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# lua/lgc.c

Go to the documentation of this file.

    00001 /*
    00002 ** $Id: lgc.c,v 2.38 2006/05/24 14:34:06 roberto Exp $
    00003 ** Garbage Collector
    00004 ** See Copyright Notice in lua.h
    00005 */
    00006
    00007 #include <string.h>
    00008
    00009 #define lgc_c
    00010 #define LUA_CORE
    00011
    00012 #include "lua.h"
    00013
    00014 #include "ldebug.h"
    00015 #include "ldo.h"
    00016 #include "lfunc.h"
    00017 #include "lgc.h"
    00018 #include "lmem.h"
    00019 #include "lobject.h"
    00020 #include "lstate.h"
    00021 #include "lstring.h"
    00022 #include "ltable.h"
    00023 #include "ltm.h"
    00024
    00025
    00026 #define GCSTEPSIZE      1024u
    00027 #define GCSWEEPMAX      40
    00028 #define GCSWEEPCOST     10
    00029 #define GCFINALIZECOST  100
    00030
    00031
    00032 #define maskmarks       cast_byte(~(bitmask(BLACKBIT)|WHITEBITS))
    00033
    00034 #define makewhite(g,x)  \
    00035    ((x)->gch.marked = cast_byte(((x)->gch.marked & maskmarks) | luaC_white(g)))
    00036
    00037 #define white2gray(x)   reset2bits((x)->gch.marked, WHITE0BIT, WHITE1BIT)
    00038 #define black2gray(x)   resetbit((x)->gch.marked, BLACKBIT)
    00039
    00040 #define stringmark(s)   reset2bits((s)->tsv.marked, WHITE0BIT, WHITE1BIT)
    00041
    00042
    00043 #define isfinalized(u)          testbit((u)->marked, FINALIZEDBIT)
    00044 #define markfinalized(u)        l_setbit((u)->marked, FINALIZEDBIT)
    00045
    00046
    00047 #define KEYWEAK         bitmask(KEYWEAKBIT)
    00048 #define VALUEWEAK       bitmask(VALUEWEAKBIT)
    00049
    00050
    00051
    00052 #define markvalue(g,o) { checkconsistency(o); \
    00053   if (iscollectable(o) && iswhite(gcvalue(o))) reallymarkobject(g,gcvalue(o)); }
    00054
    00055 #define markobject(g,t) { if (iswhite(obj2gco(t))) \
    00056                 reallymarkobject(g, obj2gco(t)); }
    00057
    00058
    00059 #define setthreshold(g)  (g->GCthreshold = (g->estimate/100) * g->gcpause)
    00060
    00061
    00062 static void removeentry (Node *n) {
    00063   lua_assert(ttisnil(gval(n)));
    00064   if (iscollectable(gkey(n)))
    00065     setttype(gkey(n), LUA_TDEADKEY);  /* dead key; remove it */
    00066 }
    00067
    00068
    00069 static void reallymarkobject (global_State *g, GCObject *o) {
    00070   lua_assert(iswhite(o) && !isdead(g, o));
    00071   white2gray(o);
    00072   switch (o->gch.tt) {
    00073     case LUA_TSTRING: {
    00074       return;
    00075     }
    00076     case LUA_TUSERDATA: {
    00077       Table *mt = gco2u(o)->metatable;
    00078       gray2black(o);  /* udata are never gray */
    00079       if (mt) markobject(g, mt);
    00080       markobject(g, gco2u(o)->env);
    00081       return;
    00082     }
    00083     case LUA_TUPVAL: {
    00084       UpVal *uv = gco2uv(o);
    00085       markvalue(g, uv->v);
    00086       if (uv->v == &uv->u.value)  /* closed? */
    00087         gray2black(o);  /* open upvalues are never black */
    00088       return;
    00089     }
    00090     case LUA_TFUNCTION: {
    00091       gco2cl(o)->c.gclist = g->gray;
    00092       g->gray = o;
    00093       break;
    00094     }
    00095     case LUA_TTABLE: {
    00096       gco2h(o)->gclist = g->gray;
    00097       g->gray = o;
