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Use separate thread for finalisation #16

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Apr 16, 2024
Merged

Use separate thread for finalisation #16

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24 changes: 21 additions & 3 deletions fnlz_mlc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -22,8 +22,10 @@
#if defined(KEEP_BACK_PTRS) || defined(MAKE_BACK_GRAPH)
/* The first bit is already used for a debug purpose. */
# define FINALIZER_CLOSURE_FLAG 0x2
# define HAS_BEEN_FINALIZED_FLAG 0x3
#else
# define FINALIZER_CLOSURE_FLAG 0x1
# define HAS_BEEN_FINALIZED_FLAG 0x2
#endif

STATIC int GC_CALLBACK GC_finalized_disclaim(void *obj)
Expand Down Expand Up @@ -135,19 +137,24 @@ GC_API GC_ATTR_MALLOC void * GC_CALL GC_finalized_malloc(size_t lb,
STATIC GC_finalization_buffer_hdr* start_buffer;
STATIC struct GC_current_buffer cur_buffer;

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());
GC_disable();
void* ptr = GC_os_get_mem(GC_page_size);
GC_enable();
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_ASSERT(I_HOLD_LOCK());
GC_remove_roots((void*) buffer, (void*) buffer + GC_page_size);
GC_unmap((void*)buffer, GC_page_size);

Expand All @@ -162,6 +169,13 @@ STATIC int GC_CALLBACK GC_push_object_to_fin_buffer(void *obj)
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 (start_buffer == NULL) {
/* This can happen for two reasons:
* 1) This is first time a finalizable object is unreachable and no
Expand Down Expand Up @@ -211,6 +225,8 @@ GC_API void GC_CALL GC_init_buffered_finalization(void)

GC_register_disclaim_proc_inner(GC_fin_q_kind, GC_push_object_to_fin_buffer, TRUE);
UNLOCK();
pthread_t t;
pthread_create(&t, NULL, init_finalize_thread, NULL /* arg */);
}

void GC_finalize_buffer(GC_finalization_buffer_hdr* buffer) {
Expand All @@ -225,6 +241,8 @@ void GC_finalize_buffer(GC_finalization_buffer_hdr* buffer) {
word finalizer_word = (*(word *)obj) & ~(word)FINALIZER_CLOSURE_FLAG;
GC_disclaim_proc finalizer = (GC_disclaim_proc) finalizer_word;
(finalizer)(obj);
/* Prevent the object from being re-added to the finalization queue */
*(word *)obj = finalizer_word | HAS_BEEN_FINALIZED_FLAG;
cursor++;
}
}
Expand Down