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lf_queue: implement wait() method

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Synchronization does not occupy additional space by reusing LSB
This commit is contained in:
Nekotekina 2019-01-11 20:44:10 +03:00
parent ac775cd75e
commit 81c50bad69
3 changed files with 53 additions and 12 deletions
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34
Utilities/lockless.h
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@ -311,17 +311,28 @@ public:
}
};
class lf_queue_base
{
protected:
atomic_t<std::uintptr_t> m_head = 0;
void imp_notify();
public:
// Wait for new elements pushed, no other thread shall call wait() or pop_all() simultaneously
bool wait(u64 usec_timeout = -1);
};
// Linked list-based multi-producer queue (the consumer drains the whole queue at once)
template <typename T>
class lf_queue
class lf_queue : public lf_queue_base
{
// Elements are added by replacing m_head
atomic_t<lf_queue_item<T>*> m_head = nullptr;
using lf_queue_base::m_head;
// Extract all elements and reverse element order (FILO to FIFO)
lf_queue_item<T>* reverse() noexcept
{
if (auto* head = m_head.load() ? m_head.exchange(nullptr) : nullptr)
if (auto* head = m_head.load() ? reinterpret_cast<lf_queue_item<T>*>(m_head.exchange(0)) : nullptr)
{
if (auto* prev = head->m_link)
{
@ -347,18 +358,23 @@ public:
~lf_queue()
{
delete m_head.load();
delete reinterpret_cast<T*>(m_head.load());
}
template <typename... Args>
void push(Args&&... args)
{
auto* old = m_head.load();
auto* item = new lf_queue_item<T>(old, std::forward<Args>(args)...);
auto _old = m_head.load();
auto* item = new lf_queue_item<T>(_old & 1 ? nullptr : reinterpret_cast<lf_queue_item<T>*>(_old), std::forward<Args>(args)...);
while (!m_head.compare_exchange(old, item))
while (!m_head.compare_exchange(_old, reinterpret_cast<std::uint64_t>(item)))
{
item->m_link = old;
item->m_link = _old & 1 ? nullptr : reinterpret_cast<lf_queue_item<T>*>(_old);
}
if (_old & 1)
{
lf_queue_base::imp_notify();
}
}