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.
21 * (Note that gc_priv.h should not be included before this, since this
22 * includes dbg_mlc.h, which wants to include gc_priv.h AFTER defining
28 # if defined(KEEP_BACK_PTRS) || defined(PRINT_BLACK_LIST)
32 # include "../gc_mark.h"
38 /* The real declarations of the following is in gc_priv.h, so that */
39 /* we can avoid scanning the following table. */
41 extern mark_proc GC_mark_procs[MAX_MARK_PROCS];
45 * Mark descriptor stuff that should remain private for now, mostly
46 * because it's hard to export WORDSZ without including gcconfig.h.
48 # define BITMAP_BITS (WORDSZ - GC_DS_TAG_BITS)
49 # define PROC(descr) \
50 (GC_mark_procs[((descr) >> GC_DS_TAG_BITS) & (GC_MAX_MARK_PROCS-1)])
52 ((descr) >> (GC_DS_TAG_BITS + GC_LOG_MAX_MARK_PROCS))
54 (((word)1 << (WORDSZ - GC_DS_TAG_BITS - GC_LOG_MAX_MARK_PROCS)) - 1)
57 extern unsigned GC_n_mark_procs;
59 /* Number of mark stack entries to discard on overflow. */
60 #define GC_MARK_STACK_DISCARDS (INITIAL_MARK_STACK_SIZE/8)
62 typedef struct GC_ms_entry {
63 ptr_t mse_start; /* First word of object */
64 GC_word mse_descr; /* Descriptor; low order two bits are tags, */
65 /* identifying the upper 30 bits as one of the */
69 extern size_t GC_mark_stack_size;
71 extern mse * GC_mark_stack_limit;
74 extern mse * volatile GC_mark_stack_top;
76 extern mse * GC_mark_stack_top;
79 extern mse * GC_mark_stack;
83 * Allow multiple threads to participate in the marking process.
84 * This works roughly as follows:
85 * The main mark stack never shrinks, but it can grow.
87 * The initiating threads holds the GC lock, and sets GC_help_wanted.
90 * 1) update helper_count (while holding mark_lock.)
91 * 2) allocate a local mark stack
93 * 3) Steal a global mark stack entry by atomically replacing
94 * its descriptor with 0.
95 * 4) Copy it to the local stack.
96 * 5) Mark on the local stack until it is empty, or
97 * it may be profitable to copy it back.
98 * 6) If necessary, copy local stack to global one,
100 * 7) Stop when the global mark stack is empty.
101 * 8) decrement helper_count (holding mark_lock).
103 * This is an experiment to see if we can do something along the lines
104 * of the University of Tokyo SGC in a less intrusive, though probably
105 * also less performant, way.
107 void GC_do_parallel_mark();
108 /* inititate parallel marking. */
110 extern GC_bool GC_help_wanted; /* Protected by mark lock */
111 extern unsigned GC_helper_count; /* Number of running helpers. */
112 /* Protected by mark lock */
113 extern unsigned GC_active_count; /* Number of active helpers. */
114 /* Protected by mark lock */
115 /* May increase and decrease */
116 /* within each mark cycle. But */
117 /* once it returns to 0, it */
118 /* stays zero for the cycle. */
119 /* GC_mark_stack_top is also protected by mark lock. */
121 * GC_notify_all_marker() is used when GC_help_wanted is first set,
122 * when the last helper becomes inactive,
123 * when something is added to the global mark stack, and just after
124 * GC_mark_no is incremented.
125 * This could be split into multiple CVs (and probably should be to
126 * scale to really large numbers of processors.)
