2 * Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
3 * Copyright (c) 2001 by Hewlett-Packard Company. All rights reserved.
5 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
6 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
8 * Permission is hereby granted to use or copy this program
9 * for any purpose, provided the above notices are retained on all copies.
10 * Permission to modify the code and to distribute modified code is granted,
11 * provided the above notices are retained, and a notice that the code was
12 * modified is included with the above copyright notice.
16 /* Private declarations of GC marker data structures and macros */
19 * Declarations of mark stack. Needed by marker and client supplied mark
20 * routines. Transitively include gc_priv.h.
26 # include "private/config.h"
33 #if defined(KEEP_BACK_PTRS) || defined(PRINT_BLACK_LIST)
39 # define GC_I_HIDE_POINTERS /* to get GC_HIDE_POINTER() and friends */
41 # include "../gc_mark.h"
48 /* The real declarations of the following is in gc_priv.h, so that */
49 /* we can avoid scanning the following table. */
51 mark_proc GC_mark_procs[MAX_MARK_PROCS];
54 #ifndef MARK_DESCR_OFFSET
55 # define MARK_DESCR_OFFSET sizeof(word)
59 * Mark descriptor stuff that should remain private for now, mostly
60 * because it's hard to export WORDSZ without including gcconfig.h.
62 #define BITMAP_BITS (WORDSZ - GC_DS_TAG_BITS)
64 (GC_mark_procs[((descr) >> GC_DS_TAG_BITS) & (GC_MAX_MARK_PROCS-1)])
66 ((descr) >> (GC_DS_TAG_BITS + GC_LOG_MAX_MARK_PROCS))
68 (((word)1 << (WORDSZ - GC_DS_TAG_BITS - GC_LOG_MAX_MARK_PROCS)) - 1)
70 GC_EXTERN unsigned GC_n_mark_procs;
72 /* Number of mark stack entries to discard on overflow. */
73 #define GC_MARK_STACK_DISCARDS (INITIAL_MARK_STACK_SIZE/8)
75 typedef struct GC_ms_entry {
76 ptr_t mse_start; /* First word of object, word aligned. */
77 GC_word mse_descr; /* Descriptor; low order two bits are tags, */
78 /* as described in gc_mark.h. */
81 GC_EXTERN size_t GC_mark_stack_size;
83 GC_EXTERN mse * GC_mark_stack_limit;
86 GC_EXTERN mse * volatile GC_mark_stack_top;
88 GC_EXTERN mse * GC_mark_stack_top;
91 GC_EXTERN mse * GC_mark_stack;
95 * Allow multiple threads to participate in the marking process.
96 * This works roughly as follows:
97 * The main mark stack never shrinks, but it can grow.
99 * The initiating threads holds the GC lock, and sets GC_help_wanted.
102 * 1) update helper_count (while holding mark_lock.)
103 * 2) allocate a local mark stack
105 * 3) Steal a global mark stack entry by atomically replacing
106 * its descriptor with 0.
107 * 4) Copy it to the local stack.
108 * 5) Mark on the local stack until it is empty, or
109 * it may be profitable to copy it back.
110 * 6) If necessary, copy local stack to global one,
112 * 7) Stop when the global mark stack is empty.
113 * 8) decrement helper_count (holding mark_lock).
115 * This is an experiment to see if we can do something along the lines
116 * of the University of Tokyo SGC in a less intrusive, though probably
117 * also less performant, way.
120 /* GC_mark_stack_top is protected by mark lock. */
123 * GC_notify_all_marker() is used when GC_help_wanted is first set,
124 * when the last helper becomes inactive,
125 * when something is added to the global mark stack, and just after
126 * GC_mark_no is incremented.
127 * This could be split into multiple CVs (and probably should be to
128 * scale to really large numbers of processors.)
