/* ** $Id: lgc.c,v 2.215.1.2 2017/08/31 16:15:27 roberto Exp $ ** Garbage Collector ** See Copyright Notice in lua.h */ #define lgc_c #define LUA_CORE #include "lprefix.h" #include #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" /* ** internal state for collector while inside the atomic phase. The ** collector should never be in this state while running regular code. */ #define GCSinsideatomic (GCSpause + 1) /* ** 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)) /* cost of calling one finalizer */ #define GCFINALIZECOST GCSWEEPCOST /* ** 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 then sets only the current white ** bit */ #define maskcolors (~(bitmask(BLACKBIT) | WHITEBITS)) #define makewhite(g,x) \ (x->marked = cast_byte((x->marked & maskcolors) | luaC_white(g))) #define white2gray(x) resetbits(x->marked, WHITEBITS) #define black2gray(x) resetbit(x->marked, BLACKBIT) #define valiswhite(x) (iscollectable(x) && iswhite(gcvalue(x))) #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 (iswhite(t)) reallymarkobject(g, obj2gco(t)); } /* ** mark an object that can be NULL (either because it is really optional, ** or it was stripped as debug info, or inside an uncompleted structure) */ #define markobjectN(g,t) { if (t) markobject(g,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 collectable object 'o' into list pointed by 'p' */ #define linkgclist(o,p) ((o)->gclist = (p), (p) = obj2gco(o)) /* ** If key is not marked, mark its entry as dead. This allows key to be ** collected, but keeps its entry in the table. A dead node is needed ** when Lua looks up for a key (it may be part of a chain) and when ** traversing a weak table (key might be removed from the table during ** traversal). Other places never manipulate dead keys, because its ** associated nil value is enough to signal that the entry is logically ** empty. */ static void removeentry (Node *n) { lua_assert(ttisnil(gval(n))); if (valiswhite(gkey(n))) setdeadvalue(wgkey(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, tsvalue(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. (If in sweep phase, clear the black ** object to white [sweep it] to avoid other barrier calls for this ** same 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)); if (keepinvariant(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. */ void luaC_barrierback_ (lua_State *L, Table *t) { global_State *g = G(L); lua_assert(isblack(t) && !isdead(g, t)); black2gray(t); /* make table gray (again) */ linkgclist(t, g->grayagain); } /* ** barrier for assignments to closed upvalues. Because upvalues are ** shared among closures, it is impossible to know the color of all ** closures pointing to it. So, we assume that the object being assigned ** must be marked. */ void luaC_upvalbarrier_ (lua_State *L, UpVal *uv) { global_State *g = G(L); GCObject *o = gcvalue(uv->v); lua_assert(!upisopen(uv)); /* ensured by macro luaC_upvalbarrier */ if (keepinvariant(g)) markobject(g, o); } void luaC_fix (lua_State *L, GCObject *o) { global_State *g = G(L); lua_assert(g->allgc == o); /* object must be 1st in 'allgc' list! */ white2gray(o); /* they will be gray forever */ g->allgc = o->next; /* remove object from 'allgc' list */ o->next = g->fixedgc; /* link it to 'fixedgc' list */ g->fixedgc = o; } /* ** create a new collectable object (with given type and size) and link ** it to 'allgc' list. */ GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) { global_State *g = G(L); GCObject *o = cast(GCObject *, luaM_newobject(L, novariant(tt), sz)); o->marked = luaC_white(g); o->tt = tt; o->next = g->allgc; g->allgc = 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) { reentry: white2gray(o); switch (o->tt) { case LUA_TSHRSTR: { gray2black(o); g->GCmemtrav += sizelstring(gco2ts(o)->shrlen); break; } case LUA_TLNGSTR: { gray2black(o); g->GCmemtrav += sizelstring(gco2ts(o)->u.lnglen); break; } case LUA_TUSERDATA: { TValue uvalue; markobjectN(g, gco2u(o)->metatable); /* mark its metatable */ gray2black(o); g->GCmemtrav += sizeudata(gco2u(o)); getuservalue(g->mainthread, gco2u(o), &uvalue); if (valiswhite(&uvalue)) { /* markvalue(g, &uvalue); */ o = gcvalue(&uvalue); goto reentry; } break; } case LUA_TLCL: { linkgclist(gco2lcl(o), g->gray); break; } case LUA_TCCL: { linkgclist(gco2ccl(o), g->gray); break; } case LUA_TTABLE: { linkgclist(gco2t(o), g->gray); break; } case LUA_TTHREAD: { linkgclist(gco2th(o), g->gray); break; } case LUA_TPROTO: { linkgclist(gco2p(o), g->gray); break; } default: lua_assert(0); break; } } /* ** mark metamethods for basic types */ static void markmt (global_State *g) { int i; for (i=0; i < LUA_NUMTAGS; i++) markobjectN(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 = o->next) markobject(g, o); } /* ** Mark all values stored in marked open upvalues from non-marked threads. ** (Values from marked threads were already marked when traversing the ** thread.) Remove from the list threads that no longer have upvalues and ** not-marked threads. */ static void remarkupvals (global_State *g) { lua_State *thread; lua_State **p = &g->twups; while ((thread = *p) != NULL) { lua_assert(!isblack(thread)); /* threads are never black */ if (isgray(thread) && thread->openupval != NULL) p = &thread->twups; /* keep marked thread with upvalues in the list */ else { /* thread is not marked or without upvalues */ UpVal *uv; *p = thread->twups; /* remove thread from the list */ thread->twups = thread; /* mark that it is out of list */ for (uv = thread->openupval; uv != NULL; uv = uv->u.open.next) { if (uv->u.open.touched) { markvalue(g, uv->v); /* remark upvalue's value */ uv->u.open.touched = 0; } } } } } /* ** mark root set and reset all gray lists, to start a new 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 ** ======================================================= */ /* ** Traverse a table with weak values and link it to proper list. During ** propagate phase, keep it in 'grayagain' list, to be revisited in the ** atomic phase. In the atomic phase, if table has any white value, ** put it in 'weak' list, to be cleared. */ static void traverseweakvalue (global_State *g, Table *h) { Node *n, *limit = gnodelast(h); /* if there is array part, assume it may have white values (it is not worth traversing it now just to check) */ int hasclears = (h->sizearray > 0); 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 */ if (!hasclears && iscleared(g, gval(n))) /* is there a white value? */ hasclears = 1; /* table will have to be cleared */ } } if (g->gcstate == GCSpropagate) linkgclist(h, g->grayagain); /* must retraverse it in atomic phase */ else if (hasclears) linkgclist(h, g->weak); /* has to be cleared later */ } /* ** Traverse an ephemeron table and link it to proper list. Returns true ** iff any object was marked during this traversal (which implies that ** convergence has to continue). During propagation phase, keep table ** in 'grayagain' list, to be visited again in the atomic phase. In ** the atomic phase, if table has any white->white entry, it has to ** be revisited during ephemeron convergence (as that key may turn ** black). Otherwise, if it has any white key, table has to be cleared ** (in the atomic phase). */ 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 hasww = 0; /* true if table has entry "white-key -> white-value" */ Node *n, *limit = gnodelast(h); unsigned int i; /* traverse array part */ 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? */ hasww = 1; /* white-white entry */ } else if (valiswhite(gval(n))) { /* value not marked yet? */ marked = 1; reallymarkobject(g, gcvalue(gval(n))); /* mark it now */ } } /* link table into proper list */ if (g->gcstate == GCSpropagate) linkgclist(h, g->grayagain); /* must retraverse it in atomic phase */ else if (hasww) /* table has white->white entries? */ linkgclist(h, g->ephemeron); /* have