Am 09.03.2026 um 23:36 schrieb Chris M. Thomasson:Actually, you should keep a counter there just for testing/profiling. Bump it every time the exception handler triggers and does its thing.
I don't think it mentions it there, but SEH is used. I prefer proxy collectors over hazard pointers, but that's just me. Well, Joe knows. Hazard pointers basically need async membar behavior or else they eat your lunch with that damn #StoreLoad.I've developed a lockfree stack with SEH. With one thread it is
lower than a SLIST, with two threads it is faster and with 32
threads it is magnitudes faster:
#pragma once
#if defined(_WIN32)
#include <Windows.h>
#endif
#include <atomic>
template<typename T>
struct lockfree_stack
{
struct node : T
{
using T::T;
private:
template<typename T>
friend struct lockfree_stack;
node *m_next;
};
void push( node *nd ) noexcept;
node *pop() noexcept;
private:
struct head { node *ptr; size_t ctr; };
static_assert(atomic_ref<head>::is_always_lock_free);
alignas(2 * sizeof(size_t)) head m_head = { 0, 0 };
};
template<typename T>
void lockfree_stack<T>::push( node *nd ) noexcept
{
using namespace std;
atomic_ref ptr( m_head.ptr );
atomic_ref ctr( m_head.ctr );
head hdRef( ptr.load( memory_order_relaxed ), ctr.load( memory_order_relaxed ) );
atomic_ref<head> aHead( m_head );
do
nd->m_next = (node *)hdRef.ptr;
while( aHead.compare_exchange_strong( hdRef, head( nd, hdRef.ctr + 1 ), memory_order_release, memory_order_relaxed ) );
}
template<typename T>
auto lockfree_stack<T>::pop() noexcept -> node *
{
using namespace std;
atomic_ref ptr( m_head.ptr );
atomic_ref ctr( m_head.ctr );
head hdRef( ptr.load( memory_order_relaxed ), ctr.load( memory_order_relaxed ) );
atomic_ref<head> aHead( m_head );
for( ; ; )
{
node *next;
if( !hdRef.ptr )
return nullptr;
__try
{
next = hdRef.ptr->m_next;
}
__except( EXCEPTION_EXECUTE_HANDLER )
{
hdRef = head( ptr.load( memory_order_relaxed ), ctr.load( memory_order_relaxed ) );
continue;
}
if( aHead.compare_exchange_strong( hdRef, head( next, hdRef.ctr + 1 ), memory_order_acquire, memory_order_relaxed ) )
return hdRef.ptr;
}
}
In the next step I make this Posix'd with my scoped_signal.
Might be interesting?
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