ref: 74fcae28e6618ef19ba1b219b05e958475423a46
dir: /lua/src/lgc.c/
/*
** $Id: lgc.c,v 1.1 2006/12/23 01:55:12 rrt Exp $
** Garbage Collector
** See Copyright Notice in lua.h
*/
#include <string.h>
#define lgc_c
#define LUA_CORE
#include "lua.h"
#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "lgc.h"
#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"
#include "ltm.h"
#define GCSTEPSIZE 1024u
#define GCSWEEPMAX 40
#define GCSWEEPCOST 10
#define GCFINALIZECOST 100
#define maskmarks cast_byte(~(bitmask(BLACKBIT)|WHITEBITS))
#define makewhite(g,x) \
((x)->gch.marked = cast_byte(((x)->gch.marked & maskmarks) | luaC_white(g)))
#define white2gray(x) reset2bits((x)->gch.marked, WHITE0BIT, WHITE1BIT)
#define black2gray(x) resetbit((x)->gch.marked, BLACKBIT)
#define stringmark(s) reset2bits((s)->tsv.marked, WHITE0BIT, WHITE1BIT)
#define isfinalized(u) testbit((u)->marked, FINALIZEDBIT)
#define markfinalized(u) l_setbit((u)->marked, FINALIZEDBIT)
#define KEYWEAK bitmask(KEYWEAKBIT)
#define VALUEWEAK bitmask(VALUEWEAKBIT)
#define markvalue(g,o) { checkconsistency(o); \
if (iscollectable(o) && iswhite(gcvalue(o))) reallymarkobject(g,gcvalue(o)); }
#define markobject(g,t) { if (iswhite(obj2gco(t))) \
reallymarkobject(g, obj2gco(t)); }
#define setthreshold(g) (g->GCthreshold = (g->estimate/100) * g->gcpause)
static void removeentry (Node *n) {
lua_assert(ttisnil(gval(n)));
if (iscollectable(gkey(n)))
setttype(gkey(n), LUA_TDEADKEY); /* dead key; remove it */
}
static void reallymarkobject (global_State *g, GCObject *o) {
lua_assert(iswhite(o) && !isdead(g, o));
white2gray(o);
switch (o->gch.tt) {
case LUA_TSTRING: {
return;
}
case LUA_TUSERDATA: {
Table *mt = gco2u(o)->metatable;
gray2black(o); /* udata are never gray */
if (mt) markobject(g, mt);
markobject(g, gco2u(o)->env);
return;
}
case LUA_TUPVAL: {
UpVal *uv = gco2uv(o);
markvalue(g, uv->v);
if (uv->v == &uv->u.value) /* closed? */
gray2black(o); /* open upvalues are never black */
return;
}
case LUA_TFUNCTION: {
gco2cl(o)->c.gclist = g->gray;
g->gray = o;
break;
}
case LUA_TTABLE: {
gco2h(o)->gclist = g->gray;
g->gray = o;
break;
}
case LUA_TTHREAD: {
gco2th(o)->gclist = g->gray;
g->gray = o;
break;
}
case LUA_TPROTO: {
gco2p(o)->gclist = g->gray;
g->gray = o;
break;
}
default: lua_assert(0);
}
}
static void marktmu (global_State *g) {
GCObject *u = g->tmudata;
if (u) {
do {
u = u->gch.next;
makewhite(g, u); /* may be marked, if left from previous GC */
reallymarkobject(g, u);
} while (u != g->tmudata);
}
}
/* move `dead' udata that need finalization to list `tmudata' */
size_t luaC_separateudata (lua_State *L, int all) {
global_State *g = G(L);
size_t deadmem = 0;
GCObject **p = &g->mainthread->next;
GCObject *curr;
while ((curr = *p) != NULL) {
if (!(iswhite(curr) || all) || isfinalized(gco2u(curr)))
p = &curr->gch.next; /* don't bother with them */
else if (fasttm(L, gco2u(curr)->metatable, TM_GC) == NULL) {
markfinalized(gco2u(curr)); /* don't need finalization */
p = &curr->gch.next;
}
else { /* must call its gc method */
deadmem += sizeudata(gco2u(curr));
markfinalized(gco2u(curr));
*p = curr->gch.next;
/* link `curr' at the end of `tmudata' list */
if (g->tmudata == NULL) /* list is empty? */
g->tmudata = curr->gch.next = curr; /* creates a circular list */
