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<GreyKnight> (cd luabuild; tar -xvf lua-5.2.1.tar.gz)
author HackBot
date Fri, 14 Dec 2012 20:33:11 +0000
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1086:64bb613b689c 1087:07b68c71b89c
1 /*
2 ** $Id: lgc.c,v 2.133 2012/05/31 21:28:59 roberto Exp $
3 ** Garbage Collector
4 ** See Copyright Notice in lua.h
5 */
6
7 #include <string.h>
8
9 #define lgc_c
10 #define LUA_CORE
11
12 #include "lua.h"
13
14 #include "ldebug.h"
15 #include "ldo.h"
16 #include "lfunc.h"
17 #include "lgc.h"
18 #include "lmem.h"
19 #include "lobject.h"
20 #include "lstate.h"
21 #include "lstring.h"
22 #include "ltable.h"
23 #include "ltm.h"
24
25
26
27 /*
28 ** cost of sweeping one element (the size of a small object divided
29 ** by some adjust for the sweep speed)
30 */
31 #define GCSWEEPCOST ((sizeof(TString) + 4) / 4)
32
33 /* maximum number of elements to sweep in each single step */
34 #define GCSWEEPMAX (cast_int((GCSTEPSIZE / GCSWEEPCOST) / 4))
35
36 /* maximum number of finalizers to call in each GC step */
37 #define GCFINALIZENUM 4
38
39
40 /*
41 ** macro to adjust 'stepmul': 'stepmul' is actually used like
42 ** 'stepmul / STEPMULADJ' (value chosen by tests)
43 */
44 #define STEPMULADJ 200
45
46 /*
47 ** macro to adjust 'pause': 'pause' is actually used like
48 ** 'pause / PAUSEADJ' (value chosen by tests)
49 */
50 #define PAUSEADJ 200
51
52
53
54
55 /*
56 ** standard negative debt for GC; a reasonable "time" to wait before
57 ** starting a new cycle
58 */
59 #define stddebtest(g,e) (-cast(l_mem, (e)/PAUSEADJ) * g->gcpause)
60 #define stddebt(g) stddebtest(g, gettotalbytes(g))
61
62
63 /*
64 ** 'makewhite' erases all color bits plus the old bit and then
65 ** sets only the current white bit
66 */
67 #define maskcolors (~(bit2mask(BLACKBIT, OLDBIT) | WHITEBITS))
68 #define makewhite(g,x) \
69 (gch(x)->marked = cast_byte((gch(x)->marked & maskcolors) | luaC_white(g)))
70
71 #define white2gray(x) resetbits(gch(x)->marked, WHITEBITS)
72 #define black2gray(x) resetbit(gch(x)->marked, BLACKBIT)
73
74
75 #define isfinalized(x) testbit(gch(x)->marked, FINALIZEDBIT)
76
77 #define checkdeadkey(n) lua_assert(!ttisdeadkey(gkey(n)) || ttisnil(gval(n)))
78
79
80 #define checkconsistency(obj) \
81 lua_longassert(!iscollectable(obj) || righttt(obj))
82
83
84 #define markvalue(g,o) { checkconsistency(o); \
85 if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); }
86
87 #define markobject(g,t) { if ((t) && iswhite(obj2gco(t))) \
88 reallymarkobject(g, obj2gco(t)); }
89
90 static void reallymarkobject (global_State *g, GCObject *o);
91
92
93 /*
94 ** {======================================================
95 ** Generic functions
96 ** =======================================================
97 */
98
99
100 /*
101 ** one after last element in a hash array
102 */
103 #define gnodelast(h) gnode(h, cast(size_t, sizenode(h)))
104
105
106 /*
107 ** link table 'h' into list pointed by 'p'
108 */
109 #define linktable(h,p) ((h)->gclist = *(p), *(p) = obj2gco(h))
110
111
112 /*
113 ** if key is not marked, mark its entry as dead (therefore removing it
114 ** from the table)
115 */
116 static void removeentry (Node *n) {
117 lua_assert(ttisnil(gval(n)));
118 if (valiswhite(gkey(n)))
119 setdeadvalue(gkey(n)); /* unused and unmarked key; remove it */
120 }
121
122
123 /*
124 ** tells whether a key or value can be cleared from a weak
125 ** table. Non-collectable objects are never removed from weak
126 ** tables. Strings behave as `values', so are never removed too. for
127 ** other objects: if really collected, cannot keep them; for objects
128 ** being finalized, keep them in keys, but not in values
129 */
130 static int iscleared (global_State *g, const TValue *o) {
131 if (!iscollectable(o)) return 0;
132 else if (ttisstring(o)) {
133 markobject(g, rawtsvalue(o)); /* strings are `values', so are never weak */
134 return 0;
135 }
136 else return iswhite(gcvalue(o));
137 }
138
139
140 /*
141 ** barrier that moves collector forward, that is, mark the white object
142 ** being pointed by a black object.
143 */
144 void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) {
145 global_State *g = G(L);
146 lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
147 lua_assert(isgenerational(g) || g->gcstate != GCSpause);
148 lua_assert(gch(o)->tt != LUA_TTABLE);
149 if (keepinvariant(g)) /* must keep invariant? */
150 reallymarkobject(g, v); /* restore invariant */
151 else { /* sweep phase */
152 lua_assert(issweepphase(g));
153 makewhite(g, o); /* mark main obj. as white to avoid other barriers */
154 }
155 }
156
157
158 /*
159 ** barrier that moves collector backward, that is, mark the black object
160 ** pointing to a white object as gray again. (Current implementation
161 ** only works for tables; access to 'gclist' is not uniform across
162 ** different types.)
