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ecl/src/gc/mark.c
Juan Jose Garcia Ripoll 3687fa0812 Upgraded Boehm-Weiser garbage collector to version 7.1
2009-04-03 18:01:00 +02:00

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/*
* Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
* Copyright (c) 1991-1995 by Xerox Corporation. All rights reserved.
* Copyright (c) 2000 by Hewlett-Packard Company. 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 <stdio.h>
# include "private/gc_pmark.h"
#if defined(MSWIN32) && defined(__GNUC__)
# include <excpt.h>
#endif
/* We put this here to minimize the risk of inlining. */
/*VARARGS*/
#ifdef __WATCOMC__
void GC_noop(void *p, ...) {}
#else
void GC_noop() {}
#endif
/* Single argument version, robust against whole program analysis. */
void GC_noop1(word x)
{
static volatile word sink;
sink = x;
}
/* mark_proc GC_mark_procs[MAX_MARK_PROCS] = {0} -- declared in gc_priv.h */
unsigned GC_n_mark_procs = GC_RESERVED_MARK_PROCS;
/* Initialize GC_obj_kinds properly and standard free lists properly. */
/* This must be done statically since they may be accessed before */
/* GC_init is called. */
/* It's done here, since we need to deal with mark descriptors. */
struct obj_kind GC_obj_kinds[MAXOBJKINDS] = {
/* PTRFREE */ { &GC_aobjfreelist[0], 0 /* filled in dynamically */,
0 | GC_DS_LENGTH, FALSE, FALSE },
/* NORMAL */ { &GC_objfreelist[0], 0,
0 | GC_DS_LENGTH, /* Adjusted in GC_init_inner for EXTRA_BYTES */
TRUE /* add length to descr */, TRUE },
/* UNCOLLECTABLE */
{ &GC_uobjfreelist[0], 0,
0 | GC_DS_LENGTH, TRUE /* add length to descr */, TRUE },
# ifdef ATOMIC_UNCOLLECTABLE
/* AUNCOLLECTABLE */
{ &GC_auobjfreelist[0], 0,
0 | GC_DS_LENGTH, FALSE /* add length to descr */, FALSE },
# endif
# ifdef STUBBORN_ALLOC
/*STUBBORN*/ { &GC_sobjfreelist[0], 0,
0 | GC_DS_LENGTH, TRUE /* add length to descr */, TRUE },
# endif
};
# ifdef ATOMIC_UNCOLLECTABLE
# ifdef STUBBORN_ALLOC
unsigned GC_n_kinds = 5;
# else
unsigned GC_n_kinds = 4;
# endif
# else
# ifdef STUBBORN_ALLOC
unsigned GC_n_kinds = 4;
# else
unsigned GC_n_kinds = 3;
# endif
# endif
# ifndef INITIAL_MARK_STACK_SIZE
# define INITIAL_MARK_STACK_SIZE (1*HBLKSIZE)
/* INITIAL_MARK_STACK_SIZE * sizeof(mse) should be a */
/* multiple of HBLKSIZE. */
/* The incremental collector actually likes a larger */
/* size, since it want to push all marked dirty objs */
/* before marking anything new. Currently we let it */
/* grow dynamically. */
# endif
/*
* Limits of stack for GC_mark routine.
* All ranges between GC_mark_stack(incl.) and GC_mark_stack_top(incl.) still
* need to be marked from.
*/
word GC_n_rescuing_pages; /* Number of dirty pages we marked from */
/* excludes ptrfree pages, etc. */
mse * GC_mark_stack;
mse * GC_mark_stack_limit;
size_t GC_mark_stack_size = 0;
#ifdef PARALLEL_MARK
# include "atomic_ops.h"
mse * volatile GC_mark_stack_top;
/* Updated only with mark lock held, but read asynchronously. */
volatile AO_t GC_first_nonempty;
/* Lowest entry on mark stack */
/* that may be nonempty. */
/* Updated only by initiating */
/* thread. */
#else
mse * GC_mark_stack_top;
#endif
static struct hblk * scan_ptr;
mark_state_t GC_mark_state = MS_NONE;
GC_bool GC_mark_stack_too_small = FALSE;
GC_bool GC_objects_are_marked = FALSE; /* Are there collectable marked */
/* objects in the heap? */
/* Is a collection in progress? Note that this can return true in the */
/* nonincremental case, if a collection has been abandoned and the */
/* mark state is now MS_INVALID. */
GC_bool GC_collection_in_progress(void)
{
return(GC_mark_state != MS_NONE);
}
/* clear all mark bits in the header */
void GC_clear_hdr_marks(hdr *hhdr)
{
size_t last_bit = FINAL_MARK_BIT(hhdr -> hb_sz);
# ifdef USE_MARK_BYTES
BZERO(hhdr -> hb_marks, MARK_BITS_SZ);
hhdr -> hb_marks[last_bit] = 1;
# else
BZERO(hhdr -> hb_marks, MARK_BITS_SZ*sizeof(word));
set_mark_bit_from_hdr(hhdr, last_bit);
# endif
hhdr -> hb_n_marks = 0;
}
/* Set all mark bits in the header. Used for uncollectable blocks. */
void GC_set_hdr_marks(hdr *hhdr)
{
unsigned i;
size_t sz = hhdr -> hb_sz;
size_t n_marks = FINAL_MARK_BIT(sz);
# ifdef USE_MARK_BYTES
for (i = 0; i <= n_marks; i += MARK_BIT_OFFSET(sz)) {
hhdr -> hb_marks[i] = 1;
}
# else
for (i = 0; i < divWORDSZ(n_marks + WORDSZ); ++i) {
hhdr -> hb_marks[i] = ONES;
}
# endif
# ifdef MARK_BIT_PER_OBJ
hhdr -> hb_n_marks = n_marks - 1;
# else
hhdr -> hb_n_marks = HBLK_OBJS(sz);
# endif
}
/*
* Clear all mark bits associated with block h.
*/
/*ARGSUSED*/
static void clear_marks_for_block(struct hblk *h, word dummy)
{
register hdr * hhdr = HDR(h);
if (IS_UNCOLLECTABLE(hhdr -> hb_obj_kind)) return;
/* Mark bit for these is cleared only once the object is */
/* explicitly deallocated. This either frees the block, or */
/* the bit is cleared once the object is on the free list. */
GC_clear_hdr_marks(hhdr);
}
/* Slow but general routines for setting/clearing/asking about mark bits */
void GC_set_mark_bit(ptr_t p)
{
struct hblk *h = HBLKPTR(p);
hdr * hhdr = HDR(h);
word bit_no = MARK_BIT_NO(p - (ptr_t)h, hhdr -> hb_sz);
if (!mark_bit_from_hdr(hhdr, bit_no)) {
set_mark_bit_from_hdr(hhdr, bit_no);
++hhdr -> hb_n_marks;
}
}
void GC_clear_mark_bit(ptr_t p)
{
struct hblk *h = HBLKPTR(p);
hdr * hhdr = HDR(h);
word bit_no = MARK_BIT_NO(p - (ptr_t)h, hhdr -> hb_sz);
if (mark_bit_from_hdr(hhdr, bit_no)) {
size_t n_marks;
clear_mark_bit_from_hdr(hhdr, bit_no);
n_marks = hhdr -> hb_n_marks - 1;
# ifdef PARALLEL_MARK
if (n_marks != 0)
hhdr -> hb_n_marks = n_marks;
/* Don't decrement to zero. The counts are approximate due to */
/* concurrency issues, but we need to ensure that a count of */
/* zero implies an empty block. */
# else
hhdr -> hb_n_marks = n_marks;
# endif
}
}
GC_bool GC_is_marked(ptr_t p)
{
struct hblk *h = HBLKPTR(p);
hdr * hhdr = HDR(h);
word bit_no = MARK_BIT_NO(p - (ptr_t)h, hhdr -> hb_sz);
return((GC_bool)mark_bit_from_hdr(hhdr, bit_no));
}
/*
* Clear mark bits in all allocated heap blocks. This invalidates
* the marker invariant, and sets GC_mark_state to reflect this.
* (This implicitly starts marking to reestablish the invariant.)