else {
curr->gch.next = g->tmudata->gch.next;
g->tmudata->gch.next = curr;
g->tmudata = curr;
}
}
}
return deadmem;
}
static int traversetable (global_State *g, Table *h) {
int i;
int weakkey = 0;
int weakvalue = 0;
const TValue *mode;
if (h->metatable)
markobject(g, h->metatable);
mode = gfasttm(g, h->metatable, TM_MODE);
if (mode && ttisstring(mode)) { /* is there a weak mode? */
weakkey = (strchr(svalue(mode), 'k') != NULL);
weakvalue = (strchr(svalue(mode), 'v') != NULL);
if (weakkey || weakvalue) { /* is really weak? */
h->marked &= ~(KEYWEAK | VALUEWEAK); /* clear bits */
h->marked |= cast_byte((weakkey << KEYWEAKBIT) |
(weakvalue << VALUEWEAKBIT));
h->gclist = g->weak; /* must be cleared after GC, ... */
g->weak = obj2gco(h); /* ... so put in the appropriate list */
}
}
if (weakkey && weakvalue) return 1;
if (!weakvalue) {
i = h->sizearray;
while (i--)
markvalue(g, &h->array[i]);
}
i = sizenode(h);
while (i--) {
Node *n = gnode(h, i);
lua_assert(ttype(gkey(n)) != LUA_TDEADKEY || ttisnil(gval(n)));
if (ttisnil(gval(n)))
removeentry(n); /* remove empty entries */
else {
lua_assert(!ttisnil(gkey(n)));
if (!weakkey) markvalue(g, gkey(n));
if (!weakvalue) markvalue(g, gval(n));
}
}
return weakkey || weakvalue;
}
/*
** All marks are conditional because a GC may happen while the
** prototype is still being created
*/
static void traverseproto (global_State *g, Proto *f) {
int i;
if (f->source) stringmark(f->source);
for (i=0; i<f->sizek; i++) /* mark literals */
markvalue(g, &f->k[i]);
for (i=0; i<f->sizeupvalues; i++) { /* mark upvalue names */
if (f->upvalues[i])
stringmark(f->upvalues[i]);
}
for (i=0; i<f->sizep; i++) { /* mark nested protos */
if (f->p[i])
markobject(g, f->p[i]);
}
for (i=0; i<f->sizelocvars; i++) { /* mark local-variable names */
if (f->locvars[i].varname)
stringmark(f->locvars[i].varname);
}
}
static void traverseclosure (global_State *g, Closure *cl) {
markobject(g, cl->c.env);
if (cl->c.isC) {
int i;
for (i=0; i<cl->c.nupvalues; i++) /* mark its upvalues */
markvalue(g, &cl->c.upvalue[i]);
}
else {
int i;
lua_assert(cl->l.nupvalues == cl->l.p->nups);
markobject(g, cl->l.p);
for (i=0; i<cl->l.nupvalues; i++) /* mark its upvalues */
markobject(g, cl->l.upvals[i]);
}
}
static void checkstacksizes (lua_State *L, StkId max) {
int ci_used = cast_int(L->ci - L->base_ci); /* number of `ci' in use */
int s_used = cast_int(max - L->stack); /* part of stack in use */
if (L->size_ci > LUAI_MAXCALLS) /* handling overflow? */
return; /* do not touch the stacks */
if (4*ci_used < L->size_ci && 2*BASIC_CI_SIZE < L->size_ci)
luaD_reallocCI(L, L->size_ci/2); /* still big enough... */
condhardstacktests(luaD_reallocCI(L, ci_used + 1));
if (4*s_used < L->stacksize &&
2*(BASIC_STACK_SIZE+EXTRA_STACK) < L->stacksize)
luaD_reallocstack(L, L->stacksize/2); /* still big enough... */
condhardstacktests(luaD_reallocstack(L, s_used));
}
static void traversestack (global_State *g, lua_State *l) {
StkId o, lim;
CallInfo *ci;
markvalue(g, gt(l));
lim = l->top;
for (ci = l->base_ci; ci <= l->ci; ci++) {
lua_assert(ci->top <= l->stack_last);
if (lim < ci->top) lim = ci->top;
}
for (o = l->stack; o < l->top; o++)
markvalue(g, o);
for (; o <= lim; o++)
setnilvalue(o);
checkstacksizes(l, lim);