163 */
164 void luaC_barrierback_ (lua_State *L, GCObject *o) {
165 global_State *g = G(L);
166 lua_assert(isblack(o) && !isdead(g, o) && gch(o)->tt == LUA_TTABLE);
167 black2gray(o); /* make object gray (again) */
168 gco2t(o)->gclist = g->grayagain;
169 g->grayagain = o;
170 }
171
172
173 /*
174 ** barrier for prototypes. When creating first closure (cache is
175 ** NULL), use a forward barrier; this may be the only closure of the
176 ** prototype (if it is a "regular" function, with a single instance)
177 ** and the prototype may be big, so it is better to avoid traversing
178 ** it again. Otherwise, use a backward barrier, to avoid marking all
179 ** possible instances.
180 */
181 LUAI_FUNC void luaC_barrierproto_ (lua_State *L, Proto *p, Closure *c) {
182 global_State *g = G(L);
183 lua_assert(isblack(obj2gco(p)));
184 if (p->cache == NULL) { /* first time? */
185 luaC_objbarrier(L, p, c);
186 }
187 else { /* use a backward barrier */
188 black2gray(obj2gco(p)); /* make prototype gray (again) */
189 p->gclist = g->grayagain;
190 g->grayagain = obj2gco(p);
191 }
192 }
193
194
195 /*
196 ** check color (and invariants) for an upvalue that was closed,
197 ** i.e., moved into the 'allgc' list
198 */
199 void luaC_checkupvalcolor (global_State *g, UpVal *uv) {
200 GCObject *o = obj2gco(uv);
201 lua_assert(!isblack(o)); /* open upvalues are never black */
202 if (isgray(o)) {
203 if (keepinvariant(g)) {
204 resetoldbit(o); /* see MOVE OLD rule */
205 gray2black(o); /* it is being visited now */
206 markvalue(g, uv->v);
207 }
208 else {
209 lua_assert(issweepphase(g));
210 makewhite(g, o);
211 }
212 }
213 }
214
215
216 /*
217 ** create a new collectable object (with given type and size) and link
218 ** it to '*list'. 'offset' tells how many bytes to allocate before the
219 ** object itself (used only by states).
220 */
221 GCObject *luaC_newobj (lua_State *L, int tt, size_t sz, GCObject **list,
222 int offset) {
223 global_State *g = G(L);
224 char *raw = cast(char *, luaM_newobject(L, novariant(tt), sz));
225 GCObject *o = obj2gco(raw + offset);
226 if (list == NULL)
227 list = &g->allgc; /* standard list for collectable objects */
228 gch(o)->marked = luaC_white(g);
229 gch(o)->tt = tt;
230 gch(o)->next = *list;
231 *list = o;
232 return o;
233 }
234
235 /* }====================================================== */
236
237
238
239 /*
240 ** {======================================================
241 ** Mark functions
242 ** =======================================================
243 */
244
245
246 /*
247 ** mark an object. Userdata, strings, and closed upvalues are visited
248 ** and turned black here. Other objects are marked gray and added
249 ** to appropriate list to be visited (and turned black) later. (Open
250 ** upvalues are already linked in 'headuv' list.)
251 */
252 static void reallymarkobject (global_State *g, GCObject *o) {
253 lu_mem size;
254 white2gray(o);
255 switch (gch(o)->tt) {
256 case LUA_TSHRSTR:
257 case LUA_TLNGSTR: {
258 size = sizestring(gco2ts(o));
259 break; /* nothing else to mark; make it black */
260 }
261 case LUA_TUSERDATA: {
262 Table *mt = gco2u(o)->metatable;
263 markobject(g, mt);
264 markobject(g, gco2u(o)->env);
265 size = sizeudata(gco2u(o));
266 break;
267 }
268 case LUA_TUPVAL: {
269 UpVal *uv = gco2uv(o);
270 markvalue(g, uv->v);
271 if (uv->v != &uv->u.value) /* open? */
272 return; /* open upvalues remain gray */
273 size = sizeof(UpVal);
274 break;
275 }
276 case LUA_TLCL: {
277 gco2lcl(o)->gclist = g->gray;
278 g->gray = o;
279 return;
280 }
281 case LUA_TCCL: {
282 gco2ccl(o)->gclist = g->gray;
283 g->gray = o;
284 return;
285 }
286 case LUA_TTABLE: {
287 linktable(gco2t(o), &g->gray);
288 return;
289 }
290 case LUA_TTHREAD: {
291 gco2th(o)->gclist = g->gray;
292 g->gray = o;
293 return;
294 }
295 case LUA_TPROTO: {
296 gco2p(o)->gclist = g->gray;
297 g->gray = o;
298 return;
299 }
300 default: lua_assert(0); return;
301 }
302 gray2black(o);
303 g->GCmemtrav += size;
304 }
305
306
307 /*
308 ** mark metamethods for basic types
309 */
310 static void markmt (global_State *g) {
311 int i;
312 for (i=0; i < LUA_NUMTAGS; i++)
313 markobject(g, g->mt[i]);
314 }
315
316
317 /*
318 ** mark all objects in list of being-finalized
319 */
320 static void markbeingfnz (global_State *g) {
321 GCObject *o;
322 for (o = g->tobefnz; o != NULL; o = gch(o)->next) {
323 makewhite(g, o);
324 reallymarkobject(g, o);
325 }
326 }
327
328
329 /*
330 ** mark all values stored in marked open upvalues. (See comment in
331 ** 'lstate.h'.)
