lib: Add epoch-based SMR

lib/lfstack.c

@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: ISC
+
+#include <zinnia/epoch.h>
+#include <zinnia/lfstack.h>
+
+void lfstack_init(struct lfstack* stack) {
+    atomic_init(&stack->top, nullptr);
+}
+
+bool lfstack_empty(struct lfstack* stack) {
+    return atomic_load(&stack->top, ATOMIC_RELAXED) == nullptr;
+}
+
+void lfstack_push(struct lfstack* stack, struct lfstack_node* node) {
+    struct lfstack_node* top = atomic_load(&stack->top, ATOMIC_RELAXED);
+    do {
+        atomic_store(&node->next, top, ATOMIC_RELAXED);
+    } while (!atomic_compare_exchange_weak(&stack->top, &top, node, ATOMIC_RELEASE, ATOMIC_RELAXED));
+}
+
+struct lfstack_node* lfstack_pop(struct lfstack* stack) {
+    epoch_enter();
+    struct lfstack_node* top = epoch_deref(&stack->top);
+    while (top) {
+        struct lfstack_node* next = atomic_load(&top->next, ATOMIC_RELAXED);
+        if (atomic_compare_exchange_weak(&stack->top, &top, next, ATOMIC_ACQUIRE, ATOMIC_ACQUIRE))
+            break;
+    }
+    epoch_exit();
+    return top;
+}
+
+struct lfstack_node* lfstack_pop_all(struct lfstack* stack) {
+    return atomic_exchange(&stack->top, nullptr, ATOMIC_ACQUIRE);
+}