128 #endif /* PARALLEL_MARK */
130 /* Return a pointer to within 1st page of object. */
131 /* Set *new_hdr_p to corr. hdr. */
132 ptr_t GC_find_start(ptr_t current, hdr *hhdr, hdr **new_hdr_p);
134 mse * GC_signal_mark_stack_overflow(mse *msp);
136 /* Push the object obj with corresponding heap block header hhdr onto */
137 /* the mark stack. */
138 # define PUSH_OBJ(obj, hhdr, mark_stack_top, mark_stack_limit) \
140 register word _descr = (hhdr) -> hb_descr; \
144 if (mark_stack_top >= mark_stack_limit) { \
145 mark_stack_top = GC_signal_mark_stack_overflow(mark_stack_top); \
147 mark_stack_top -> mse_start = (obj); \
148 mark_stack_top -> mse_descr = _descr; \
152 /* Push the contents of current onto the mark stack if it is a valid */
153 /* ptr to a currently unmarked object. Mark it. */
154 /* If we assumed a standard-conforming compiler, we could probably */
155 /* generate the exit_label transparently. */
156 # define PUSH_CONTENTS(current, mark_stack_top, mark_stack_limit, \
157 source, exit_label) \
161 HC_GET_HDR(current, my_hhdr, source, exit_label); \
162 PUSH_CONTENTS_HDR(current, mark_stack_top, mark_stack_limit, \
163 source, exit_label, my_hhdr, TRUE); \
167 /* Set mark bit, exit if it was already set. */
169 # ifdef USE_MARK_BITS
170 # ifdef PARALLEL_MARK
171 /* The following may fail to exit even if the bit was already set. */
172 /* For our uses, that's benign: */
173 # define OR_WORD_EXIT_IF_SET(addr, bits, exit_label) \
175 if (!(*(addr) & (mask))) { \
176 AO_or((AO_t *)(addr), (mask); \
182 # define OR_WORD_EXIT_IF_SET(addr, bits, exit_label) \
184 word old = *(addr); \
185 word my_bits = (bits); \
186 if (old & my_bits) goto exit_label; \
187 *(addr) = (old | my_bits); \
189 # endif /* !PARALLEL_MARK */
190 # define SET_MARK_BIT_EXIT_IF_SET(hhdr,bit_no,exit_label) \
192 word * mark_word_addr = hhdr -> hb_marks + divWORDSZ(bit_no); \
194 OR_WORD_EXIT_IF_SET(mark_word_addr, (word)1 << modWORDSZ(bit_no), \
200 #ifdef USE_MARK_BYTES
201 # if defined(I386) && defined(__GNUC__)
202 # define LONG_MULT(hprod, lprod, x, y) { \
203 asm("mull %2" : "=a"(lprod), "=d"(hprod) : "g"(y), "0"(x)); \
205 # else /* No in-line X86 assembly code */
206 # define LONG_MULT(hprod, lprod, x, y) { \
207 unsigned long long prod = (unsigned long long)x \
208 * (unsigned long long)y; \
209 hprod = prod >> 32; \
210 lprod = (unsigned32)prod; \
214 /* There is a race here, and we may set */
215 /* the bit twice in the concurrent case. This can result in the */
216 /* object being pushed twice. But that's only a performance issue. */
217 # define SET_MARK_BIT_EXIT_IF_SET(hhdr,bit_no,exit_label) \
219 char * mark_byte_addr = (char *)hhdr -> hb_marks + (bit_no); \
220 char mark_byte = *mark_byte_addr; \
222 if (mark_byte) goto exit_label; \
223 *mark_byte_addr = 1; \
225 #endif /* USE_MARK_BYTES */
228 # define INCR_MARKS(hhdr) \
229 AO_store(&(hhdr -> hb_n_marks), AO_load(&(hhdr -> hb_n_marks))+1);
231 # define INCR_MARKS(hhdr) ++(hhdr -> hb_n_marks)
235 # define TRACE(source, cmd) \
236 if (GC_trace_addr != 0 && (ptr_t)(source) == GC_trace_addr) cmd
237 # define TRACE_TARGET(target, cmd) \
238 if (GC_trace_addr != 0 && (target) == *(ptr_t *)GC_trace_addr) cmd
240 # define TRACE(source, cmd)
241 # define TRACE_TARGET(source, cmd)
243 /* If the mark bit corresponding to current is not set, set it, and */
244 /* push the contents of the object on the mark stack. Current points */
245 /* to the bginning of the object. We rely on the fact that the */
246 /* preceding header calculation will succeed for a pointer past the */
247 /* forst page of an object, only if it is in fact a valid pointer */
248 /* to the object. Thus we can omit the otherwise necessary tests */
249 /* here. Note in particular tha the "displ" value is the displacement */
250 /* from the beggining of the heap block, which may itself be in the */
