORITY

    // if there is a default priority ceiling defined, use that to initialize

    // the ceiling.

    ceiling = CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_DEFAULT_PRIORITY;

#else

    // Otherwise set it to zero.

    ceiling = 0;

#endif    

#endif

    CYG_REPORT_RETURN();

}

#endif

// -------------------------------------------------------------------------

// Destructor

Cyg_Mutex::~Cyg_Mutex()

{

    CYG_REPORT_FUNCTION();

    CYG_ASSERT( owner == NULL, "Deleting mutex with owner");

    CYG_ASSERT( queue.empty(), "Deleting mutex with waiting threads");

    CYG_REPORT_RETURN();

}

// -------------------------------------------------------------------------

#ifdef CYGDBG_USE_ASSERTS

cyg_bool

Cyg_Mutex::check_this( cyg_assert_class_zeal zeal) const

{

//    CYG_REPORT_FUNCTION();

    // check that we have a non-NULL pointer first

    if( this == NULL ) return false;

    switch( zeal )

    {

    case cyg_system_test:

    case cyg_extreme:

    case cyg_thorough:

    case cyg_quick:

    case cyg_trivial:

        if(  locked && owner == NULL ) return false;

        if( !locked && owner != NULL ) return false;

    case cyg_none:

    default:

        break;

    };

    return true;

}

#endif

// -------------------------------------------------------------------------

// Lock and/or wait

cyg_bool

Cyg_Mutex::lock(void)

{

    CYG_REPORT_FUNCTYPE("returning %d");

    cyg_bool result = true;

    Cyg_Thread *self = Cyg_Thread::self();

    // Prevent preemption

    Cyg_Scheduler::lock();

    CYG_ASSERTCLASS( this, "Bad this pointer");

    CYG_INSTRUMENT_MUTEX(LOCK, this, 0);

    // Loop while the mutex is locked, sleeping each time around

    // the loop. This copes with the possibility of a higher priority

    // thread grabbing the mutex between the wakeup in unlock() and

    // this thread actually starting.

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL

    IF_PROTOCOL_ACTIVE

        self->count_mutex();

#endif

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_CEILING

    IF_PROTOCOL_CEILING

        self->set_priority_ceiling(ceiling);

#endif        

    while( locked && result )

    {

        CYG_ASSERT( self != owner, "Locking mutex I already own");

        self->set_sleep_reason( Cyg_Thread::WAIT );

        self->sleep();

        queue.enqueue( self );

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_INHERIT

        IF_PROTOCOL_INHERIT

            owner->inherit_priority(self);

#endif

        CYG_INSTRUMENT_MUTEX(WAIT, this, 0);

        // Allow other threads to run

        Cyg_Scheduler::reschedule();

        CYG_ASSERTCLASS( this, "Bad this pointer");

        switch( self->get_wake_reason() )

        {

        case Cyg_Thread::DESTRUCT:

        case Cyg_Thread::BREAK:

            result = false;

            break;

        case Cyg_Thread::EXIT:

            self->exit();

            break;

        default:

            break;

        }

    }

    if( result )

    {

        locked      = true;

        owner       = self;

        CYG_INSTRUMENT_MUTEX(LOCKED, this, 0);

    }

    else

    {

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL

       IF_PROTOCOL_ACTIVE

           self->uncount_mutex();

#endif    

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_INHERIT

        IF_PROTOCOL_INHERIT

            self->disinherit_priority();

#endif

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_CEILING

        IF_PROTOCOL_CEILING

            self->clear_priority_ceiling();

#endif

    }

    // Unlock the scheduler and maybe switch threads

    Cyg_Scheduler::unlock();

    CYG_ASSERTCLASS( this, "Bad this pointer");

    CYG_REPORT_RETVAL(result);

    return result;

}

// -------------------------------------------------------------------------

// Try to lock and return success

cyg_bool

Cyg_Mutex::trylock(void)

{

    CYG_REPORT_FUNCTYPE("returning %d");

    CYG_ASSERTCLASS( this, "Bad this pointer");

    cyg_bool result = true;

    // Prevent preemption

    Cyg_Scheduler::lock();

    // If the mutex is not locked, grab it

    // for ourself. Otherwise return failure.

    if( !locked )

    {

        Cyg_Thread *self = Cyg_Thread::self();

        locked  = true;

        owner   = self;

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL

       IF_PROTOCOL_ACTIVE

            self->count_mutex();

#endif

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_CEILING

        IF_PROTOCOL_CEILING

            self->set_priority_ceiling(ceiling);

#endif        

    }

    else result = false;

    CYG_INSTRUMENT_MUTEX(TRY, this, result);

    // Unlock the scheduler and maybe switch threads

    Cyg_Scheduler::unlock();

    CYG_REPORT_RETVAL(result);

    return result;

}

// -------------------------------------------------------------------------

// unlock

void

Cyg_Mutex::unlock(void)

{

    CYG_REPORT_FUNCTION();

    // Prevent preemption

    Cyg_Scheduler::lock();

    CYG_INSTRUMENT_MUTEX(UNLOCK, this, 0);

    CYG_ASSERTCLASS( this, "Bad this pointer");

    CYG_ASSERT( locked, "Unlock mutex that is not locked");

    CYG_ASSERT( owner == Cyg_Thread::self(), "Unlock mutex I do not own");

    if( !queue.empty() ) {

        // The queue is non-empty, so grab the next

        // thread from it and wake it up.