130 #endif /* PARALLEL_MARK */
132 GC_INNER mse * GC_signal_mark_stack_overflow(mse *msp);
134 /* Push the object obj with corresponding heap block header hhdr onto */
135 /* the mark stack. */
136 #define PUSH_OBJ(obj, hhdr, mark_stack_top, mark_stack_limit) \
138 register word _descr = (hhdr) -> hb_descr; \
140 GC_ASSERT(!HBLK_IS_FREE(hhdr)); \
143 if (mark_stack_top >= mark_stack_limit) { \
144 mark_stack_top = GC_signal_mark_stack_overflow(mark_stack_top); \
146 mark_stack_top -> mse_start = (obj); \
147 mark_stack_top -> mse_descr = _descr; \
151 /* Push the contents of current onto the mark stack if it is a valid */
152 /* ptr to a currently unmarked object. Mark it. */
153 /* If we assumed a standard-conforming compiler, we could probably */
154 /* generate the exit_label transparently. */
155 #define PUSH_CONTENTS(current, mark_stack_top, mark_stack_limit, \
156 source, exit_label) \
160 HC_GET_HDR(current, my_hhdr, source, exit_label); \
161 PUSH_CONTENTS_HDR(current, mark_stack_top, mark_stack_limit, \
162 source, exit_label, my_hhdr, TRUE); \
166 /* Set mark bit, exit if it was already set. */
169 # ifdef PARALLEL_MARK
170 /* The following may fail to exit even if the bit was already set. */
171 /* For our uses, that's benign: */
172 # define OR_WORD_EXIT_IF_SET(addr, bits, exit_label) \
174 if (!(*(addr) & (bits))) { \
175 AO_or((AO_t *)(addr), (bits)); \
181 # define OR_WORD_EXIT_IF_SET(addr, bits, exit_label) \
183 word old = *(addr); \
184 word my_bits = (bits); \
185 if (old & my_bits) goto exit_label; \
186 *(addr) = (old | my_bits); \
188 # endif /* !PARALLEL_MARK */
189 # define SET_MARK_BIT_EXIT_IF_SET(hhdr,bit_no,exit_label) \
191 word * mark_word_addr = hhdr -> hb_marks + divWORDSZ(bit_no); \
193 OR_WORD_EXIT_IF_SET(mark_word_addr, (word)1 << modWORDSZ(bit_no), \
198 #if defined(I386) && defined(__GNUC__)
199 # define LONG_MULT(hprod, lprod, x, y) { \
200 asm("mull %2" : "=a"(lprod), "=d"(hprod) : "g"(y), "0"(x)); \
202 #else /* No in-line X86 assembly code */
203 # define LONG_MULT(hprod, lprod, x, y) { \
204 unsigned long long prod = (unsigned long long)x \
205 * (unsigned long long)y; \
206 hprod = prod >> 32; \
207 lprod = (unsigned32)prod; \
211 #ifdef USE_MARK_BYTES
212 /* There is a race here, and we may set */
213 /* the bit twice in the concurrent case. This can result in the */
214 /* object being pushed twice. But that's only a performance issue. */
215 # define SET_MARK_BIT_EXIT_IF_SET(hhdr,bit_no,exit_label) \
217 char * mark_byte_addr = (char *)hhdr -> hb_marks + (bit_no); \
218 char mark_byte = *mark_byte_addr; \
220 if (mark_byte) goto exit_label; \
221 *mark_byte_addr = 1; \
223 #endif /* USE_MARK_BYTES */
226 # define INCR_MARKS(hhdr) \
227 AO_store(&(hhdr -> hb_n_marks), AO_load(&(hhdr -> hb_n_marks))+1);
229 # define INCR_MARKS(hhdr) ++(hhdr -> hb_n_marks)
233 # define TRACE(source, cmd) \
234 if (GC_trace_addr != 0 && (ptr_t)(source) == GC_trace_addr) cmd
235 # define TRACE_TARGET(target, cmd) \
236 if (GC_trace_addr != 0 && (target) == *(ptr_t *)GC_trace_addr) cmd
238 # define TRACE(source, cmd)
239 # define TRACE_TARGET(source, cmd)