    00098       break;
    00099     }
    00100     case LUA_TTHREAD: {
    00101       gco2th(o)->gclist = g->gray;
    00102       g->gray = o;
    00103       break;
    00104     }
    00105     case LUA_TPROTO: {
    00106       gco2p(o)->gclist = g->gray;
    00107       g->gray = o;
    00108       break;
    00109     }
    00110     default: lua_assert(0);
    00111   }
    00112 }
    00113
    00114
    00115 static void marktmu (global_State *g) {
    00116   GCObject *u = g->tmudata;
    00117   if (u) {
    00118     do {
    00119       u = u->gch.next;
    00120       makewhite(g, u);  /* may be marked, if left from previous GC */
    00121       reallymarkobject(g, u);
    00122     } while (u != g->tmudata);
    00123   }
    00124 }
    00125
    00126
    00127 /* move `dead' udata that need finalization to list `tmudata' */
    00128 size_t luaC_separateudata (lua_State *L, int all) {
    00129   global_State *g = G(L);
    00130   size_t deadmem = 0;
    00131   GCObject **p = &g->mainthread->next;
    00132   GCObject *curr;
    00133   while ((curr = *p) != NULL) {
    00134     if (!(iswhite(curr) || all) || isfinalized(gco2u(curr)))
    00135       p = &curr->gch.next;  /* don't bother with them */
    00136     else if (fasttm(L, gco2u(curr)->metatable, TM_GC) == NULL) {
    00137       markfinalized(gco2u(curr));  /* don't need finalization */
    00138       p = &curr->gch.next;
    00139     }
    00140     else {  /* must call its gc method */
    00141       deadmem += sizeudata(gco2u(curr));
    00142       markfinalized(gco2u(curr));
    00143       *p = curr->gch.next;
    00144       /* link `curr' at the end of `tmudata' list */
    00145       if (g->tmudata == NULL)  /* list is empty? */
    00146         g->tmudata = curr->gch.next = curr;  /* creates a circular list */
    00147       else {
    00148         curr->gch.next = g->tmudata->gch.next;
    00149         g->tmudata->gch.next = curr;
    00150         g->tmudata = curr;
    00151       }
    00152     }
    00153   }
    00154   return deadmem;
    00155 }
    00156
    00157
    00158 static int traversetable (global_State *g, Table *h) {
    00159   int i;
    00160   int weakkey = 0;
    00161   int weakvalue = 0;
    00162   const TValue *mode;
    00163   if (h->metatable)
    00164     markobject(g, h->metatable);
    00165   mode = gfasttm(g, h->metatable, TM_MODE);
    00166   if (mode && ttisstring(mode)) {  /* is there a weak mode? */
    00167     weakkey = (strchr(svalue(mode), 'k') != NULL);
    00168     weakvalue = (strchr(svalue(mode), 'v') != NULL);
    00169     if (weakkey || weakvalue) {  /* is really weak? */
    00170       h->marked &= ~(KEYWEAK | VALUEWEAK);  /* clear bits */
    00171       h->marked |= cast_byte((weakkey << KEYWEAKBIT) |
    00172                              (weakvalue << VALUEWEAKBIT));
    00173       h->gclist = g->weak;  /* must be cleared after GC, ... */
    00174       g->weak = obj2gco(h);  /* ... so put in the appropriate list */
    00175     }
    00176   }
    00177   if (weakkey && weakvalue) return 1;
    00178   if (!weakvalue) {
    00179     i = h->sizearray;
    00180     while (i--)
    00181       markvalue(g, &h->array[i]);
    00182   }
    00183   i = sizenode(h);
    00184   while (i--) {
    00185     Node *n = gnode(h, i);
    00186     lua_assert(ttype(gkey(n)) != LUA_TDEADKEY || ttisnil(gval(n)));