*/
void GC_clear_marks(void)
{
GC_apply_to_all_blocks(clear_marks_for_block, (word)0);
GC_objects_are_marked = FALSE;
GC_mark_state = MS_INVALID;
scan_ptr = 0;
}
/* Initiate a garbage collection. Initiates a full collection if the */
/* mark state is invalid. */
/*ARGSUSED*/
void GC_initiate_gc(void)
{
if (GC_dirty_maintained) GC_read_dirty();
# ifdef STUBBORN_ALLOC
GC_read_changed();
# endif
# ifdef CHECKSUMS
{
extern void GC_check_dirty();
if (GC_dirty_maintained) GC_check_dirty();
}
# endif
GC_n_rescuing_pages = 0;
if (GC_mark_state == MS_NONE) {
GC_mark_state = MS_PUSH_RESCUERS;
} else if (GC_mark_state != MS_INVALID) {
ABORT("unexpected state");
} /* else this is really a full collection, and mark */
/* bits are invalid. */
scan_ptr = 0;
}
static void alloc_mark_stack(size_t);
# if defined(MSWIN32) || defined(USE_PROC_FOR_LIBRARIES) && defined(THREADS)
/* Under rare conditions, we may end up marking from nonexistent memory. */
/* Hence we need to be prepared to recover by running GC_mark_some */
/* with a suitable handler in place. */
# define WRAP_MARK_SOME
# endif
/* Perform a small amount of marking. */
/* We try to touch roughly a page of memory. */
/* Return TRUE if we just finished a mark phase. */
/* Cold_gc_frame is an address inside a GC frame that */
/* remains valid until all marking is complete. */
/* A zero value indicates that it's OK to miss some */
/* register values. */
/* We hold the allocation lock. In the case of */
/* incremental collection, the world may not be stopped.*/
#ifdef WRAP_MARK_SOME
/* For win32, this is called after we establish a structured */
/* exception handler, in case Windows unmaps one of our root */
/* segments. See below. In either case, we acquire the */
/* allocator lock long before we get here. */
GC_bool GC_mark_some_inner(ptr_t cold_gc_frame)
#else
GC_bool GC_mark_some(ptr_t cold_gc_frame)
#endif
{
switch(GC_mark_state) {
case MS_NONE:
return(FALSE);
case MS_PUSH_RESCUERS:
if (GC_mark_stack_top
>= GC_mark_stack_limit - INITIAL_MARK_STACK_SIZE/2) {
/* Go ahead and mark, even though that might cause us to */
/* see more marked dirty objects later on. Avoid this */
/* in the future. */
GC_mark_stack_too_small = TRUE;
MARK_FROM_MARK_STACK();
return(FALSE);
} else {
scan_ptr = GC_push_next_marked_dirty(scan_ptr);
if (scan_ptr == 0) {
if (GC_print_stats) {
GC_log_printf("Marked from %u dirty pages\n",
GC_n_rescuing_pages);
}
GC_push_roots(FALSE, cold_gc_frame);
GC_objects_are_marked = TRUE;
if (GC_mark_state != MS_INVALID) {
GC_mark_state = MS_ROOTS_PUSHED;
}
}
}
return(FALSE);
case MS_PUSH_UNCOLLECTABLE:
if (GC_mark_stack_top
>= GC_mark_stack + GC_mark_stack_size/4) {
# ifdef PARALLEL_MARK
/* Avoid this, since we don't parallelize the marker */
/* here. */
if (GC_parallel) GC_mark_stack_too_small = TRUE;
# endif
MARK_FROM_MARK_STACK();
return(FALSE);
} else {
scan_ptr = GC_push_next_marked_uncollectable(scan_ptr);
if (scan_ptr == 0) {
GC_push_roots(TRUE, cold_gc_frame);
GC_objects_are_marked = TRUE;
if (GC_mark_state != MS_INVALID) {
GC_mark_state = MS_ROOTS_PUSHED;
}
}
}
return(FALSE);
case MS_ROOTS_PUSHED:
# ifdef PARALLEL_MARK
/* In the incremental GC case, this currently doesn't */
/* quite do the right thing, since it runs to */
/* completion. On the other hand, starting a */
/* parallel marker is expensive, so perhaps it is */
/* the right thing? */
/* Eventually, incremental marking should run */
/* asynchronously in multiple threads, without grabbing */
/* the allocation lock. */
if (GC_parallel) {
GC_do_parallel_mark();
GC_ASSERT(GC_mark_stack_top < (mse *)GC_first_nonempty);
GC_mark_stack_top = GC_mark_stack - 1;
if (GC_mark_stack_too_small) {
alloc_mark_stack(2*GC_mark_stack_size);
}
if (GC_mark_state == MS_ROOTS_PUSHED) {
GC_mark_state = MS_NONE;
return(TRUE);
} else {
return(FALSE);
}
}
# endif
if (GC_mark_stack_top >= GC_mark_stack) {
MARK_FROM_MARK_STACK();
return(FALSE);
} else {
GC_mark_state = MS_NONE;
if (GC_mark_stack_too_small) {
alloc_mark_stack(2*GC_mark_stack_size);
}
return(TRUE);
}
case MS_INVALID:
case MS_PARTIALLY_INVALID:
if (!GC_objects_are_marked) {
GC_mark_state = MS_PUSH_UNCOLLECTABLE;
return(FALSE);
}
if (GC_mark_stack_top >= GC_mark_stack) {
MARK_FROM_MARK_STACK();
return(FALSE);
}
if (scan_ptr == 0 && GC_mark_state == MS_INVALID) {
/* About to start a heap scan for marked objects. */
/* Mark stack is empty. OK to reallocate. */
if (GC_mark_stack_too_small) {
alloc_mark_stack(2*GC_mark_stack_size);
}
GC_mark_state = MS_PARTIALLY_INVALID;
}
scan_ptr = GC_push_next_marked(scan_ptr);
if (scan_ptr == 0 && GC_mark_state == MS_PARTIALLY_INVALID) {
GC_push_roots(TRUE, cold_gc_frame);
GC_objects_are_marked = TRUE;
if (GC_mark_state != MS_INVALID) {
GC_mark_state = MS_ROOTS_PUSHED;
}
}
return(FALSE);
default:
ABORT("GC_mark_some: bad state");
return(FALSE);
}
}
#if defined(MSWIN32) && defined(__GNUC__)
typedef struct {
EXCEPTION_REGISTRATION ex_reg;
void *alt_path;
} ext_ex_regn;
static EXCEPTION_DISPOSITION mark_ex_handler(
struct _EXCEPTION_RECORD *ex_rec,
void *est_frame,
struct _CONTEXT *context,
void *disp_ctxt)
{
if (ex_rec->ExceptionCode == STATUS_ACCESS_VIOLATION) {
ext_ex_regn *xer = (ext_ex_regn *)est_frame;
/* Unwind from the inner function assuming the standard */
/* function prologue. */
/* Assumes code has not been compiled with */
/* -fomit-frame-pointer. */
context->Esp = context->Ebp;
context->Ebp = *((DWORD *)context->Esp);
context->Esp = context->Esp - 8;
/* Resume execution at the "real" handler within the */
/* wrapper function. */
context->Eip = (DWORD )(xer->alt_path);
return ExceptionContinueExecution;
} else {
return ExceptionContinueSearch;
}
}
# endif /* __GNUC__ && MSWIN32 */
#ifdef GC_WIN32_THREADS
extern GC_bool GC_started_thread_while_stopped(void);
/* In win32_threads.c. Did we invalidate mark phase with an */
/* unexpected thread start? */
#endif
# ifdef WRAP_MARK_SOME
GC_bool GC_mark_some(ptr_t cold_gc_frame)
{
GC_bool ret_val;
# ifdef MSWIN32
# ifndef __GNUC__
/* Windows 98 appears to asynchronously create and remove */
/* writable memory mappings, for reasons we haven't yet */
/* understood. Since we look for writable regions to */
/* determine the root set, we may try to mark from an */
/* address range that disappeared since we started the */
/* collection. Thus we have to recover from faults here. */
/* This code does not appear to be necessary for Windows */
/* 95/NT/2000. Note that this code should never generate */
/* an incremental GC write fault. */
/* It's conceivable that this is the same issue with */
/* terminating threads that we see with Linux and */
/* USE_PROC_FOR_LIBRARIES. */
__try {
ret_val = GC_mark_some_inner(cold_gc_frame);
} __except (GetExceptionCode() == EXCEPTION_ACCESS_VIOLATION ?
EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH) {
goto handle_ex;
}
# ifdef GC_WIN32_THREADS
/* With DllMain-based thread tracking, a thread may have */
/* started while we were marking. This is logically equivalent */
/* to the exception case; our results are invalid and we have */
/* to start over. This cannot be prevented since we can't */
/* block in DllMain. */
if (GC_started_thread_while_stopped()) goto handle_ex;
# endif
rm_handler:
return ret_val;
# else /* __GNUC__ */
/* Manually install an exception handler since GCC does */
/* not yet support Structured Exception Handling (SEH) on */
/* Win32. */
ext_ex_regn er;
er.alt_path = &&handle_ex;
er.ex_reg.handler = mark_ex_handler;
asm volatile ("movl %%fs:0, %0" : "=r" (er.ex_reg.prev));
asm volatile ("movl %0, %%fs:0" : : "r" (&er));
ret_val = GC_mark_some_inner(cold_gc_frame);
/* Prevent GCC from considering the following code unreachable */
/* and thus eliminating it. */
if (er.alt_path == 0)
goto handle_ex;
rm_handler:
/* Uninstall the exception handler */
asm volatile ("mov %0, %%fs:0" : : "r" (er.ex_reg.prev));
return ret_val;
# endif /* __GNUC__ */
# else /* !MSWIN32 */
/* Here we are handling the case in which /proc is used for root */
/* finding, and we have threads. We may find a stack for a */
/* thread that is in the process of exiting, and disappears */
/* while we are marking it. This seems extremely difficult to */
/* avoid otherwise. */
if (GC_incremental)
WARN("Incremental GC incompatible with /proc roots\n", 0);
/* I'm not sure if this could still work ... */
GC_setup_temporary_fault_handler();
if(SETJMP(GC_jmp_buf) != 0) goto handle_ex;
ret_val = GC_mark_some_inner(cold_gc_frame);
rm_handler:
GC_reset_fault_handler();
return ret_val;
# endif /* !MSWIN32 */
handle_ex:
/* Exception handler starts here for all cases. */
if (GC_print_stats) {
GC_log_printf("Caught ACCESS_VIOLATION in marker. "
"Memory mapping disappeared.\n");
}
/* We have bad roots on the stack. Discard mark stack. */
/* Rescan from marked objects. Redetermine roots. */
GC_invalidate_mark_state();
scan_ptr = 0;
ret_val = FALSE;
goto rm_handler; // Back to platform-specific code.
}
#endif /* WRAP_MARK_SOME */
GC_bool GC_mark_stack_empty(void)
{
return(GC_mark_stack_top < GC_mark_stack);
}
void GC_invalidate_mark_state(void)
{
GC_mark_state = MS_INVALID;
GC_mark_stack_top = GC_mark_stack-1;
}
mse * GC_signal_mark_stack_overflow(mse *msp)
{
GC_mark_state = MS_INVALID;
GC_mark_stack_too_small = TRUE;
if (GC_print_stats) {
GC_log_printf("Mark stack overflow; current size = %lu entries\n",
GC_mark_stack_size);
}
return(msp - GC_MARK_STACK_DISCARDS);
}
/*
* Mark objects pointed to by the regions described by
* mark stack entries between mark_stack and mark_stack_top,
* inclusive. Assumes the upper limit of a mark stack entry
* is never 0. A mark stack entry never has size 0.
* We try to traverse on the order of a hblk of memory before we return.
* Caller is responsible for calling this until the mark stack is empty.
* Note that this is the most performance critical routine in the
* collector. Hence it contains all sorts of ugly hacks to speed
* things up. In particular, we avoid procedure calls on the common
* path, we take advantage of peculiarities of the mark descriptor
* encoding, we optionally maintain a cache for the block address to
* header mapping, we prefetch when an object is "grayed", etc.
*/
mse * GC_mark_from(mse *mark_stack_top, mse *mark_stack, mse *mark_stack_limit)
{
signed_word credit = HBLKSIZE; /* Remaining credit for marking work */
ptr_t current_p; /* Pointer to current candidate ptr. */
word current; /* Candidate pointer. */
ptr_t limit; /* (Incl) limit of current candidate */
/* range */
word descr;
ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
ptr_t least_ha = GC_least_plausible_heap_addr;
DECLARE_HDR_CACHE;
# define SPLIT_RANGE_WORDS 128 /* Must be power of 2. */
GC_objects_are_marked = TRUE;
INIT_HDR_CACHE;
# ifdef OS2 /* Use untweaked version to circumvent compiler problem */
while (mark_stack_top >= mark_stack && credit >= 0) {
# else
while ((((ptr_t)mark_stack_top - (ptr_t)mark_stack) | credit)
>= 0) {
# endif
current_p = mark_stack_top -> mse_start;
descr = mark_stack_top -> mse_descr;
retry:
/* current_p and descr describe the current object. */
/* *mark_stack_top is vacant. */
/* The following is 0 only for small objects described by a simple */
/* length descriptor. For many applications this is the common */
/* case, so we try to detect it quickly. */
if (descr & ((~(WORDS_TO_BYTES(SPLIT_RANGE_WORDS) - 1)) | GC_DS_TAGS)) {
word tag = descr & GC_DS_TAGS;
switch(tag) {
case GC_DS_LENGTH:
/* Large length. */
/* Process part of the range to avoid pushing too much on the */
/* stack. */
GC_ASSERT(descr < (word)GC_greatest_plausible_heap_addr
- (word)GC_least_plausible_heap_addr);
# ifdef ENABLE_TRACE
if (GC_trace_addr >= current_p
&& GC_trace_addr < current_p + descr) {
GC_log_printf("GC:%d Large section; start %p len %lu\n",
GC_gc_no, current_p, (unsigned long) descr);
}
# endif /* ENABLE_TRACE */
# ifdef PARALLEL_MARK
# define SHARE_BYTES 2048
if (descr > SHARE_BYTES && GC_parallel
&& mark_stack_top < mark_stack_limit - 1) {
int new_size = (descr/2) & ~(sizeof(word)-1);
mark_stack_top -> mse_start = current_p;
mark_stack_top -> mse_descr = new_size + sizeof(word);
/* makes sure we handle */
/* misaligned pointers. */
mark_stack_top++;
# ifdef ENABLE_TRACE
if (GC_trace_addr >= current_p
&& GC_trace_addr < current_p + descr) {
GC_log_printf("GC:%d splitting (parallel) %p at %p\n",
GC_gc_no, current_p, current_p + new_size);
}
# endif /* ENABLE_TRACE */
current_p += new_size;
descr -= new_size;
goto retry;
}
# endif /* PARALLEL_MARK */
mark_stack_top -> mse_start =
limit = current_p + WORDS_TO_BYTES(SPLIT_RANGE_WORDS-1);
mark_stack_top -> mse_descr =
descr - WORDS_TO_BYTES(SPLIT_RANGE_WORDS-1);
# ifdef ENABLE_TRACE
if (GC_trace_addr >= current_p
&& GC_trace_addr < current_p + descr) {
GC_log_printf("GC:%d splitting %p at %p\n",
GC_gc_no, current_p, limit);
}
# endif /* ENABLE_TRACE */
/* Make sure that pointers overlapping the two ranges are */
/* considered. */
limit += sizeof(word) - ALIGNMENT;
break;
case GC_DS_BITMAP:
mark_stack_top--;
# ifdef ENABLE_TRACE
if (GC_trace_addr >= current_p
&& GC_trace_addr < current_p + WORDS_TO_BYTES(WORDSZ-2)) {
GC_log_printf("GC:%d Tracing from %p bitmap descr %lu\n",
GC_gc_no, current_p, (unsigned long) descr);
}
# endif /* ENABLE_TRACE */
descr &= ~GC_DS_TAGS;
credit -= WORDS_TO_BYTES(WORDSZ/2); /* guess */
while (descr != 0) {
