hakmem/core/box/free_remote_box.h

// free_remote_box.h - Box: Cross-thread free to remote queue (transition publishes)
#pragma once
#include <stdint.h>
#include <stdio.h>
#include <stdatomic.h>
#include "hakmem_tiny_superslab.h"
#include "ptr_type_box.h"  // Phase 10
#include "free_publish_box.h"
#include "hakmem_tiny.h"
#include "hakmem_tiny_integrity.h"  // HAK_CHECK_CLASS_IDX

// Performs remote push. On transition (0->nonzero), publishes via Ready/Mailbox.
// Returns 1 if transition occurred, 0 otherwise.
static inline int tiny_free_remote_box(SuperSlab* ss, int slab_idx, TinySlabMeta* meta, hak_base_ptr_t base, uint32_t my_tid) {
    extern _Atomic uint64_t g_free_remote_box_calls;
    atomic_fetch_add_explicit(&g_free_remote_box_calls, 1, memory_order_relaxed);
    if (!(ss && ss->magic == SUPERSLAB_MAGIC)) return 0;
    if (slab_idx < 0 || slab_idx >= ss_slabs_capacity(ss)) return 0;
    (void)my_tid;

    void* raw_base = HAK_BASE_TO_RAW(base);

    // BUGFIX: Decrement used BEFORE remote push to maintain visibility consistency
    // Remote push uses memory_order_release, so drainer must see updated used count
    uint8_t cls_raw = meta ? meta->class_idx : 0xFFu;
    HAK_CHECK_CLASS_IDX((int)cls_raw, "tiny_free_remote_box");
    if (__builtin_expect(cls_raw >= TINY_NUM_CLASSES, 0)) {
        static _Atomic int g_remote_push_cls_oob = 0;
        if (atomic_fetch_add_explicit(&g_remote_push_cls_oob, 1, memory_order_relaxed) == 0) {
            fprintf(stderr,
                    "[REMOTE_PUSH_CLASS_OOB] ss=%p slab_idx=%d meta=%p cls=%u ptr=%p\n",
                    (void*)ss, slab_idx, (void*)meta, (unsigned)cls_raw, raw_base);
        }
        return 0;
    }
    meta->used--;
    int transitioned = ss_remote_push(ss, slab_idx, raw_base);  // ss_active_dec_one() called inside
    // ss_active_dec_one(ss);  // REMOVED: Already called inside ss_remote_push()
    if (transitioned) {
        // Phase 12: use per-slab class for publish metadata
        uint8_t cls = (meta && meta->class_idx < TINY_NUM_CLASSES) ? meta->class_idx : 0;
        tiny_free_publish_remote_transition((int)cls, ss, slab_idx);
        return 1;
    }
    return 0;
}