251 /* interior of a large object. */
252 #ifdef MARK_BIT_PER_GRANULE
253 # define PUSH_CONTENTS_HDR(current, mark_stack_top, mark_stack_limit, \
254 source, exit_label, hhdr, do_offset_check) \
256 size_t displ = HBLKDISPL(current); /* Displacement in block; in bytes. */\
257 /* displ is always within range. If current doesn't point to */ \
258 /* first block, then we are in the all_interior_pointers case, and */ \
259 /* it is safe to use any displacement value. */ \
260 size_t gran_displ = BYTES_TO_GRANULES(displ); \
261 size_t gran_offset = hhdr -> hb_map[gran_displ]; \
262 size_t byte_offset = displ & (GRANULE_BYTES - 1); \
263 ptr_t base = current; \
264 /* The following always fails for large block references. */ \
265 if (EXPECT((gran_offset | byte_offset) != 0, FALSE)) { \
266 if (hhdr -> hb_large_block) { \
267 /* gran_offset is bogus. */ \
269 base = (ptr_t)(hhdr -> hb_block); \
270 obj_displ = (ptr_t)(current) - base; \
271 if (obj_displ != displ) { \
272 GC_ASSERT(obj_displ < hhdr -> hb_sz); \
273 /* Must be in all_interior_pointer case, not first block */ \
274 /* already did validity check on cache miss. */ \
277 if (do_offset_check && !GC_valid_offsets[obj_displ]) { \
278 GC_ADD_TO_BLACK_LIST_NORMAL(current, source); \
283 GC_ASSERT(hhdr -> hb_sz > HBLKSIZE || \
284 hhdr -> hb_block == HBLKPTR(current)); \
285 GC_ASSERT((ptr_t)(hhdr -> hb_block) <= (ptr_t) current); \
287 size_t obj_displ = GRANULES_TO_BYTES(gran_offset) \
289 if (do_offset_check && !GC_valid_offsets[obj_displ]) { \
290 GC_ADD_TO_BLACK_LIST_NORMAL(current, source); \
293 gran_displ -= gran_offset; \
297 GC_ASSERT(hhdr == GC_find_header(base)); \
298 GC_ASSERT(gran_displ % BYTES_TO_GRANULES(hhdr -> hb_sz) == 0); \
299 TRACE(source, GC_log_printf("GC:%d: passed validity tests\n",GC_gc_no)); \
300 SET_MARK_BIT_EXIT_IF_SET(hhdr, gran_displ, exit_label); \
301 TRACE(source, GC_log_printf("GC:%d: previously unmarked\n",GC_gc_no)); \
303 GC_log_printf("GC:%d: marking %p from %p instead\n", GC_gc_no, \
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, offset_fraction; \
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. */ \
333 if (do_offset_check && !GC_valid_offsets[obj_displ]) { \
334 GC_ADD_TO_BLACK_LIST_NORMAL(current, source); \
338 GC_ASSERT(hhdr -> hb_sz > HBLKSIZE || \
339 hhdr -> hb_block == HBLKPTR(current)); \
340 GC_ASSERT((ptr_t)(hhdr -> hb_block) < (ptr_t) current); \
342 /* Accurate enough if HBLKSIZE <= 2**15. */ \
343 GC_ASSERT(HBLKSIZE <= (1 << 15)); \
344 size_t obj_displ = (((low_prod >> 16) + 1) * (hhdr -> hb_sz)) >> 16; \
345 if (do_offset_check && !GC_valid_offsets[obj_displ]) { \
346 GC_ADD_TO_BLACK_LIST_NORMAL(current, source); \
352 /* May get here for pointer to start of block not at */ \
353 /* beginning of object. If so, it's valid, and we're fine. */ \
354 GC_ASSERT(high_prod >= 0 && high_prod <= HBLK_OBJS(hhdr -> hb_sz)); \
355 TRACE(source, GC_log_printf("GC:%d: passed validity tests\n",GC_gc_no)); \
356 SET_MARK_BIT_EXIT_IF_SET(hhdr, high_prod, exit_label); \
357 TRACE(source, GC_log_printf("GC:%d: previously unmarked\n",GC_gc_no)); \
359 GC_log_printf("GC:%d: marking %p from %p instead\n", GC_gc_no, \
362 GC_STORE_BACK_PTR((ptr_t)source, base); \
363 PUSH_OBJ(base, hhdr, mark_stack_top, mark_stack_limit); \
365 #endif /* MARK_BIT_PER_OBJ */
367 #if defined(PRINT_BLACK_LIST) || defined(KEEP_BACK_PTRS)
368 # define PUSH_ONE_CHECKED_STACK(p, source) \
369 GC_mark_and_push_stack(p, (ptr_t)(source))
371 # define PUSH_ONE_CHECKED_STACK(p, source) \
372 GC_mark_and_push_stack(p)
376 * Push a single value onto mark stack. Mark from the object pointed to by p.
377 * Invoke FIXUP_POINTER(p) before any further processing.
378 * P is considered valid even if it is an interior pointer.
379 * Previously marked objects are not pushed. Hence we make progress even
380 * if the mark stack overflows.
