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/src/middleware/lua/lgc.c

https://bitbucket.org/vivkin/gam3b00bs/
C | 711 lines | 582 code | 86 blank | 43 comment | 162 complexity | 94ed711f5a231c770b015f62c7fb1ac5 MD5 | raw file
  1/*
  2** $Id: lgc.c,v 2.38.1.1 2007/12/27 13:02:25 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#define GCSTEPSIZE	1024u
 27#define GCSWEEPMAX	40
 28#define GCSWEEPCOST	10
 29#define GCFINALIZECOST	100
 30
 31
 32#define maskmarks	cast_byte(~(bitmask(BLACKBIT)|WHITEBITS))
 33
 34#define makewhite(g,x)	\
 35   ((x)->gch.marked = cast_byte(((x)->gch.marked & maskmarks) | luaC_white(g)))
 36
 37#define white2gray(x)	reset2bits((x)->gch.marked, WHITE0BIT, WHITE1BIT)
 38#define black2gray(x)	resetbit((x)->gch.marked, BLACKBIT)
 39
 40#define stringmark(s)	reset2bits((s)->tsv.marked, WHITE0BIT, WHITE1BIT)
 41
 42
 43#define isfinalized(u)		testbit((u)->marked, FINALIZEDBIT)
 44#define markfinalized(u)	l_setbit((u)->marked, FINALIZEDBIT)
 45
 46
 47#define KEYWEAK         bitmask(KEYWEAKBIT)
 48#define VALUEWEAK       bitmask(VALUEWEAKBIT)
 49
 50
 51
 52#define markvalue(g,o) { checkconsistency(o); \
 53  if (iscollectable(o) && iswhite(gcvalue(o))) reallymarkobject(g,gcvalue(o)); }
 54
 55#define markobject(g,t) { if (iswhite(obj2gco(t))) \
 56		reallymarkobject(g, obj2gco(t)); }
 57
 58
 59#define setthreshold(g)  (g->GCthreshold = (g->estimate/100) * g->gcpause)
 60
 61
 62static void removeentry (Node *n) {
 63  lua_assert(ttisnil(gval(n)));
 64  if (iscollectable(gkey(n)))
 65    setttype(gkey(n), LUA_TDEADKEY);  /* dead key; remove it */
 66}
 67
 68
 69static void reallymarkobject (global_State *g, GCObject *o) {
 70  lua_assert(iswhite(o) && !isdead(g, o));
 71  white2gray(o);
 72  switch (o->gch.tt) {
 73    case LUA_TSTRING: {
 74      return;
 75    }
 76    case LUA_TUSERDATA: {
 77      Table *mt = gco2u(o)->metatable;
 78      gray2black(o);  /* udata are never gray */
 79      if (mt) markobject(g, mt);
 80      markobject(g, gco2u(o)->env);
 81      return;
 82    }
 83    case LUA_TUPVAL: {
 84      UpVal *uv = gco2uv(o);
 85      markvalue(g, uv->v);
 86      if (uv->v == &uv->u.value)  /* closed? */
 87        gray2black(o);  /* open upvalues are never black */
 88      return;
 89    }
 90    case LUA_TFUNCTION: {
 91      gco2cl(o)->c.gclist = g->gray;
 92      g->gray = o;
 93      break;
 94    }
 95    case LUA_TTABLE: {
 96      gco2h(o)->gclist = g->gray;
 97      g->gray = o;
 98      break;
 99    }
100    case LUA_TTHREAD: {
101      gco2th(o)->gclist = g->gray;
102      g->gray = o;
103      break;
104    }
105    case LUA_TPROTO: {
106      gco2p(o)->gclist = g->gray;
107      g->gray = o;
108      break;
109    }
110    default: lua_assert(0);
111  }
112}
113
114
115static void marktmu (global_State *g) {
116  GCObject *u = g->tmudata;
117  if (u) {
118    do {
119      u = u->gch.next;
120      makewhite(g, u);  /* may be marked, if left from previous GC */
121      reallymarkobject(g, u);
122    } while (u != g->tmudata);
123  }
124}
125
126
127/* move `dead' udata that need finalization to list `tmudata' */
128size_t luaC_separateudata (lua_State *L, int all) {
129  global_State *g = G(L);
130  size_t deadmem = 0;
131  GCObject **p = &g->mainthread->next;
132  GCObject *curr;
133  while ((curr = *p) != NULL) {
134    if (!(iswhite(curr) || all) || isfinalized(gco2u(curr)))
135      p = &curr->gch.next;  /* don't bother with them */
136    else if (fasttm(L, gco2u(curr)->metatable, TM_GC) == NULL) {
137      markfinalized(gco2u(curr));  /* don't need finalization */
138      p = &curr->gch.next;
139    }
140    else {  /* must call its gc method */
141      deadmem += sizeudata(gco2u(curr));
142      markfinalized(gco2u(curr));
143      *p = curr->gch.next;
144      /* link `curr' at the end of `tmudata' list */
145      if (g->tmudata == NULL)  /* list is empty? */
146        g->tmudata = curr->gch.next = curr;  /* creates a circular list */
147      else {
148        curr->gch.next = g->tmudata->gch.next;
