+++ /dev/null
-/*
-** $Id: lgc.c,v 2.140.1.2 2013/04/26 18:22:05 roberto 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"
-
-
-
-/*
-** cost of sweeping one element (the size of a small object divided
-** by some adjust for the sweep speed)
-*/
-#define GCSWEEPCOST ((sizeof(TString) + 4) / 4)
-
-/* maximum number of elements to sweep in each single step */
-#define GCSWEEPMAX (cast_int((GCSTEPSIZE / GCSWEEPCOST) / 4))
-
-/* maximum number of finalizers to call in each GC step */
-#define GCFINALIZENUM 4
-
-
-/*
-** macro to adjust 'stepmul': 'stepmul' is actually used like
-** 'stepmul / STEPMULADJ' (value chosen by tests)
-*/
-#define STEPMULADJ 200
-
-
-/*
-** macro to adjust 'pause': 'pause' is actually used like
-** 'pause / PAUSEADJ' (value chosen by tests)
-*/
-#define PAUSEADJ 100
-
-
-/*
-** 'makewhite' erases all color bits plus the old bit and then
-** sets only the current white bit
-*/
-#define maskcolors (~(bit2mask(BLACKBIT, OLDBIT) | WHITEBITS))
-#define makewhite(g,x) \
- (gch(x)->marked = cast_byte((gch(x)->marked & maskcolors) | luaC_white(g)))
-
-#define white2gray(x) resetbits(gch(x)->marked, WHITEBITS)
-#define black2gray(x) resetbit(gch(x)->marked, BLACKBIT)
-
-
-#define isfinalized(x) testbit(gch(x)->marked, FINALIZEDBIT)
-
-#define checkdeadkey(n) lua_assert(!ttisdeadkey(gkey(n)) || ttisnil(gval(n)))
-
-
-#define checkconsistency(obj) \
- lua_longassert(!iscollectable(obj) || righttt(obj))
-
-
-#define markvalue(g,o) { checkconsistency(o); \
- if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); }
-
-#define markobject(g,t) { if ((t) && iswhite(obj2gco(t))) \
- reallymarkobject(g, obj2gco(t)); }
-
-static void reallymarkobject (global_State *g, GCObject *o);
-
-
-/*
-** {======================================================
-** Generic functions
-** =======================================================
-*/
-
-
-/*
-** one after last element in a hash array
-*/
-#define gnodelast(h) gnode(h, cast(size_t, sizenode(h)))
-
-
-/*
-** link table 'h' into list pointed by 'p'
-*/
-#define linktable(h,p) ((h)->gclist = *(p), *(p) = obj2gco(h))
-
-
-/*
-** if key is not marked, mark its entry as dead (therefore removing it
-** from the table)
-*/
-static void removeentry (Node *n) {
- lua_assert(ttisnil(gval(n)));
- if (valiswhite(gkey(n)))
- setdeadvalue(gkey(n)); /* unused and unmarked key; remove it */
-}
-
-
-/*
-** 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 objects
-** being finalized, keep them in keys, but not in values
-*/
-static int iscleared (global_State *g, const TValue *o) {
- if (!iscollectable(o)) return 0;
- else if (ttisstring(o)) {
- markobject(g, rawtsvalue(o)); /* strings are `values', so are never weak */
- return 0;
- }
- else return iswhite(gcvalue(o));
-}
-
-
-/*
-** barrier that moves collector forward, that is, mark the white object
-** being pointed by a black object.
-*/
-void luaC_barrier_ (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 != GCSpause);
- lua_assert(gch(o)->tt != LUA_TTABLE);
- if (keepinvariantout(g)) /* must keep invariant? */
- reallymarkobject(g, v); /* restore invariant */
- else { /* sweep phase */
- lua_assert(issweepphase(g));
- makewhite(g, o); /* mark main obj. as white to avoid other barriers */
- }
-}
-
-
-/*
-** barrier that moves collector backward, that is, mark the black object
-** pointing to a white object as gray again. (Current implementation
-** only works for tables; access to 'gclist' is not uniform across
-** different types.)
-*/
-void luaC_barrierback_ (lua_State *L, GCObject *o) {
- global_State *g = G(L);
- lua_assert(isblack(o) && !isdead(g, o) && gch(o)->tt == LUA_TTABLE);
- black2gray(o); /* make object gray (again) */
- gco2t(o)->gclist = g->grayagain;
- g->grayagain = o;
-}
-
-
-/*
-** barrier for prototypes. When creating first closure (cache is
-** NULL), use a forward barrier; this may be the only closure of the
-** prototype (if it is a "regular" function, with a single instance)
-** and the prototype may be big, so it is better to avoid traversing
-** it again. Otherwise, use a backward barrier, to avoid marking all
-** possible instances.