to propagate again */ else if (hasclears) /* table has white keys? */ linkgclist(h, g->allweak); /* may have to clean white keys */ return marked; } static void traversestrongtable (global_State *g, Table *h) { Node *n, *limit = gnodelast(h); unsigned 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); markobjectN(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(h); /* keep table gray */ if (!weakkey) /* strong keys? */ traverseweakvalue(g, h); else if (!weakvalue) /* strong values? */ traverseephemeron(g, h); else /* all weak */ linkgclist(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, allocsizenode(h)); } /* ** Traverse a prototype. (While a prototype is being build, its ** arrays can be larger than needed; the extra slots are filled with ** NULL, so the use of 'markobjectN') */ static int traverseproto (global_State *g, Proto *f) { int i; if (f->cache && iswhite(f->cache)) f->cache = NULL; /* allow cache to be collected */ markobjectN(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 */ markobjectN(g, f->upvalues[i].name); for (i = 0; i < f->sizep; i++) /* mark nested protos */ markobjectN(g, f->p[i]); for (i = 0; i < f->sizelocvars; i++) /* mark local-variable names */ markobjectN(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); } /* ** open upvalues point to values in a thread, so those values should ** be marked when the thread is traversed except in the atomic phase ** (because then the value cannot be changed by the thread and the ** thread may not be traversed again) */ static lu_mem traverseLclosure (global_State *g, LClosure *cl) { int i; markobjectN(g, cl->p); /* mark its prototype */ for (i = 0; i < cl->nupvalues; i++) { /* mark its upvalues */ UpVal *uv = cl->upvals[i]; if (uv != NULL) { if (upisopen(uv) && g->gcstate != GCSinsideatomic) uv->u.open.touched = 1; /* can be marked in 'remarkupvals' */ else markvalue(g, uv->v); } } return sizeLclosure(cl->nupvalues); } static lu_mem traversethread (global_State *g, lua_State *th) { StkId o = th->stack; if (o == NULL) return 1; /* stack not completely built yet */ lua_assert(g->gcstate == GCSinsideatomic || th->openupval == NULL || isintwups(th)); for (; o < th->top; o++) /* mark live elements in the stack */ markvalue(g, o); if (g->gcstate == GCSinsideatomic) { /* final traversal? */ StkId lim = th->stack + th->stacksize; /* real end of stack */ for (; o < lim; o++) /* clear not-marked stack slice */ setnilvalue(o); /* 'remarkupvals' may have removed thread from 'twups' list */ if (!isintwups(th) && th->openupval != NULL) { th->twups = g->twups; /* link it back to the list */ g->twups = th; } } else if (g->gckind != KGC_EMERGENCY) luaD_shrinkstack(th); /* do not change stack in emergency cycle */ return (sizeof(lua_State) + sizeof(TValue) * th->stacksize + sizeof(CallInfo) * th->nci); } /* ** 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 (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 */ linkgclist(th, g->grayagain); /* insert into 'grayagain' list */ black2gray(o); size = traversethread(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 convergeephemerons (global_State *g) { int changed; do { GCObject *w; GCObject *next = g->ephemeron; /* get ephemeron list */ g->ephemeron = NULL; /* tables may 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 ... */ } if (ttisnil(gval(n))) /* is entry empty? */ removeentry(n); /* 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); unsigned 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 */ } } } } void luaC_upvdeccount (lua_State *L, UpVal *uv) { lua_assert(uv->refcount > 0); uv->refcount--; if (uv->refcount == 0 && !upisopen(uv)) luaM_free(L, uv); } static void freeLclosure (lua_State *L, LClosure *cl) { int i; for (i = 0; i < cl->nupvalues; i++) { UpVal *uv = cl->upvals[i]; if (uv) luaC_upvdeccount(L, uv); } luaM_freemem(L, cl, sizeLclosure(cl->nupvalues)); } static void freeobj (lua_State *L, GCObject *o) { switch (o->tt) { case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break; case LUA_TLCL: { freeLclosure(L, gco2lcl(o)); break; } case LUA_TCCL: { luaM_freemem(L, o, sizeCclosure(gco2ccl(o)->nupvalues)); 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: luaS_remove(L, gco2ts(o)); /* remove it from hash table */ luaM_freemem(L, o, sizelstring(gco2ts(o)->shrlen)); break; case LUA_TLNGSTR: { luaM_freemem(L, o, sizelstring(gco2ts(o)->u.lnglen)); 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 at most 'count' elements from a list of GCObjects erasing dead ** objects, where a dead object is one marked with the old (non current) ** white; change all non-dead objects back to white, preparing for next ** collection cycle. Return where to continue the traversal or NULL if ** list is finished. */ static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) { global_State *g = G(L); int ow = otherwhite(g); int white = luaC_white(g); /* current white */ while (*p != NULL && count-- > 0) { GCObject *curr = *p; int marked = curr->marked; if (isdeadm(ow, marked)) { /* is 'curr' dead? */ *p = curr->next; /* remove 'curr' from list */ freeobj(L, curr); /* erase 'curr' */ } else { /* change mark to 'white' */ curr->marked = cast_byte((marked & maskcolors) | white); p = &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) { GCObject **old = p; do { p = sweeplist(L, p, 1); } while (p == old); return p; } /* }====================================================== */ /* ** {====================================================== ** Finalization ** ======================================================= */ /* ** If possible, shrink string table */ static void checkSizes (lua_State *L, global_State *g) { if (g->gckind != KGC_EMERGENCY) { l_mem olddebt = g->GCdebt; if (g->strt.nuse < g->strt.size / 4) /* string table too big? */ luaS_resize(L, g->strt.size / 2); /* shrink it a little */ g->GCestimate += g->GCdebt - olddebt; /* update estimate */ } } static GCObject *udata2finalize (global_State *g) { GCObject *o = g->tobefnz; /* get first element */ lua_assert(tofinalize(o)); g->tobefnz = o->next; /* remove it from 'tobefnz' list */ o->next = g->allgc; /* return it to 'allgc' list */ g->allgc = o; resetbit(o->marked, FINALIZEDBIT); /* object is "normal" again */ if (issweepphase(g)) makewhite(g, o); /* "sweep" object */ return o; } static void dothecall (lua_State *L, void *ud) { UNUSED(ud); luaD_callnoyield(L, L->top - 2, 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 */ L->ci->callstatus |= CIST_FIN; /* will run a finalizer */ status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top - 2), 0); L->ci->callstatus &= ~CIST_FIN; /* not running a finalizer anymore */ L->allowhook = oldah; /* restore hooks */ g->gcrunning = 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 */ } } } /* ** call a few (up to 'g->gcfinnum') finalizers */ static int runafewfinalizers (lua_State *L) { global_State *g = G(L); unsigned int i; lua_assert(!g->tobefnz || g->gcfinnum > 0); for (i = 0; g->tobefnz && i < g->gcfinnum; i++) GCTM(L, 1); /* call one finalizer */ g->gcfinnum = (!g->tobefnz) ? 0 /* nothing more to finalize? */ : g->gcfinnum * 2; /* else call a few more next time */ return i; } /* ** call all pending finalizers */ static void callallpendingfinalizers (lua_State *L) { global_State *g = G(L); while (g->tobefnz) GCTM(L, 0); } /* ** find last 'next' field in list 'p' list (to add elements in its end) */ static GCObject **findlast (GCObject **p) { while (*p != NULL) p = &(*p)->next; return p; } /* ** move all unreachable objects (or 'all' objects) that need ** finalization from list 'finobj' to list 'tobefnz' (to be finalized) */ static void separatetobefnz (global_State *g, int all) { GCObject *curr; GCObject **p = &g->finobj; GCObject **lastnext = findlast(&g->tobefnz); while ((curr = *p) != NULL) { /* traverse all finalizable objects */ lua_assert(tofinalize(curr)); if (!