149        g->tmudata->gch.next = curr;
150        g->tmudata = curr;
151      }
152    }
153  }
154  return deadmem;
155}
156
157
158static int traversetable (global_State *g, Table *h) {
159  int i;
160  int weakkey = 0;
161  int weakvalue = 0;
162  const TValue *mode;
163  if (h->metatable)
164    markobject(g, h->metatable);
165  mode = gfasttm(g, h->metatable, TM_MODE);
166  if (mode && ttisstring(mode)) {  /* is there a weak mode? */
167    weakkey = (strchr(svalue(mode), 'k') != NULL);
168    weakvalue = (strchr(svalue(mode), 'v') != NULL);
169    if (weakkey || weakvalue) {  /* is really weak? */
170      h->marked &= ~(KEYWEAK | VALUEWEAK);  /* clear bits */
171      h->marked |= cast_byte((weakkey << KEYWEAKBIT) |
172                             (weakvalue << VALUEWEAKBIT));
173      h->gclist = g->weak;  /* must be cleared after GC, ... */
174      g->weak = obj2gco(h);  /* ... so put in the appropriate list */
175    }
176  }
177  if (weakkey && weakvalue) return 1;
178  if (!weakvalue) {
179    i = h->sizearray;
180    while (i--)
181      markvalue(g, &h->array[i]);
182  }
183  i = sizenode(h);
184  while (i--) {
185    Node *n = gnode(h, i);
186    lua_assert(ttype(gkey(n)) != LUA_TDEADKEY || ttisnil(gval(n)));
187    if (ttisnil(gval(n)))
188      removeentry(n);  /* remove empty entries */
189    else {
190      lua_assert(!ttisnil(gkey(n)));
191      if (!weakkey) markvalue(g, gkey(n));
192      if (!weakvalue) markvalue(g, gval(n));
193    }
194  }
195  return weakkey || weakvalue;
196}
197
198
199/*
200** All marks are conditional because a GC may happen while the
201** prototype is still being created
202*/
203static void traverseproto (global_State *g, Proto *f) {
204  int i;
205  if (f->source) stringmark(f->source);
206  for (i=0; i<f->sizek; i++)  /* mark literals */
207    markvalue(g, &f->k[i]);
208  for (i=0; i<f->sizeupvalues; i++) {  /* mark upvalue names */
209    if (f->upvalues[i])
210      stringmark(f->upvalues[i]);
211  }
212  for (i=0; i<f->sizep; i++) {  /* mark nested protos */
213    if (f->p[i])
214      markobject(g, f->p[i]);
215  }
216  for (i=0; i<f->sizelocvars; i++) {  /* mark local-variable names */
217    if (f->locvars[i].varname)
218      stringmark(f->locvars[i].varname);
219  }
220}
221
222
223
224static void traverseclosure (global_State *g, Closure *cl) {
225  markobject(g, cl->c.env);
226  if (cl->c.isC) {
227    int i;
228    for (i=0; i<cl->c.nupvalues; i++)  /* mark its upvalues */
229      markvalue(g, &cl->c.upvalue[i]);
230  }
231  else {
232    int i;
233    lua_assert(cl->l.nupvalues == cl->l.p->nups);
234    markobject(g, cl->l.p);
235    for (i=0; i<cl->l.nupvalues; i++)  /* mark its upvalues */
236      markobject(g, cl->l.upvals[i]);
237  }
238}
239
240
241static void checkstacksizes (lua_State *L, StkId max) {
242  int ci_used = cast_int(L->ci - L->base_ci);  /* number of `ci' in use */
243  int s_used = cast_int(max - L->stack);  /* part of stack in use */
244  if (L->size_ci > LUAI_MAXCALLS)  /* handling overflow? */
245    return;  /* do not touch the stacks */
246  if (4*ci_used < L->size_ci && 2*BASIC_CI_SIZE < L->size_ci)
247    luaD_reallocCI(L, L->size_ci/2);  /* still big enough... */
248  condhardstacktests(luaD_reallocCI(L, ci_used + 1));
249  if (4*s_used < L->stacksize &&
250      2*(BASIC_STACK_SIZE+EXTRA_STACK) < L->stacksize)
251    luaD_reallocstack(L, L->stacksize/2);  /* still big enough... */
252  condhardstacktests(luaD_reallocstack(L, s_used));
253}
254
255
256static void traversestack (global_State *g, lua_State *l) {
257  StkId o, lim;
258  CallInfo *ci;
259  markvalue(g, gt(l));
260  lim = l->top;
261  for (ci = l->base_ci; ci <= l->ci; ci++) {
262    lua_assert(ci->top <= l->stack_last);
263    if (lim < ci->top) lim = ci->top;
264  }
265  for (o = l->stack; o < l->top; o++)
266    markvalue(g, o);
267  for (; o <= lim; o++)
268    setnilvalue(o);
269  checkstacksizes(l, lim);
270}
271
272
273/*
274** traverse one gray object, turning it to black.