}
/*
** traverse one gray object, turning it to black.
** Returns `quantity' traversed.
*/
static l_mem propagatemark (global_State *g) {
GCObject *o = g->gray;
lua_assert(isgray(o));
gray2black(o);
switch (o->gch.tt) {
case LUA_TTABLE: {
Table *h = gco2h(o);
g->gray = h->gclist;
if (traversetable(g, h)) /* table is weak? */
black2gray(o); /* keep it gray */
return sizeof(Table) + sizeof(TValue) * h->sizearray +
sizeof(Node) * sizenode(h);
}
case LUA_TFUNCTION: {
Closure *cl = gco2cl(o);
g->gray = cl->c.gclist;
traverseclosure(g, cl);
return (cl->c.isC) ? sizeCclosure(cl->c.nupvalues) :
sizeLclosure(cl->l.nupvalues);
}
case LUA_TTHREAD: {
lua_State *th = gco2th(o);
g->gray = th->gclist;
th->gclist = g->grayagain;
g->grayagain = o;
black2gray(o);
traversestack(g, th);
return sizeof(lua_State) + sizeof(TValue) * th->stacksize +
sizeof(CallInfo) * th->size_ci;
}
case LUA_TPROTO: {
Proto *p = gco2p(o);
g->gray = p->gclist;
traverseproto(g, p);
return sizeof(Proto) + sizeof(Instruction) * p->sizecode +
sizeof(Proto *) * p->sizep +
sizeof(TValue) * p->sizek +
sizeof(int) * p->sizelineinfo +
sizeof(LocVar) * p->sizelocvars +
sizeof(TString *) * p->sizeupvalues;
}
default: lua_assert(0); return 0;
}
}
static size_t propagateall (global_State *g) {
size_t m = 0;
while (g->gray) m += propagatemark(g);
return m;
}
/*
** The next function tells whether a key or value can be cleared from
** a weak table. Non-collectable objects are never removed from weak
** tables. Strings behave as `values', so are never removed too. for
** other objects: if really collected, cannot keep them; for userdata
** being finalized, keep them in keys, but not in values
*/
static int iscleared (const TValue *o, int iskey) {
if (!iscollectable(o)) return 0;
if (ttisstring(o)) {
stringmark(rawtsvalue(o)); /* strings are `values', so are never weak */
return 0;
}
return iswhite(gcvalue(o)) ||
(ttisuserdata(o) && (!iskey && isfinalized(uvalue(o))));
}
/*
** clear collected entries from weaktables
*/
static void cleartable (GCObject *l) {
while (l) {
Table *h = gco2h(l);
int i = h->sizearray;
lua_assert(testbit(h->marked, VALUEWEAKBIT) ||
testbit(h->marked, KEYWEAKBIT));
if (testbit(h->marked, VALUEWEAKBIT)) {
while (i--) {
TValue *o = &h->array[i];
if (iscleared(o, 0)) /* value was collected? */
setnilvalue(o); /* remove value */
}
}
i = sizenode(h);
while (i--) {
Node *n = gnode(h, i);
if (!ttisnil(gval(n)) && /* non-empty entry? */
(iscleared(key2tval(n), 1) || iscleared(gval(n), 0))) {
setnilvalue(gval(n)); /* remove value ... */
removeentry(n); /* remove entry from table */
}
}
l = h->gclist;
}
}
static void freeobj (lua_State *L, GCObject *o) {
switch (o->gch.tt) {
case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break;
case LUA_TFUNCTION: luaF_freeclosure(L, gco2cl(o)); break;
case LUA_TUPVAL: luaF_freeupval(L, gco2uv(o)); break;
case LUA_TTABLE: luaH_free(L, gco2h(o)); break;
case LUA_TTHREAD: {
lua_assert(gco2th(o) != L && gco2th(o) != G(L)->mainthread);
luaE_freethread(L, gco2th(o));
break;
}
case LUA_TSTRING: {
G(L)->strt.nuse--;
luaM_freemem(L, o, sizestring(gco2ts(o)));
break;
}
case LUA_TUSERDATA: {
luaM_freemem(L, o, sizeudata(gco2u(o)));
break;
}
default: lua_assert(0);
}
}
#define sweepwholelist(L,p) sweeplist(L,p,MAX_LUMEM)
static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
GCObject *curr;
global_State *g = G(L);
int deadmask = otherwhite(g);
while ((curr = *p) != NULL && count-- > 0) {
if (curr->gch.tt == LUA_TTHREAD) /* sweep open upvalues of each thread */
sweepwholelist(L, &gco2th(curr)->openupval);
if ((curr->gch.marked ^ WHITEBITS) & deadmask) { /* not dead? */
lua_assert(!isdead(g, curr) || testbit(curr->gch.marked, FIXEDBIT));