332 */
333 static void remarkupvals (global_State *g) {
334 UpVal *uv;
335 for (uv = g->uvhead.u.l.next; uv != &g->uvhead; uv = uv->u.l.next) {
336 if (isgray(obj2gco(uv)))
337 markvalue(g, uv->v);
338 }
339 }
340
341
342 /*
343 ** mark root set and reset all gray lists, to start a new
344 ** incremental (or full) collection
345 */
346 static void markroot (global_State *g) {
347 g->gray = g->grayagain = NULL;
348 g->weak = g->allweak = g->ephemeron = NULL;
349 markobject(g, g->mainthread);
350 markvalue(g, &g->l_registry);
351 markmt(g);
352 markbeingfnz(g); /* mark any finalizing object left from previous cycle */
353 }
354
355 /* }====================================================== */
356
357
358 /*
359 ** {======================================================
360 ** Traverse functions
361 ** =======================================================
362 */
363
364 static void traverseweakvalue (global_State *g, Table *h) {
365 Node *n, *limit = gnodelast(h);
366 /* if there is array part, assume it may have white values (do not
367 traverse it just to check) */
368 int hasclears = (h->sizearray > 0);
369 for (n = gnode(h, 0); n < limit; n++) {
370 checkdeadkey(n);
371 if (ttisnil(gval(n))) /* entry is empty? */
372 removeentry(n); /* remove it */
373 else {
374 lua_assert(!ttisnil(gkey(n)));
375 markvalue(g, gkey(n)); /* mark key */
376 if (!hasclears && iscleared(g, gval(n))) /* is there a white value? */
377 hasclears = 1; /* table will have to be cleared */
378 }
379 }
380 if (hasclears)
381 linktable(h, &g->weak); /* has to be cleared later */
382 else /* no white values */
383 linktable(h, &g->grayagain); /* no need to clean */
384 }
385
386
387 static int traverseephemeron (global_State *g, Table *h) {
388 int marked = 0; /* true if an object is marked in this traversal */
389 int hasclears = 0; /* true if table has white keys */
390 int prop = 0; /* true if table has entry "white-key -> white-value" */
391 Node *n, *limit = gnodelast(h);
392 int i;
393 /* traverse array part (numeric keys are 'strong') */
394 for (i = 0; i < h->sizearray; i++) {
395 if (valiswhite(&h->array[i])) {
396 marked = 1;
397 reallymarkobject(g, gcvalue(&h->array[i]));
398 }
399 }
400 /* traverse hash part */
401 for (n = gnode(h, 0); n < limit; n++) {
402 checkdeadkey(n);
403 if (ttisnil(gval(n))) /* entry is empty? */
404 removeentry(n); /* remove it */
405 else if (iscleared(g, gkey(n))) { /* key is not marked (yet)? */
406 hasclears = 1; /* table must be cleared */
407 if (valiswhite(gval(n))) /* value not marked yet? */
408 prop = 1; /* must propagate again */
409 }
410 else if (valiswhite(gval(n))) { /* value not marked yet? */
411 marked = 1;
412 reallymarkobject(g, gcvalue(gval(n))); /* mark it now */
413 }
414 }
415 if (prop)
416 linktable(h, &g->ephemeron); /* have to propagate again */
417 else if (hasclears) /* does table have white keys? */
418 linktable(h, &g->allweak); /* may have to clean white keys */
419 else /* no white keys */
420 linktable(h, &g->grayagain); /* no need to clean */
421 return marked;
422 }
423
424
425 static void traversestrongtable (global_State *g, Table *h) {
426 Node *n, *limit = gnodelast(h);
427 int i;
428 for (i = 0; i < h->sizearray; i++) /* traverse array part */
429 markvalue(g, &h->array[i]);
430 for (n = gnode(h, 0); n < limit; n++) { /* traverse hash part */
431 checkdeadkey(n);
432 if (ttisnil(gval(n))) /* entry is empty? */
433 removeentry(n); /* remove it */
434 else {
435 lua_assert(!ttisnil(gkey(n)));
436 markvalue(g, gkey(n)); /* mark key */
437 markvalue(g, gval(n)); /* mark value */
438 }
439 }
440 }
441
442
443 static lu_mem traversetable (global_State *g, Table *h) {
444 const char *weakkey, *weakvalue;
445 const TValue *mode = gfasttm(g, h->metatable, TM_MODE);
446 markobject(g, h->metatable);
447 if (mode && ttisstring(mode) && /* is there a weak mode? */
448 ((weakkey = strchr(svalue(mode), 'k')),
449 (weakvalue = strchr(svalue(mode), 'v')),
450 (weakkey || weakvalue))) { /* is really weak? */
451 black2gray(obj2gco(h)); /* keep table gray */
452 if (!weakkey) /* strong keys? */
453 traverseweakvalue(g, h);
454 else if (!weakvalue) /* strong values? */
455 traverseephemeron(g, h);
456 else /* all weak */
457 linktable(h, &g->allweak); /* nothing to traverse now */
458 }
459 else /* not weak */
460 traversestrongtable(g, h);
461 return sizeof(Table) + sizeof(TValue) * h->sizearray +
462 sizeof(Node) * sizenode(h);
463 }
464
465
466 static int traverseproto (global_State *g, Proto *f) {
467 int i;
468 if (f->cache && iswhite(obj2gco(f->cache)))
469 f->cache = NULL; /* allow cache to be collected */
470 markobject(g, f->source);
471 for (i = 0; i < f->sizek; i++) /* mark literals */
472 markvalue(g, &f->k[i]);
473 for (i = 0; i < f->sizeupvalues; i++) /* mark upvalue names */
474 markobject(g, f->upvalues[i].name);
475 for (i = 0; i < f->sizep; i++) /* mark nested protos */
476 markobject(g, f->p[i]);
477 for (i = 0; i < f->sizelocvars; i++) /* mark local-variable names */
478 markobject(g, f->locvars[i].varname);
479 return sizeof(Proto) + sizeof(Instruction) * f->sizecode +
480 sizeof(Proto *) * f->sizep +
481 sizeof(TValue) * f->sizek +
482 sizeof(int) * f->sizelineinfo +
483 sizeof(LocVar) * f->sizelocvars +
484 sizeof(Upvaldesc) * f->sizeupvalues;
485 }
486
487
488 static lu_mem traverseCclosure (global_State *g, CClosure *cl) {
489 int i;
490 for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */
491 markvalue(g, &cl->upvalue[i]);
492 return sizeCclosure(cl->nupvalues);
493 }
494
495 static lu_mem traverseLclosure (global_State *g, LClosure *cl) {
496 int i;
497 markobject(g, cl->p); /* mark its prototype */
498 for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */
499 markobject(g, cl->upvals[i]);
500 return sizeLclosure(cl->nupvalues);
501 }
502
503
504 static lu_mem traversestack (global_State *g, lua_State *th) {
505 StkId o = th->stack;
506 if (o == NULL)
507 return 1; /* stack not completely built yet */
508 for (; o < th->top; o++)
509 markvalue(g, o);
510 if (g->gcstate == GCSatomic) { /* final traversal? */
511 StkId lim = th->stack + th->stacksize; /* real end of stack */
512 for (; o < lim; o++) /* clear not-marked stack slice */
513 setnilvalue(o);
514 }
515 return sizeof(lua_State) + sizeof(TValue) * th->stacksize;
516 }
517
518
519 /*
520 ** traverse one gray object, turning it to black (except for threads,
521 ** which are always gray).