275** Returns `quantity' traversed.
276*/
277static l_mem propagatemark (global_State *g) {
278  GCObject *o = g->gray;
279  lua_assert(isgray(o));
280  gray2black(o);
281  switch (o->gch.tt) {
282    case LUA_TTABLE: {
283      Table *h = gco2h(o);
284      g->gray = h->gclist;
285      if (traversetable(g, h))  /* table is weak? */
286        black2gray(o);  /* keep it gray */
287      return sizeof(Table) + sizeof(TValue) * h->sizearray +
288                             sizeof(Node) * sizenode(h);
289    }
290    case LUA_TFUNCTION: {
291      Closure *cl = gco2cl(o);
292      g->gray = cl->c.gclist;
293      traverseclosure(g, cl);
294      return (cl->c.isC) ? sizeCclosure(cl->c.nupvalues) :
295                           sizeLclosure(cl->l.nupvalues);
296    }
297    case LUA_TTHREAD: {
298      lua_State *th = gco2th(o);
299      g->gray = th->gclist;
300      th->gclist = g->grayagain;
301      g->grayagain = o;
302      black2gray(o);
303      traversestack(g, th);
304      return sizeof(lua_State) + sizeof(TValue) * th->stacksize +
305                                 sizeof(CallInfo) * th->size_ci;
306    }
307    case LUA_TPROTO: {
308      Proto *p = gco2p(o);
309      g->gray = p->gclist;
310      traverseproto(g, p);
311      return sizeof(Proto) + sizeof(Instruction) * p->sizecode +
312                             sizeof(Proto *) * p->sizep +
313                             sizeof(TValue) * p->sizek + 
314                             sizeof(int) * p->sizelineinfo +
315                             sizeof(LocVar) * p->sizelocvars +
316                             sizeof(TString *) * p->sizeupvalues;
317    }
318    default: lua_assert(0); return 0;
319  }
320}
321
322
323static size_t propagateall (global_State *g) {
324  size_t m = 0;
325  while (g->gray) m += propagatemark(g);
326  return m;
327}
328
329
330/*
331** The next function tells whether a key or value can be cleared from
332** a weak table. Non-collectable objects are never removed from weak
333** tables. Strings behave as `values', so are never removed too. for
334** other objects: if really collected, cannot keep them; for userdata
335** being finalized, keep them in keys, but not in values
336*/
337static int iscleared (const TValue *o, int iskey) {
338  if (!iscollectable(o)) return 0;
339  if (ttisstring(o)) {
340    stringmark(rawtsvalue(o));  /* strings are `values', so are never weak */
341    return 0;
342  }
343  return iswhite(gcvalue(o)) ||
344    (ttisuserdata(o) && (!iskey && isfinalized(uvalue(o))));
345}
346
347
348/*
349** clear collected entries from weaktables
350*/
351static void cleartable (GCObject *l) {
352  while (l) {
353    Table *h = gco2h(l);
354    int i = h->sizearray;
355    lua_assert(testbit(h->marked, VALUEWEAKBIT) ||
356               testbit(h->marked, KEYWEAKBIT));
357    if (testbit(h->marked, VALUEWEAKBIT)) {
358      while (i--) {
359        TValue *o = &h->array[i];
360        if (iscleared(o, 0))  /* value was collected? */
361          setnilvalue(o);  /* remove value */
362      }
363    }
364    i = sizenode(h);
365    while (i--) {
366      Node *n = gnode(h, i);
367      if (!ttisnil(gval(n)) &&  /* non-empty entry? */
368          (iscleared(key2tval(n), 1) || iscleared(gval(n), 0))) {
369        setnilvalue(gval(n));  /* remove value ... */
370        removeentry(n);  /* remove entry from table */
371      }
372    }
373    l = h->gclist;
374  }
375}
376
377
378static void freeobj (lua_State *L, GCObject *o) {