makewhite(g, curr); /* make it white (for next cycle) */
p = &curr->gch.next;
}
else { /* must erase `curr' */
lua_assert(isdead(g, curr) || deadmask == bitmask(SFIXEDBIT));
*p = curr->gch.next;
if (curr == g->rootgc) /* is the first element of the list? */
g->rootgc = curr->gch.next; /* adjust first */
freeobj(L, curr);
}
}
return p;
}
static void checkSizes (lua_State *L) {
global_State *g = G(L);
/* check size of string hash */
if (g->strt.nuse < cast(lu_int32, g->strt.size/4) &&
g->strt.size > MINSTRTABSIZE*2)
luaS_resize(L, g->strt.size/2); /* table is too big */
/* check size of buffer */
if (luaZ_sizebuffer(&g->buff) > LUA_MINBUFFER*2) { /* buffer too big? */
size_t newsize = luaZ_sizebuffer(&g->buff) / 2;
luaZ_resizebuffer(L, &g->buff, newsize);
}
}
static void GCTM (lua_State *L) {
global_State *g = G(L);
GCObject *o = g->tmudata->gch.next; /* get first element */
Udata *udata = rawgco2u(o);
const TValue *tm;
/* remove udata from `tmudata' */
if (o == g->tmudata) /* last element? */
g->tmudata = NULL;
else
g->tmudata->gch.next = udata->uv.next;
udata->uv.next = g->mainthread->next; /* return it to `root' list */
g->mainthread->next = o;
makewhite(g, o);
tm = fasttm(L, udata->uv.metatable, TM_GC);
if (tm != NULL) {
lu_byte oldah = L->allowhook;
lu_mem oldt = g->GCthreshold;
L->allowhook = 0; /* stop debug hooks during GC tag method */
g->GCthreshold = 2*g->totalbytes; /* avoid GC steps */
setobj2s(L, L->top, tm);
setuvalue(L, L->top+1, udata);
L->top += 2;
luaD_call(L, L->top - 2, 0);
L->allowhook = oldah; /* restore hooks */
g->GCthreshold = oldt; /* restore threshold */
}
}
/*
** Call all GC tag methods
*/
void luaC_callGCTM (lua_State *L) {
while (G(L)->tmudata)
GCTM(L);
}
void luaC_freeall (lua_State *L) {
global_State *g = G(L);
int i;
g->currentwhite = WHITEBITS | bitmask(SFIXEDBIT); /* mask to collect all elements */
sweepwholelist(L, &g->rootgc);
for (i = 0; i < g->strt.size; i++) /* free all string lists */
sweepwholelist(L, &g->strt.hash[i]);
}
static void markmt (global_State *g) {
int i;
for (i=0; i<NUM_TAGS; i++)
if (g->mt[i]) markobject(g, g->mt[i]);
}
/* mark root set */
static void markroot (lua_State *L) {
global_State *g = G(L);
g->gray = NULL;
g->grayagain = NULL;
g->weak = NULL;
markobject(g, g->mainthread);
/* make global table be traversed before main stack */
markvalue(g, gt(g->mainthread));
markvalue(g, registry(L));
markmt(g);
g->gcstate = GCSpropagate;
}
static void remarkupvals (global_State *g) {
UpVal *uv;
for (uv = g->uvhead.u.l.next; uv != &g->uvhead; uv = uv->u.l.next) {
lua_assert(uv->u.l.next->u.l.prev == uv && uv->u.l.prev->u.l.next == uv);
if (isgray(obj2gco(uv)))
markvalue(g, uv->v);
}
}
static void atomic (lua_State *L) {
global_State *g = G(L);
size_t udsize; /* total size of userdata to be finalized */
/* remark occasional upvalues of (maybe) dead threads */
remarkupvals(g);
/* traverse objects cautch by write barrier and by 'remarkupvals' */
propagateall(g);
/* remark weak tables */
g->gray = g->weak;
g->weak = NULL;
lua_assert(!iswhite(obj2gco(g->mainthread)));
markobject(g, L); /* mark running thread */
markmt(g); /* mark basic metatables (again) */
propagateall(g);
/* remark gray again */
g->gray = g->grayagain;
g->grayagain = NULL;
propagateall(g);
udsize = luaC_separateudata(L, 0); /* separate userdata to be finalized */
marktmu(g); /* mark `preserved' userdata */
udsize += propagateall(g); /* remark, to propagate `preserveness' */
cleartable(g->weak); /* remove collected objects from weak tables */
/* flip current white */
g->currentwhite = cast_byte(otherwhite(g));
g->sweepstrgc = 0;
g->sweepgc = &g->rootgc;
g->gcstate = GCSsweepstring;
g->estimate = g->totalbytes - udsize; /* first estimate */
