hakmem/core/box/sp_rebind_slot_box.h

// sp_rebind_slot_box.h - SuperSlab Slot Rebinding (atomic class change)
// Purpose: Atomically rebind a slab slot to a new class with consistent state
// License: MIT
// Date: 2025-11-30

#ifndef HAKMEM_SP_REBIND_SLOT_BOX_H
#define HAKMEM_SP_REBIND_SLOT_BOX_H

#include "hakmem_tiny_superslab_internal.h"
#include "box/tls_sll_box.h"  // TLS_SLL_RESET

// ========== SuperSlab Slot Rebinding ==========
//
// Atomically rebind a slab slot when:
// - Stage 1: EMPTY → ACTIVE (same or different class)
// - Stage 2: UNUSED → ACTIVE (new class)
// - Stage 3: New SuperSlab (initial class assignment)
//
// Operations (in order):
// 1. Remember old class (for TLS cleanup)
// 2. Fix geometry if needed (update capacity/class_idx)
// 3. Reset TLS SLL for BOTH old and new class (防御的)
// 4. Update class_map (out-of-band lookup)
//
// Box Theory:
//  - Single Responsibility: Ensure slab→class binding consistency
//  - Clear Contract: (ss, slab_idx, new_class) → consistent state
//  - Observable: Debug log shows old_cls→new_cls transitions
//  - Composable: Called from all acquire paths

#if !HAKMEM_BUILD_RELEASE
#define SP_REBIND_SLOT(ss, slab_idx, new_class_idx) \
    do { \
        static __thread int s_trace = -1; \
        if (__builtin_expect(s_trace == -1, 0)) { \
            const char* e = getenv("HAKMEM_SP_REBIND_TRACE"); \
            s_trace = (e && *e && *e != '0') ? 1 : 0; \
        } \
        \
        /* Step 1: Remember old class for TLS cleanup */ \
        uint8_t old_class_idx = (ss)->slabs[slab_idx].class_idx; \
        \
        /* Step 2: Fix geometry (updates capacity, class_idx, etc) */ \
        sp_fix_geometry_if_needed((ss), (slab_idx), (new_class_idx)); \
        \
        /* Step 3: Reset TLS SLL for old class (if different) */ \
        if (old_class_idx != (uint8_t)(new_class_idx) && \
            old_class_idx < TINY_NUM_CLASSES) { \
            TLS_SLL_RESET(old_class_idx); \
            if (s_trace) { \
                fprintf(stderr, \
                        "[SP_REBIND_SLOT] OLD class TLS reset: cls=%d ss=%p slab=%d (old_cls=%d -> new_cls=%d)\n", \
                        old_class_idx, (void*)(ss), (slab_idx), old_class_idx, (new_class_idx)); \
            } \
        } \
        \
        /* Step 4: Reset TLS SLL for new class (防御的 - 常にクリア) */ \
        if ((new_class_idx) < TINY_NUM_CLASSES) { \
            TLS_SLL_RESET(new_class_idx); \
            if (s_trace) { \
                fprintf(stderr, \
                        "[SP_REBIND_SLOT] NEW class TLS reset: cls=%d ss=%p slab=%d\n", \
                        (new_class_idx), (void*)(ss), (slab_idx)); \
            } \
        } \
        \
        /* Step 5: Update class_map (out-of-band lookup) */ \
        ss_slab_meta_class_idx_set((ss), (slab_idx), (uint8_t)(new_class_idx)); \
        \
        if (s_trace) { \
            fprintf(stderr, \
                    "[SP_REBIND_SLOT] COMPLETE: ss=%p slab=%d old_cls=%d -> new_cls=%d cap=%u\n", \
                    (void*)(ss), (slab_idx), old_class_idx, (new_class_idx), \
                    (unsigned)(ss)->slabs[slab_idx].capacity); \
        } \
    } while (0)
#else
// Release build: no trace, just execute operations
#define SP_REBIND_SLOT(ss, slab_idx, new_class_idx) \
    do { \
        uint8_t old_class_idx = (ss)->slabs[slab_idx].class_idx; \
        sp_fix_geometry_if_needed((ss), (slab_idx), (new_class_idx)); \
        if (old_class_idx != (uint8_t)(new_class_idx) && \
            old_class_idx < TINY_NUM_CLASSES) { \
            TLS_SLL_RESET(old_class_idx); \
        } \
        if ((new_class_idx) < TINY_NUM_CLASSES) { \
            TLS_SLL_RESET(new_class_idx); \
        } \
        ss_slab_meta_class_idx_set((ss), (slab_idx), (uint8_t)(new_class_idx)); \
    } while (0)
#endif

#endif // HAKMEM_SP_REBIND_SLOT_BOX_H