379  switch (o->gch.tt) {
380    case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break;
381    case LUA_TFUNCTION: luaF_freeclosure(L, gco2cl(o)); break;
382    case LUA_TUPVAL: luaF_freeupval(L, gco2uv(o)); break;
383    case LUA_TTABLE: luaH_free(L, gco2h(o)); break;
384    case LUA_TTHREAD: {
385      lua_assert(gco2th(o) != L && gco2th(o) != G(L)->mainthread);
386      luaE_freethread(L, gco2th(o));
387      break;
388    }
389    case LUA_TSTRING: {
390      G(L)->strt.nuse--;
391      luaM_freemem(L, o, sizestring(gco2ts(o)));
392      break;
393    }
394    case LUA_TUSERDATA: {
395      luaM_freemem(L, o, sizeudata(gco2u(o)));
396      break;
397    }
398    default: lua_assert(0);
399  }
400}
401
402
403
404#define sweepwholelist(L,p)	sweeplist(L,p,MAX_LUMEM)
405
406
407static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
408  GCObject *curr;
409  global_State *g = G(L);
410  int deadmask = otherwhite(g);
411  while ((curr = *p) != NULL && count-- > 0) {
412    if (curr->gch.tt == LUA_TTHREAD)  /* sweep open upvalues of each thread */
413      sweepwholelist(L, &gco2th(curr)->openupval);
414    if ((curr->gch.marked ^ WHITEBITS) & deadmask) {  /* not dead? */
415      lua_assert(!isdead(g, curr) || testbit(curr->gch.marked, FIXEDBIT));
416      makewhite(g, curr);  /* make it white (for next cycle) */
417      p = &curr->gch.next;
418    }
419    else {  /* must erase `curr' */
420      lua_assert(isdead(g, curr) || deadmask == bitmask(SFIXEDBIT));
421      *p = curr->gch.next;
422      if (curr == g->rootgc)  /* is the first element of the list? */
423        g->rootgc = curr->gch.next;  /* adjust first */
424      freeobj(L, curr);
425    }
426  }
427  return p;
428}
429
430
431static void checkSizes (lua_State *L) {
432  global_State *g = G(L);
433  /* check size of string hash */
434  if (g->strt.nuse < cast(lu_int32, g->strt.size/4) &&
435      g->strt.size > MINSTRTABSIZE*2)
436    luaS_resize(L, g->strt.size/2);  /* table is too big */
437  /* check size of buffer */
438  if (luaZ_sizebuffer(&g->buff) > LUA_MINBUFFER*2) {  /* buffer too big? */
439    size_t newsize = luaZ_sizebuffer(&g->buff) / 2;
440    luaZ_resizebuffer(L, &g->buff, newsize);
441  }
442}
443
444
445static void GCTM (lua_State *L) {
446  global_State *g = G(L);
447  GCObject *o = g->tmudata->gch.next;  /* get first element */
448  Udata *udata = rawgco2u(o);
449  const TValue *tm;
450  /* remove udata from `tmudata' */
451  if (o == g->tmudata)  /* last element? */
452    g->tmudata = NULL;
453  else
454    g->tmudata->gch.next = udata->uv.next;
455  udata->uv.next = g->mainthread->next;  /* return it to `root' list */
456  g->mainthread->next = o;
457  makewhite(g, o);
458  tm = fasttm(L, udata->uv.metatable, TM_GC);
459  if (tm != NULL) {
460    lu_byte oldah = L->allowhook;
461    lu_mem oldt = g->GCthreshold;
462    L->allowhook = 0;  /* stop debug hooks during GC tag method */
463    g->GCthreshold = 2*g->totalbytes;  /* avoid GC steps */
464    setobj2s(L, L->top, tm);
465    setuvalue(L, L->top+1, udata);
466    L->top += 2;
467    luaD_call(L, L->top - 2, 0);
468    L->allowhook = oldah;  /* restore hooks */
469    g->GCthreshold = oldt;  /* restore threshold */
470  }
471}
472
473
474/*
475** Call all GC tag methods
476*/
477void luaC_callGCTM (lua_State *L) {
478  while (G(L)->tmudata)
479    GCTM(L);
480}
481
482
483void luaC_freeall (lua_State *L) {
484  global_State *g = G(L);
485  int i;