if ((signed_word)descr < 0) {
current = *(word *)current_p;
FIXUP_POINTER(current);
if ((ptr_t)current >= least_ha && (ptr_t)current < greatest_ha) {
PREFETCH((ptr_t)current);
# ifdef ENABLE_TRACE
if (GC_trace_addr == current_p) {
GC_log_printf("GC:%d Considering(3) %p -> %p\n",
GC_gc_no, current_p, (ptr_t) current);
}
# endif /* ENABLE_TRACE */
PUSH_CONTENTS((ptr_t)current, mark_stack_top,
mark_stack_limit, current_p, exit1);
}
}
descr <<= 1;
current_p += sizeof(word);
}
continue;
case GC_DS_PROC:
mark_stack_top--;
# ifdef ENABLE_TRACE
if (GC_trace_addr >= current_p
&& GC_base(current_p) != 0
&& GC_base(current_p) == GC_base(GC_trace_addr)) {
GC_log_printf("GC:%d Tracing from %p proc descr %lu\n",
GC_gc_no, current_p, (unsigned long) descr);
}
# endif /* ENABLE_TRACE */
credit -= GC_PROC_BYTES;
mark_stack_top =
(*PROC(descr))
((word *)current_p, mark_stack_top,
mark_stack_limit, ENV(descr));
continue;
case GC_DS_PER_OBJECT:
if ((signed_word)descr >= 0) {
/* Descriptor is in the object. */
descr = *(word *)(current_p + descr - GC_DS_PER_OBJECT);
} else {
/* Descriptor is in type descriptor pointed to by first */
/* word in object. */
ptr_t type_descr = *(ptr_t *)current_p;
/* type_descr is either a valid pointer to the descriptor */
/* structure, or this object was on a free list. If it */
/* it was anything but the last object on the free list, */
/* we will misinterpret the next object on the free list as */
/* the type descriptor, and get a 0 GC descriptor, which */
/* is ideal. Unfortunately, we need to check for the last */
/* object case explicitly. */
if (0 == type_descr) {
/* Rarely executed. */
mark_stack_top--;
continue;
}
descr = *(word *)(type_descr
- (descr + (GC_INDIR_PER_OBJ_BIAS
- GC_DS_PER_OBJECT)));
}
if (0 == descr) {
/* Can happen either because we generated a 0 descriptor */
/* or we saw a pointer to a free object. */
mark_stack_top--;
continue;
}
goto retry;
}
} else /* Small object with length descriptor */ {
mark_stack_top--;
limit = current_p + (word)descr;
}
# ifdef ENABLE_TRACE
if (GC_trace_addr >= current_p
&& GC_trace_addr < limit) {
GC_log_printf("GC:%d Tracing from %p len %lu\n",
GC_gc_no, current_p, (unsigned long) descr);
}
# endif /* ENABLE_TRACE */
/* The simple case in which we're scanning a range. */
GC_ASSERT(!((word)current_p & (ALIGNMENT-1)));
credit -= limit - current_p;
limit -= sizeof(word);
{
# define PREF_DIST 4
# ifndef SMALL_CONFIG
word deferred;
/* Try to prefetch the next pointer to be examined asap. */
/* Empirically, this also seems to help slightly without */
/* prefetches, at least on linux/X86. Presumably this loop */
/* ends up with less register pressure, and gcc thus ends up */
/* generating slightly better code. Overall gcc code quality */
/* for this loop is still not great. */
for(;;) {
PREFETCH(limit - PREF_DIST*CACHE_LINE_SIZE);
GC_ASSERT(limit >= current_p);
deferred = *(word *)limit;
FIXUP_POINTER(deferred);
limit -= ALIGNMENT;
if ((ptr_t)deferred >= least_ha && (ptr_t)deferred < greatest_ha) {
PREFETCH((ptr_t)deferred);
break;
}
if (current_p > limit) goto next_object;
/* Unroll once, so we don't do too many of the prefetches */
/* based on limit. */
deferred = *(word *)limit;
FIXUP_POINTER(deferred);
limit -= ALIGNMENT;
if ((ptr_t)deferred >= least_ha && (ptr_t)deferred < greatest_ha) {
PREFETCH((ptr_t)deferred);
break;
}
if (current_p > limit) goto next_object;
}
# endif
while (current_p <= limit) {
/* Empirically, unrolling this loop doesn't help a lot. */
/* Since PUSH_CONTENTS expands to a lot of code, */
/* we don't. */
current = *(word *)current_p;
FIXUP_POINTER(current);
PREFETCH(current_p + PREF_DIST*CACHE_LINE_SIZE);
if ((ptr_t)current >= least_ha && (ptr_t)current < greatest_ha) {
/* Prefetch the contents of the object we just pushed. It's */
/* likely we will need them soon. */
PREFETCH((ptr_t)current);
# ifdef ENABLE_TRACE
if (GC_trace_addr == current_p) {
GC_log_printf("GC:%d Considering(1) %p -> %p\n",
GC_gc_no, current_p, (ptr_t) current);
}
# endif /* ENABLE_TRACE */
PUSH_CONTENTS((ptr_t)current, mark_stack_top,
mark_stack_limit, current_p, exit2);
}
current_p += ALIGNMENT;
}
# ifndef SMALL_CONFIG
/* We still need to mark the entry we previously prefetched. */
/* We already know that it passes the preliminary pointer */
/* validity test. */
# ifdef ENABLE_TRACE
if (GC_trace_addr == current_p) {
GC_log_printf("GC:%d Considering(2) %p -> %p\n",
GC_gc_no, current_p, (ptr_t) deferred);
}
# endif /* ENABLE_TRACE */
PUSH_CONTENTS((ptr_t)deferred, mark_stack_top,
mark_stack_limit, current_p, exit4);
next_object:;
# endif
}
}
return mark_stack_top;
}
#ifdef PARALLEL_MARK
/* We assume we have an ANSI C Compiler. */
GC_bool GC_help_wanted = FALSE;
unsigned GC_helper_count = 0;
unsigned GC_active_count = 0;
word GC_mark_no = 0;
#define LOCAL_MARK_STACK_SIZE HBLKSIZE
/* Under normal circumstances, this is big enough to guarantee */
/* We don't overflow half of it in a single call to */
/* GC_mark_from. */
/* Steal mark stack entries starting at mse low into mark stack local */
/* until we either steal mse high, or we have max entries. */
/* Return a pointer to the top of the local mark stack. */
/* *next is replaced by a pointer to the next unscanned mark stack */
/* entry. */
mse * GC_steal_mark_stack(mse * low, mse * high, mse * local,
unsigned max, mse **next)
{
mse *p;
mse *top = local - 1;
unsigned i = 0;
GC_ASSERT(high >= low-1 && high - low + 1 <= GC_mark_stack_size);
for (p = low; p <= high && i <= max; ++p) {
word descr = AO_load((volatile AO_t *) &(p -> mse_descr));
if (descr != 0) {
/* Must be ordered after read of descr: */
AO_store_release_write((volatile AO_t *) &(p -> mse_descr), 0);
/* More than one thread may get this entry, but that's only */
/* a minor performance problem. */
++top;
top -> mse_descr = descr;
top -> mse_start = p -> mse_start;
GC_ASSERT((top -> mse_descr & GC_DS_TAGS) != GC_DS_LENGTH ||
top -> mse_descr < (ptr_t)GC_greatest_plausible_heap_addr
- (ptr_t)GC_least_plausible_heap_addr);
/* If this is a big object, count it as */
/* size/256 + 1 objects. */
++i;
if ((descr & GC_DS_TAGS) == GC_DS_LENGTH) i += (descr >> 8);
}
}
*next = p;
return top;
}
/* Copy back a local mark stack. */
/* low and high are inclusive bounds. */
void GC_return_mark_stack(mse * low, mse * high)
{
mse * my_top;
mse * my_start;
size_t stack_size;
if (high < low) return;
stack_size = high - low + 1;
GC_acquire_mark_lock();
my_top = GC_mark_stack_top; /* Concurrent modification impossible. */
my_start = my_top + 1;
if (my_start - GC_mark_stack + stack_size > GC_mark_stack_size) {
