std::pair<bool, T>
try_pop_front()
{
retry:
unique_lock l(head_->mutex_);
node_ptr first = head_->next_;
if (unlikely(!first))
return std::make_pair(false, T());
unique_lock l0(first->mutex_);
T t = first->value_;
bool is_tail = !first->next_;
if (is_tail) {
l0.unlock();
tail_ptr_mutex_.lock();
l0.lock();
assert(head_->next_ == first);
if (first->next_) {
// no longer tail, retry
tail_ptr_mutex_.unlock();
goto retry;
}
assert(tail_ == first);
}
head_->next_ = first->next_;
if (is_tail) {
tail_ = head_;
tail_ptr_mutex_.unlock();
}
return std::make_pair(true, t);
}
void
pop_front()
{
retry:
unique_lock l(head_->mutex_);
node_ptr first = head_->next_;
assert(first);
unique_lock l0(first->mutex_);
bool is_tail = !first->next_;
if (is_tail) {
l0.unlock();
tail_ptr_mutex_.lock();
l0.lock();
assert(head_->next_ == first);
if (first->next_) {
// no longer tail, retry
tail_ptr_mutex_.unlock();
goto retry;
}
assert(tail_ == first);
}
head_->next_ = first->next_;
if (is_tail) {
tail_ = head_;
tail_ptr_mutex_.unlock();
}
}
inline void
remove(const T &val)
{
node_ptr prev = head_;
prev->mutex_.lock();
node_ptr cur = prev->next_;
while (cur) {
cur->mutex_.lock();
if (cur->value_ == val) {
// unlink
bool is_tail = !cur->next_;
if (is_tail) {
cur->mutex_.unlock();
tail_ptr_mutex_.lock();
cur->mutex_.lock();
assert(tail_ == cur);
}
prev->next_ = cur->next_;
if (is_tail) {
tail_ = prev;
tail_ptr_mutex_.unlock();
}
cur->mutex_.unlock();
cur = prev->next_;
} else {
prev->mutex_.unlock();
prev = cur;
cur = cur->next_;
}
}
prev->mutex_.unlock();
}
void wait(lock_type& m)
{
int res=0;
{
detail::interruption_checker check_for_interruption(&cond);
{
boost::pthread::pthread_mutex_scoped_lock internal_lock(&internal_mutex);
m.unlock();
res=pthread_cond_wait(&cond,&internal_mutex);
}
m.lock();
}
if(res)
{
boost::throw_exception(condition_error());
}
}
bool timed_wait(lock_type& m,boost::system_time const& wait_until)
{
struct timespec const timeout=detail::get_timespec(wait_until);
int res=0;
{
detail::interruption_checker check_for_interruption(&cond);
{
boost::pthread::pthread_mutex_scoped_lock internal_lock(&internal_mutex);
m.unlock();
res=pthread_cond_timedwait(&cond,&internal_mutex,&timeout);
}
m.lock();
}
if(res==ETIMEDOUT)
{
return false;
}
if(res)
{
boost::throw_exception(condition_error());
}
return true;
}
~thread_safe_agent_t()
{
lock_.unlock();
}