242 /* If the mark bit corresponding to current is not set, set it, and */
243 /* push the contents of the object on the mark stack. Current points */
244 /* to the beginning of the object. We rely on the fact that the */
245 /* preceding header calculation will succeed for a pointer past the */
246 /* first page of an object, only if it is in fact a valid pointer */
247 /* to the object. Thus we can omit the otherwise necessary tests */
248 /* here. Note in particular that the "displ" value is the displacement */
249 /* from the beginning of the heap block, which may itself be in the */
250 /* interior of a large object. */
251 #ifdef MARK_BIT_PER_GRANULE
252 # define PUSH_CONTENTS_HDR(current, mark_stack_top, mark_stack_limit, \
253 source, exit_label, hhdr, do_offset_check) \
255 size_t displ = HBLKDISPL(current); /* Displacement in block; in bytes. */\
256 /* displ is always within range. If current doesn't point to */ \
257 /* first block, then we are in the all_interior_pointers case, and */ \
258 /* it is safe to use any displacement value. */ \
259 size_t gran_displ = BYTES_TO_GRANULES(displ); \
260 size_t gran_offset = hhdr -> hb_map[gran_displ]; \
261 size_t byte_offset = displ & (GRANULE_BYTES - 1); \
262 ptr_t base = current; \
263 /* The following always fails for large block references. */ \
264 if (EXPECT((gran_offset | byte_offset) != 0, FALSE)) { \
265 if (hhdr -> hb_large_block) { \
266 /* gran_offset is bogus. */ \
268 base = (ptr_t)(hhdr -> hb_block); \
269 obj_displ = (ptr_t)(current) - base; \
270 if (obj_displ != displ) { \
271 GC_ASSERT(obj_displ < hhdr -> hb_sz); \
272 /* Must be in all_interior_pointer case, not first block */ \
273 /* already did validity check on cache miss. */ \
275 if (do_offset_check && !GC_valid_offsets[obj_displ]) { \
276 GC_ADD_TO_BLACK_LIST_NORMAL(current, source); \
281 GC_ASSERT(hhdr -> hb_sz > HBLKSIZE || \
282 hhdr -> hb_block == HBLKPTR(current)); \
283 GC_ASSERT((ptr_t)(hhdr -> hb_block) <= (ptr_t) current); \
285 size_t obj_displ = GRANULES_TO_BYTES(gran_offset) \
287 if (do_offset_check && !GC_valid_offsets[obj_displ]) { \
288 GC_ADD_TO_BLACK_LIST_NORMAL(current, source); \
291 gran_displ -= gran_offset; \
295 GC_ASSERT(hhdr == GC_find_header(base)); \
296 GC_ASSERT(gran_displ % BYTES_TO_GRANULES(hhdr -> hb_sz) == 0); \
297 TRACE(source, GC_log_printf("GC:%u: passed validity tests\n", \
298 (unsigned)GC_gc_no)); \
299 SET_MARK_BIT_EXIT_IF_SET(hhdr, gran_displ, exit_label); \
300 TRACE(source, GC_log_printf("GC:%u: previously unmarked\n", \
301 (unsigned)GC_gc_no)); \
303 GC_log_printf("GC:%u: marking %p from %p instead\n", \
304 (unsigned)GC_gc_no, base, source)); \
306 GC_STORE_BACK_PTR((ptr_t)source, base); \
307 PUSH_OBJ(base, hhdr, mark_stack_top, mark_stack_limit); \
309 #endif /* MARK_BIT_PER_GRANULE */
311 #ifdef MARK_BIT_PER_OBJ
312 # define PUSH_CONTENTS_HDR(current, mark_stack_top, mark_stack_limit, \
313 source, exit_label, hhdr, do_offset_check) \
315 size_t displ = HBLKDISPL(current); /* Displacement in block; in bytes. */\
316 unsigned32 low_prod, high_prod; \
317 unsigned32 inv_sz = hhdr -> hb_inv_sz; \
318 ptr_t base = current; \