522 */
523 static void propagatemark (global_State *g) {
524 lu_mem size;
525 GCObject *o = g->gray;
526 lua_assert(isgray(o));
527 gray2black(o);
528 switch (gch(o)->tt) {
529 case LUA_TTABLE: {
530 Table *h = gco2t(o);
531 g->gray = h->gclist; /* remove from 'gray' list */
532 size = traversetable(g, h);
533 break;
534 }
535 case LUA_TLCL: {
536 LClosure *cl = gco2lcl(o);
537 g->gray = cl->gclist; /* remove from 'gray' list */
538 size = traverseLclosure(g, cl);
539 break;
540 }
541 case LUA_TCCL: {
542 CClosure *cl = gco2ccl(o);
543 g->gray = cl->gclist; /* remove from 'gray' list */
544 size = traverseCclosure(g, cl);
545 break;
546 }
547 case LUA_TTHREAD: {
548 lua_State *th = gco2th(o);
549 g->gray = th->gclist; /* remove from 'gray' list */
550 th->gclist = g->grayagain;
551 g->grayagain = o; /* insert into 'grayagain' list */
552 black2gray(o);
553 size = traversestack(g, th);
554 break;
555 }
556 case LUA_TPROTO: {
557 Proto *p = gco2p(o);
558 g->gray = p->gclist; /* remove from 'gray' list */
559 size = traverseproto(g, p);
560 break;
561 }
562 default: lua_assert(0); return;
563 }
564 g->GCmemtrav += size;
565 }
566
567
568 static void propagateall (global_State *g) {
569 while (g->gray) propagatemark(g);
570 }
571
572
573 static void propagatelist (global_State *g, GCObject *l) {
574 lua_assert(g->gray == NULL); /* no grays left */
575 g->gray = l;
576 propagateall(g); /* traverse all elements from 'l' */
577 }
578
579 /*
580 ** retraverse all gray lists. Because tables may be reinserted in other
581 ** lists when traversed, traverse the original lists to avoid traversing
582 ** twice the same table (which is not wrong, but inefficient)
583 */
584 static void retraversegrays (global_State *g) {
585 GCObject *weak = g->weak; /* save original lists */
586 GCObject *grayagain = g->grayagain;
587 GCObject *ephemeron = g->ephemeron;
588 g->weak = g->grayagain = g->ephemeron = NULL;
589 propagateall(g); /* traverse main gray list */
590 propagatelist(g, grayagain);
591 propagatelist(g, weak);
592 propagatelist(g, ephemeron);
593 }
594
595
596 static void convergeephemerons (global_State *g) {
597 int changed;
598 do {
599 GCObject *w;
600 GCObject *next = g->ephemeron; /* get ephemeron list */
601 g->ephemeron = NULL; /* tables will return to this list when traversed */
602 changed = 0;
603 while ((w = next) != NULL) {
604 next = gco2t(w)->gclist;
605 if (traverseephemeron(g, gco2t(w))) { /* traverse marked some value? */
606 propagateall(g); /* propagate changes */
607 changed = 1; /* will have to revisit all ephemeron tables */
608 }
609 }
610 } while (changed);
611 }
612
613 /* }====================================================== */
614
615
616 /*
617 ** {======================================================
618 ** Sweep Functions
619 ** =======================================================
620 */
621
622
623 /*
624 ** clear entries with unmarked keys from all weaktables in list 'l' up
625 ** to element 'f'
626 */
627 static void clearkeys (global_State *g, GCObject *l, GCObject *f) {
628 for (; l != f; l = gco2t(l)->gclist) {
629 Table *h = gco2t(l);
630 Node *n, *limit = gnodelast(h);
631 for (n = gnode(h, 0); n < limit; n++) {
632 if (!ttisnil(gval(n)) && (iscleared(g, gkey(n)))) {
633 setnilvalue(gval(n)); /* remove value ... */
634 removeentry(n); /* and remove entry from table */
635 }
636 }
637 }
638 }
639
640
641 /*
642 ** clear entries with unmarked values from all weaktables in list 'l' up
643 ** to element 'f'
644 */
645 static void clearvalues (global_State *g, GCObject *l, GCObject *f) {
646 for (; l != f; l = gco2t(l)->gclist) {
647 Table *h = gco2t(l);
648 Node *n, *limit = gnodelast(h);
649 int i;
650 for (i = 0; i < h->sizearray; i++) {
651 TValue *o = &h->array[i];
652 if (iscleared(g, o)) /* value was collected? */
653 setnilvalue(o); /* remove value */
654 }
655 for (n = gnode(h, 0); n < limit; n++) {
656 if (!ttisnil(gval(n)) && iscleared(g, gval(n))) {
657 setnilvalue(gval(n)); /* remove value ... */
658 removeentry(n); /* and remove entry from table */
659 }
660 }
661 }
662 }
663
664
665 static void freeobj (lua_State *L, GCObject *o) {
666 switch (gch(o)->tt) {
667 case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break;
668 case LUA_TLCL: {
669 luaM_freemem(L, o, sizeLclosure(gco2lcl(o)->nupvalues));
670 break;
671 }
672 case LUA_TCCL: {
673 luaM_freemem(L, o, sizeCclosure(gco2ccl(o)->nupvalues));
