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/*
* Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
* Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
*
* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
*
* Permission is hereby granted to use or copy this program
* for any purpose, provided the above notices are retained on all copies.
* Permission to modify the code and to distribute modified code is granted,
* provided the above notices are retained, and a notice that the code was
* modified is included with the above copyright notice.
*/
#include "private/gc_priv.h"
/*
* We maintain several hash tables of hblks that have had false hits.
* Each contains one bit per hash bucket; If any page in the bucket
* has had a false hit, we assume that all of them have.
* See the definition of page_hash_table in gc_private.h.
* False hits from the stack(s) are much more dangerous than false hits
* from elsewhere, since the former can pin a large object that spans the
* block, even though it does not start on the dangerous block.
*/
/*
* Externally callable routines are:
* GC_add_to_black_list_normal
* GC_add_to_black_list_stack
* GC_promote_black_lists
* GC_is_black_listed
*
* All require that the allocator lock is held.
*/
/* Pointers to individual tables. We replace one table by another by */
/* switching these pointers. */
STATIC word * GC_old_normal_bl = NULL;
/* Nonstack false references seen at last full */
/* collection. */
STATIC word * GC_incomplete_normal_bl = NULL;
/* Nonstack false references seen since last */
/* full collection. */
STATIC word * GC_old_stack_bl = NULL;
STATIC word * GC_incomplete_stack_bl = NULL;
STATIC word GC_total_stack_black_listed = 0;
/* Number of bytes on stack blacklist. */
GC_INNER word GC_black_list_spacing = MINHINCR * HBLKSIZE;
/* Initial rough guess. */
STATIC void GC_clear_bl(word *);
GC_INNER void GC_default_print_heap_obj_proc(ptr_t p)
{
ptr_t base = GC_base(p);
int kind = HDR(base)->hb_obj_kind;
GC_err_printf("object at %p of appr. %lu bytes (%s)\n",
base, (unsigned long)GC_size(base),
kind == PTRFREE ? "atomic" :
IS_UNCOLLECTABLE(kind) ? "uncollectable" : "composite");
}
GC_INNER void (*GC_print_heap_obj)(ptr_t p) = GC_default_print_heap_obj_proc;
#ifdef PRINT_BLACK_LIST
STATIC void GC_print_blacklisted_ptr(word p, ptr_t source,
const char *kind_str)
{
ptr_t base = GC_base(source);
if (0 == base) {
GC_err_printf("Black listing (%s) %p referenced from %p in %s\n",
kind_str, (ptr_t)p, source,
NULL != source ? "root set" : "register");
} else {
/* FIXME: We can't call the debug version of GC_print_heap_obj */
/* (with PRINT_CALL_CHAIN) here because the lock is held and */
/* the world is stopped. */
GC_err_printf("Black listing (%s) %p referenced from %p in"
" object at %p of appr. %lu bytes\n",
kind_str, (ptr_t)p, source,
base, (unsigned long)GC_size(base));
}
}
#endif /* PRINT_BLACK_LIST */
GC_INNER void GC_bl_init_no_interiors(void)
{
if (GC_incomplete_normal_bl == 0) {
GC_old_normal_bl = (word *)GC_scratch_alloc(sizeof(page_hash_table));
GC_incomplete_normal_bl = (word *)GC_scratch_alloc(
sizeof(page_hash_table));
if (GC_old_normal_bl == 0 || GC_incomplete_normal_bl == 0) {
GC_err_printf("Insufficient memory for black list\n");
EXIT();
}
GC_clear_bl(GC_old_normal_bl);
GC_clear_bl(GC_incomplete_normal_bl);
}
}
GC_INNER void GC_bl_init(void)
{
if (!GC_all_interior_pointers) {
GC_bl_init_no_interiors();
}
GC_old_stack_bl = (word *)GC_scratch_alloc(sizeof(page_hash_table));
GC_incomplete_stack_bl = (word *)GC_scratch_alloc(sizeof(page_hash_table));
if (GC_old_stack_bl == 0 || GC_incomplete_stack_bl == 0) {
GC_err_printf("Insufficient memory for black list\n");
EXIT();
}
GC_clear_bl(GC_old_stack_bl);
GC_clear_bl(GC_incomplete_stack_bl);
}
STATIC void GC_clear_bl(word *doomed)
{
BZERO(doomed, sizeof(page_hash_table));
}
STATIC void GC_copy_bl(word *old, word *new)
{
BCOPY(old, new, sizeof(page_hash_table));
}
static word total_stack_black_listed(void);
/* Signal the completion of a collection. Turn the incomplete black */
/* lists into new black lists, etc. */
GC_INNER void GC_promote_black_lists(void)
{
word * very_old_normal_bl = GC_old_normal_bl;
word * very_old_stack_bl = GC_old_stack_bl;
GC_old_normal_bl = GC_incomplete_normal_bl;
GC_old_stack_bl = GC_incomplete_stack_bl;
if (!GC_all_interior_pointers) {