-*/
-LUAI_FUNC void luaC_barrierproto_ (lua_State *L, Proto *p, Closure *c) {
- global_State *g = G(L);
- lua_assert(isblack(obj2gco(p)));
- if (p->cache == NULL) { /* first time? */
- luaC_objbarrier(L, p, c);
- }
- else { /* use a backward barrier */
- black2gray(obj2gco(p)); /* make prototype gray (again) */
- p->gclist = g->grayagain;
- g->grayagain = obj2gco(p);
- }
-}
-
-
-/*
-** check color (and invariants) for an upvalue that was closed,
-** i.e., moved into the 'allgc' list
-*/
-void luaC_checkupvalcolor (global_State *g, UpVal *uv) {
- GCObject *o = obj2gco(uv);
- lua_assert(!isblack(o)); /* open upvalues are never black */
- if (isgray(o)) {
- if (keepinvariant(g)) {
- resetoldbit(o); /* see MOVE OLD rule */
- gray2black(o); /* it is being visited now */
- markvalue(g, uv->v);
- }
- else {
- lua_assert(issweepphase(g));
- makewhite(g, o);
- }
- }
-}
-
-
-/*
-** create a new collectable object (with given type and size) and link
-** it to '*list'. 'offset' tells how many bytes to allocate before the
-** object itself (used only by states).
-*/
-GCObject *luaC_newobj (lua_State *L, int tt, size_t sz, GCObject **list,
- int offset) {
- global_State *g = G(L);
- char *raw = cast(char *, luaM_newobject(L, novariant(tt), sz));
- GCObject *o = obj2gco(raw + offset);
- if (list == NULL)
- list = &g->allgc; /* standard list for collectable objects */
- gch(o)->marked = luaC_white(g);
- gch(o)->tt = (lu_byte)tt;
- gch(o)->next = *list;
- *list = o;
- return o;
-}
-
-/* }====================================================== */
-
-
-
-/*
-** {======================================================
-** Mark functions
-** =======================================================
-*/
-
-
-/*
-** mark an object. Userdata, strings, and closed upvalues are visited
-** and turned black here. Other objects are marked gray and added
-** to appropriate list to be visited (and turned black) later. (Open
-** upvalues are already linked in 'headuv' list.)
-*/
-static void reallymarkobject (global_State *g, GCObject *o) {
- lu_mem size;
- white2gray(o);
- switch (gch(o)->tt) {
- case LUA_TSHRSTR:
- case LUA_TLNGSTR: {
- size = sizestring(gco2ts(o));
- break; /* nothing else to mark; make it black */
- }
- case LUA_TUSERDATA: {
- Table *mt = gco2u(o)->metatable;
- markobject(g, mt);
- markobject(g, gco2u(o)->env);
- size = sizeudata(gco2u(o));
- break;
- }
- case LUA_TUPVAL: {
- UpVal *uv = gco2uv(o);
- markvalue(g, uv->v);
- if (uv->v != &uv->u.value) /* open? */
- return; /* open upvalues remain gray */
- size = sizeof(UpVal);
- break;
- }
- case LUA_TLCL: {
- gco2lcl(o)->gclist = g->gray;
- g->gray = o;
- return;
- }
- case LUA_TCCL: {
- gco2ccl(o)->gclist = g->gray;
- g->gray = o;
- return;
- }
- case LUA_TTABLE: {
- linktable(gco2t(o), &g->gray);
- return;
- }
- case LUA_TTHREAD: {
- gco2th(o)->gclist = g->gray;
- g->gray = o;
- return;
- }
- case LUA_TPROTO: {
- gco2p(o)->gclist = g->gray;
- g->gray = o;
- return;
- }
- default: lua_assert(0); return;
- }
- gray2black(o);
- g->GCmemtrav += size;
-}
-
-
-/*
-** mark metamethods for basic types
-*/
-static void markmt (global_State *g) {
- int i;
- for (i=0; i < LUA_NUMTAGS; i++)
- markobject(g, g->mt[i]);
-}
-
-
-/*
-** mark all objects in list of being-finalized
-*/
-static void markbeingfnz (global_State *g) {
- GCObject *o;
- for (o = g->tobefnz; o != NULL; o = gch(o)->next) {
- makewhite(g, o);
- reallymarkobject(g, o);
- }
-}
-
-
-/*
-** mark all values stored in marked open upvalues. (See comment in
-** 'lstate.h'.)