    00187     if (ttisnil(gval(n)))
    00188       removeentry(n);  /* remove empty entries */
    00189     else {
    00190       lua_assert(!ttisnil(gkey(n)));
    00191       if (!weakkey) markvalue(g, gkey(n));
    00192       if (!weakvalue) markvalue(g, gval(n));
    00193     }
    00194   }
    00195   return weakkey || weakvalue;
    00196 }
    00197
    00198
    00199 /*
    00200 ** All marks are conditional because a GC may happen while the
    00201 ** prototype is still being created
    00202 */
    00203 static void traverseproto (global_State *g, Proto *f) {
    00204   int i;
    00205   if (f->source) stringmark(f->source);
    00206   for (i=0; i<f->sizek; i++)  /* mark literals */
    00207     markvalue(g, &f->k[i]);
    00208   for (i=0; i<f->sizeupvalues; i++) {  /* mark upvalue names */
    00209     if (f->upvalues[i])
    00210       stringmark(f->upvalues[i]);
    00211   }
    00212   for (i=0; i<f->sizep; i++) {  /* mark nested protos */
    00213     if (f->p[i])
    00214       markobject(g, f->p[i]);
    00215   }
    00216   for (i=0; i<f->sizelocvars; i++) {  /* mark local-variable names */
    00217     if (f->locvars[i].varname)
    00218       stringmark(f->locvars[i].varname);
    00219   }
    00220 }
    00221
    00222
    00223
    00224 static void traverseclosure (global_State *g, Closure *cl) {
    00225   markobject(g, cl->c.env);
    00226   if (cl->c.isC) {
    00227     int i;
    00228     for (i=0; i<cl->c.nupvalues; i++)  /* mark its upvalues */
    00229       markvalue(g, &cl->c.upvalue[i]);
    00230   }
    00231   else {
    00232     int i;
    00233     lua_assert(cl->l.nupvalues == cl->l.p->nups);
    00234     markobject(g, cl->l.p);
    00235     for (i=0; i<cl->l.nupvalues; i++)  /* mark its upvalues */
    00236       markobject(g, cl->l.upvals[i]);
    00237   }
    00238 }
    00239
    00240
    00241 static void checkstacksizes (lua_State *L, StkId max) {
    00242   int ci_used = cast_int(L->ci - L->base_ci);  /* number of `ci' in use */
    00243   int s_used = cast_int(max - L->stack);  /* part of stack in use */
    00244   if (L->size_ci > LUAI_MAXCALLS)  /* handling overflow? */
    00245     return;  /* do not touch the stacks */
    00246   if (4*ci_used < L->size_ci && 2*BASIC_CI_SIZE < L->size_ci)
    00247     luaD_reallocCI(L, L->size_ci/2);  /* still big enough... */
    00248   condhardstacktests(luaD_reallocCI(L, ci_used + 1));
    00249   if (4*s_used < L->stacksize &&
    00250       2*(BASIC_STACK_SIZE+EXTRA_STACK) < L->stacksize)
    00251     luaD_reallocstack(L, L->stacksize/2);  /* still big enough... */
    00252   condhardstacktests(luaD_reallocstack(L, s_used));
    00253 }
    00254
    00255
    00256 static void traversestack (global_State *g, lua_State *l) {
    00257   StkId o, lim;
    00258   CallInfo *ci;
    00259   markvalue(g, gt(l));
    00260   lim = l->top;
    00261   for (ci = l->base_ci; ci <= l->ci; ci++) {
    00262     lua_assert(ci->top <= l->stack_last);
    00263     if (lim < ci->top) lim = ci->top;
    00264   }
    00265   for (o = l->stack; o < l->top; o++)
    00266     markvalue(g, o);
    00267   for (; o <= lim; o++)
    00268     setnilvalue(o);
    00269   checkstacksizes(l, lim);
    00270 }
    00271
    00272
    00273 /*
    00274 ** traverse one gray object, turning it to black.
    00275 ** Returns `quantity' traversed.