319 LONG_MULT(high_prod, low_prod, displ, inv_sz); \
320 /* product is > and within sz_in_bytes of displ * sz_in_bytes * 2**32 */ \
321 if (EXPECT(low_prod >> 16 != 0, FALSE)) { \
322 FIXME: fails if offset is a multiple of HBLKSIZE which becomes 0 \
323 if (inv_sz == LARGE_INV_SZ) { \
325 base = (ptr_t)(hhdr -> hb_block); \
326 obj_displ = (ptr_t)(current) - base; \
327 if (obj_displ != displ) { \
328 GC_ASSERT(obj_displ < hhdr -> hb_sz); \
329 /* Must be in all_interior_pointer case, not first block */ \
330 /* already did validity check on cache miss. */ \
332 if (do_offset_check && !GC_valid_offsets[obj_displ]) { \
333 GC_ADD_TO_BLACK_LIST_NORMAL(current, source); \
337 GC_ASSERT(hhdr -> hb_sz > HBLKSIZE || \
338 hhdr -> hb_block == HBLKPTR(current)); \
339 GC_ASSERT((ptr_t)(hhdr -> hb_block) < (ptr_t) current); \
341 /* Accurate enough if HBLKSIZE <= 2**15. */ \
342 GC_STATIC_ASSERT(HBLKSIZE <= (1 << 15)); \
343 size_t obj_displ = (((low_prod >> 16) + 1) * (hhdr->hb_sz)) >> 16; \
344 if (do_offset_check && !GC_valid_offsets[obj_displ]) { \
345 GC_ADD_TO_BLACK_LIST_NORMAL(current, source); \
351 /* May get here for pointer to start of block not at */ \
352 /* beginning of object. If so, it's valid, and we're fine. */ \
353 GC_ASSERT(high_prod >= 0 && high_prod <= HBLK_OBJS(hhdr -> hb_sz)); \
354 TRACE(source, GC_log_printf("GC:%u: passed validity tests\n", \
355 (unsigned)GC_gc_no)); \
356 SET_MARK_BIT_EXIT_IF_SET(hhdr, high_prod, exit_label); \
357 TRACE(source, GC_log_printf("GC:%u: previously unmarked\n", \
358 (unsigned)GC_gc_no)); \
360 GC_log_printf("GC:%u: marking %p from %p instead\n", \
361 (unsigned)GC_gc_no, \
364 GC_STORE_BACK_PTR((ptr_t)source, base); \
365 PUSH_OBJ(base, hhdr, mark_stack_top, mark_stack_limit); \
367 #endif /* MARK_BIT_PER_OBJ */
369 #if defined(PRINT_BLACK_LIST) || defined(KEEP_BACK_PTRS)
370 # define PUSH_ONE_CHECKED_STACK(p, source) \
371 GC_mark_and_push_stack((ptr_t)(p), (ptr_t)(source))
373 # define PUSH_ONE_CHECKED_STACK(p, source) \
374 GC_mark_and_push_stack((ptr_t)(p))
378 * Push a single value onto mark stack. Mark from the object pointed to by p.
379 * Invoke FIXUP_POINTER(p) before any further processing.
380 * P is considered valid even if it is an interior pointer.
381 * Previously marked objects are not pushed. Hence we make progress even
382 * if the mark stack overflows.
385 #if NEED_FIXUP_POINTER
386 /* Try both the raw version and the fixed up one. */
387 # define GC_PUSH_ONE_STACK(p, source) \
388 if ((ptr_t)(p) >= (ptr_t)GC_least_plausible_heap_addr \
389 && (ptr_t)(p) < (ptr_t)GC_greatest_plausible_heap_addr) { \
390 PUSH_ONE_CHECKED_STACK(p, source); \
393 if ((ptr_t)(p) >= (ptr_t)GC_least_plausible_heap_addr \
394 && (ptr_t)(p) < (ptr_t)GC_greatest_plausible_heap_addr) { \
395 PUSH_ONE_CHECKED_STACK(p, source); \
397 #else /* !NEED_FIXUP_POINTER */
398 # define GC_PUSH_ONE_STACK(p, source) \
399 if ((ptr_t)(p) >= (ptr_t)GC_least_plausible_heap_addr \
400 && (ptr_t)(p) < (ptr_t)GC_greatest_plausible_heap_addr) { \
401 PUSH_ONE_CHECKED_STACK(p, source); \
407 * As above, but interior pointer recognition as for
408 * normal heap pointers.