-*/
-static void remarkupvals (global_State *g) {
- UpVal *uv;
- for (uv = g->uvhead.u.l.next; uv != &g->uvhead; uv = uv->u.l.next) {
- if (isgray(obj2gco(uv)))
- markvalue(g, uv->v);
- }
-}
-
-
-/*
-** mark root set and reset all gray lists, to start a new
-** incremental (or full) collection
-*/
-static void restartcollection (global_State *g) {
- g->gray = g->grayagain = NULL;
- g->weak = g->allweak = g->ephemeron = NULL;
- markobject(g, g->mainthread);
- markvalue(g, &g->l_registry);
- markmt(g);
- markbeingfnz(g); /* mark any finalizing object left from previous cycle */
-}
-
-/* }====================================================== */
-
-
-/*
-** {======================================================
-** Traverse functions
-** =======================================================
-*/
-
-static void traverseweakvalue (global_State *g, Table *h) {
- Node *n, *limit = gnodelast(h);
- /* if there is array part, assume it may have white values (do not
- traverse it just to check) */
- int hasclears = (h->sizearray > 0);
- for (n = gnode(h, 0); n < limit; n++) {
- checkdeadkey(n);
- if (ttisnil(gval(n))) /* entry is empty? */
- removeentry(n); /* remove it */
- else {
- lua_assert(!ttisnil(gkey(n)));
- markvalue(g, gkey(n)); /* mark key */
- if (!hasclears && iscleared(g, gval(n))) /* is there a white value? */
- hasclears = 1; /* table will have to be cleared */
- }
- }
- if (hasclears)
- linktable(h, &g->weak); /* has to be cleared later */
- else /* no white values */
- linktable(h, &g->grayagain); /* no need to clean */
-}
-
-
-static int traverseephemeron (global_State *g, Table *h) {
- int marked = 0; /* true if an object is marked in this traversal */
- int hasclears = 0; /* true if table has white keys */
- int prop = 0; /* true if table has entry "white-key -> white-value" */
- Node *n, *limit = gnodelast(h);
- int i;
- /* traverse array part (numeric keys are 'strong') */
- for (i = 0; i < h->sizearray; i++) {
- if (valiswhite(&h->array[i])) {
- marked = 1;
- reallymarkobject(g, gcvalue(&h->array[i]));
- }
- }
- /* traverse hash part */
- for (n = gnode(h, 0); n < limit; n++) {
- checkdeadkey(n);
- if (ttisnil(gval(n))) /* entry is empty? */
- removeentry(n); /* remove it */
- else if (iscleared(g, gkey(n))) { /* key is not marked (yet)? */
- hasclears = 1; /* table must be cleared */
- if (valiswhite(gval(n))) /* value not marked yet? */
- prop = 1; /* must propagate again */
- }
- else if (valiswhite(gval(n))) { /* value not marked yet? */
- marked = 1;
- reallymarkobject(g, gcvalue(gval(n))); /* mark it now */
- }
- }
- if (prop)
- linktable(h, &g->ephemeron); /* have to propagate again */
- else if (hasclears) /* does table have white keys? */
- linktable(h, &g->allweak); /* may have to clean white keys */
- else /* no white keys */
- linktable(h, &g->grayagain); /* no need to clean */
- return marked;
-}
-
-
-static void traversestrongtable (global_State *g, Table *h) {
- Node *n, *limit = gnodelast(h);
- int i;
- for (i = 0; i < h->sizearray; i++) /* traverse array part */
- markvalue(g, &h->array[i]);
- for (n = gnode(h, 0); n < limit; n++) { /* traverse hash part */
- checkdeadkey(n);
- if (ttisnil(gval(n))) /* entry is empty? */
- removeentry(n); /* remove it */
- else {
- lua_assert(!ttisnil(gkey(n)));
- markvalue(g, gkey(n)); /* mark key */
- markvalue(g, gval(n)); /* mark value */
- }
- }
-}
-
-
-static lu_mem traversetable (global_State *g, Table *h) {
- const char *weakkey, *weakvalue;
- const TValue *mode = gfasttm(g, h->metatable, TM_MODE);
- markobject(g, h->metatable);
- if (mode && ttisstring(mode) && /* is there a weak mode? */
- ((weakkey = strchr(svalue(mode), 'k')),
- (weakvalue = strchr(svalue(mode), 'v')),
- (weakkey || weakvalue))) { /* is really weak? */
- black2gray(obj2gco(h)); /* keep table gray */
- if (!weakkey) /* strong keys? */
- traverseweakvalue(g, h);
- else if (!weakvalue) /* strong values? */
- traverseephemeron(g, h);
- else /* all weak */
- linktable(h, &g->allweak); /* nothing to traverse now */
- }
- else /* not weak */
- traversestrongtable(g, h);
- return sizeof(Table) + sizeof(TValue) * h->sizearray +
- sizeof(Node) * cast(size_t, sizenode(h));
-}
-
-
-static int traverseproto (global_State *g, Proto *f) {
- int i;
- if (f->cache && iswhite(obj2gco(f->cache)))
- f->cache = NULL; /* allow cache to be collected */
- markobject(g, 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 */
- markobject(g, f->upvalues[i].name);
- for (i = 0; i < f->sizep; i++) /* mark nested protos */
- markobject(g, f->p[i]);
- for (i = 0; i < f->sizelocvars; i++) /* mark local-variable names */
- markobject(g, f->locvars[i].varname);
- return sizeof(Proto) + sizeof(Instruction) * f->sizecode +
- sizeof(Proto *) * f->sizep +
- sizeof(TValue) * f->sizek +
- sizeof(int) * f->sizelineinfo +
- sizeof(LocVar) * f->sizelocvars +
- sizeof(Upvaldesc) * f->sizeupvalues;
-}
-
-
-static lu_mem traverseCclosure (global_State *g, CClosure *cl) {
- int i;
- for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */
- markvalue(g, &cl->upvalue[i]);
- return sizeCclosure(cl->nupvalues);
-}
-
-static lu_mem traverseLclosure (global_State *g, LClosure *cl) {
- int i;
- markobject(g, cl->p); /* mark its prototype */
- for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */
- markobject(g, cl->upvals[i]);
- return sizeLclosure(cl->nupvalues);
-}
-
-
-static lu_mem traversestack (global_State *g, lua_State *th) {
- int n = 0;
- StkId o = th->stack;
- if (o == NULL)
- return 1; /* stack not completely built yet */
- for (; o < th->top; o++) /* mark live elements in the stack */
- markvalue(g, o);
- if (g->gcstate == GCSatomic) { /* final traversal? */
- StkId lim = th->stack + th->stacksize; /* real end of stack */
- for (; o < lim; o++) /* clear not-marked stack slice */
- setnilvalue(o);
- }
- else { /* count call infos to compute size */
- CallInfo *ci;
- for (ci = &th->base_ci; ci != th->ci; ci = ci->next)
- n++;
- }
- return sizeof(lua_State) + sizeof(TValue) * th->stacksize +
- sizeof(CallInfo) * n;
-}
-
-
-/*
-** traverse one gray object, turning it to black (except for threads,
-** which are always gray).