    00276 */
    00277 static l_mem propagatemark (global_State *g) {
    00278   GCObject *o = g->gray;
    00279   lua_assert(isgray(o));
    00280   gray2black(o);
    00281   switch (o->gch.tt) {
    00282     case LUA_TTABLE: {
    00283       Table *h = gco2h(o);
    00284       g->gray = h->gclist;
    00285       if (traversetable(g, h))  /* table is weak? */
    00286         black2gray(o);  /* keep it gray */
    00287       return sizeof(Table) + sizeof(TValue) * h->sizearray +
    00288                              sizeof(Node) * sizenode(h);
    00289     }
    00290     case LUA_TFUNCTION: {
    00291       Closure *cl = gco2cl(o);
    00292       g->gray = cl->c.gclist;
    00293       traverseclosure(g, cl);
    00294       return (cl->c.isC) ? sizeCclosure(cl->c.nupvalues) :
    00295                            sizeLclosure(cl->l.nupvalues);
    00296     }
    00297     case LUA_TTHREAD: {
    00298       lua_State *th = gco2th(o);
    00299       g->gray = th->gclist;
    00300       th->gclist = g->grayagain;
    00301       g->grayagain = o;
    00302       black2gray(o);
    00303       traversestack(g, th);
    00304       return sizeof(lua_State) + sizeof(TValue) * th->stacksize +
    00305                                  sizeof(CallInfo) * th->size_ci;
    00306     }
    00307     case LUA_TPROTO: {
    00308       Proto *p = gco2p(o);
    00309       g->gray = p->gclist;
    00310       traverseproto(g, p);
    00311       return sizeof(Proto) + sizeof(Instruction) * p->sizecode +
    00312                              sizeof(Proto *) * p->sizep +
    00313                              sizeof(TValue) * p->sizek +
    00314                              sizeof(int) * p->sizelineinfo +
    00315                              sizeof(LocVar) * p->sizelocvars +
    00316                              sizeof(TString *) * p->sizeupvalues;
    00317     }
    00318     default: lua_assert(0); return 0;
    00319   }
    00320 }
    00321
    00322
    00323 static size_t propagateall (global_State *g) {
    00324   size_t m = 0;
    00325   while (g->gray) m += propagatemark(g);
    00326   return m;
    00327 }
    00328
    00329
    00330 /*
    00331 ** The next function tells whether a key or value can be cleared from
    00332 ** a weak table. Non-collectable objects are never removed from weak
    00333 ** tables. Strings behave as `values', so are never removed too. for
    00334 ** other objects: if really collected, cannot keep them; for userdata
    00335 ** being finalized, keep them in keys, but not in values
    00336 */
    00337 static int iscleared (const TValue *o, int iskey) {
    00338   if (!iscollectable(o)) return 0;
    00339   if (ttisstring(o)) {
    00340     stringmark(rawtsvalue(o));  /* strings are `values', so are never weak */
    00341     return 0;
    00342   }
    00343   return iswhite(gcvalue(o)) ||
    00344     (ttisuserdata(o) && (!iskey && isfinalized(uvalue(o))));
    00345 }
    00346
    00347
    00348 /*
    00349 ** clear collected entries from weaktables
    00350 */
    00351 static void cleartable (GCObject *l) {
    00352   while (l) {
    00353     Table *h = gco2h(l);
    00354     int i = h->sizearray;
    00355     lua_assert(testbit(h->marked, VALUEWEAKBIT) ||
    00356                testbit(h->marked, KEYWEAKBIT));
    00357     if (testbit(h->marked, VALUEWEAKBIT)) {
    00358       while (i--) {
    00359         TValue *o = &h->array[i];
    00360         if (iscleared(o, 0))  /* value was collected? */
    00361           setnilvalue(o);  /* remove value */
    00362       }
    00363     }
    00364     i = sizenode(h);
    00365     while (i--) {
    00366       Node *n = gnode(h, i);
    00367       if (!ttisnil(gval(n)) &&  /* non-empty entry? */
    00368           (iscleared(key2tval(n), 1) || iscleared(gval(n), 0))) {
    00369         setnilvalue(gval(n));  /* remove value ... */
    00370         removeentry(n);  /* remove entry from table */
    00371       }
    00372     }
    00373     l = h->gclist;
    00374   }
    00375 }
    00376
    00377
    00378 static void freeobj (lua_State *L, GCObject *o) {
    00379   switch (o->gch.tt) {