        Cyg_Thread *thread = queue.dequeue();

        CYG_ASSERTCLASS( thread, "Bad thread pointer");

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_INHERIT

        // Give the owner-to-be a chance to inherit from the remaining

        // queue or the relinquishing thread:

        IF_PROTOCOL_INHERIT

            thread->relay_priority(owner, &queue);

#endif

        thread->set_wake_reason( Cyg_Thread::DONE );

        thread->wake();

        CYG_INSTRUMENT_MUTEX(WAKE, this, thread);

    }

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL

    IF_PROTOCOL_ACTIVE

        owner->uncount_mutex();

#endif    

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_INHERIT

    IF_PROTOCOL_INHERIT

        owner->disinherit_priority();

#endif

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_CEILING

    IF_PROTOCOL_CEILING

        owner->clear_priority_ceiling();

#endif

    locked      = false;

    owner       = NULL;

    CYG_ASSERTCLASS( this, "Bad this pointer");

    // Unlock the scheduler and maybe switch threads

    Cyg_Scheduler::unlock();

    CYG_REPORT_RETURN();

}

// -------------------------------------------------------------------------

// Release all waiting threads.

void Cyg_Mutex::release()

{

    CYG_REPORT_FUNCTION();

    // Prevent preemption

    Cyg_Scheduler::lock();

    CYG_INSTRUMENT_MUTEX(RELEASE, this, 0);

    CYG_ASSERTCLASS( this, "Bad this pointer");

    while( !queue.empty() )

    {

        // The queue is non-empty, so grab each

        // thread from it and release it.

        Cyg_Thread *thread = queue.dequeue();

        CYG_ASSERTCLASS( thread, "Bad thread pointer");

        thread->release();

        CYG_INSTRUMENT_MUTEX(RELEASED, this, thread);

    }

    CYG_ASSERTCLASS( this, "Bad this pointer");

    // Unlock the scheduler and maybe switch threads

    Cyg_Scheduler::unlock();

    CYG_REPORT_RETURN();

}

// -------------------------------------------------------------------------

// Set ceiling priority for priority ceiling protocol

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_CEILING

void Cyg_Mutex::set_ceiling( cyg_priority priority )

{

    CYG_REPORT_FUNCTION();

//    CYG_ASSERT( priority >=  CYG_THREAD_MAX_PRIORITY, "Priority out of range");

//    CYG_ASSERT( priority <=  CYG_THREAD_MIN_PRIORITY, "Priority out of range");

    // Prevent preemption

    Cyg_Scheduler::lock();

    ceiling = priority;

    // Unlock the scheduler

    Cyg_Scheduler::unlock();

    CYG_REPORT_RETURN();

}

#endif

// -------------------------------------------------------------------------

// Set priority inversion protocol

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_DYNAMIC

void Cyg_Mutex::set_protocol( cyg_protcol new_protocol )

{

    CYG_REPORT_FUNCTION();

    // Prevent preemption

    Cyg_Scheduler::lock();

    protocol = new_protocol;

    // Unlock the scheduler

    Cyg_Scheduler::unlock();

    CYG_REPORT_RETURN();

}

#endif

//==========================================================================

// Condition variables

Cyg_Condition_Variable::Cyg_Condition_Variable(

    Cyg_Mutex   &mx                // linked mutex

    )

{

    CYG_REPORT_FUNCTION();

    mutex       = &mx;

    CYG_ASSERTCLASS( mutex, "Invalid mutex argument");

    CYG_REPORT_RETURN();

}

Cyg_Condition_Variable::Cyg_Condition_Variable()

{

    CYG_REPORT_FUNCTION();

    mutex       = NULL;

    CYG_REPORT_RETURN();

}

// -------------------------------------------------------------------------

// Destructor

Cyg_Condition_Variable::~Cyg_Condition_Variable()

{

    CYG_REPORT_FUNCTION();

    CYG_ASSERT( queue.empty(), "Deleting condvar with waiting threads");

    CYG_REPORT_RETURN();

}

// -------------------------------------------------------------------------

#ifdef CYGDBG_USE_ASSERTS

cyg_bool

Cyg_Condition_Variable::check_this( cyg_assert_class_zeal zeal) const

{

    bool result = true;

    CYG_REPORT_FUNCTYPE("returning %d");