}
static l_mem singlestep (lua_State *L) {
global_State *g = G(L);
/*lua_checkmemory(L);*/
switch (g->gcstate) {
case GCSpause: {
markroot(L); /* start a new collection */
return 0;
}
case GCSpropagate: {
if (g->gray)
return propagatemark(g);
else { /* no more `gray' objects */
atomic(L); /* finish mark phase */
return 0;
}
}
case GCSsweepstring: {
lu_mem old = g->totalbytes;
sweepwholelist(L, &g->strt.hash[g->sweepstrgc++]);
if (g->sweepstrgc >= g->strt.size) /* nothing more to sweep? */
g->gcstate = GCSsweep; /* end sweep-string phase */
lua_assert(old >= g->totalbytes);
g->estimate -= old - g->totalbytes;
return GCSWEEPCOST;
}
case GCSsweep: {
lu_mem old = g->totalbytes;
g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
if (*g->sweepgc == NULL) { /* nothing more to sweep? */
checkSizes(L);
g->gcstate = GCSfinalize; /* end sweep phase */
}
lua_assert(old >= g->totalbytes);
g->estimate -= old - g->totalbytes;
return GCSWEEPMAX*GCSWEEPCOST;
}
case GCSfinalize: {
if (g->tmudata) {
GCTM(L);
if (g->estimate > GCFINALIZECOST)
g->estimate -= GCFINALIZECOST;
return GCFINALIZECOST;
}
else {
g->gcstate = GCSpause; /* end collection */
g->gcdept = 0;
return 0;
}
}
default: lua_assert(0); return 0;
}
}
void luaC_step (lua_State *L) {
global_State *g = G(L);
l_mem lim = (GCSTEPSIZE/100) * g->gcstepmul;
if (lim == 0)
lim = (MAX_LUMEM-1)/2; /* no limit */
g->gcdept += g->totalbytes - g->GCthreshold;
do {
lim -= singlestep(L);
if (g->gcstate == GCSpause)
break;
} while (lim > 0);
if (g->gcstate != GCSpause) {
if (g->gcdept < GCSTEPSIZE)
g->GCthreshold = g->totalbytes + GCSTEPSIZE; /* - lim/g->gcstepmul;*/
else {
g->gcdept -= GCSTEPSIZE;
g->GCthreshold = g->totalbytes;
}
}
else {
lua_assert(g->totalbytes >= g->estimate);
setthreshold(g);
}
}
void luaC_fullgc (lua_State *L) {
global_State *g = G(L);
if (g->gcstate <= GCSpropagate) {
/* reset sweep marks to sweep all elements (returning them to white) */
g->sweepstrgc = 0;
g->sweepgc = &g->rootgc;
/* reset other collector lists */
g->gray = NULL;
g->grayagain = NULL;
g->weak = NULL;
g->gcstate = GCSsweepstring;
}
lua_assert(g->gcstate != GCSpause && g->gcstate != GCSpropagate);
/* finish any pending sweep phase */
while (g->gcstate != GCSfinalize) {
lua_assert(g->gcstate == GCSsweepstring || g->gcstate == GCSsweep);
singlestep(L);
}
markroot(L);
while (g->gcstate != GCSpause) {
singlestep(L);
}
setthreshold(g);
}
void luaC_barrierf (lua_State *L, GCObject *o, GCObject *v) {
global_State *g = G(L);
lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
lua_assert(ttype(&o->gch) != LUA_TTABLE);
/* must keep invariant? */
if (g->gcstate == GCSpropagate)
reallymarkobject(g, v); /* restore invariant */
else /* don't mind */
makewhite(g, o); /* mark as white just to avoid other barriers */
}
void luaC_barrierback (lua_State *L, Table *t) {
global_State *g = G(L);
GCObject *o = obj2gco(t);
lua_assert(isblack(o) && !isdead(g, o));
lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
black2gray(o); /* make table gray (again) */
t->gclist = g->grayagain;
g->grayagain = o;
}
void luaC_link (lua_State *L, GCObject *o, lu_byte tt) {
global_State *g = G(L);
o->gch.next = g->rootgc;
g->rootgc = o;
o->gch.marked = luaC_white(g);
o->gch.tt = tt;
}
void luaC_linkupval (lua_State *L, UpVal *uv) {
global_State *g = G(L);
GCObject *o = obj2gco(uv);
o->gch.next = g->rootgc; /* link upvalue into `rootgc' list */
g->rootgc = o;
if (isgray(o)) {
if (g->gcstate == GCSpropagate) {
gray2black(o); /* closed upvalues need barrier */
luaC_barrier(L, uv, uv->v);
}
else { /* sweep phase: sweep it (turning it into white) */
makewhite(g, o);
lua_assert(g->gcstate != GCSfinalize && g->gcstate != GCSpause);
}
}
}