GC_clear_bl(very_old_normal_bl);
}
GC_clear_bl(very_old_stack_bl);
GC_incomplete_normal_bl = very_old_normal_bl;
GC_incomplete_stack_bl = very_old_stack_bl;
GC_total_stack_black_listed = total_stack_black_listed();
GC_VERBOSE_LOG_PRINTF(
"%lu bytes in heap blacklisted for interior pointers\n",
(unsigned long)GC_total_stack_black_listed);
if (GC_total_stack_black_listed != 0) {
GC_black_list_spacing =
HBLKSIZE*(GC_heapsize/GC_total_stack_black_listed);
}
if (GC_black_list_spacing < 3 * HBLKSIZE) {
GC_black_list_spacing = 3 * HBLKSIZE;
}
if (GC_black_list_spacing > MAXHINCR * HBLKSIZE) {
GC_black_list_spacing = MAXHINCR * HBLKSIZE;
/* Makes it easier to allocate really huge blocks, which otherwise */
/* may have problems with nonuniform blacklist distributions. */
/* This way we should always succeed immediately after growing the */
/* heap. */
}
}
GC_INNER void GC_unpromote_black_lists(void)
{
if (!GC_all_interior_pointers) {
GC_copy_bl(GC_old_normal_bl, GC_incomplete_normal_bl);
}
GC_copy_bl(GC_old_stack_bl, GC_incomplete_stack_bl);
}
/* P is not a valid pointer reference, but it falls inside */
/* the plausible heap bounds. */
/* Add it to the normal incomplete black list if appropriate. */
#ifdef PRINT_BLACK_LIST
GC_INNER void GC_add_to_black_list_normal(word p, ptr_t source)
#else
GC_INNER void GC_add_to_black_list_normal(word p)
#endif
{
if (GC_modws_valid_offsets[p & (sizeof(word)-1)]) {
word index = PHT_HASH((word)p);
if (HDR(p) == 0 || get_pht_entry_from_index(GC_old_normal_bl, index)) {
# ifdef PRINT_BLACK_LIST
if (!get_pht_entry_from_index(GC_incomplete_normal_bl, index)) {
GC_print_blacklisted_ptr(p, source, "normal");
}
# endif
set_pht_entry_from_index(GC_incomplete_normal_bl, index);
} /* else this is probably just an interior pointer to an allocated */
/* object, and isn't worth black listing. */
}
}
/* And the same for false pointers from the stack. */
#ifdef PRINT_BLACK_LIST
GC_INNER void GC_add_to_black_list_stack(word p, ptr_t source)
#else
GC_INNER void GC_add_to_black_list_stack(word p)
#endif
{
word index = PHT_HASH((word)p);
if (HDR(p) == 0 || get_pht_entry_from_index(GC_old_stack_bl, index)) {
# ifdef PRINT_BLACK_LIST
if (!get_pht_entry_from_index(GC_incomplete_stack_bl, index)) {
GC_print_blacklisted_ptr(p, source, "stack");
}
# endif
set_pht_entry_from_index(GC_incomplete_stack_bl, index);
}
}
/*
* Is the block starting at h of size len bytes black listed? If so,
* return the address of the next plausible r such that (r, len) might not
* be black listed. (R may not actually be in the heap. We guarantee only
* that every smaller value of r after h is also black listed.)
* If (h,len) is not black listed, return 0.
* Knows about the structure of the black list hash tables.
*/
struct hblk * GC_is_black_listed(struct hblk *h, word len)
{
word index = PHT_HASH((word)h);
word i;
word nblocks;
if (!GC_all_interior_pointers
&& (get_pht_entry_from_index(GC_old_normal_bl, index)
|| get_pht_entry_from_index(GC_incomplete_normal_bl, index))) {
return (h+1);
}
nblocks = divHBLKSZ(len);
for (i = 0;;) {
if (GC_old_stack_bl[divWORDSZ(index)] == 0
&& GC_incomplete_stack_bl[divWORDSZ(index)] == 0) {
/* An easy case */
i += WORDSZ - modWORDSZ(index);
} else {
if (get_pht_entry_from_index(GC_old_stack_bl, index)
|| get_pht_entry_from_index(GC_incomplete_stack_bl, index)) {
return(h+i+1);
}
i++;
}
if (i >= nblocks) break;
index = PHT_HASH((word)(h+i));
}
return(0);
}
/* Return the number of blacklisted blocks in a given range. */
/* Used only for statistical purposes. */
/* Looks only at the GC_incomplete_stack_bl. */
STATIC word GC_number_stack_black_listed(struct hblk *start,
struct hblk *endp1)
{
register struct hblk * h;
word result = 0;
for (h = start; (word)h < (word)endp1; h++) {
word index = PHT_HASH((word)h);
if (get_pht_entry_from_index(GC_old_stack_bl, index)) result++;
}
return(result);
}
/* Return the total number of (stack) black-listed bytes. */
static word total_stack_black_listed(void)
{
register unsigned i;
word total = 0;
for (i = 0; i < GC_n_heap_sects; i++) {
struct hblk * start = (struct hblk *) GC_heap_sects[i].hs_start;
struct hblk * endp1 = start + GC_heap_sects[i].hs_bytes/HBLKSIZE;
total += GC_number_stack_black_listed(start, endp1);
}
return(total * HBLKSIZE);
}
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