if (GC_print_stats) {
GC_log_printf("No room to copy back mark stack.");
}
GC_mark_state = MS_INVALID;
GC_mark_stack_too_small = TRUE;
/* We drop the local mark stack. We'll fix things later. */
} else {
BCOPY(low, my_start, stack_size * sizeof(mse));
GC_ASSERT((mse *)AO_load((volatile AO_t *)(&GC_mark_stack_top))
== my_top);
AO_store_release_write((volatile AO_t *)(&GC_mark_stack_top),
(AO_t)(my_top + stack_size));
/* Ensures visibility of previously written stack contents. */
}
GC_release_mark_lock();
GC_notify_all_marker();
}
/* Mark from the local mark stack. */
/* On return, the local mark stack is empty. */
/* But this may be achieved by copying the */
/* local mark stack back into the global one. */
void GC_do_local_mark(mse *local_mark_stack, mse *local_top)
{
unsigned n;
# define N_LOCAL_ITERS 1
# ifdef GC_ASSERTIONS
/* Make sure we don't hold mark lock. */
GC_acquire_mark_lock();
GC_release_mark_lock();
# endif
for (;;) {
for (n = 0; n < N_LOCAL_ITERS; ++n) {
local_top = GC_mark_from(local_top, local_mark_stack,
local_mark_stack + LOCAL_MARK_STACK_SIZE);
if (local_top < local_mark_stack) return;
if (local_top - local_mark_stack >= LOCAL_MARK_STACK_SIZE/2) {
GC_return_mark_stack(local_mark_stack, local_top);
return;
}
}
if ((mse *)AO_load((volatile AO_t *)(&GC_mark_stack_top))
< (mse *)AO_load(&GC_first_nonempty)
&& GC_active_count < GC_helper_count
&& local_top > local_mark_stack + 1) {
/* Try to share the load, since the main stack is empty, */
/* and helper threads are waiting for a refill. */
/* The entries near the bottom of the stack are likely */
/* to require more work. Thus we return those, eventhough */
/* it's harder. */
mse * new_bottom = local_mark_stack
+ (local_top - local_mark_stack)/2;
GC_ASSERT(new_bottom > local_mark_stack
&& new_bottom < local_top);
GC_return_mark_stack(local_mark_stack, new_bottom - 1);
memmove(local_mark_stack, new_bottom,
(local_top - new_bottom + 1) * sizeof(mse));
local_top -= (new_bottom - local_mark_stack);
}
}
}
#define ENTRIES_TO_GET 5
long GC_markers = 2; /* Normally changed by thread-library- */
/* -specific code. */
/* Mark using the local mark stack until the global mark stack is empty */
/* and there are no active workers. Update GC_first_nonempty to reflect */
/* progress. */
/* Caller does not hold mark lock. */
/* Caller has already incremented GC_helper_count. We decrement it, */
/* and maintain GC_active_count. */
void GC_mark_local(mse *local_mark_stack, int id)
{
mse * my_first_nonempty;
GC_acquire_mark_lock();
GC_active_count++;
my_first_nonempty = (mse *)AO_load(&GC_first_nonempty);
GC_ASSERT((mse *)AO_load(&GC_first_nonempty) >= GC_mark_stack &&
(mse *)AO_load(&GC_first_nonempty) <=
(mse *)AO_load((volatile AO_t *)(&GC_mark_stack_top)) + 1);
if (GC_print_stats == VERBOSE)
GC_log_printf("Starting mark helper %lu\n", (unsigned long)id);
GC_release_mark_lock();
for (;;) {
size_t n_on_stack;
size_t n_to_get;
mse * my_top;
mse * local_top;
mse * global_first_nonempty = (mse *)AO_load(&GC_first_nonempty);
GC_ASSERT(my_first_nonempty >= GC_mark_stack &&
my_first_nonempty <=
(mse *)AO_load((volatile AO_t *)(&GC_mark_stack_top)) + 1);
GC_ASSERT(global_first_nonempty >= GC_mark_stack &&
global_first_nonempty <=
(mse *)AO_load((volatile AO_t *)(&GC_mark_stack_top)) + 1);
if (my_first_nonempty < global_first_nonempty) {
my_first_nonempty = global_first_nonempty;
} else if (global_first_nonempty < my_first_nonempty) {
AO_compare_and_swap(&GC_first_nonempty,
(AO_t) global_first_nonempty,
(AO_t) my_first_nonempty);
/* If this fails, we just go ahead, without updating */
/* GC_first_nonempty. */
}
/* Perhaps we should also update GC_first_nonempty, if it */
/* is less. But that would require using atomic updates. */
my_top = (mse *)AO_load_acquire((volatile AO_t *)(&GC_mark_stack_top));
n_on_stack = my_top - my_first_nonempty + 1;
if (0 == n_on_stack) {
GC_acquire_mark_lock();
my_top = GC_mark_stack_top;
/* Asynchronous modification impossible here, */
/* since we hold mark lock. */
n_on_stack = my_top - my_first_nonempty + 1;
if (0 == n_on_stack) {
GC_active_count--;
GC_ASSERT(GC_active_count <= GC_helper_count);
/* Other markers may redeposit objects */
/* on the stack. */
if (0 == GC_active_count) GC_notify_all_marker();
while (GC_active_count > 0
&& (mse *)AO_load(&GC_first_nonempty)
> GC_mark_stack_top) {
/* We will be notified if either GC_active_count */
/* reaches zero, or if more objects are pushed on */
/* the global mark stack. */
GC_wait_marker();
}
if (GC_active_count == 0 &&
(mse *)AO_load(&GC_first_nonempty) > GC_mark_stack_top) {
GC_bool need_to_notify = FALSE;
/* The above conditions can't be falsified while we */
/* hold the mark lock, since neither */
/* GC_active_count nor GC_mark_stack_top can */
/* change. GC_first_nonempty can only be */
/* incremented asynchronously. Thus we know that */
/* both conditions actually held simultaneously. */
GC_helper_count--;
if (0 == GC_helper_count) need_to_notify = TRUE;
if (GC_print_stats == VERBOSE)
GC_log_printf(
"Finished mark helper %lu\n", (unsigned long)id);
GC_release_mark_lock();
if (need_to_notify) GC_notify_all_marker();
return;
}
/* else there's something on the stack again, or */
/* another helper may push something. */
GC_active_count++;
GC_ASSERT(GC_active_count > 0);
GC_release_mark_lock();
continue;
} else {
GC_release_mark_lock();
}
}
n_to_get = ENTRIES_TO_GET;
if (n_on_stack < 2 * ENTRIES_TO_GET) n_to_get = 1;
local_top = GC_steal_mark_stack(my_first_nonempty, my_top,
local_mark_stack, n_to_get,
&my_first_nonempty);
GC_ASSERT(my_first_nonempty >= GC_mark_stack &&
my_first_nonempty <=
(mse *)AO_load((volatile AO_t *)(&GC_mark_stack_top)) + 1);
GC_do_local_mark(local_mark_stack, local_top);
}
}
/* Perform Parallel mark. */
/* We hold the GC lock, not the mark lock. */
/* Currently runs until the mark stack is */
/* empty. */
void GC_do_parallel_mark()
{
mse local_mark_stack[LOCAL_MARK_STACK_SIZE];
GC_acquire_mark_lock();
GC_ASSERT(I_HOLD_LOCK());
/* This could be a GC_ASSERT, but it seems safer to keep it on */
/* all the time, especially since it's cheap. */
if (GC_help_wanted || GC_active_count != 0 || GC_helper_count != 0)
ABORT("Tried to start parallel mark in bad state");
if (GC_print_stats == VERBOSE)
GC_log_printf("Starting marking for mark phase number %lu\n",
(unsigned long)GC_mark_no);
GC_first_nonempty = (AO_t)GC_mark_stack;
GC_active_count = 0;
GC_helper_count = 1;
GC_help_wanted = TRUE;
GC_release_mark_lock();
GC_notify_all_marker();
/* Wake up potential helpers. */
GC_mark_local(local_mark_stack, 0);
GC_acquire_mark_lock();