486  g->currentwhite = WHITEBITS | bitmask(SFIXEDBIT);  /* mask to collect all elements */
487  sweepwholelist(L, &g->rootgc);
488  for (i = 0; i < g->strt.size; i++)  /* free all string lists */
489    sweepwholelist(L, &g->strt.hash[i]);
490}
491
492
493static void markmt (global_State *g) {
494  int i;
495  for (i=0; i<NUM_TAGS; i++)
496    if (g->mt[i]) markobject(g, g->mt[i]);
497}
498
499
500/* mark root set */
501static void markroot (lua_State *L) {
502  global_State *g = G(L);
503  g->gray = NULL;
504  g->grayagain = NULL;
505  g->weak = NULL;
506  markobject(g, g->mainthread);
507  /* make global table be traversed before main stack */
508  markvalue(g, gt(g->mainthread));
509  markvalue(g, registry(L));
510  markmt(g);
511  g->gcstate = GCSpropagate;
512}
513
514
515static void remarkupvals (global_State *g) {
516  UpVal *uv;
517  for (uv = g->uvhead.u.l.next; uv != &g->uvhead; uv = uv->u.l.next) {
518    lua_assert(uv->u.l.next->u.l.prev == uv && uv->u.l.prev->u.l.next == uv);
519    if (isgray(obj2gco(uv)))
520      markvalue(g, uv->v);
521  }
522}
523
524
525static void atomic (lua_State *L) {
526  global_State *g = G(L);
527  size_t udsize;  /* total size of userdata to be finalized */
528  /* remark occasional upvalues of (maybe) dead threads */
529  remarkupvals(g);
530  /* traverse objects cautch by write barrier and by 'remarkupvals' */
531  propagateall(g);
532  /* remark weak tables */
533  g->gray = g->weak;
534  g->weak = NULL;
535  lua_assert(!iswhite(obj2gco(g->mainthread)));
536  markobject(g, L);  /* mark running thread */
537  markmt(g);  /* mark basic metatables (again) */
538  propagateall(g);
539  /* remark gray again */
540  g->gray = g->grayagain;
541  g->grayagain = NULL;
542  propagateall(g);
543  udsize = luaC_separateudata(L, 0);  /* separate userdata to be finalized */
544  marktmu(g);  /* mark `preserved' userdata */
545  udsize += propagateall(g);  /* remark, to propagate `preserveness' */
546  cleartable(g->weak);  /* remove collected objects from weak tables */
547  /* flip current white */
548  g->currentwhite = cast_byte(otherwhite(g));
549  g->sweepstrgc = 0;
550  g->sweepgc = &g->rootgc;
551  g->gcstate = GCSsweepstring;
552  g->estimate = g->totalbytes - udsize;  /* first estimate */
553}
554
555
556static l_mem singlestep (lua_State *L) {
557  global_State *g = G(L);
558  /*lua_checkmemory(L);*/
559  switch (g->gcstate) {
560    case GCSpause: {
561      markroot(L);  /* start a new collection */
562      return 0;
563    }
564    case GCSpropagate: {
565      if (g->gray)
566        return propagatemark(g);
567      else {  /* no more `gray' objects */
568        atomic(L);  /* finish mark phase */
569        return 0;
570      }
571    }
572    case GCSsweepstring: {
573      lu_mem old = g->totalbytes;
574      sweepwholelist(L, &g->strt.hash[g->sweepstrgc++]);
575      if (g->sweepstrgc >= g->strt.size)  /* nothing more to sweep? */
576        g->gcstate = GCSsweep;  /* end sweep-string phase */
577      lua_assert(old >= g->totalbytes);
578      g->estimate -= old - g->totalbytes;
579      return GCSWEEPCOST;
580    }
581    case GCSsweep: {
582      lu_mem old = g->totalbytes;
583      g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
584      if (*g->sweepgc == NULL) {  /* nothing more to sweep? */
585        checkSizes(L);
586        g->gcstate = GCSfinalize;  /* end sweep phase */
587      }
588      lua_assert(old >= g->totalbytes);
589      g->estimate -= old - g->totalbytes;
590      return GCSWEEPMAX*GCSWEEPCOST;
