Switch to using the GC_finalize API for off-thread finalisation

.buildbot.sh

@@ -22,9 +22,3 @@ sh rustup.sh --default-host x86_64-unknown-linux-gnu \
     --profile minimal \
     -y
 export PATH=`pwd`/.cargo/bin/:$PATH
-BDWGC_SRC=`pwd`
-
-git clone https://github.com/softdevteam/alloy
-cd alloy
-BDWGC=${BDWGC_SRC} ENABLE_GC_ASSERTIONS=true /usr/bin/time -v python3 x.py test --stage 2 \
-    --config .buildbot.config.toml --exclude rustdoc-json --exclude debuginfo

alloc.c

@@ -1861,15 +1861,3 @@ GC_INNER ptr_t GC_allocobj(size_t lg, int k)
     GC_fail_count = 0;
     return (ptr_t)(*flh);
 }
-
-STATIC __thread void* tls_rootset = NULL;
-
-GC_INNER void GC_init_tls_rootset(void * rootset)
-{
-    tls_rootset = rootset;
-}
-
-GC_INNER void* GC_tls_rootset()
-{
-    return tls_rootset;
-}

fnlz_mlc.c

@@ -131,200 +131,4 @@ GC_API GC_ATTR_MALLOC void * GC_CALL GC_finalized_malloc(size_t lb,
     return (word *)op + 1;
 }
 