(iswhite(curr) || all)) /* not being collected? */ p = &curr->next; /* don't bother with it */ else { *p = curr->next; /* remove 'curr' from 'finobj' list */ curr->next = *lastnext; /* link at the end of 'tobefnz' list */ *lastnext = curr; lastnext = &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 (tofinalize(o) || /* obj. is already marked... */ gfasttm(g, mt, TM_GC) == NULL) /* or has no finalizer? */ return; /* nothing to be done */ else { /* move 'o' to 'finobj' list */ GCObject **p; if (issweepphase(g)) { makewhite(g, o); /* "sweep" object 'o' */ if (g->sweepgc == &o->next) /* should not remove 'sweepgc' object */ g->sweepgc = sweeptolive(L, g->sweepgc); /* change 'sweepgc' */ } /* search for pointer pointing to 'o' */ for (p = &g->allgc; *p != o; p = &(*p)->next) { /* empty */ } *p = o->next; /* remove 'o' from 'allgc' list */ o->next = g->finobj; /* link it in 'finobj' list */ g->finobj = o; l_setbit(o->marked, FINALIZEDBIT); /* mark it as such */ } } /* }====================================================== */ /* ** {====================================================== ** GC control ** ======================================================= */ /* ** Set a reasonable "time" to wait before starting a new GC cycle; cycle ** will start when memory use hits threshold. (Division by 'estimate' ** should be OK: it cannot be zero (because Lua cannot even start with ** less than PAUSEADJ bytes). */ static void setpause (global_State *g) { l_mem threshold, debt; l_mem estimate = g->GCestimate / PAUSEADJ; /* adjust 'estimate' */ lua_assert(estimate > 0); threshold = (g->gcpause < MAX_LMEM / estimate) /* overflow? */ ? estimate * g->gcpause /* no overflow */ : MAX_LMEM; /* overflow; truncate to maximum */ debt = gettotalbytes(g) - threshold; luaE_setdebt(g, debt); } /* ** Enter first sweep phase. ** The call to 'sweeplist' tries to make pointer 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. */ static void entersweep (lua_State *L) { global_State *g = G(L); g->gcstate = GCSswpallgc; lua_assert(g->sweepgc == NULL); g->sweepgc = sweeplist(L, &g->allgc, 1); } void luaC_freeallobjects (lua_State *L) { global_State *g = G(L); separatetobefnz(g, 1); /* separate all objects with finalizers */ lua_assert(g->finobj == NULL); callallpendingfinalizers(L); lua_assert(g->tobefnz == NULL); g->currentwhite = WHITEBITS; /* this "white" makes all objects look dead */ g->gckind = KGC_NORMAL; sweepwholelist(L, &g->finobj); sweepwholelist(L, &g->allgc); sweepwholelist(L, &g->fixedgc); /* collect fixed objects */ lua_assert(g->strt.nuse == 0); } static l_mem atomic (lua_State *L) { global_State *g = G(L); l_mem work; GCObject *origweak, *origall; GCObject *grayagain = g->grayagain; /* save original list */ lua_assert(g->ephemeron == NULL && g->weak == NULL); lua_assert(!iswhite(g->mainthread)); g->gcstate = GCSinsideatomic; g->GCmemtrav = 0; /* start counting work */ markobject(g, L); /* mark running thread */ /* registry and global metatables may be changed by API */ markvalue(g, &g->l_registry); markmt(g); /* mark global metatables */ /* remark occasional upvalues of (maybe) dead threads */ remarkupvals(g); propagateall(g); /* propagate changes */ work = g->GCmemtrav; /* stop counting (do not recount 'grayagain') */ g->gray = grayagain; propagateall(g); /* traverse 'grayagain' list */ g->GCmemtrav = 0; /* 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(g, 0); /* separate objects to be finalized */ g->gcfinnum = 1; /* there may be objects to be finalized */ markbeingfnz(g); /* mark objects that will be finalized */ propagateall(g); /* remark, to propagate 'resurrection' */ g->GCmemtrav = 0; /* 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); luaS_clearcache(g); 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 sweepstep (lua_State *L, global_State *g, int nextstate, GCObject **nextlist) { if (g->sweepgc) { l_mem olddebt = g->GCdebt; g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX); g->GCestimate += g->GCdebt - olddebt; /* update estimate */ if (g->sweepgc) /* is there still something to sweep? */ return (GCSWEEPMAX * GCSWEEPCOST); } /* else enter next state */ g->gcstate = nextstate; g->sweepgc = nextlist; return 0; } static lu_mem singlestep (lua_State *L) { global_State *g = G(L); switch (g->gcstate) { case GCSpause: { g->GCmemtrav = g->strt.size * sizeof(GCObject*); restartcollection(g); g->gcstate = GCSpropagate; return g->GCmemtrav; } case GCSpropagate: { g->GCmemtrav = 0; lua_assert(g->gray); propagatemark(g); if (g->gray == NULL) /* no more gray objects? */ g->gcstate = GCSatomic; /* finish propagate phase */ return g->GCmemtrav; /* memory traversed in this step */ } case GCSatomic: { lu_mem work; propagateall(g); /* make sure gray list is empty */ work = atomic(L); /* work is what was traversed by 'atomic' */ entersweep(L); g->GCestimate = gettotalbytes(g); /* first estimate */; return work; } case GCSswpallgc: { /* sweep "regular" objects */ return sweepstep(L, g, GCSswpfinobj, &g->finobj); } case GCSswpfinobj: { /* sweep objects with finalizers */ return sweepstep(L, g, GCSswptobefnz, &g->tobefnz); } case GCSswptobefnz: { /* sweep objects to be finalized */ return sweepstep(L, g, GCSswpend, NULL); } case GCSswpend: { /* finish sweeps */ makewhite(g, g->mainthread); /* sweep main thread */ checkSizes(L, g); g->gcstate = GCScallfin; return 0; } case GCScallfin: { /* call remaining finalizers */ if (g->tobefnz && g->gckind != KGC_EMERGENCY) { int n = runafewfinalizers(L); return (n * GCFINALIZECOST); } else { /* emergency mode or no more finalizers */ g->gcstate = GCSpause; /* finish collection */ return 0; } } 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); } /* ** get GC debt and convert it from Kb to 'work units' (avoid zero debt ** and overflows) */ static l_mem getdebt (global_State *g) { l_mem debt = g->GCdebt; int stepmul = g->gcstepmul; if (debt <= 0) return 0; /* minimal debt */ else { debt = (debt / STEPMULADJ) + 1; debt = (debt < MAX_LMEM / stepmul) ? debt * stepmul : MAX_LMEM; return debt; } } /* ** performs a basic GC step when collector is running */ void luaC_step (lua_State *L) { global_State *g = G(L); l_mem debt = getdebt(g); /* GC deficit (be paid now) */ if (!g->gcrunning) { /* not running? */ luaE_setdebt(g, -GCSTEPSIZE * 10); /* avoid being called too often */ return; } do { /* repeat until pause or enough "credit" (negative debt) */ lu_mem work = singlestep(L); /* perform one single step */ debt -= work; } while (debt > -GCSTEPSIZE && g->gcstate != GCSpause); if (g->gcstate == GCSpause) setpause(g); /* pause until next cycle */ else { debt = (debt / g->gcstepmul) * STEPMULADJ; /* convert 'work units' to Kb */ luaE_setdebt(g, debt); runafewfinalizers(L); } } /* ** Performs a full GC cycle; if 'isemergency', set a flag to avoid ** some operations which could change the interpreter state in some ** unexpected ways (running finalizers and shrinking some structures). ** Before running the collection, check 'keepinvariant'; if it is true, ** there may be some objects marked as black, so the collector has ** to sweep all objects to turn them back to white (as white has not ** changed, nothing will be collected). */ void luaC_fullgc (lua_State *L, int isemergency) { global_State *g = G(L); lua_assert(g->gckind == KGC_NORMAL); if (isemergency) g->gckind = KGC_EMERGENCY; /* set flag */ if (keepinvariant(g)) { /* black objects? */ entersweep(L); /* sweep everything to turn them back to white */ } /* 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(GCScallfin)); /* run up to finalizers */ /* estimate must be correct after a full GC cycle */ lua_assert(g->GCestimate == gettotalbytes(g)); luaC_runtilstate(L, bitmask(GCSpause)); /* finish collection */ g->gckind = KGC_NORMAL; setpause(g); } /* }====================================================== */