/vendor/gc/mark.c
C | 1867 lines | 1349 code | 171 blank | 347 comment | 316 complexity | 6685c52592117f6d166c04bfe92d8c4f MD5 | raw file
Possible License(s): BSD-3-Clause, GPL-2.0
- /*
- * 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));
- }