std::shared_ptr<T> pop()
{
std::atomic<void*>& hp = get_hazard_pointer_for_current_thread();
node* old_head = head.load();
do {
node* temp;
do { // loop until you've set the harzard pointer to head
temp = old_head;
hp.store(old_head);
old_head = head.load();
} while (old_head != temp);
}
while (old_head &&
!head.compare_exchange_strong(old_head, old_head->next));
hp.store(nullptr); // clear hazard pointer once you're finished
std::shared_ptr<T> res;
if (old_head) {
res.swap(old_head->data);
if (outstanding_hazard_pointers_for(old_head)) {
// check for hazard pointers referencing
// a node before you delete it
reclaim_later(old_head);
}
else {
delete old_head;
}
delete_nodes_with_no_hazards();
}
return res;
}
std::shared_ptr<T> pop()
{
// get the hazard pointers for the current thread
std::atomic<void*>& hp=get_hazard_pointer_for_current_thread();
node* old_head=head.load();
do
{
node* temp;
do
{
temp=old_head;
// store old_head in the hazard pointer
hp.store(old_head);
old_head=head.load();
} while(old_head!=temp);
}
// check old_head before deleting.
while(old_head &&
!head.compare_exchange_strong(old_head,old_head->next));
hp.store(nullptr);
std::shared_ptr<T> res;
if(old_head)
{
res.swap(old_head->data);
if(outstanding_hazard_pointers_for(old_head))
{
// old head being accessed by other threads.
// add to reclaim later list
reclaim_later(old_head);
}
else
{
delete old_head;
}
// traverse through the reclaim later list and delete nodes which are not hazardous.
delete_nodes_with_no_hazards();
}
return res;
}
