vspace::Semaphore Class Reference

#include <vspace.h>

Public Member Functions
	Semaphore (size_t value=0)
size_t	value ()
void	post ()
bool	try_wait ()
void	wait ()
bool	start_wait (internals::ipc_signal_t sig=0)
bool	stop_wait ()

Private Member Functions
void	next (int &index)
bool	_idle ()

Private Attributes
int	_owner
int	_waiting [internals::MAX_PROCESS+1]
internals::ipc_signal_t	_signals [internals::MAX_PROCESS+1]
int	_head
int	_tail
size_t	_value
FastLock	_lock

Friends
template<typename T >
class	SyncVar

Detailed Description

Definition at line 2345 of file vspace.h.

Constructor & Destructor Documentation

Semaphore()

vspace::Semaphore::Semaphore ( size_t  value = 0 )

inline

Definition at line 2366 of file vspace.h.

                              :
      _owner(0), _head(0), _tail(0), _value(value), _lock() {
  }

Member Function Documentation

_idle()

bool vspace::Semaphore::_idle ( )

inlineprivate

Definition at line 2359 of file vspace.h.

               {
    return _head == _tail;
  }

next()

void vspace::Semaphore::next ( int &  index )

inlineprivate

Definition at line 2351 of file vspace.h.

                        {
    if (index == internals::MAX_PROCESS)
      index = 0;
    else
      index++;
  }

post()

void Semaphore::post

(

)

Definition at line 1023 of file vspace.cc.

                     {
  int wakeup = -1;
  internals::ipc_signal_t sig;
  _lock.lock();
  if (_head == _tail) {
    _value++;
  } else {
    // don't increment value, as we'll pass that on to the next process.
    wakeup = _waiting[_head];
    sig = _signals[_head];
    next(_head);
  }
  _lock.unlock();
  if (wakeup >= 0) {
    internals::send_signal(wakeup, sig);
  }
}

start_wait()

bool Semaphore::start_wait

(

internals::ipc_signal_t

sig = 0

)

Definition at line 1066 of file vspace.cc.

                                                    {
  _lock.lock();
  if (_value > 0) {
    if (internals::send_signal(internals::vmem.current_process, sig))
      _value--;
    _lock.unlock();
    return false;
  }
  _waiting[_tail] = internals::vmem.current_process;
  _signals[_tail] = sig;
  next(_tail);
  _lock.unlock();
  return true;
}

stop_wait()

bool Semaphore::stop_wait

(

)

Definition at line 1081 of file vspace.cc.

                          {
  bool result = false;
  _lock.lock();
  for (int i = _head; i != _tail; next(i)) {
    if (_waiting[i] == internals::vmem.current_process) {
      int last = i;
      next(i);
      while (i != _tail) {
        _waiting[last] = _waiting[i];
        _signals[last] = _signals[i];
        last = i;
        next(i);
      }
      _tail = last;
      result = true;
      break;
    }
  }
  _lock.unlock();
  return result;
}

try_wait()

bool Semaphore::try_wait

(

)

Definition at line 1041 of file vspace.cc.

                         {
  bool result = false;
  _lock.lock();
  if (_value > 0) {
    _value--;
    result = true;
  }
  _lock.unlock();
  return result;
}

value()

size_t vspace::Semaphore::value ( )

inline

Definition at line 2369 of file vspace.h.

                 {
    return _value;
  }

wait()

void Semaphore::wait

(

)

Definition at line 1052 of file vspace.cc.

                     {
  _lock.lock();
  if (_value > 0) {
    _value--;
    _lock.unlock();
    return;
  }
  _waiting[_tail] = internals::vmem.current_process;
  _signals[_tail] = 0;
  next(_tail);
  _lock.unlock();
  internals::wait_signal();
}

Friends And Related Function Documentation

SyncVar

template<typename T >

friend class SyncVar

friend

Definition at line 2363 of file vspace.h.

Field Documentation

_head

int vspace::Semaphore::_head

private

Definition at line 2350 of file vspace.h.

_lock

FastLock vspace::Semaphore::_lock

private

Definition at line 2358 of file vspace.h.

_owner

int vspace::Semaphore::_owner

private

Definition at line 2347 of file vspace.h.

_signals

internals::ipc_signal_t vspace::Semaphore::_signals[internals::MAX_PROCESS+1]

private

Definition at line 2349 of file vspace.h.

_tail

int vspace::Semaphore::_tail

private

Definition at line 2350 of file vspace.h.

_value

size_t vspace::Semaphore::_value

private

Definition at line 2357 of file vspace.h.

_waiting

int vspace::Semaphore::_waiting[internals::MAX_PROCESS+1]

private

Definition at line 2348 of file vspace.h.

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The documentation for this class was generated from the following files:

• kernel/oswrapper/vspace.h
• kernel/oswrapper/vspace.cc