-*/
-static void propagatemark (global_State *g) {
- lu_mem size;
- GCObject *o = g->gray;
- lua_assert(isgray(o));
- gray2black(o);
- switch (gch(o)->tt) {
- case LUA_TTABLE: {
- Table *h = gco2t(o);
- g->gray = h->gclist; /* remove from 'gray' list */
- size = traversetable(g, h);
- break;
- }
- case LUA_TLCL: {
- LClosure *cl = gco2lcl(o);
- g->gray = cl->gclist; /* remove from 'gray' list */
- size = traverseLclosure(g, cl);
- break;
- }
- case LUA_TCCL: {
- CClosure *cl = gco2ccl(o);
- g->gray = cl->gclist; /* remove from 'gray' list */
- size = traverseCclosure(g, cl);
- break;
- }
- case LUA_TTHREAD: {
- lua_State *th = gco2th(o);
- g->gray = th->gclist; /* remove from 'gray' list */
- th->gclist = g->grayagain;
- g->grayagain = o; /* insert into 'grayagain' list */
- black2gray(o);
- size = traversestack(g, th);
- break;
- }
- case LUA_TPROTO: {
- Proto *p = gco2p(o);
- g->gray = p->gclist; /* remove from 'gray' list */
- size = traverseproto(g, p);
- break;
- }
- default: lua_assert(0); return;
- }
- g->GCmemtrav += size;
-}
-
-
-static void propagateall (global_State *g) {
- while (g->gray) propagatemark(g);
-}
-
-
-static void propagatelist (global_State *g, GCObject *l) {
- lua_assert(g->gray == NULL); /* no grays left */
- g->gray = l;
- propagateall(g); /* traverse all elements from 'l' */
-}
-
-/*
-** retraverse all gray lists. Because tables may be reinserted in other
-** lists when traversed, traverse the original lists to avoid traversing
-** twice the same table (which is not wrong, but inefficient)
-*/
-static void retraversegrays (global_State *g) {
- GCObject *weak = g->weak; /* save original lists */
- GCObject *grayagain = g->grayagain;
- GCObject *ephemeron = g->ephemeron;
- g->weak = g->grayagain = g->ephemeron = NULL;
- propagateall(g); /* traverse main gray list */
- propagatelist(g, grayagain);
- propagatelist(g, weak);
- propagatelist(g, ephemeron);
-}
-
-
-static void convergeephemerons (global_State *g) {
- int changed;
- do {
- GCObject *w;
- GCObject *next = g->ephemeron; /* get ephemeron list */
- g->ephemeron = NULL; /* tables will return to this list when traversed */
- changed = 0;
- while ((w = next) != NULL) {
- next = gco2t(w)->gclist;
- if (traverseephemeron(g, gco2t(w))) { /* traverse marked some value? */
- propagateall(g); /* propagate changes */
- changed = 1; /* will have to revisit all ephemeron tables */
- }
- }
- } while (changed);
-}
-
-/* }====================================================== */
-
-
-/*
-** {======================================================
-** Sweep Functions
-** =======================================================
-*/
-
-
-/*
-** clear entries with unmarked keys from all weaktables in list 'l' up
-** to element 'f'
-*/
-static void clearkeys (global_State *g, GCObject *l, GCObject *f) {
- for (; l != f; l = gco2t(l)->gclist) {
- Table *h = gco2t(l);
- Node *n, *limit = gnodelast(h);
- for (n = gnode(h, 0); n < limit; n++) {
- if (!ttisnil(gval(n)) && (iscleared(g, gkey(n)))) {
- setnilvalue(gval(n)); /* remove value ... */
- removeentry(n); /* and remove entry from table */
- }
- }
- }
-}
-
-
-/*
-** clear entries with unmarked values from all weaktables in list 'l' up
-** to element 'f'
-*/
-static void clearvalues (global_State *g, GCObject *l, GCObject *f) {
- for (; l != f; l = gco2t(l)->gclist) {
- Table *h = gco2t(l);
- Node *n, *limit = gnodelast(h);
- int i;
- for (i = 0; i < h->sizearray; i++) {
- TValue *o = &h->array[i];
- if (iscleared(g, o)) /* value was collected? */
- setnilvalue(o); /* remove value */
- }
- for (n = gnode(h, 0); n < limit; n++) {
- if (!ttisnil(gval(n)) && iscleared(g, gval(n))) {
- setnilvalue(gval(n)); /* remove value ... */
- removeentry(n); /* and remove entry from table */
- }
- }
- }
-}
-
-
-static void freeobj (lua_State *L, GCObject *o) {
- switch (gch(o)->tt) {
- case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break;
- case LUA_TLCL: {
- luaM_freemem(L, o, sizeLclosure(gco2lcl(o)->nupvalues));
- break;
- }
- case LUA_TCCL: {
- luaM_freemem(L, o, sizeCclosure(gco2ccl(o)->nupvalues));
- break;
- }
- case LUA_TUPVAL: luaF_freeupval(L, gco2uv(o)); break;
- case LUA_TTABLE: luaH_free(L, gco2t(o)); break;
- case LUA_TTHREAD: luaE_freethread(L, gco2th(o)); break;
- case LUA_TUSERDATA: luaM_freemem(L, o, sizeudata(gco2u(o))); break;
- case LUA_TSHRSTR:
- G(L)->strt.nuse--;
- /* go through */
- case LUA_TLNGSTR: {
- luaM_freemem(L, o, sizestring(gco2ts(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);
-
-
-/*
-** sweep the (open) upvalues of a thread and resize its stack and
-** list of call-info structures.