674 break;
675 }
676 case LUA_TUPVAL: luaF_freeupval(L, gco2uv(o)); break;
677 case LUA_TTABLE: luaH_free(L, gco2t(o)); break;
678 case LUA_TTHREAD: luaE_freethread(L, gco2th(o)); break;
679 case LUA_TUSERDATA: luaM_freemem(L, o, sizeudata(gco2u(o))); break;
680 case LUA_TSHRSTR:
681 G(L)->strt.nuse--;
682 /* go through */
683 case LUA_TLNGSTR: {
684 luaM_freemem(L, o, sizestring(gco2ts(o)));
685 break;
686 }
687 default: lua_assert(0);
688 }
689 }
690
691
692 #define sweepwholelist(L,p) sweeplist(L,p,MAX_LUMEM)
693 static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count);
694
695
696 /*
697 ** sweep the (open) upvalues of a thread and resize its stack and
698 ** list of call-info structures.
699 */
700 static void sweepthread (lua_State *L, lua_State *L1) {
701 if (L1->stack == NULL) return; /* stack not completely built yet */
702 sweepwholelist(L, &L1->openupval); /* sweep open upvalues */
703 luaE_freeCI(L1); /* free extra CallInfo slots */
704 /* should not change the stack during an emergency gc cycle */
705 if (G(L)->gckind != KGC_EMERGENCY)
706 luaD_shrinkstack(L1);
707 }
708
709
710 /*
711 ** sweep at most 'count' elements from a list of GCObjects erasing dead
712 ** objects, where a dead (not alive) object is one marked with the "old"
713 ** (non current) white and not fixed.
714 ** In non-generational mode, change all non-dead objects back to white,
715 ** preparing for next collection cycle.
716 ** In generational mode, keep black objects black, and also mark them as
717 ** old; stop when hitting an old object, as all objects after that
718 ** one will be old too.
719 ** When object is a thread, sweep its list of open upvalues too.
720 */
721 static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
722 global_State *g = G(L);
723 int ow = otherwhite(g);
724 int toclear, toset; /* bits to clear and to set in all live objects */
725 int tostop; /* stop sweep when this is true */
726 if (isgenerational(g)) { /* generational mode? */
727 toclear = ~0; /* clear nothing */
728 toset = bitmask(OLDBIT); /* set the old bit of all surviving objects */
729 tostop = bitmask(OLDBIT); /* do not sweep old generation */
730 }
731 else { /* normal mode */
732 toclear = maskcolors; /* clear all color bits + old bit */
733 toset = luaC_white(g); /* make object white */
734 tostop = 0; /* do not stop */
735 }
736 while (*p != NULL && count-- > 0) {
737 GCObject *curr = *p;
738 int marked = gch(curr)->marked;
739 if (isdeadm(ow, marked)) { /* is 'curr' dead? */
740 *p = gch(curr)->next; /* remove 'curr' from list */
741 freeobj(L, curr); /* erase 'curr' */
742 }
743 else {
744 if (testbits(marked, tostop))
745 return NULL; /* stop sweeping this list */
746 if (gch(curr)->tt == LUA_TTHREAD)
747 sweepthread(L, gco2th(curr)); /* sweep thread's upvalues */
748 /* update marks */
749 gch(curr)->marked = cast_byte((marked & toclear) | toset);
750 p = &gch(curr)->next; /* go to next element */
751 }
752 }
753 return (*p == NULL) ? NULL : p;
754 }
755
756
757 /*
758 ** sweep a list until a live object (or end of list)
759 */
760 static GCObject **sweeptolive (lua_State *L, GCObject **p, int *n) {
761 GCObject ** old = p;
762 int i = 0;
763 do {
764 i++;
765 p = sweeplist(L, p, 1);
766 } while (p == old);
767 if (n) *n += i;
768 return p;
769 }
770
771 /* }====================================================== */
772
773
774 /*
775 ** {======================================================
776 ** Finalization
777 ** =======================================================
778 */
779
780 static void checkSizes (lua_State *L) {
781 global_State *g = G(L);
782 if (g->gckind != KGC_EMERGENCY) { /* do not change sizes in emergency */
783 int hs = g->strt.size / 2; /* half the size of the string table */
784 if (g->strt.nuse < cast(lu_int32, hs)) /* using less than that half? */
785 luaS_resize(L, hs); /* halve its size */
786 luaZ_freebuffer(L, &g->buff); /* free concatenation buffer */
787 }
788 }
789
790
791 static GCObject *udata2finalize (global_State *g) {
792 GCObject *o = g->tobefnz; /* get first element */
793 lua_assert(isfinalized(o));
794 g->tobefnz = gch(o)->next; /* remove it from 'tobefnz' list */
795 gch(o)->next = g->allgc; /* return it to 'allgc' list */
796 g->allgc = o;
797 resetbit(gch(o)->marked, SEPARATED); /* mark that it is not in 'tobefnz' */
798 lua_assert(!isold(o)); /* see MOVE OLD rule */
799 if (!keepinvariant(g)) /* not keeping invariant? */