    CYG_REPORT_FUNCARG1("zeal = %d", zeal);

    // check that we have a non-NULL pointer first

    if( this == NULL )

        result = false;

    else {

        switch( zeal )

        {

        case cyg_system_test:

        case cyg_extreme:

        case cyg_thorough:

            if( mutex != NULL && !mutex->check_this(zeal) )

                result = false;

        case cyg_quick:

        case cyg_trivial:

        case cyg_none:

        default:

            break;

        }

    }

    CYG_REPORT_RETVAL(result);

    return result;

}

#endif

// -------------------------------------------------------------------------

// Wait for condition to be true    

// Note: if this function is entered with the scheduler locked (e.g. to

// suspend DSR processing) then there is no need to take the lock.  Also

// in this case, exit with the scheduler locked, which allows this function

// to be used in a totally thread-safe manner.

cyg_bool

Cyg_Condition_Variable::wait_inner( Cyg_Mutex *mx )

{

    CYG_REPORT_FUNCTION();

    cyg_bool result = true;

    Cyg_Thread *self = Cyg_Thread::self();

    Cyg_Scheduler::lock();

    CYG_ASSERTCLASS( this, "Bad this pointer");

    CYG_ASSERTCLASS( mx, "Corrupt mutex");

    CYG_ASSERTCLASS( self, "Bad self thread");

    CYG_INSTRUMENT_CONDVAR(WAIT, this, 0);

    mx->unlock();

    self->set_sleep_reason( Cyg_Thread::WAIT );

    self->sleep();

    queue.enqueue( self );

    // Avoid calling ASRs during the following unlock.

    self->set_asr_inhibit();

    // Unlock the scheduler and switch threads

    Cyg_Scheduler::unlock_reschedule();

    // Allow ASRs again

    self->clear_asr_inhibit();

    CYG_INSTRUMENT_CONDVAR(WOKE, this, self->get_wake_reason());

    CYG_ASSERTCLASS( this, "Bad this pointer");

    CYG_ASSERTCLASS( mx, "Corrupt mutex");

    switch( self->get_wake_reason() )

    {

    case Cyg_Thread::DESTRUCT:          // which, the cv or the mutex?

    case Cyg_Thread::BREAK:

        result = false;

        break;

    case Cyg_Thread::EXIT:

        self->exit();

        break;

    default:

        break;

    }

    // When we awake, we must re-acquire the mutex.  Note that while

    // it is essential to release the mutex and queue on the CV

    // atomically relative to other threads, to avoid races, it is not

    // necessary for us to re-acquire the mutex in the same atomic

    // action. Hence we can do it after unlocking the scheduler.

    // We need to loop here in case the thread is released while waiting

    // for the mutex. It is essential that we exit this function with the

    // mutex claimed.

    while ( !mx->lock() )

        continue;

    CYG_ASSERTCLASS( this, "Bad this pointer");

    CYG_ASSERTCLASS( mx, "Corrupt mutex");

    CYG_ASSERT( mx->owner == self, "Not mutex owner");

    CYG_REPORT_RETURN();

    return result;

}

// -------------------------------------------------------------------------

// Wake one thread

void

Cyg_Condition_Variable::signal(void)

{

    CYG_REPORT_FUNCTION();

    CYG_ASSERTCLASS( this, "Bad this pointer");

    // Prevent preemption

    Cyg_Scheduler::lock();

    CYG_INSTRUMENT_CONDVAR(SIGNAL, this, 0);

    if( !queue.empty() )

    {

        // The queue is non-empty, so grab the next

        // thread from it and wake it up.

        Cyg_Thread *thread = queue.dequeue();

        CYG_ASSERTCLASS( thread, "Bad thread pointer");

        thread->set_wake_reason( Cyg_Thread::DONE );

        thread->wake();

        CYG_INSTRUMENT_CONDVAR(WAKE, this, thread);

    }

    CYG_ASSERTCLASS( this, "Bad this pointer");

    // Unlock the scheduler and maybe switch threads

    Cyg_Scheduler::unlock();

    CYG_REPORT_RETURN();

}

// -------------------------------------------------------------------------

// Set cond true, wake all threads

void

Cyg_Condition_Variable::broadcast(void)

{

    CYG_REPORT_FUNCTION();

    CYG_ASSERTCLASS( this, "Bad this pointer");

    // Prevent preemption

    Cyg_Scheduler::lock();

    CYG_INSTRUMENT_CONDVAR(BROADCAST, this, 0);

    // Grab all the threads from the queue and let them

    // go.

    while( !queue.empty() )

    {

        Cyg_Thread *thread = queue.dequeue();

        CYG_ASSERTCLASS( thread, "Bad thread pointer");

        thread->set_wake_reason( Cyg_Thread::DONE );

        thread->wake();

        CYG_INSTRUMENT_CONDVAR(WAKE, this, thread);