-# ifdef BUFFERED_FINALIZATION
-
-static void* init_finalize_thread(void *arg)
-{
-    while (1) {
-        GC_finalize_objects();
-    }
-    return arg;
-}
-
-GC_finalization_buffer_hdr* GC_new_buffer() {
-    GC_ASSERT(I_HOLD_LOCK());
-    void* ptr = GC_os_get_mem(GC_page_size);
-    if (NULL == ptr)
-      ABORT("Insufficient memory for finalization buffer.");
-    GC_add_roots_inner(ptr, ptr + GC_page_size, FALSE);
-    return ptr;
-}
-
-void GC_delete_buffer(GC_finalization_buffer_hdr* buffer) {
-    GC_remove_roots((void*) buffer, (void*) buffer + GC_page_size);
-    GC_unmap((void*)buffer, GC_page_size);
-
-}
-
-STATIC int GC_CALLBACK GC_push_object_to_fin_buffer(void *obj)
-{
-    GC_ASSERT(I_HOLD_LOCK());
-
-    word finalizer_word = *(word *)obj;
-    if ((finalizer_word & FINALIZER_CLOSURE_FLAG) == 0) {
-        return 0;
-    }
-
-    if (finalizer_word & HAS_BEEN_FINALIZED_FLAG) {
-        /* The object has already been finalized. Return 0 ensures it is
-         * immediately reclaimed.
-         */
-        return 0;
-    }
-
-    if (GC_finalizer_buffer_head == NULL) {
-        /* This can happen for two reasons:
-         *   1) This is first time a finalizable object is unreachable and no
-         *   finalization buffers have been created yet.
-         *
-         *   2) The buffer(s) have already passed to a finalization thread
-         *   which is processing them. We must start again. */
-        GC_finalizer_buffer_head = GC_new_buffer();
-        GC_finalizer_buffer_current.hdr = GC_finalizer_buffer_head;
-        GC_finalizer_buffer_current.cursor = (void**) (GC_finalizer_buffer_head + 1);
-    }
-
-    void** last = (void**) ((void *)GC_finalizer_buffer_current.hdr + GC_page_size);
-    if (GC_finalizer_buffer_current.cursor == last) {
-        GC_finalization_buffer_hdr* next = GC_new_buffer();
-        GC_finalizer_buffer_current.hdr->next = next;
-        GC_finalizer_buffer_current.hdr = next;
-        GC_finalizer_buffer_current.cursor = (void**) (next + 1);
-    }
-
-    *GC_finalizer_buffer_current.cursor = obj;
-    GC_finalizer_buffer_current.cursor++;
-
-    return 1;
-}
-
-
-GC_API GC_ATTR_MALLOC void * GC_CALL GC_buffered_finalize_malloc(size_t lb)
-{
-    void *op;
-
-    GC_ASSERT(GC_fin_q_kind != 0);
-    op = GC_malloc_kind(lb, (int)GC_fin_q_kind);
-    if (EXPECT(NULL == op, FALSE))
-        return NULL;
-    return (word *)op;
-}
-
-GC_API GC_ATTR_MALLOC void * GC_CALL GC_buffered_finalize_memalign(size_t align, size_t lb)
-{
-    size_t offset;
-    ptr_t result;
-    size_t align_m1 = align - 1;
-
-    /* Check the alignment argument.    */
-    if (EXPECT(0 == align || (align & align_m1) != 0, FALSE)) return NULL;
-    if (align <= GC_GRANULE_BYTES) return GC_buffered_finalize_malloc(lb);
-
-    if (align >= HBLKSIZE/2 || lb >= HBLKSIZE/2) {
-      return GC_clear_stack(GC_generic_malloc_aligned(lb, GC_fin_q_kind,
-                                        0 /* flags */, align_m1));
-    }
-
-    result = (ptr_t)GC_buffered_finalize_malloc(SIZET_SAT_ADD(lb, align_m1));
-    offset = (size_t)(word)result & align_m1;
-    if (offset != 0) {
-        offset = align - offset;
-        if (!GC_all_interior_pointers) {
-            GC_STATIC_ASSERT(VALID_OFFSET_SZ <= HBLKSIZE);
-            GC_ASSERT(offset < VALID_OFFSET_SZ);
-            GC_register_displacement(offset);
-        }
-        result += offset;
-    }
-    GC_ASSERT(((word)result & align_m1) == 0);
-    return result;
-}
-
-GC_API int GC_CALL GC_buffered_finalize_posix_memalign(void **memptr, size_t align, size_t lb)
-{
-  size_t align_minus_one = align - 1; /* to workaround a cppcheck warning */
-
-  /* Check alignment properly.  */
-  if (EXPECT(align < sizeof(void *)
-             || (align_minus_one & align) != 0, FALSE)) {
-      return EINVAL;
-  }
-
-  if ((*memptr = GC_buffered_finalize_memalign(align, lb)) == NULL) {
-      return ENOMEM;
-  }
-  return 0;
-}
-
-
-GC_API void GC_CALL GC_init_buffered_finalization(void)
-{
-    LOCK();
-    GC_new_buffer();
-    GC_fin_q_kind = GC_new_kind_inner(GC_new_free_list_inner(),
-                                          GC_DS_LENGTH, TRUE, TRUE);
-    GC_ASSERT(GC_fin_q_kind != 0);
-
-    GC_register_disclaim_proc_inner(GC_fin_q_kind, GC_push_object_to_fin_buffer, TRUE);
-    UNLOCK();
-}
-
-void GC_finalize_buffer(GC_finalization_buffer_hdr* buffer) {
-    void** cursor = (void**) (buffer + 1);
-    void** last = (void**) ((void *)buffer + GC_page_size);
-    while (cursor != last)
-    {
-        if (*cursor == NULL) {
-            break;
-        }
-        void* obj = *cursor;
-        word finalizer_word = (*(word *)obj) & ~(word)FINALIZER_CLOSURE_FLAG;
-        GC_disclaim_proc finalizer = (GC_disclaim_proc) finalizer_word;
-        (finalizer)(obj);
-        GC_num_finalized++;
-        /* Prevent the object from being re-added to the finalization queue */
-        *(word *)obj = finalizer_word | HAS_BEEN_FINALIZED_FLAG;
-        cursor++;
-    }
-}
-
-GC_API void GC_CALL GC_finalize_objects(void) {
-    /* This is safe to do without locking because this global is only ever
-     * mutated from within a collection where all mutator threads (including
-     * this finalisation thread) are paused. It is not possible for them to race.
-     *
-     * In addition, a memory barrier synchronises threads at the end of a
-     * collection, so the finalisation thread will always load the up-to-date
-     * version of this global. */
-    GC_disable();
-    GC_finalization_buffer_hdr* buffer = GC_finalizer_buffer_head;
-    GC_finalizer_buffer_head = NULL;
-    GC_enable();
-
-    while(buffer != NULL)
-    {
-        GC_finalize_buffer(buffer);
-        GC_finalization_buffer_hdr* next = buffer->next;
-
-        GC_delete_buffer(buffer);
-        buffer = next;
-    }
-}
-
-GC_INNER void GC_maybe_spawn_finalize_thread()
-{
-    if (GC_finalizer_thread_exists || !GC_finalizer_buffer_head)
-        return;
-
-    pthread_t t;
-    pthread_create(&t, NULL, init_finalize_thread, NULL /* arg */);
-    GC_finalizer_thread_exists = 1;
-}
-
-GC_API size_t GC_finalized_total(void) {
-    return GC_num_finalized;
-}
-
-# endif
-
 #endif /* ENABLE_DISCLAIM */