800 makewhite(g, o); /* "sweep" object */
801 return o;
802 }
803
804
805 static void dothecall (lua_State *L, void *ud) {
806 UNUSED(ud);
807 luaD_call(L, L->top - 2, 0, 0);
808 }
809
810
811 static void GCTM (lua_State *L, int propagateerrors) {
812 global_State *g = G(L);
813 const TValue *tm;
814 TValue v;
815 setgcovalue(L, &v, udata2finalize(g));
816 tm = luaT_gettmbyobj(L, &v, TM_GC);
817 if (tm != NULL && ttisfunction(tm)) { /* is there a finalizer? */
818 int status;
819 lu_byte oldah = L->allowhook;
820 int running = g->gcrunning;
821 L->allowhook = 0; /* stop debug hooks during GC metamethod */
822 g->gcrunning = 0; /* avoid GC steps */
823 setobj2s(L, L->top, tm); /* push finalizer... */
824 setobj2s(L, L->top + 1, &v); /* ... and its argument */
825 L->top += 2; /* and (next line) call the finalizer */
826 status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top - 2), 0);
827 L->allowhook = oldah; /* restore hooks */
828 g->gcrunning = running; /* restore state */
829 if (status != LUA_OK && propagateerrors) { /* error while running __gc? */
830 if (status == LUA_ERRRUN) { /* is there an error object? */
831 const char *msg = (ttisstring(L->top - 1))
832 ? svalue(L->top - 1)
833 : "no message";
834 luaO_pushfstring(L, "error in __gc metamethod (%s)", msg);
835 status = LUA_ERRGCMM; /* error in __gc metamethod */
836 }
837 luaD_throw(L, status); /* re-throw error */
838 }
839 }
840 }
841
842
843 /*
844 ** move all unreachable objects (or 'all' objects) that need
845 ** finalization from list 'finobj' to list 'tobefnz' (to be finalized)
846 */
847 static void separatetobefnz (lua_State *L, int all) {
848 global_State *g = G(L);
849 GCObject **p = &g->finobj;
850 GCObject *curr;
851 GCObject **lastnext = &g->tobefnz;
852 /* find last 'next' field in 'tobefnz' list (to add elements in its end) */
853 while (*lastnext != NULL)
854 lastnext = &gch(*lastnext)->next;
855 while ((curr = *p) != NULL) { /* traverse all finalizable objects */
856 lua_assert(!isfinalized(curr));
857 lua_assert(testbit(gch(curr)->marked, SEPARATED));
858 if (!(all || iswhite(curr))) /* not being collected? */
859 p = &gch(curr)->next; /* don't bother with it */
860 else {
861 l_setbit(gch(curr)->marked, FINALIZEDBIT); /* won't be finalized again */
862 *p = gch(curr)->next; /* remove 'curr' from 'finobj' list */
863 gch(curr)->next = *lastnext; /* link at the end of 'tobefnz' list */
864 *lastnext = curr;
865 lastnext = &gch(curr)->next;
866 }
867 }
868 }
869
870
871 /*
872 ** if object 'o' has a finalizer, remove it from 'allgc' list (must
873 ** search the list to find it) and link it in 'finobj' list.
874 */
875 void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
876 global_State *g = G(L);
877 if (testbit(gch(o)->marked, SEPARATED) || /* obj. is already separated... */
878 isfinalized(o) || /* ... or is finalized... */
879 gfasttm(g, mt, TM_GC) == NULL) /* or has no finalizer? */
880 return; /* nothing to be done */
881 else { /* move 'o' to 'finobj' list */
882 GCObject **p;
883 GCheader *ho = gch(o);
884 if (g->sweepgc == &ho->next) { /* avoid removing current sweep object */
885 lua_assert(issweepphase(g));
886 g->sweepgc = sweeptolive(L, g->sweepgc, NULL);
887 }
888 /* search for pointer pointing to 'o' */
889 for (p = &g->allgc; *p != o; p = &gch(*p)->next) { /* empty */ }
890 *p = ho->next; /* remove 'o' from root list */
891 ho->next = g->finobj; /* link it in list 'finobj' */
892 g->finobj = o;
893 l_setbit(ho->marked, SEPARATED); /* mark it as such */
894 if (!keepinvariant(g)) /* not keeping invariant? */
895 makewhite(g, o); /* "sweep" object */
896 else
897 resetoldbit(o); /* see MOVE OLD rule */
898 }
899 }
900
901 /* }====================================================== */
902
903
904 /*
905 ** {======================================================
906 ** GC control
907 ** =======================================================
908 */
909
910
911 #define sweepphases \
912 (bitmask(GCSsweepstring) | bitmask(GCSsweepudata) | bitmask(GCSsweep))
913
914
915 /*
916 ** enter first sweep phase (strings) and prepare pointers for other
917 ** sweep phases. The calls to 'sweeptolive' make pointers point to an
918 ** object inside the list (instead of to the header), so that the real
919 ** sweep do not need to skip objects created between "now" and the start
920 ** of the real sweep.
921 ** Returns how many objects it sweeped.