GC_help_wanted = FALSE;
/* Done; clean up. */
while (GC_helper_count > 0) GC_wait_marker();
/* GC_helper_count cannot be incremented while GC_help_wanted == FALSE */
if (GC_print_stats == VERBOSE)
GC_log_printf(
"Finished marking for mark phase number %lu\n",
(unsigned long)GC_mark_no);
GC_mark_no++;
GC_release_mark_lock();
GC_notify_all_marker();
}
/* Try to help out the marker, if it's running. */
/* We do not hold the GC lock, but the requestor does. */
void GC_help_marker(word my_mark_no)
{
mse local_mark_stack[LOCAL_MARK_STACK_SIZE];
unsigned my_id;
if (!GC_parallel) return;
GC_acquire_mark_lock();
while (GC_mark_no < my_mark_no
|| (!GC_help_wanted && GC_mark_no == my_mark_no)) {
GC_wait_marker();
}
my_id = GC_helper_count;
if (GC_mark_no != my_mark_no || my_id >= GC_markers) {
/* Second test is useful only if original threads can also */
/* act as helpers. Under Linux they can't. */
GC_release_mark_lock();
return;
}
GC_helper_count = my_id + 1;
GC_release_mark_lock();
GC_mark_local(local_mark_stack, my_id);
/* GC_mark_local decrements GC_helper_count. */
}
#endif /* PARALLEL_MARK */
/* Allocate or reallocate space for mark stack of size n entries. */
/* May silently fail. */
static void alloc_mark_stack(size_t n)
{
mse * new_stack = (mse *)GC_scratch_alloc(n * sizeof(struct GC_ms_entry));
# ifdef GWW_VDB
/* Don't recycle a stack segment obtained with the wrong flags. */
/* Win32 GetWriteWatch requires the right kind of memory. */
static GC_bool GC_incremental_at_stack_alloc = 0;
GC_bool recycle_old = (!GC_incremental || GC_incremental_at_stack_alloc);
GC_incremental_at_stack_alloc = GC_incremental;
# else
# define recycle_old 1
# endif
GC_mark_stack_too_small = FALSE;
if (GC_mark_stack_size != 0) {
if (new_stack != 0) {
if (recycle_old) {
/* Recycle old space */
size_t page_offset = (word)GC_mark_stack & (GC_page_size - 1);
size_t size = GC_mark_stack_size * sizeof(struct GC_ms_entry);
size_t displ = 0;
if (0 != page_offset) displ = GC_page_size - page_offset;
size = (size - displ) & ~(GC_page_size - 1);
if (size > 0) {
GC_add_to_heap((struct hblk *)
((word)GC_mark_stack + displ), (word)size);
}
}
GC_mark_stack = new_stack;
GC_mark_stack_size = n;
GC_mark_stack_limit = new_stack + n;
if (GC_print_stats) {
GC_log_printf("Grew mark stack to %lu frames\n",
(unsigned long) GC_mark_stack_size);
}
} else {
if (GC_print_stats) {
GC_log_printf("Failed to grow mark stack to %lu frames\n",
(unsigned long) n);
}
}
} else {
if (new_stack == 0) {
GC_err_printf("No space for mark stack\n");
EXIT();
}
GC_mark_stack = new_stack;
GC_mark_stack_size = n;
GC_mark_stack_limit = new_stack + n;
}
GC_mark_stack_top = GC_mark_stack-1;
}
void GC_mark_init()
{
alloc_mark_stack(INITIAL_MARK_STACK_SIZE);
}
/*
* Push all locations between b and t onto the mark stack.
* b is the first location to be checked. t is one past the last
* location to be checked.
* Should only be used if there is no possibility of mark stack
* overflow.
*/
void GC_push_all(ptr_t bottom, ptr_t top)
{
register word length;
bottom = (ptr_t)(((word) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1));
top = (ptr_t)(((word) top) & ~(ALIGNMENT-1));
if (top == 0 || bottom == top) return;
GC_mark_stack_top++;
if (GC_mark_stack_top >= GC_mark_stack_limit) {
ABORT("unexpected mark stack overflow");
}
length = top - bottom;
# if GC_DS_TAGS > ALIGNMENT - 1
length += GC_DS_TAGS;
length &= ~GC_DS_TAGS;
# endif
GC_mark_stack_top -> mse_start = bottom;
GC_mark_stack_top -> mse_descr = length;
}
/*
* Analogous to the above, but push only those pages h with dirty_fn(h) != 0.
* We use push_fn to actually push the block.
* Used both to selectively push dirty pages, or to push a block
* in piecemeal fashion, to allow for more marking concurrency.
* Will not overflow mark stack if push_fn pushes a small fixed number
* of entries. (This is invoked only if push_fn pushes a single entry,
* or if it marks each object before pushing it, thus ensuring progress
* in the event of a stack overflow.)
*/
void GC_push_selected(ptr_t bottom, ptr_t top,
int (*dirty_fn) (struct hblk *),
void (*push_fn) (ptr_t, ptr_t))
{
struct hblk * h;
bottom = (ptr_t)(((word) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1));
top = (ptr_t)(((word) top) & ~(ALIGNMENT-1));
if (top == 0 || bottom == top) return;
h = HBLKPTR(bottom + HBLKSIZE);
if (top <= (ptr_t) h) {
if ((*dirty_fn)(h-1)) {
(*push_fn)(bottom, top);
}
return;
}
if ((*dirty_fn)(h-1)) {
(*push_fn)(bottom, (ptr_t)h);
}
while ((ptr_t)(h+1) <= top) {
if ((*dirty_fn)(h)) {
if ((word)(GC_mark_stack_top - GC_mark_stack)
> 3 * GC_mark_stack_size / 4) {
/* Danger of mark stack overflow */
(*push_fn)((ptr_t)h, top);
return;
} else {
(*push_fn)((ptr_t)h, (ptr_t)(h+1));
}
}
h++;
}
if ((ptr_t)h != top) {
if ((*dirty_fn)(h)) {
(*push_fn)((ptr_t)h, top);
}
}
if (GC_mark_stack_top >= GC_mark_stack_limit) {
ABORT("unexpected mark stack overflow");
}
}
# ifndef SMALL_CONFIG
#ifdef PARALLEL_MARK
/* Break up root sections into page size chunks to better spread */
/* out work. */
GC_bool GC_true_func(struct hblk *h) { return TRUE; }
# define GC_PUSH_ALL(b,t) GC_push_selected(b,t,GC_true_func,GC_push_all);
#else
# define GC_PUSH_ALL(b,t) GC_push_all(b,t);
#endif
void GC_push_conditional(ptr_t bottom, ptr_t top, GC_bool all)
{
if (all) {
if (GC_dirty_maintained) {
# ifdef PROC_VDB
/* Pages that were never dirtied cannot contain pointers */
GC_push_selected(bottom, top, GC_page_was_ever_dirty, GC_push_all);
# else
GC_push_all(bottom, top);
# endif
} else {
GC_push_all(bottom, top);
}
} else {
GC_push_selected(bottom, top, GC_page_was_dirty, GC_push_all);
}
}
#endif
# if defined(MSWIN32) || defined(MSWINCE)
void __cdecl GC_push_one(word p)
# else
void GC_push_one(word p)
# endif
{
GC_PUSH_ONE_STACK((ptr_t)p, MARKED_FROM_REGISTER);
}
struct GC_ms_entry *GC_mark_and_push(void *obj,
mse *mark_stack_ptr,
mse *mark_stack_limit,
void **src)
{
hdr * hhdr;
PREFETCH(obj);
GET_HDR(obj, hhdr);
if (EXPECT(IS_FORWARDING_ADDR_OR_NIL(hhdr),FALSE)) {
if (GC_all_interior_pointers) {
hhdr = GC_find_header(GC_base(obj));
if (hhdr == 0) {
GC_ADD_TO_BLACK_LIST_NORMAL(obj, src);
return mark_stack_ptr;
}
} else {
GC_ADD_TO_BLACK_LIST_NORMAL(obj, src);
return mark_stack_ptr;
}
}
if (EXPECT(HBLK_IS_FREE(hhdr),0)) {
GC_ADD_TO_BLACK_LIST_NORMAL(obj, src);
return mark_stack_ptr;
}
PUSH_CONTENTS_HDR(obj, mark_stack_ptr /* modified */, mark_stack_limit,
src, was_marked, hhdr, TRUE);
was_marked:
return mark_stack_ptr;
}
/* Mark and push (i.e. gray) a single object p onto the main */
/* mark stack. Consider p to be valid if it is an interior */