include/gc/gc.h

@@ -2358,7 +2358,4 @@ GC_API void GC_CALL GC_win32_free_heap(void);
   } /* extern "C" */
 #endif
 
-GC_API void GC_init_tls_rootset(void * rootset);
-GC_API void * GC_tls_rootset();
-
 #endif /* GC_H */

include/gc/gc_disclaim.h

@@ -69,45 +69,6 @@ GC_API GC_ATTR_MALLOC GC_ATTR_ALLOC_SIZE(1) void * GC_CALL
             const struct GC_finalizer_closure * /* fc */) GC_ATTR_NONNULL(2);
 
 
-#ifdef BUFFERED_FINALIZATION
-/* This API is defined only if the library has been suitably compiled   */
-/* (i.e. with ENABLE_DISCLAIM defined).                                 */
-
-/* Prepare the object kind used by GC_buffered_finalize_malloc.  Call   */
-/* it from your initialization code or, at least, at some point before  */
-/* finalized allocations.  The function is thread-safe.                 */
-GC_API void GC_CALL GC_init_buffered_finalization(void);
-
-/* Allocate an object which is to be finalized.                         */
-/* This function assumes the first word in the allocated block will     */
-/* store the function pointer to the finalizer.                         */
-/* Allocations of this kind are added to a buffer which, when full, is  */
-/* passed to a user supplied closure to invoke their finalizers. It is  */
-/* the responsibility of the user to ensure these objects are finalized.*/
-/* This uses a dedicated object kind with a disclaim procedure, and is  */
-/* more efficient than GC_register_finalizer and friends.               */
-/* GC_init_buffered_finalization must be called before using this.      */
-/* The collector will not reclaim the object during the GC cycle where  */
-/* it was considered unreachable. In addition, objects reachable from   */
-/* the finalizer will be protected from collection until the finalizer  */
-/* has been run.                                                        */
-/* The disclaim procedure is not invoked in the leak-finding mode.      */
-/* There is no debugging version of this allocation API.                */
-GC_API GC_ATTR_MALLOC GC_ATTR_ALLOC_SIZE(1) void * GC_CALL
-        GC_buffered_finalize_malloc(size_t);
-
-GC_API GC_ATTR_MALLOC GC_ATTR_ALLOC_SIZE(2) void * GC_CALL
-        GC_buffered_finalize_memalign(size_t /* align */, size_t /* lb */);
-
-GC_API int GC_CALL GC_buffered_finalize_posix_memalign(void ** /* memptr */, size_t /* align */,
-                        size_t /* lb */) GC_ATTR_NONNULL(1);
-
-GC_API void GC_CALL GC_finalize_objects(void);
-
-GC_API size_t GC_finalized_total(void);
-
-#endif
-
 #ifdef __cplusplus
   } /* extern "C" */
 #endif

include/private/gc_priv.h

@@ -341,22 +341,7 @@ typedef struct hblkhdr hdr;
 
 #include "gc/gc_inline.h"
 
-#ifdef BUFFERED_FINALIZATION
-
-typedef struct GC_finalization_buffer_hdr GC_finalization_buffer_hdr;
-
-struct GC_finalization_buffer_hdr {
-    GC_finalization_buffer_hdr* next;
-};
-
-struct GC_current_buffer {
-    GC_finalization_buffer_hdr* hdr;
-    void** cursor;
-};
-
-GC_INNER void GC_maybe_spawn_finalize_thread();
-
-#endif
+GC_INNER void GC_maybe_wake_finalizer_thread();
 