-*/
-static void sweepthread (lua_State *L, lua_State *L1) {
- if (L1->stack == NULL) return; /* stack not completely built yet */
- sweepwholelist(L, &L1->openupval); /* sweep open upvalues */
- luaE_freeCI(L1); /* free extra CallInfo slots */
- /* should not change the stack during an emergency gc cycle */
- if (G(L)->gckind != KGC_EMERGENCY)
- luaD_shrinkstack(L1);
-}
-
-
-/*
-** sweep at most 'count' elements from a list of GCObjects erasing dead
-** objects, where a dead (not alive) object is one marked with the "old"
-** (non current) white and not fixed.
-** In non-generational mode, change all non-dead objects back to white,
-** preparing for next collection cycle.
-** In generational mode, keep black objects black, and also mark them as
-** old; stop when hitting an old object, as all objects after that
-** one will be old too.
-** When object is a thread, sweep its list of open upvalues too.
-*/
-static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
- global_State *g = G(L);
- int ow = otherwhite(g);
- int toclear, toset; /* bits to clear and to set in all live objects */
- int tostop; /* stop sweep when this is true */
- if (isgenerational(g)) { /* generational mode? */
- toclear = ~0; /* clear nothing */
- toset = bitmask(OLDBIT); /* set the old bit of all surviving objects */
- tostop = bitmask(OLDBIT); /* do not sweep old generation */
- }
- else { /* normal mode */
- toclear = maskcolors; /* clear all color bits + old bit */
- toset = luaC_white(g); /* make object white */
- tostop = 0; /* do not stop */
- }
- while (*p != NULL && count-- > 0) {
- GCObject *curr = *p;
- int marked = gch(curr)->marked;
- if (isdeadm(ow, marked)) { /* is 'curr' dead? */
- *p = gch(curr)->next; /* remove 'curr' from list */
- freeobj(L, curr); /* erase 'curr' */
- }
- else {
- if (testbits(marked, tostop))
- return NULL; /* stop sweeping this list */
- if (gch(curr)->tt == LUA_TTHREAD)
- sweepthread(L, gco2th(curr)); /* sweep thread's upvalues */
- /* update marks */
- gch(curr)->marked = cast_byte((marked & toclear) | toset);
- p = &gch(curr)->next; /* go to next element */
- }
- }
- return (*p == NULL) ? NULL : p;
-}
-
-
-/*
-** sweep a list until a live object (or end of list)
-*/
-static GCObject **sweeptolive (lua_State *L, GCObject **p, int *n) {
- GCObject ** old = p;
- int i = 0;
- do {
- i++;
- p = sweeplist(L, p, 1);
- } while (p == old);
- if (n) *n += i;
- return p;
-}
-
-/* }====================================================== */
-
-
-/*
-** {======================================================
-** Finalization
-** =======================================================
-*/
-
-static void checkSizes (lua_State *L) {
- global_State *g = G(L);
- if (g->gckind != KGC_EMERGENCY) { /* do not change sizes in emergency */
- int hs = g->strt.size / 2; /* half the size of the string table */
- if (g->strt.nuse < cast(lu_int32, hs)) /* using less than that half? */
- luaS_resize(L, hs); /* halve its size */
- luaZ_freebuffer(L, &g->buff); /* free concatenation buffer */
- }
-}
-
-
-static GCObject *udata2finalize (global_State *g) {
- GCObject *o = g->tobefnz; /* get first element */
- lua_assert(isfinalized(o));
- g->tobefnz = gch(o)->next; /* remove it from 'tobefnz' list */
- gch(o)->next = g->allgc; /* return it to 'allgc' list */
- g->allgc = o;
- resetbit(gch(o)->marked, SEPARATED); /* mark that it is not in 'tobefnz' */
- lua_assert(!isold(o)); /* see MOVE OLD rule */
- if (!keepinvariantout(g)) /* not keeping invariant? */
- makewhite(g, o); /* "sweep" object */
- return o;
-}
-
-
-static void dothecall (lua_State *L, void *ud) {
- UNUSED(ud);
- luaD_call(L, L->top - 2, 0, 0);
-}
-
-
-static void GCTM (lua_State *L, int propagateerrors) {
- global_State *g = G(L);
- const TValue *tm;
- TValue v;
- setgcovalue(L, &v, udata2finalize(g));
- tm = luaT_gettmbyobj(L, &v, TM_GC);
- if (tm != NULL && ttisfunction(tm)) { /* is there a finalizer? */
- int status;
- lu_byte oldah = L->allowhook;
- int running = g->gcrunning;
- L->allowhook = 0; /* stop debug hooks during GC metamethod */