/* pointer. */
/* The object p has passed a preliminary pointer validity */
/* test, but we do not definitely know whether it is valid. */
/* Mark bits are NOT atomically updated. Thus this must be the */
/* only thread setting them. */
# if defined(PRINT_BLACK_LIST) || defined(KEEP_BACK_PTRS)
void GC_mark_and_push_stack(ptr_t p, ptr_t source)
# else
void GC_mark_and_push_stack(ptr_t p)
# define source 0
# endif
{
hdr * hhdr;
ptr_t r = p;
PREFETCH(p);
GET_HDR(p, hhdr);
if (EXPECT(IS_FORWARDING_ADDR_OR_NIL(hhdr),FALSE)) {
if (hhdr != 0) {
r = GC_base(p);
hhdr = HDR(r);
}
if (hhdr == 0) {
GC_ADD_TO_BLACK_LIST_STACK(p, source);
return;
}
}
if (EXPECT(HBLK_IS_FREE(hhdr),0)) {
GC_ADD_TO_BLACK_LIST_NORMAL(p, src);
return;
}
# if defined(MANUAL_VDB) && defined(THREADS)
/* Pointer is on the stack. We may have dirtied the object */
/* it points to, but not yet have called GC_dirty(); */
GC_dirty(p); /* Implicitly affects entire object. */
# endif
PUSH_CONTENTS_HDR(r, GC_mark_stack_top, GC_mark_stack_limit,
source, mark_and_push_exit, hhdr, FALSE);
mark_and_push_exit: ;
/* We silently ignore pointers to near the end of a block, */
/* which is very mildly suboptimal. */
/* FIXME: We should probably add a header word to address */
/* this. */
}
# ifdef TRACE_BUF
# define TRACE_ENTRIES 1000
struct trace_entry {
char * kind;
word gc_no;
word bytes_allocd;
word arg1;
word arg2;
} GC_trace_buf[TRACE_ENTRIES];
int GC_trace_buf_ptr = 0;
void GC_add_trace_entry(char *kind, word arg1, word arg2)
{
GC_trace_buf[GC_trace_buf_ptr].kind = kind;
GC_trace_buf[GC_trace_buf_ptr].gc_no = GC_gc_no;
GC_trace_buf[GC_trace_buf_ptr].bytes_allocd = GC_bytes_allocd;
GC_trace_buf[GC_trace_buf_ptr].arg1 = arg1 ^ 0x80000000;
GC_trace_buf[GC_trace_buf_ptr].arg2 = arg2 ^ 0x80000000;
GC_trace_buf_ptr++;
if (GC_trace_buf_ptr >= TRACE_ENTRIES) GC_trace_buf_ptr = 0;
}
void GC_print_trace(word gc_no, GC_bool lock)
{
int i;
struct trace_entry *p;
if (lock) LOCK();
for (i = GC_trace_buf_ptr-1; i != GC_trace_buf_ptr; i--) {
if (i < 0) i = TRACE_ENTRIES-1;
p = GC_trace_buf + i;
if (p -> gc_no < gc_no || p -> kind == 0) return;
printf("Trace:%s (gc:%d,bytes:%d) 0x%X, 0x%X\n",
p -> kind, p -> gc_no, p -> bytes_allocd,
(p -> arg1) ^ 0x80000000, (p -> arg2) ^ 0x80000000);
}
printf("Trace incomplete\n");
if (lock) UNLOCK();
}
# endif /* TRACE_BUF */
/*
* A version of GC_push_all that treats all interior pointers as valid
* and scans the entire region immediately, in case the contents
* change.
*/
void GC_push_all_eager(ptr_t bottom, ptr_t top)
{
word * b = (word *)(((word) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1));
word * t = (word *)(((word) top) & ~(ALIGNMENT-1));
register word *p;
register ptr_t q;
register word *lim;
register ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
register ptr_t least_ha = GC_least_plausible_heap_addr;
# define GC_greatest_plausible_heap_addr greatest_ha
# define GC_least_plausible_heap_addr least_ha
if (top == 0) return;
/* check all pointers in range and push if they appear */
/* to be valid. */
lim = t - 1 /* longword */;
for (p = b; p <= lim; p = (word *)(((ptr_t)p) + ALIGNMENT)) {
q = (ptr_t)(*p);
GC_PUSH_ONE_STACK((ptr_t)q, p);
}
# undef GC_greatest_plausible_heap_addr
# undef GC_least_plausible_heap_addr
}
#ifndef THREADS
/*
* A version of GC_push_all that treats all interior pointers as valid
* and scans part of the area immediately, to make sure that saved
* register values are not lost.
* Cold_gc_frame delimits the stack section that must be scanned
* eagerly. A zero value indicates that no eager scanning is needed.
* We don't need to worry about the MANUAL_VDB case here, since this
* is only called in the single-threaded case. We assume that we
* cannot collect between an assignment and the corresponding
* GC_dirty() call.
*/
void GC_push_all_stack_partially_eager(ptr_t bottom, ptr_t top,
ptr_t cold_gc_frame)
{
if (!NEED_FIXUP_POINTER && GC_all_interior_pointers) {
/* Push the hot end of the stack eagerly, so that register values */
/* saved inside GC frames are marked before they disappear. */
/* The rest of the marking can be deferred until later. */
if (0 == cold_gc_frame) {
GC_push_all_stack(bottom, top);
return;
}
GC_ASSERT(bottom <= cold_gc_frame && cold_gc_frame <= top);
# ifdef STACK_GROWS_DOWN
GC_push_all(cold_gc_frame - sizeof(ptr_t), top);
GC_push_all_eager(bottom, cold_gc_frame);
# else /* STACK_GROWS_UP */
GC_push_all(bottom, cold_gc_frame + sizeof(ptr_t));
GC_push_all_eager(cold_gc_frame, top);
# endif /* STACK_GROWS_UP */
} else {
GC_push_all_eager(bottom, top);
}
# ifdef TRACE_BUF
GC_add_trace_entry("GC_push_all_stack", bottom, top);
# endif
}
#endif /* !THREADS */
void GC_push_all_stack(ptr_t bottom, ptr_t top)
{
# if defined(THREADS) && defined(MPROTECT_VDB)
GC_push_all_eager(bottom, top);
# else
if (!NEED_FIXUP_POINTER && GC_all_interior_pointers) {
GC_push_all(bottom, top);
} else {
GC_push_all_eager(bottom, top);
}
# endif
}
#if !defined(SMALL_CONFIG) && !defined(USE_MARK_BYTES) && \
defined(MARK_BIT_PER_GRANULE)
# if GC_GRANULE_WORDS == 1
# define USE_PUSH_MARKED_ACCELERATORS
# define PUSH_GRANULE(q) \
{ ptr_t qcontents = (ptr_t)((q)[0]); \
GC_PUSH_ONE_HEAP(qcontents, (q)); }
# elif GC_GRANULE_WORDS == 2
# define USE_PUSH_MARKED_ACCELERATORS
# define PUSH_GRANULE(q) \
{ ptr_t qcontents = (ptr_t)((q)[0]); \
GC_PUSH_ONE_HEAP(qcontents, (q)); \
qcontents = (ptr_t)((q)[1]); \
GC_PUSH_ONE_HEAP(qcontents, (q)+1); }
# elif GC_GRANULE_WORDS == 4
# define USE_PUSH_MARKED_ACCELERATORS
# define PUSH_GRANULE(q) \
{ ptr_t qcontents = (ptr_t)((q)[0]); \
GC_PUSH_ONE_HEAP(qcontents, (q)); \
qcontents = (ptr_t)((q)[1]); \
GC_PUSH_ONE_HEAP(qcontents, (q)+1); \
qcontents = (ptr_t)((q)[2]); \
GC_PUSH_ONE_HEAP(qcontents, (q)+2); \
qcontents = (ptr_t)((q)[3]); \
GC_PUSH_ONE_HEAP(qcontents, (q)+3); }
# endif
#endif
#ifdef USE_PUSH_MARKED_ACCELERATORS
/* Push all objects reachable from marked objects in the given block */
/* containing objects of size 1 granule. */
void GC_push_marked1(struct hblk *h, hdr *hhdr)
{
word * mark_word_addr = &(hhdr->hb_marks[0]);
word *p;
word *plim;
word *q;
word mark_word;
/* Allow registers to be used for some frequently acccessed */
/* global variables. Otherwise aliasing issues are likely */
/* to prevent that. */
ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
ptr_t least_ha = GC_least_plausible_heap_addr;
mse * mark_stack_top = GC_mark_stack_top;
mse * mark_stack_limit = GC_mark_stack_limit;
# define GC_mark_stack_top mark_stack_top
# define GC_mark_stack_limit mark_stack_limit
# define GC_greatest_plausible_heap_addr greatest_ha
# define GC_least_plausible_heap_addr least_ha
p = (word *)(h->hb_body);