922 */
923 static int entersweep (lua_State *L) {
924 global_State *g = G(L);
925 int n = 0;
926 g->gcstate = GCSsweepstring;
927 lua_assert(g->sweepgc == NULL && g->sweepfin == NULL);
928 /* prepare to sweep strings, finalizable objects, and regular objects */
929 g->sweepstrgc = 0;
930 g->sweepfin = sweeptolive(L, &g->finobj, &n);
931 g->sweepgc = sweeptolive(L, &g->allgc, &n);
932 return n;
933 }
934
935
936 /*
937 ** change GC mode
938 */
939 void luaC_changemode (lua_State *L, int mode) {
940 global_State *g = G(L);
941 if (mode == g->gckind) return; /* nothing to change */
942 if (mode == KGC_GEN) { /* change to generational mode */
943 /* make sure gray lists are consistent */
944 luaC_runtilstate(L, bitmask(GCSpropagate));
945 g->GCestimate = gettotalbytes(g);
946 g->gckind = KGC_GEN;
947 }
948 else { /* change to incremental mode */
949 /* sweep all objects to turn them back to white
950 (as white has not changed, nothing extra will be collected) */
951 g->gckind = KGC_NORMAL;
952 entersweep(L);
953 luaC_runtilstate(L, ~sweepphases);
954 }
955 }
956
957
958 /*
959 ** call all pending finalizers
960 */
961 static void callallpendingfinalizers (lua_State *L, int propagateerrors) {
962 global_State *g = G(L);
963 while (g->tobefnz) {
964 resetoldbit(g->tobefnz);
965 GCTM(L, propagateerrors);
966 }
967 }
968
969
970 void luaC_freeallobjects (lua_State *L) {
971 global_State *g = G(L);
972 int i;
973 separatetobefnz(L, 1); /* separate all objects with finalizers */
974 lua_assert(g->finobj == NULL);
975 callallpendingfinalizers(L, 0);
976 g->currentwhite = WHITEBITS; /* this "white" makes all objects look dead */
977 g->gckind = KGC_NORMAL;
978 sweepwholelist(L, &g->finobj); /* finalizers can create objs. in 'finobj' */
979 sweepwholelist(L, &g->allgc);
980 for (i = 0; i < g->strt.size; i++) /* free all string lists */
981 sweepwholelist(L, &g->strt.hash[i]);
982 lua_assert(g->strt.nuse == 0);
983 }
984
985
986 static l_mem atomic (lua_State *L) {
987 global_State *g = G(L);
988 l_mem work = -g->GCmemtrav; /* start counting work */
989 GCObject *origweak, *origall;
990 lua_assert(!iswhite(obj2gco(g->mainthread)));
991 markobject(g, L); /* mark running thread */
992 /* registry and global metatables may be changed by API */
993 markvalue(g, &g->l_registry);
994 markmt(g); /* mark basic metatables */
995 /* remark occasional upvalues of (maybe) dead threads */
996 remarkupvals(g);
997 propagateall(g); /* propagate changes */
998 work += g->GCmemtrav; /* stop counting (do not (re)count grays) */
999 /* traverse objects caught by write barrier and by 'remarkupvals' */
1000 retraversegrays(g);
1001 work -= g->GCmemtrav; /* restart counting */
1002 convergeephemerons(g);
1003 /* at this point, all strongly accessible objects are marked. */
1004 /* clear values from weak tables, before checking finalizers */
1005 clearvalues(g, g->weak, NULL);
1006 clearvalues(g, g->allweak, NULL);
1007 origweak = g->weak; origall = g->allweak;
1008 work += g->GCmemtrav; /* stop counting (objects being finalized) */
1009 separatetobefnz(L, 0); /* separate objects to be finalized */
1010 markbeingfnz(g); /* mark objects that will be finalized */
1011 propagateall(g); /* remark, to propagate `preserveness' */
1012 work -= g->GCmemtrav; /* restart counting */
1013 convergeephemerons(g);
1014 /* at this point, all resurrected objects are marked. */
1015 /* remove dead objects from weak tables */
1016 clearkeys(g, g->ephemeron, NULL); /* clear keys from all ephemeron tables */
1017 clearkeys(g, g->allweak, NULL); /* clear keys from all allweak tables */
1018 /* clear values from resurrected weak tables */
1019 clearvalues(g, g->weak, origweak);
1020 clearvalues(g, g->allweak, origall);
1021 g->currentwhite = cast_byte(otherwhite(g)); /* flip current white */
1022 work += g->GCmemtrav; /* complete counting */
1023 return work; /* estimate of memory marked by 'atomic' */
1024 }
1025
1026
1027 static lu_mem singlestep (lua_State *L) {
1028 global_State *g = G(L);
1029 switch (g->gcstate) {
1030 case GCSpause: {
1031 g->GCmemtrav = 0; /* start to count memory traversed */
1032 if (!isgenerational(g))
1033 markroot(g); /* start a new collection */
1034 /* in any case, root must be marked at this point */
1035 lua_assert(!iswhite(obj2gco(g->mainthread))
1036 && !iswhite(gcvalue(&g->l_registry)));
1037 g->gcstate = GCSpropagate;
1038 return g->GCmemtrav;
1039 }
1040 case GCSpropagate: {
1041 if (g->gray) {
1042 lu_mem oldtrav = g->GCmemtrav;
1043 propagatemark(g);
1044 return g->GCmemtrav - oldtrav; /* memory traversed in this step */
1045 }
1046 else { /* no more `gray' objects */
1047 lu_mem work;
1048 int sw;
1049 g->gcstate = GCSatomic; /* finish mark phase */
1050 g->GCestimate = g->GCmemtrav; /* save what was counted */;
1051 work = atomic(L); /* add what was traversed by 'atomic' */
1052 g->GCestimate += work; /* estimate of total memory traversed */