- g->gcrunning = 0; /* avoid GC steps */
- setobj2s(L, L->top, tm); /* push finalizer... */
- setobj2s(L, L->top + 1, &v); /* ... and its argument */
- L->top += 2; /* and (next line) call the finalizer */
- status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top - 2), 0);
- L->allowhook = oldah; /* restore hooks */
- g->gcrunning = (lu_byte)running; /* restore state */
- if (status != LUA_OK && propagateerrors) { /* error while running __gc? */
- if (status == LUA_ERRRUN) { /* is there an error object? */
- const char *msg = (ttisstring(L->top - 1))
- ? svalue(L->top - 1)
- : "no message";
- luaO_pushfstring(L, "error in __gc metamethod (%s)", msg);
- status = LUA_ERRGCMM; /* error in __gc metamethod */
- }
- luaD_throw(L, status); /* re-throw error */
- }
- }
-}
-
-
-/*
-** move all unreachable objects (or 'all' objects) that need
-** finalization from list 'finobj' to list 'tobefnz' (to be finalized)
-*/
-static void separatetobefnz (lua_State *L, int all) {
- global_State *g = G(L);
- GCObject **p = &g->finobj;
- GCObject *curr;
- GCObject **lastnext = &g->tobefnz;
- /* find last 'next' field in 'tobefnz' list (to add elements in its end) */
- while (*lastnext != NULL)
- lastnext = &gch(*lastnext)->next;
- while ((curr = *p) != NULL) { /* traverse all finalizable objects */
- lua_assert(!isfinalized(curr));
- lua_assert(testbit(gch(curr)->marked, SEPARATED));
- if (!(iswhite(curr) || all)) /* not being collected? */
- p = &gch(curr)->next; /* don't bother with it */
- else {
- l_setbit(gch(curr)->marked, FINALIZEDBIT); /* won't be finalized again */
- *p = gch(curr)->next; /* remove 'curr' from 'finobj' list */
- gch(curr)->next = *lastnext; /* link at the end of 'tobefnz' list */
- *lastnext = curr;
- lastnext = &gch(curr)->next;
- }
- }
-}
-
-
-/*
-** if object 'o' has a finalizer, remove it from 'allgc' list (must
-** search the list to find it) and link it in 'finobj' list.
-*/
-void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
- global_State *g = G(L);
- if (testbit(gch(o)->marked, SEPARATED) || /* obj. is already separated... */
- isfinalized(o) || /* ... or is finalized... */
- gfasttm(g, mt, TM_GC) == NULL) /* or has no finalizer? */
- return; /* nothing to be done */
- else { /* move 'o' to 'finobj' list */
- GCObject **p;
- GCheader *ho = gch(o);
- if (g->sweepgc == &ho->next) { /* avoid removing current sweep object */
- lua_assert(issweepphase(g));
- g->sweepgc = sweeptolive(L, g->sweepgc, NULL);
- }
- /* search for pointer pointing to 'o' */
- for (p = &g->allgc; *p != o; p = &gch(*p)->next) { /* empty */ }
- *p = ho->next; /* remove 'o' from root list */
- ho->next = g->finobj; /* link it in list 'finobj' */
- g->finobj = o;
- l_setbit(ho->marked, SEPARATED); /* mark it as such */
- if (!keepinvariantout(g)) /* not keeping invariant? */
- makewhite(g, o); /* "sweep" object */
- else
- resetoldbit(o); /* see MOVE OLD rule */
- }
-}
-
-/* }====================================================== */
-
-
-/*
-** {======================================================
-** GC control
-** =======================================================
-*/
-
-
-/*
-** set a reasonable "time" to wait before starting a new GC cycle;
-** cycle will start when memory use hits threshold
-*/
-static void setpause (global_State *g, l_mem estimate) {
- l_mem debt, threshold;
- estimate = estimate / PAUSEADJ; /* adjust 'estimate' */
- threshold = (g->gcpause < MAX_LMEM / estimate) /* overflow? */
- ? estimate * g->gcpause /* no overflow */
- : MAX_LMEM; /* overflow; truncate to maximum */
- debt = -cast(l_mem, threshold - gettotalbytes(g));
- luaE_setdebt(g, debt);
-}
-
-
-#define sweepphases \
- (bitmask(GCSsweepstring) | bitmask(GCSsweepudata) | bitmask(GCSsweep))
-
-
-/*
-** enter first sweep phase (strings) and prepare pointers for other
-** sweep phases. The calls to 'sweeptolive' make pointers point to an
-** object inside the list (instead of to the header), so that the real
-** sweep do not need to skip objects created between "now" and the start
-** of the real sweep.
-** Returns how many objects it swept.