    00380     case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break;
    00381     case LUA_TFUNCTION: luaF_freeclosure(L, gco2cl(o)); break;
    00382     case LUA_TUPVAL: luaF_freeupval(L, gco2uv(o)); break;
    00383     case LUA_TTABLE: luaH_free(L, gco2h(o)); break;
    00384     case LUA_TTHREAD: {
    00385       lua_assert(gco2th(o) != L && gco2th(o) != G(L)->mainthread);
    00386       luaE_freethread(L, gco2th(o));
    00387       break;
    00388     }
    00389     case LUA_TSTRING: {
    00390       G(L)->strt.nuse--;
    00391       luaM_freemem(L, o, sizestring(gco2ts(o)));
    00392       break;
    00393     }
    00394     case LUA_TUSERDATA: {
    00395       luaM_freemem(L, o, sizeudata(gco2u(o)));
    00396       break;
    00397     }
    00398     default: lua_assert(0);
    00399   }
    00400 }
    00401
    00402
    00403
    00404 #define sweepwholelist(L,p)     sweeplist(L,p,MAX_LUMEM)
    00405
    00406
    00407 static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
    00408   GCObject *curr;
    00409   global_State *g = G(L);
    00410   int deadmask = otherwhite(g);
    00411   while ((curr = *p) != NULL && count-- > 0) {
    00412     if (curr->gch.tt == LUA_TTHREAD)  /* sweep open upvalues of each thread */
    00413       sweepwholelist(L, &gco2th(curr)->openupval);
    00414     if ((curr->gch.marked ^ WHITEBITS) & deadmask) {  /* not dead? */
    00415       lua_assert(!isdead(g, curr) || testbit(curr->gch.marked, FIXEDBIT));
    00416       makewhite(g, curr);  /* make it white (for next cycle) */
    00417       p = &curr->gch.next;
    00418     }
    00419     else {  /* must erase `curr' */
    00420       lua_assert(isdead(g, curr) || deadmask == bitmask(SFIXEDBIT));
    00421       *p = curr->gch.next;
    00422       if (curr == g->rootgc)  /* is the first element of the list? */
    00423         g->rootgc = curr->gch.next;  /* adjust first */
    00424       freeobj(L, curr);
    00425     }
    00426   }
    00427   return p;
    00428 }
    00429
    00430
    00431 static void checkSizes (lua_State *L) {
    00432   global_State *g = G(L);
    00433   /* check size of string hash */
    00434   if (g->strt.nuse < cast(lu_int32, g->strt.size/4) &&
    00435       g->strt.size > MINSTRTABSIZE*2)
    00436     luaS_resize(L, g->strt.size/2);  /* table is too big */
    00437   /* check size of buffer */
    00438   if (luaZ_sizebuffer(&g->buff) > LUA_MINBUFFER*2) {  /* buffer too big? */
    00439     size_t newsize = luaZ_sizebuffer(&g->buff) / 2;
    00440     luaZ_resizebuffer(L, &g->buff, newsize);
    00441   }
    00442 }
    00443
    00444
    00445 static void GCTM (lua_State *L) {
    00446   global_State *g = G(L);
    00447   GCObject *o = g->tmudata->gch.next;  /* get first element */
    00448   Udata *udata = rawgco2u(o);
    00449   const TValue *tm;
    00450   /* remove udata from `tmudata' */
    00451   if (o == g->tmudata)  /* last element? */
    00452     g->tmudata = NULL;
    00453   else
    00454     g->tmudata->gch.next = udata->uv.next;
    00455   udata->uv.next = g->mainthread->next;  /* return it to `root' list */
    00456   g->mainthread->next = o;
    00457   makewhite(g, o);
    00458   tm = fasttm(L, udata->uv.metatable, TM_GC);
    00459   if (tm != NULL) {
    00460     lu_byte oldah = L->allowhook;
    00461     lu_mem oldt = g->GCthreshold;
    00462     L->allowhook = 0;  /* stop debug hooks during GC tag method */
    00463     g->GCthreshold = 2*g->totalbytes;  /* avoid GC steps */
    00464     setobj2s(L, L->top, tm);
    00465     setuvalue(L, L->top+1, udata);
    00466     L->top += 2;
    00467     luaD_call(L, L->top - 2, 0);
    00468     L->allowhook = oldah;  /* restore hooks */
    00469     g->GCthreshold = oldt;  /* restore threshold */
    00470   }
    00471 }
    00472
    00473
    00474 /*
    00475 ** Call all GC tag methods
    00476 */
    00477 void luaC_callGCTM (lua_State *L) {
    00478   while (G(L)->tmudata)
    00479     GCTM(L);
    00480 }
    00481
    00482
    00483 void luaC_freeall (lua_State *L) {
    00484   global_State *g = G(L);
    00485   int i;
    00486   g->currentwhite = WHITEBITS | bitmask(SFIXEDBIT);  /* mask to collect all elements */
