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view src/lua/lgc.c @ 575:15876b1a0906
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author | Robert McIntyre <rlm@mit.edu> |
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date | Sat, 01 Sep 2012 04:15:32 -0500 (2012-09-01) |
parents | 27763b933818 |
children |
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1 /*2 ** $Id: lgc.c,v 2.38.1.1 2007/12/27 13:02:25 roberto Exp $3 ** Garbage Collector4 ** See Copyright Notice in lua.h5 */7 #include <string.h>9 #define lgc_c10 #define LUA_CORE12 #include "lua.h"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"26 #define GCSTEPSIZE 1024u27 #define GCSWEEPMAX 4028 #define GCSWEEPCOST 1029 #define GCFINALIZECOST 10032 #define maskmarks cast_byte(~(bitmask(BLACKBIT)|WHITEBITS))34 #define makewhite(g,x) \35 ((x)->gch.marked = cast_byte(((x)->gch.marked & maskmarks) | luaC_white(g)))37 #define white2gray(x) reset2bits((x)->gch.marked, WHITE0BIT, WHITE1BIT)38 #define black2gray(x) resetbit((x)->gch.marked, BLACKBIT)40 #define stringmark(s) reset2bits((s)->tsv.marked, WHITE0BIT, WHITE1BIT)43 #define isfinalized(u) testbit((u)->marked, FINALIZEDBIT)44 #define markfinalized(u) l_setbit((u)->marked, FINALIZEDBIT)47 #define KEYWEAK bitmask(KEYWEAKBIT)48 #define VALUEWEAK bitmask(VALUEWEAKBIT)52 #define markvalue(g,o) { checkconsistency(o); \53 if (iscollectable(o) && iswhite(gcvalue(o))) reallymarkobject(g,gcvalue(o)); }55 #define markobject(g,t) { if (iswhite(obj2gco(t))) \56 reallymarkobject(g, obj2gco(t)); }59 #define setthreshold(g) (g->GCthreshold = (g->estimate/100) * g->gcpause)62 static 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 }69 static 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 }115 static 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 }127 /* move `dead' udata that need finalization to list `tmudata' */128 size_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 }158 static 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 }199 /*200 ** All marks are conditional because a GC may happen while the201 ** prototype is still being created202 */203 static 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 }224 static 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 }241 static 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 }256 static 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 }273 /*274 ** traverse one gray object, turning it to black.275 ** Returns `quantity' traversed.276 */277 static 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 }323 static size_t propagateall (global_State *g) {324 size_t m = 0;325 while (g->gray) m += propagatemark(g);326 return m;327 }330 /*331 ** The next function tells whether a key or value can be cleared from332 ** a weak table. Non-collectable objects are never removed from weak333 ** tables. Strings behave as `values', so are never removed too. for334 ** other objects: if really collected, cannot keep them; for userdata335 ** being finalized, keep them in keys, but not in values336 */337 static 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 }348 /*349 ** clear collected entries from weaktables350 */351 static 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 }378 static 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 }404 #define sweepwholelist(L,p) sweeplist(L,p,MAX_LUMEM)407 static 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 }431 static 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 }445 static 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 else454 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 }474 /*475 ** Call all GC tag methods476 */477 void luaC_callGCTM (lua_State *L) {478 while (G(L)->tmudata)479 GCTM(L);480 }483 void 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 }493 static 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 }500 /* mark root set */501 static 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 }515 static 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 }525 static 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 }556 static 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 }610 void 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 }636 void 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 }662 void 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 }675 void 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 }686 void 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 }695 void 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 }