-*/
-static int entersweep (lua_State *L) {
- global_State *g = G(L);
- int n = 0;
- g->gcstate = GCSsweepstring;
- lua_assert(g->sweepgc == NULL && g->sweepfin == NULL);
- /* prepare to sweep strings, finalizable objects, and regular objects */
- g->sweepstrgc = 0;
- g->sweepfin = sweeptolive(L, &g->finobj, &n);
- g->sweepgc = sweeptolive(L, &g->allgc, &n);
- return n;
-}
-
-
-/*
-** change GC mode
-*/
-void luaC_changemode (lua_State *L, int mode) {
- global_State *g = G(L);
- if (mode == g->gckind) return; /* nothing to change */
- if (mode == KGC_GEN) { /* change to generational mode */
- /* make sure gray lists are consistent */
- luaC_runtilstate(L, bitmask(GCSpropagate));
- g->GCestimate = gettotalbytes(g);
- g->gckind = KGC_GEN;
- }
- else { /* change to incremental mode */
- /* sweep all objects to turn them back to white
- (as white has not changed, nothing extra will be collected) */
- g->gckind = KGC_NORMAL;
- entersweep(L);
- luaC_runtilstate(L, ~sweepphases);
- }
-}
-
-
-/*
-** call all pending finalizers
-*/
-static void callallpendingfinalizers (lua_State *L, int propagateerrors) {
- global_State *g = G(L);
- while (g->tobefnz) {
- resetoldbit(g->tobefnz);
- GCTM(L, propagateerrors);
- }
-}
-
-
-void luaC_freeallobjects (lua_State *L) {
- global_State *g = G(L);
- int i;
- separatetobefnz(L, 1); /* separate all objects with finalizers */
- lua_assert(g->finobj == NULL);
- callallpendingfinalizers(L, 0);
- g->currentwhite = WHITEBITS; /* this "white" makes all objects look dead */
- g->gckind = KGC_NORMAL;
- sweepwholelist(L, &g->finobj); /* finalizers can create objs. in 'finobj' */
- sweepwholelist(L, &g->allgc);
- for (i = 0; i < g->strt.size; i++) /* free all string lists */
- sweepwholelist(L, &g->strt.hash[i]);
- lua_assert(g->strt.nuse == 0);
-}
-
-
-static l_mem atomic (lua_State *L) {
- global_State *g = G(L);
- l_mem work = -cast(l_mem, g->GCmemtrav); /* start counting work */
- GCObject *origweak, *origall;
- lua_assert(!iswhite(obj2gco(g->mainthread)));
- markobject(g, L); /* mark running thread */
- /* registry and global metatables may be changed by API */
- markvalue(g, &g->l_registry);
- markmt(g); /* mark basic metatables */
- /* remark occasional upvalues of (maybe) dead threads */
- remarkupvals(g);
- propagateall(g); /* propagate changes */
- work += g->GCmemtrav; /* stop counting (do not (re)count grays) */
- /* traverse objects caught by write barrier and by 'remarkupvals' */
- retraversegrays(g);
- work -= g->GCmemtrav; /* restart counting */
- convergeephemerons(g);
- /* at this point, all strongly accessible objects are marked. */
- /* clear values from weak tables, before checking finalizers */
- clearvalues(g, g->weak, NULL);
- clearvalues(g, g->allweak, NULL);
- origweak = g->weak; origall = g->allweak;
- work += g->GCmemtrav; /* stop counting (objects being finalized) */
- separatetobefnz(L, 0); /* separate objects to be finalized */
- markbeingfnz(g); /* mark objects that will be finalized */
- propagateall(g); /* remark, to propagate `preserveness' */
- work -= g->GCmemtrav; /* restart counting */
- convergeephemerons(g);
- /* at this point, all resurrected objects are marked. */
- /* remove dead objects from weak tables */
- clearkeys(g, g->ephemeron, NULL); /* clear keys from all ephemeron tables */
- clearkeys(g, g->allweak, NULL); /* clear keys from all allweak tables */
- /* clear values from resurrected weak tables */
- clearvalues(g, g->weak, origweak);
- clearvalues(g, g->allweak, origall);
- g->currentwhite = cast_byte(otherwhite(g)); /* flip current white */
- work += g->GCmemtrav; /* complete counting */
- return work; /* estimate of memory marked by 'atomic' */
-}
-
-
-static lu_mem singlestep (lua_State *L) {
- global_State *g = G(L);
- switch (g->gcstate) {
- case GCSpause: {
- /* start to count memory traversed */
- g->GCmemtrav = g->strt.size * sizeof(GCObject*);
- lua_assert(!isgenerational(g));
- restartcollection(g);
- g->gcstate = GCSpropagate;
- return g->GCmemtrav;
- }
- case GCSpropagate: {
- if (g->gray) {
- lu_mem oldtrav = g->GCmemtrav;
- propagatemark(g);
- return g->GCmemtrav - oldtrav; /* memory traversed in this step */
- }
- else { /* no more `gray' objects */
- lu_mem work;
- int sw;
- g->gcstate = GCSatomic; /* finish mark phase */
- g->GCestimate = g->GCmemtrav; /* save what was counted */;
- work = atomic(L); /* add what was traversed by 'atomic' */
- g->GCestimate += work; /* estimate of total memory traversed */
- sw = entersweep(L);
- return work + sw * GCSWEEPCOST;
- }
- }
- case GCSsweepstring: {
- int i;