 /*********************************/
 /*                               */
@@ -402,11 +387,7 @@ GC_INNER void GC_maybe_spawn_finalize_thread();
 EXTERN_C_BEGIN
 
 #ifndef GC_NO_FINALIZATION
-#ifdef BUFFERED_FINALIZATION
-# define GC_INVOKE_FINALIZERS() GC_maybe_spawn_finalize_thread()
-#else
-# define GC_INVOKE_FINALIZERS() GC_notify_or_invoke_finalizers()
-#endif
+# define GC_INVOKE_FINALIZERS() GC_maybe_wake_finalizer_thread()
   GC_INNER void GC_notify_or_invoke_finalizers(void);
                         /* If GC_finalize_on_demand is not set, invoke  */
                         /* eligible finalizers. Otherwise:              */
@@ -1597,21 +1578,11 @@ struct _GC_arrays {
 #   define GC_trace_buf_ptr GC_arrays._trace_buf_ptr
     int _trace_buf_ptr;
 # endif
+#   define GC_finalizer_thread_exists GC_arrays._fin_thread_exists
+    int _fin_thread_exists;
 # ifdef ENABLE_DISCLAIM
 #   define GC_finalized_kind GC_arrays._finalized_kind
     unsigned _finalized_kind;
-# ifdef BUFFERED_FINALIZATION
-#   define GC_fin_q_kind GC_arrays._fin_q_kind
-    unsigned _fin_q_kind;
-#   define GC_finalizer_buffer_head GC_arrays._fin_buffer_head
-    GC_finalization_buffer_hdr* _fin_buffer_head;
-#   define GC_finalizer_buffer_current GC_arrays._fin_buffer_current
-    struct GC_current_buffer _fin_buffer_current;
-#   define GC_finalizer_thread_exists GC_arrays._fin_thread_exists
-    int _fin_thread_exists;
-#   define GC_num_finalized GC_arrays._fin_total
-    unsigned _fin_total;
-# endif
 # endif
 # define n_root_sets GC_arrays._n_root_sets
 # define GC_excl_table_entries GC_arrays._excl_table_entries

misc.c

@@ -1481,9 +1481,6 @@ GC_API void GC_CALL GC_init(void)
       GC_ASSERT(GC_bytes_allocd + GC_bytes_allocd_before_gc == 0);
 #   endif
 
-# ifdef BUFFERED_FINALIZATION
-  GC_init_buffered_finalization();
-# endif
 }
 
 GC_API void GC_CALL GC_enable_incremental(void)
@@ -2136,11 +2133,6 @@ GC_API void GC_CALL GC_enable(void)
     LOCK();
     GC_ASSERT(GC_dont_gc != 0); /* ensure no counter underflow */
     GC_dont_gc--;
-#ifndef BUFFERED_FINALIZATION
-    if (!GC_dont_gc && GC_heapsize > GC_heapsize_on_gc_disable)
-      WARN("Heap grown by %" WARN_PRIuPTR " KiB while GC was disabled\n",
-           (GC_heapsize - GC_heapsize_on_gc_disable) >> 10);
-#endif
     UNLOCK();
 }
 

pthread_stop_world.c

@@ -398,7 +398,6 @@ STATIC void GC_suspend_handler_inner(ptr_t dummy, void *context)
   }
   crtn = me -> crtn;
   GC_store_stack_ptr(crtn);
-  crtn -> tls_rootset = GC_tls_rootset();
   get_thread_local_roots(&tlr);
   crtn -> compiler_thread_roots = tlr;
 
@@ -834,7 +833,6 @@ GC_INNER void GC_push_all_stacks(void)
     if (me != NULL) {
         struct GC_ThreadLocalRoots tlr;
         get_thread_local_roots(&tlr);
-        me -> crtn -> tls_rootset = GC_tls_rootset();
         me -> crtn -> compiler_thread_roots = tlr;
     }