plim = (word *)(((word)h) + HBLKSIZE);
/* go through all words in block */
while( p < plim ) {
mark_word = *mark_word_addr++;
q = p;
while(mark_word != 0) {
if (mark_word & 1) {
PUSH_GRANULE(q);
}
q += GC_GRANULE_WORDS;
mark_word >>= 1;
}
p += WORDSZ*GC_GRANULE_WORDS;
}
# undef GC_greatest_plausible_heap_addr
# undef GC_least_plausible_heap_addr
# undef GC_mark_stack_top
# undef GC_mark_stack_limit
GC_mark_stack_top = mark_stack_top;
}
#ifndef UNALIGNED
/* Push all objects reachable from marked objects in the given block */
/* of size 2 (granules) objects. */
void GC_push_marked2(struct hblk *h, hdr *hhdr)
{
word * mark_word_addr = &(hhdr->hb_marks[0]);
word *p;
word *plim;
word *q;
word mark_word;
ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
ptr_t least_ha = GC_least_plausible_heap_addr;
mse * mark_stack_top = GC_mark_stack_top;
mse * mark_stack_limit = GC_mark_stack_limit;
# define GC_mark_stack_top mark_stack_top
# define GC_mark_stack_limit mark_stack_limit
# define GC_greatest_plausible_heap_addr greatest_ha
# define GC_least_plausible_heap_addr least_ha
p = (word *)(h->hb_body);
plim = (word *)(((word)h) + HBLKSIZE);
/* go through all words in block */
while( p < plim ) {
mark_word = *mark_word_addr++;
q = p;
while(mark_word != 0) {
if (mark_word & 1) {
PUSH_GRANULE(q);
PUSH_GRANULE(q + GC_GRANULE_WORDS);
}
q += 2 * GC_GRANULE_WORDS;
mark_word >>= 2;
}
p += WORDSZ*GC_GRANULE_WORDS;
}
# undef GC_greatest_plausible_heap_addr
# undef GC_least_plausible_heap_addr
# undef GC_mark_stack_top
# undef GC_mark_stack_limit
GC_mark_stack_top = mark_stack_top;
}
# if GC_GRANULE_WORDS < 4
/* Push all objects reachable from marked objects in the given block */
/* of size 4 (granules) objects. */
/* There is a risk of mark stack overflow here. But we handle that. */
/* And only unmarked objects get pushed, so it's not very likely. */
void GC_push_marked4(struct hblk *h, hdr *hhdr)
{
word * mark_word_addr = &(hhdr->hb_marks[0]);
word *p;
word *plim;
word *q;
word mark_word;
ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
ptr_t least_ha = GC_least_plausible_heap_addr;
mse * mark_stack_top = GC_mark_stack_top;
mse * mark_stack_limit = GC_mark_stack_limit;
# define GC_mark_stack_top mark_stack_top
# define GC_mark_stack_limit mark_stack_limit
# define GC_greatest_plausible_heap_addr greatest_ha
# define GC_least_plausible_heap_addr least_ha
p = (word *)(h->hb_body);
plim = (word *)(((word)h) + HBLKSIZE);
/* go through all words in block */
while( p < plim ) {
mark_word = *mark_word_addr++;
q = p;
while(mark_word != 0) {
if (mark_word & 1) {
PUSH_GRANULE(q);
PUSH_GRANULE(q + GC_GRANULE_WORDS);
PUSH_GRANULE(q + 2*GC_GRANULE_WORDS);
PUSH_GRANULE(q + 3*GC_GRANULE_WORDS);
}
q += 4 * GC_GRANULE_WORDS;
mark_word >>= 4;
}
p += WORDSZ*GC_GRANULE_WORDS;
}
# undef GC_greatest_plausible_heap_addr
# undef GC_least_plausible_heap_addr
# undef GC_mark_stack_top
# undef GC_mark_stack_limit
GC_mark_stack_top = mark_stack_top;
}
#endif /* GC_GRANULE_WORDS < 4 */
#endif /* UNALIGNED */
#endif /* USE_PUSH_MARKED_ACCELERATORS */
/* Push all objects reachable from marked objects in the given block */
void GC_push_marked(struct hblk *h, hdr *hhdr)
{
size_t sz = hhdr -> hb_sz;
word descr = hhdr -> hb_descr;
ptr_t p;
word bit_no;
ptr_t lim;
mse * GC_mark_stack_top_reg;
mse * mark_stack_limit = GC_mark_stack_limit;
/* Some quick shortcuts: */
if ((0 | GC_DS_LENGTH) == descr) return;
if (GC_block_empty(hhdr)/* nothing marked */) return;
GC_n_rescuing_pages++;
GC_objects_are_marked = TRUE;
if (sz > MAXOBJBYTES) {
lim = h -> hb_body;
} else {
lim = (h + 1)->hb_body - sz;
}
switch(BYTES_TO_GRANULES(sz)) {
# if defined(USE_PUSH_MARKED_ACCELERATORS)
case 1:
GC_push_marked1(h, hhdr);
break;
# if !defined(UNALIGNED)
case 2:
GC_push_marked2(h, hhdr);
break;
# if GC_GRANULE_WORDS < 4
case 4:
GC_push_marked4(h, hhdr);
break;
# endif
# endif
# endif
default:
GC_mark_stack_top_reg = GC_mark_stack_top;
for (p = h -> hb_body, bit_no = 0; p <= lim;
p += sz, bit_no += MARK_BIT_OFFSET(sz)) {
if (mark_bit_from_hdr(hhdr, bit_no)) {
/* Mark from fields inside the object */
PUSH_OBJ(p, hhdr, GC_mark_stack_top_reg, mark_stack_limit);
}
}
GC_mark_stack_top = GC_mark_stack_top_reg;
}
}
#ifndef SMALL_CONFIG
/* Test whether any page in the given block is dirty */
GC_bool GC_block_was_dirty(struct hblk *h, hdr *hhdr)
{
size_t sz = hhdr -> hb_sz;
if (sz <= MAXOBJBYTES) {
return(GC_page_was_dirty(h));
} else {
ptr_t p = (ptr_t)h;
while (p < (ptr_t)h + sz) {
if (GC_page_was_dirty((struct hblk *)p)) return(TRUE);
p += HBLKSIZE;
}
return(FALSE);
}
}
#endif /* SMALL_CONFIG */
/* Similar to GC_push_marked, but skip over unallocated blocks */
/* and return address of next plausible block. */
struct hblk * GC_push_next_marked(struct hblk *h)
{
hdr * hhdr = HDR(h);
if (EXPECT(IS_FORWARDING_ADDR_OR_NIL(hhdr), FALSE)) {
h = GC_next_used_block(h);
if (h == 0) return(0);
hhdr = GC_find_header((ptr_t)h);
}
GC_push_marked(h, hhdr);
return(h + OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz));
}
#ifndef SMALL_CONFIG
/* Identical to above, but mark only from dirty pages */
struct hblk * GC_push_next_marked_dirty(struct hblk *h)
{
hdr * hhdr = HDR(h);
if (!GC_dirty_maintained) { ABORT("dirty bits not set up"); }
for (;;) {
if (EXPECT(IS_FORWARDING_ADDR_OR_NIL(hhdr), FALSE)) {
h = GC_next_used_block(h);
if (h == 0) return(0);
hhdr = GC_find_header((ptr_t)h);
}
# ifdef STUBBORN_ALLOC
if (hhdr -> hb_obj_kind == STUBBORN) {
if (GC_page_was_changed(h) && GC_block_was_dirty(h, hhdr)) {
break;
}
} else {
if (GC_block_was_dirty(h, hhdr)) break;
}
# else
if (GC_block_was_dirty(h, hhdr)) break;
# endif
h += OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz);
hhdr = HDR(h);
}
GC_push_marked(h, hhdr);
return(h + OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz));
}
#endif
/* Similar to above, but for uncollectable pages. Needed since we */
/* do not clear marks for such pages, even for full collections. */
struct hblk * GC_push_next_marked_uncollectable(struct hblk *h)
{
hdr * hhdr = HDR(h);
for (;;) {
if (EXPECT(IS_FORWARDING_ADDR_OR_NIL(hhdr), FALSE)) {
h = GC_next_used_block(h);
if (h == 0) return(0);
hhdr = GC_find_header((ptr_t)h);
}
if (hhdr -> hb_obj_kind == UNCOLLECTABLE) break;
h += OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz);
hhdr = HDR(h);
}
GC_push_marked(h, hhdr);
return(h + OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz));
}
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