410 #define GC_PUSH_ONE_HEAP(p,source) \
412 if ((ptr_t)(p) >= (ptr_t)GC_least_plausible_heap_addr \
413 && (ptr_t)(p) < (ptr_t)GC_greatest_plausible_heap_addr) { \
414 GC_mark_stack_top = GC_mark_and_push( \
415 (void *)(p), GC_mark_stack_top, \
416 GC_mark_stack_limit, (void * *)(source)); \
419 /* Mark starting at mark stack entry top (incl.) down to */
420 /* mark stack entry bottom (incl.). Stop after performing */
421 /* about one page worth of work. Return the new mark stack */
423 GC_INNER mse * GC_mark_from(mse * top, mse * bottom, mse *limit);
425 #define MARK_FROM_MARK_STACK() \
426 GC_mark_stack_top = GC_mark_from(GC_mark_stack_top, \
428 GC_mark_stack + GC_mark_stack_size);
431 * Mark from one finalizable object using the specified
432 * mark proc. May not mark the object pointed to by
433 * real_ptr. That is the job of the caller, if appropriate.
434 * Note that this is called with the mutator running, but
435 * with us holding the allocation lock. This is safe only if the
436 * mutator needs the allocation lock to reveal hidden pointers.
437 * FIXME: Why do we need the GC_mark_state test below?
439 #define GC_MARK_FO(real_ptr, mark_proc) \
441 (*(mark_proc))(real_ptr); \
442 while (!GC_mark_stack_empty()) MARK_FROM_MARK_STACK(); \
443 if (GC_mark_state != MS_NONE) { \
444 GC_set_mark_bit(real_ptr); \
445 while (!GC_mark_some((ptr_t)0)) {} \
449 GC_EXTERN GC_bool GC_mark_stack_too_small;
450 /* We need a larger mark stack. May be */
451 /* set by client supplied mark routines.*/
453 typedef int mark_state_t; /* Current state of marking, as follows:*/
454 /* Used to remember where we are during */
455 /* concurrent marking. */
457 /* We say something is dirty if it was */
458 /* written since the last time we */
459 /* retrieved dirty bits. We say it's */
460 /* grungy if it was marked dirty in the */
461 /* last set of bits we retrieved. */
463 /* Invariant I: all roots and marked */
464 /* objects p are either dirty, or point */
465 /* to objects q that are either marked */
466 /* or a pointer to q appears in a range */
467 /* on the mark stack. */
469 #define MS_NONE 0 /* No marking in progress. I holds. */
470 /* Mark stack is empty. */
472 #define MS_PUSH_RESCUERS 1 /* Rescuing objects are currently */
473 /* being pushed. I holds, except */
474 /* that grungy roots may point to */
475 /* unmarked objects, as may marked */
476 /* grungy objects above scan_ptr. */
478 #define MS_PUSH_UNCOLLECTABLE 2 /* I holds, except that marked */
479 /* uncollectable objects above scan_ptr */
480 /* may point to unmarked objects. */
481 /* Roots may point to unmarked objects */
483 #define MS_ROOTS_PUSHED 3 /* I holds, mark stack may be nonempty */
485 #define MS_PARTIALLY_INVALID 4 /* I may not hold, e.g. because of M.S. */
486 /* overflow. However marked heap */
487 /* objects below scan_ptr point to */
488 /* marked or stacked objects. */
490 #define MS_INVALID 5 /* I may not hold. */
492 GC_EXTERN mark_state_t GC_mark_state;
494 #endif /* GC_PMARK_H */