1053 sw = entersweep(L);
1054 return work + sw * GCSWEEPCOST;
1055 }
1056 }
1057 case GCSsweepstring: {
1058 int i;
1059 for (i = 0; i < GCSWEEPMAX && g->sweepstrgc + i < g->strt.size; i++)
1060 sweepwholelist(L, &g->strt.hash[g->sweepstrgc + i]);
1061 g->sweepstrgc += i;
1062 if (g->sweepstrgc >= g->strt.size) /* no more strings to sweep? */
1063 g->gcstate = GCSsweepudata;
1064 return i * GCSWEEPCOST;
1065 }
1066 case GCSsweepudata: {
1067 if (g->sweepfin) {
1068 g->sweepfin = sweeplist(L, g->sweepfin, GCSWEEPMAX);
1069 return GCSWEEPMAX*GCSWEEPCOST;
1070 }
1071 else {
1072 g->gcstate = GCSsweep;
1073 return 0;
1074 }
1075 }
1076 case GCSsweep: {
1077 if (g->sweepgc) {
1078 g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
1079 return GCSWEEPMAX*GCSWEEPCOST;
1080 }
1081 else {
1082 /* sweep main thread */
1083 GCObject *mt = obj2gco(g->mainthread);
1084 sweeplist(L, &mt, 1);
1085 checkSizes(L);
1086 g->gcstate = GCSpause; /* finish collection */
1087 return GCSWEEPCOST;
1088 }
1089 }
1090 default: lua_assert(0); return 0;
1091 }
1092 }
1093
1094
1095 /*
1096 ** advances the garbage collector until it reaches a state allowed
1097 ** by 'statemask'
1098 */
1099 void luaC_runtilstate (lua_State *L, int statesmask) {
1100 global_State *g = G(L);
1101 while (!testbit(statesmask, g->gcstate))
1102 singlestep(L);
1103 }
1104
1105
1106 static void generationalcollection (lua_State *L) {
1107 global_State *g = G(L);
1108 if (g->GCestimate == 0) { /* signal for another major collection? */
1109 luaC_fullgc(L, 0); /* perform a full regular collection */
1110 g->GCestimate = gettotalbytes(g); /* update control */
1111 }
1112 else {
1113 lu_mem estimate = g->GCestimate;
1114 luaC_runtilstate(L, ~bitmask(GCSpause)); /* run complete cycle */
1115 luaC_runtilstate(L, bitmask(GCSpause));
1116 if (gettotalbytes(g) > (estimate / 100) * g->gcmajorinc)
1117 g->GCestimate = 0; /* signal for a major collection */
1118 }
1119 luaE_setdebt(g, stddebt(g));
1120 }
1121
1122
1123 static void incstep (lua_State *L) {
1124 global_State *g = G(L);
1125 l_mem debt = g->GCdebt;
1126 int stepmul = g->gcstepmul;
1127 if (stepmul < 40) stepmul = 40; /* avoid ridiculous low values */
1128 /* convert debt from Kb to 'work units' (avoid zero debt and overflows) */
1129 debt = (debt / STEPMULADJ) + 1;
1130 debt = (debt < MAX_LMEM / stepmul) ? debt * stepmul : MAX_LMEM;
1131 do { /* always perform at least one single step */
1132 lu_mem work = singlestep(L); /* do some work */
1133 debt -= work;
1134 } while (debt > -GCSTEPSIZE && g->gcstate != GCSpause);
1135 if (g->gcstate == GCSpause)
1136 debt = stddebtest(g, g->GCestimate); /* pause until next cycle */
1137 else
1138 debt = (debt / stepmul) * STEPMULADJ; /* convert 'work units' to Kb */
1139 luaE_setdebt(g, debt);
1140 }
1141
1142
1143 /*
1144 ** performs a basic GC step
1145 */
1146 void luaC_forcestep (lua_State *L) {
1147 global_State *g = G(L);
1148 int i;
1149 if (isgenerational(g)) generationalcollection(L);
1150 else incstep(L);
1151 /* run a few finalizers (or all of them at the end of a collect cycle) */
1152 for (i = 0; g->tobefnz && (i < GCFINALIZENUM || g->gcstate == GCSpause); i++)
1153 GCTM(L, 1); /* call one finalizer */
1154 }
1155
1156
1157 /*
1158 ** performs a basic GC step only if collector is running
1159 */
1160 void luaC_step (lua_State *L) {
1161 global_State *g = G(L);
1162 if (g->gcrunning) luaC_forcestep(L);
1163 else luaE_setdebt(g, -GCSTEPSIZE); /* avoid being called too often */
1164 }
1165
1166
1167
1168 /*
1169 ** performs a full GC cycle; if "isemergency", does not call
1170 ** finalizers (which could change stack positions)
1171 */
1172 void luaC_fullgc (lua_State *L, int isemergency) {
1173 global_State *g = G(L);
1174 int origkind = g->gckind;
1175 int someblack = keepinvariant(g);
1176 lua_assert(origkind != KGC_EMERGENCY);
1177 if (isemergency) /* do not run finalizers during emergency GC */
1178 g->gckind = KGC_EMERGENCY;
1179 else {
1180 g->gckind = KGC_NORMAL;
1181 callallpendingfinalizers(L, 1);
1182 }
1183 if (someblack) { /* may there be some black objects? */
1184 /* must sweep all objects to turn them back to white
1185 (as white has not changed, nothing will be collected) */
1186 entersweep(L);
1187 }
1188 /* finish any pending sweep phase to start a new cycle */
1189 luaC_runtilstate(L, bitmask(GCSpause));
1190 /* run entire collector */
1191 luaC_runtilstate(L, ~bitmask(GCSpause));
1192 luaC_runtilstate(L, bitmask(GCSpause));
1193 if (origkind == KGC_GEN) { /* generational mode? */
1194 /* generational mode must always start in propagate phase */
1195 luaC_runtilstate(L, bitmask(GCSpropagate));
1196 }
1197 g->gckind = origkind;
1198 luaE_setdebt(g, stddebt(g));
1199 if (!isemergency) /* do not run finalizers during emergency GC */
1200 callallpendingfinalizers(L, 1);
1201 }
1202
1203 /* }====================================================== */
1204
1205