- for (i = 0; i < GCSWEEPMAX && g->sweepstrgc + i < g->strt.size; i++)
- sweepwholelist(L, &g->strt.hash[g->sweepstrgc + i]);
- g->sweepstrgc += i;
- if (g->sweepstrgc >= g->strt.size) /* no more strings to sweep? */
- g->gcstate = GCSsweepudata;
- return i * GCSWEEPCOST;
- }
- case GCSsweepudata: {
- if (g->sweepfin) {
- g->sweepfin = sweeplist(L, g->sweepfin, GCSWEEPMAX);
- return GCSWEEPMAX*GCSWEEPCOST;
- }
- else {
- g->gcstate = GCSsweep;
- return 0;
- }
- }
- case GCSsweep: {
- if (g->sweepgc) {
- g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
- return GCSWEEPMAX*GCSWEEPCOST;
- }
- else {
- /* sweep main thread */
- GCObject *mt = obj2gco(g->mainthread);
- sweeplist(L, &mt, 1);
- checkSizes(L);
- g->gcstate = GCSpause; /* finish collection */
- return GCSWEEPCOST;
- }
- }
- default: lua_assert(0); return 0;
- }
-}
-
-
-/*
-** advances the garbage collector until it reaches a state allowed
-** by 'statemask'
-*/
-void luaC_runtilstate (lua_State *L, int statesmask) {
- global_State *g = G(L);
- while (!testbit(statesmask, g->gcstate))
- singlestep(L);
-}
-
-
-static void generationalcollection (lua_State *L) {
- global_State *g = G(L);
- lua_assert(g->gcstate == GCSpropagate);
- if (g->GCestimate == 0) { /* signal for another major collection? */
- luaC_fullgc(L, 0); /* perform a full regular collection */
- g->GCestimate = gettotalbytes(g); /* update control */
- }
- else {
- lu_mem estimate = g->GCestimate;
- luaC_runtilstate(L, bitmask(GCSpause)); /* run complete (minor) cycle */
- g->gcstate = GCSpropagate; /* skip restart */
- if (gettotalbytes(g) > (estimate / 100) * g->gcmajorinc)
- g->GCestimate = 0; /* signal for a major collection */
- else
- g->GCestimate = estimate; /* keep estimate from last major coll. */
-
- }
- setpause(g, gettotalbytes(g));
- lua_assert(g->gcstate == GCSpropagate);
-}
-
-
-static void incstep (lua_State *L) {
- global_State *g = G(L);
- l_mem debt = g->GCdebt;
- int stepmul = g->gcstepmul;
- if (stepmul < 40) stepmul = 40; /* avoid ridiculous low values (and 0) */
- /* convert debt from Kb to 'work units' (avoid zero debt and overflows) */
- debt = (debt / STEPMULADJ) + 1;
- debt = (debt < MAX_LMEM / stepmul) ? debt * stepmul : MAX_LMEM;
- do { /* always perform at least one single step */
- lu_mem work = singlestep(L); /* do some work */
- debt -= work;
- } while (debt > -GCSTEPSIZE && g->gcstate != GCSpause);
- if (g->gcstate == GCSpause)
- setpause(g, g->GCestimate); /* pause until next cycle */
- else {
- debt = (debt / stepmul) * STEPMULADJ; /* convert 'work units' to Kb */
- luaE_setdebt(g, debt);
- }
-}
-
-
-/*
-** performs a basic GC step
-*/
-void luaC_forcestep (lua_State *L) {
- global_State *g = G(L);
- int i;
- if (isgenerational(g)) generationalcollection(L);
- else incstep(L);
- /* run a few finalizers (or all of them at the end of a collect cycle) */
- for (i = 0; g->tobefnz && (i < GCFINALIZENUM || g->gcstate == GCSpause); i++)
- GCTM(L, 1); /* call one finalizer */
-}
-
-
-/*
-** performs a basic GC step only if collector is running
-*/
-void luaC_step (lua_State *L) {
- global_State *g = G(L);
- if (g->gcrunning) luaC_forcestep(L);
- else luaE_setdebt(g, -GCSTEPSIZE); /* avoid being called too often */
-}
-
-
-
-/*
-** performs a full GC cycle; if "isemergency", does not call
-** finalizers (which could change stack positions)
-*/
-void luaC_fullgc (lua_State *L, int isemergency) {
- global_State *g = G(L);
- int origkind = g->gckind;
- lua_assert(origkind != KGC_EMERGENCY);
- if (isemergency) /* do not run finalizers during emergency GC */
- g->gckind = KGC_EMERGENCY;
- else {
- g->gckind = KGC_NORMAL;
- callallpendingfinalizers(L, 1);
- }
- if (keepinvariant(g)) { /* may there be some black objects? */
- /* must sweep all objects to turn them back to white
- (as white has not changed, nothing will be collected) */
- entersweep(L);
- }
- /* finish any pending sweep phase to start a new cycle */
- luaC_runtilstate(L, bitmask(GCSpause));
- luaC_runtilstate(L, ~bitmask(GCSpause)); /* start new collection */
- luaC_runtilstate(L, bitmask(GCSpause)); /* run entire collection */
- if (origkind == KGC_GEN) { /* generational mode? */
- /* generational mode must be kept in propagate phase */
- luaC_runtilstate(L, bitmask(GCSpropagate));
- }
- g->gckind = (lu_byte)origkind;
- setpause(g, gettotalbytes(g));
- if (!isemergency) /* do not run finalizers during emergency GC */
- callallpendingfinalizers(L, 1);
-}
-
-/* }====================================================== */
-
-
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