383 # if NEED_FIXUP_POINTER
384 /* Try both the raw version and the fixed up one. */
385 # define GC_PUSH_ONE_STACK(p, source) \
386 if ((p) >= (ptr_t)GC_least_plausible_heap_addr \
387 && (p) < (ptr_t)GC_greatest_plausible_heap_addr) { \
388 PUSH_ONE_CHECKED_STACK(p, source); \
391 if ((p) >= (ptr_t)GC_least_plausible_heap_addr \
392 && (p) < (ptr_t)GC_greatest_plausible_heap_addr) { \
393 PUSH_ONE_CHECKED_STACK(p, source); \
395 # else /* !NEED_FIXUP_POINTER */
396 # define GC_PUSH_ONE_STACK(p, source) \
397 if ((ptr_t)(p) >= (ptr_t)GC_least_plausible_heap_addr \
398 && (ptr_t)(p) < (ptr_t)GC_greatest_plausible_heap_addr) { \
399 PUSH_ONE_CHECKED_STACK(p, source); \
405 * As above, but interior pointer recognition as for
406 * normal heap pointers.
408 # define GC_PUSH_ONE_HEAP(p,source) \
410 if ((p) >= (ptr_t)GC_least_plausible_heap_addr \
411 && (p) < (ptr_t)GC_greatest_plausible_heap_addr) { \
412 GC_mark_stack_top = GC_mark_and_push( \
413 (void *)(p), GC_mark_stack_top, \
414 GC_mark_stack_limit, (void * *)(source)); \
417 /* Mark starting at mark stack entry top (incl.) down to */
418 /* mark stack entry bottom (incl.). Stop after performing */
419 /* about one page worth of work. Return the new mark stack */
421 mse * GC_mark_from(mse * top, mse * bottom, mse *limit);
423 #define MARK_FROM_MARK_STACK() \
424 GC_mark_stack_top = GC_mark_from(GC_mark_stack_top, \
426 GC_mark_stack + GC_mark_stack_size);
429 * Mark from one finalizable object using the specified
430 * mark proc. May not mark the object pointed to by
431 * real_ptr. That is the job of the caller, if appropriate.
432 * Note that this is called with the mutator running, but
433 * with us holding the allocation lock. This is safe only if the
434 * mutator needs tha allocation lock to reveal hidden pointers.
435 * FIXME: Why do we need the GC_mark_state test below?
437 # define GC_MARK_FO(real_ptr, mark_proc) \
439 (*(mark_proc))(real_ptr); \
440 while (!GC_mark_stack_empty()) MARK_FROM_MARK_STACK(); \
441 if (GC_mark_state != MS_NONE) { \
442 GC_set_mark_bit(real_ptr); \
443 while (!GC_mark_some((ptr_t)0)) {} \
447 extern GC_bool GC_mark_stack_too_small;
448 /* We need a larger mark stack. May be */
449 /* set by client supplied mark routines.*/
451 typedef int mark_state_t; /* Current state of marking, as follows:*/
452 /* Used to remember where we are during */
453 /* concurrent marking. */
455 /* We say something is dirty if it was */
456 /* written since the last time we */
457 /* retrieved dirty bits. We say it's */
458 /* grungy if it was marked dirty in the */
459 /* last set of bits we retrieved. */
461 /* Invariant I: all roots and marked */
462 /* objects p are either dirty, or point */
463 /* to objects q that are either marked */
464 /* or a pointer to q appears in a range */
465 /* on the mark stack. */
467 # define MS_NONE 0 /* No marking in progress. I holds. */
468 /* Mark stack is empty. */
470 # define MS_PUSH_RESCUERS 1 /* Rescuing objects are currently */
471 /* being pushed. I holds, except */
472 /* that grungy roots may point to */
473 /* unmarked objects, as may marked */
474 /* grungy objects above scan_ptr. */
476 # define MS_PUSH_UNCOLLECTABLE 2
477 /* I holds, except that marked */
478 /* uncollectable objects above scan_ptr */
479 /* may point to unmarked objects. */
480 /* Roots may point to unmarked objects */
482 # define MS_ROOTS_PUSHED 3 /* I holds, mark stack may be nonempty */
484 # define MS_PARTIALLY_INVALID 4 /* I may not hold, e.g. because of M.S. */
485 /* overflow. However marked heap */
486 /* objects below scan_ptr point to */
487 /* marked or stacked objects. */
489 # define MS_INVALID 5 /* I may not hold. */
491 extern mark_state_t GC_mark_state;
493 #endif /* GC_PMARK_H */