    00487   sweepwholelist(L, &g->rootgc);
    00488   for (i = 0; i < g->strt.size; i++)  /* free all string lists */
    00489     sweepwholelist(L, &g->strt.hash[i]);
    00490 }
    00491
    00492
    00493 static void markmt (global_State *g) {
    00494   int i;
    00495   for (i=0; i<NUM_TAGS; i++)
    00496     if (g->mt[i]) markobject(g, g->mt[i]);
    00497 }
    00498
    00499
    00500 /* mark root set */
    00501 static void markroot (lua_State *L) {
    00502   global_State *g = G(L);
    00503   g->gray = NULL;
    00504   g->grayagain = NULL;
    00505   g->weak = NULL;
    00506   markobject(g, g->mainthread);
    00507   /* make global table be traversed before main stack */
    00508   markvalue(g, gt(g->mainthread));
    00509   markvalue(g, registry(L));
    00510   markmt(g);
    00511   g->gcstate = GCSpropagate;
    00512 }
    00513
    00514
    00515 static void remarkupvals (global_State *g) {
    00516   UpVal *uv;
    00517   for (uv = g->uvhead.u.l.next; uv != &g->uvhead; uv = uv->u.l.next) {
    00518     lua_assert(uv->u.l.next->u.l.prev == uv && uv->u.l.prev->u.l.next == uv);
    00519     if (isgray(obj2gco(uv)))
    00520       markvalue(g, uv->v);
    00521   }
    00522 }
    00523
    00524
    00525 static void atomic (lua_State *L) {
    00526   global_State *g = G(L);
    00527   size_t udsize;  /* total size of userdata to be finalized */
    00528   /* remark occasional upvalues of (maybe) dead threads */
    00529   remarkupvals(g);
    00530   /* traverse objects cautch by write barrier and by 'remarkupvals' */
    00531   propagateall(g);
    00532   /* remark weak tables */
    00533   g->gray = g->weak;
    00534   g->weak = NULL;
    00535   lua_assert(!iswhite(obj2gco(g->mainthread)));
    00536   markobject(g, L);  /* mark running thread */
    00537   markmt(g);  /* mark basic metatables (again) */
    00538   propagateall(g);
    00539   /* remark gray again */
    00540   g->gray = g->grayagain;
    00541   g->grayagain = NULL;
    00542   propagateall(g);
    00543   udsize = luaC_separateudata(L, 0);  /* separate userdata to be finalized */
    00544   marktmu(g);  /* mark `preserved' userdata */
    00545   udsize += propagateall(g);  /* remark, to propagate `preserveness' */
    00546   cleartable(g->weak);  /* remove collected objects from weak tables */
    00547   /* flip current white */
    00548   g->currentwhite = cast_byte(otherwhite(g));
    00549   g->sweepstrgc = 0;
    00550   g->sweepgc = &g->rootgc;
    00551   g->gcstate = GCSsweepstring;
    00552   g->estimate = g->totalbytes - udsize;  /* first estimate */
    00553 }
    00554
    00555
    00556 static l_mem singlestep (lua_State *L) {
    00557   global_State *g = G(L);
    00558   /*lua_checkmemory(L);*/
    00559   switch (g->gcstate) {
    00560     case GCSpause: {
    00561       markroot(L);  /* start a new collection */
    00562       return 0;
    00563     }
    00564     case GCSpropagate: {
    00565       if (g->gray)
    00566         return propagatemark(g);
    00567       else {  /* no more `gray' objects */
    00568         atomic(L);  /* finish mark phase */
    00569         return 0;
    00570       }
    00571     }
    00572     case GCSsweepstring: {
    00573       lu_mem old = g->totalbytes;
    00574       sweepwholelist(L, &g->strt.hash[g->sweepstrgc++]);
    00575       if (g->sweepstrgc >= g->strt.size)  /* nothing more to sweep? */
    00576         g->gcstate = GCSsweep;  /* end sweep-string phase */
    00577       lua_assert(old >= g->totalbytes);
    00578       g->estimate -= old - g->totalbytes;
    00579       return GCSWEEPCOST;
    00580     }
    00581     case GCSsweep: {
    00582       lu_mem old = g->totalbytes;
    00583       g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
    00584       if (*g->sweepgc == NULL) {  /* nothing more to sweep? */
    00585         checkSizes(L);
    00586         g->gcstate = GCSfinalize;  /* end sweep phase */
    00587       }
    00588       lua_assert(old >= g->totalbytes);
    00589       g->estimate -= old - g->totalbytes;
    00590       return GCSWEEPMAX*GCSWEEPCOST;
    00591     }
    00592     case GCSfinalize: {
    00593       if (g->tmudata) {