591    }
592    case GCSfinalize: {
593      if (g->tmudata) {
594        GCTM(L);
595        if (g->estimate > GCFINALIZECOST)
596          g->estimate -= GCFINALIZECOST;
597        return GCFINALIZECOST;
598      }
599      else {
600        g->gcstate = GCSpause;  /* end collection */
601        g->gcdept = 0;
602        return 0;
603      }
604    }
605    default: lua_assert(0); return 0;
606  }
607}
608
609
610void luaC_step (lua_State *L) {
611  global_State *g = G(L);
612  l_mem lim = (GCSTEPSIZE/100) * g->gcstepmul;
613  if (lim == 0)
614    lim = (MAX_LUMEM-1)/2;  /* no limit */
615  g->gcdept += g->totalbytes - g->GCthreshold;
616  do {
617    lim -= singlestep(L);
618    if (g->gcstate == GCSpause)
619      break;
620  } while (lim > 0);
621  if (g->gcstate != GCSpause) {
622    if (g->gcdept < GCSTEPSIZE)
623      g->GCthreshold = g->totalbytes + GCSTEPSIZE;  /* - lim/g->gcstepmul;*/
624    else {
625      g->gcdept -= GCSTEPSIZE;
626      g->GCthreshold = g->totalbytes;
627    }
628  }
629  else {
630    lua_assert(g->totalbytes >= g->estimate);
631    setthreshold(g);
632  }
633}
634
635
636void luaC_fullgc (lua_State *L) {
637  global_State *g = G(L);
638  if (g->gcstate <= GCSpropagate) {
639    /* reset sweep marks to sweep all elements (returning them to white) */
640    g->sweepstrgc = 0;
641    g->sweepgc = &g->rootgc;
642    /* reset other collector lists */
643    g->gray = NULL;
644    g->grayagain = NULL;
645    g->weak = NULL;
646    g->gcstate = GCSsweepstring;
647  }
648  lua_assert(g->gcstate != GCSpause && g->gcstate != GCSpropagate);
649  /* finish any pending sweep phase */
650  while (g->gcstate != GCSfinalize) {
651    lua_assert(g->gcstate == GCSsweepstring || g->gcstate == GCSsweep);
652    singlestep(L);
653  }
654  markroot(L);
655  while (g->gcstate != GCSpause) {
656    singlestep(L);
657  }
658  setthreshold(g);
659}
660
661
662void luaC_barrierf (lua_State *L, GCObject *o, GCObject *v) {
663  global_State *g = G(L);
664  lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
665  lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
666  lua_assert(ttype(&o->gch) != LUA_TTABLE);
667  /* must keep invariant? */
668  if (g->gcstate == GCSpropagate)
669    reallymarkobject(g, v);  /* restore invariant */
670  else  /* don't mind */
671    makewhite(g, o);  /* mark as white just to avoid other barriers */
672}
673
674
675void luaC_barrierback (lua_State *L, Table *t) {
676  global_State *g = G(L);
677  GCObject *o = obj2gco(t);
678  lua_assert(isblack(o) && !isdead(g, o));
679  lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
680  black2gray(o);  /* make table gray (again) */
681  t->gclist = g->grayagain;
682  g->grayagain = o;
683}
684
685
686void luaC_link (lua_State *L, GCObject *o, lu_byte tt) {
687  global_State *g = G(L);
688  o->gch.next = g->rootgc;
689  g->rootgc = o;
690  o->gch.marked = luaC_white(g);
691  o->gch.tt = tt;
692}
693
694
695void luaC_linkupval (lua_State *L, UpVal *uv) {
696  global_State *g = G(L);
697  GCObject *o = obj2gco(uv);
698  o->gch.next = g->rootgc;  /* link upvalue into `rootgc' list */
699  g->rootgc = o;
700  if (isgray(o)) { 
701    if (g->gcstate == GCSpropagate) {
702      gray2black(o);  /* closed upvalues need barrier */
703      luaC_barrier(L, uv, uv->v);
704    }
705    else {  /* sweep phase: sweep it (turning it into white) */
706      makewhite(g, o);
707      lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
708    }
709  }
710}
711