    00594         GCTM(L);
    00595         if (g->estimate > GCFINALIZECOST)
    00596           g->estimate -= GCFINALIZECOST;
    00597         return GCFINALIZECOST;
    00598       }
    00599       else {
    00600         g->gcstate = GCSpause;  /* end collection */
    00601         g->gcdept = 0;
    00602         return 0;
    00603       }
    00604     }
    00605     default: lua_assert(0); return 0;
    00606   }
    00607 }
    00608
    00609
    00610 void luaC_step (lua_State *L) {
    00611   global_State *g = G(L);
    00612   l_mem lim = (GCSTEPSIZE/100) * g->gcstepmul;
    00613   if (lim == 0)
    00614     lim = (MAX_LUMEM-1)/2;  /* no limit */
    00615   g->gcdept += g->totalbytes - g->GCthreshold;
    00616   do {
    00617     lim -= singlestep(L);
    00618     if (g->gcstate == GCSpause)
    00619       break;
    00620   } while (lim > 0);
    00621   if (g->gcstate != GCSpause) {
    00622     if (g->gcdept < GCSTEPSIZE)
    00623       g->GCthreshold = g->totalbytes + GCSTEPSIZE;  /* - lim/g->gcstepmul;*/
    00624     else {
    00625       g->gcdept -= GCSTEPSIZE;
    00626       g->GCthreshold = g->totalbytes;
    00627     }
    00628   }
    00629   else {
    00630     lua_assert(g->totalbytes >= g->estimate);
    00631     setthreshold(g);
    00632   }
    00633 }
    00634
    00635
    00636 void luaC_fullgc (lua_State *L) {
    00637   global_State *g = G(L);
    00638   if (g->gcstate <= GCSpropagate) {
    00639     /* reset sweep marks to sweep all elements (returning them to white) */
    00640     g->sweepstrgc = 0;
    00641     g->sweepgc = &g->rootgc;
    00642     /* reset other collector lists */
    00643     g->gray = NULL;
    00644     g->grayagain = NULL;
    00645     g->weak = NULL;
    00646     g->gcstate = GCSsweepstring;
    00647   }
    00648   lua_assert(g->gcstate != GCSpause && g->gcstate != GCSpropagate);
    00649   /* finish any pending sweep phase */
    00650   while (g->gcstate != GCSfinalize) {
    00651     lua_assert(g->gcstate == GCSsweepstring || g->gcstate == GCSsweep);
    00652     singlestep(L);
    00653   }
    00654   markroot(L);
    00655   while (g->gcstate != GCSpause) {
    00656     singlestep(L);
    00657   }
    00658   setthreshold(g);
    00659 }
    00660
    00661
    00662 void luaC_barrierf (lua_State *L, GCObject *o, GCObject *v) {
    00663   global_State *g = G(L);
    00664   lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
    00665   lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
    00666   lua_assert(ttype(&o->gch) != LUA_TTABLE);
    00667   /* must keep invariant? */
    00668   if (g->gcstate == GCSpropagate)
    00669     reallymarkobject(g, v);  /* restore invariant */
    00670   else  /* don't mind */
    00671     makewhite(g, o);  /* mark as white just to avoid other barriers */
    00672 }
    00673
    00674
    00675 void luaC_barrierback (lua_State *L, Table *t) {
    00676   global_State *g = G(L);
    00677   GCObject *o = obj2gco(t);
    00678   lua_assert(isblack(o) && !isdead(g, o));
    00679   lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
    00680   black2gray(o);  /* make table gray (again) */
    00681   t->gclist = g->grayagain;
    00682   g->grayagain = o;
    00683 }
    00684
    00685
    00686 void luaC_link (lua_State *L, GCObject *o, lu_byte tt) {
    00687   global_State *g = G(L);
    00688   o->gch.next = g->rootgc;
    00689   g->rootgc = o;
    00690   o->gch.marked = luaC_white(g);
    00691   o->gch.tt = tt;
    00692 }
    00693
    00694
    00695 void luaC_linkupval (lua_State *L, UpVal *uv) {
    00696   global_State *g = G(L);
    00697   GCObject *o = obj2gco(uv);
    00698   o->gch.next = g->rootgc;  /* link upvalue into `rootgc' list */
    00699   g->rootgc = o;
    00700   if (isgray(o)) {
    00701     if (g->gcstate == GCSpropagate) {
    00702       gray2black(o);  /* closed upvalues need barrier */
    00703       luaC_barrier(L, uv, uv->v);
    00704     }
    00705     else {  /* sweep phase: sweep it (turning it into white) */
    00706       makewhite(g, o);
    00707       lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
    00708     }
    00709   }
    00710 }
    00711