You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
1640 lines
51 KiB
1640 lines
51 KiB
/*
|
|
** $Id: lgc.c,v 2.215 2016/12/22 13:08:50 roberto Exp $
|
|
** Garbage Collector
|
|
** See Copyright Notice in lua.h
|
|
*/
|
|
|
|
#define lgc_c
|
|
#define LUA_CORE
|
|
|
|
#include "lprefix.h"
|
|
|
|
#include <stdio.h>
|
|
#include <string.h>
|
|
|
|
#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"
|
|
|
|
|
|
/*
|
|
** Maximum number of elements to sweep in each single step.
|
|
** (Large enough to dissipate fixed overheads but small enough
|
|
** to allow small steps for the collector.)
|
|
*/
|
|
#define GCSWEEPMAX 100
|
|
|
|
/*
|
|
** Maximum number of finalizers to call in each single step.
|
|
*/
|
|
#define GCFINMAX 10
|
|
|
|
|
|
/*
|
|
** Cost of calling one finalizer.
|
|
*/
|
|
#define GCFINALIZECOST 50
|
|
|
|
|
|
/*
|
|
** The equivalent, in bytes, of one unit of "work" (visiting a slot,
|
|
** sweeping an object, etc.)
|
|
*/
|
|
#define WORK2MEM sizeof(TValue)
|
|
|
|
|
|
/*
|
|
** macro to adjust 'pause': 'pause' is actually used like
|
|
** 'pause / PAUSEADJ' (value chosen by tests)
|
|
*/
|
|
#define PAUSEADJ 100
|
|
|
|
|
|
/* mask to erase all color bits (plus gen. related stuff) */
|
|
#define maskcolors (~(bitmask(BLACKBIT) | WHITEBITS | AGEBITS))
|
|
|
|
|
|
/* macro to erase all color bits then sets only the current white bit */
|
|
#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 keyiswhite(n) (keyiscollectable(n) && iswhite(gckey(n)))
|
|
|
|
|
|
#define checkconsistency(obj) \
|
|
lua_longassert(!iscollectable(obj) || righttt(obj))
|
|
|
|
|
|
#define markvalue(g,o) { checkconsistency(o); \
|
|
if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); }
|
|
|
|
#define markkey(g, n) { if keyiswhite(n) reallymarkobject(g,gckey(n)); }
|
|
|
|
#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);
|
|
static lu_mem atomic (lua_State *L);
|
|
|
|
|
|
/*
|
|
** {======================================================
|
|
** 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))
|
|
|
|
|
|
/*
|
|
** Clear keys for empty entries in tables. If entry is empty
|
|
** and its key is not marked, mark its entry as dead. This allows the
|
|
** collection of the key, but keeps its entry in the table (its removal
|
|
** could break a chain). 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 (keyiswhite(n))
|
|
setdeadkey(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 GCObject *o) {
|
|
if (o == NULL) return 0; /* non-collectable value */
|
|
else if (novariant(o->tt) == LUA_TSTRING) {
|
|
markobject(g, o); /* strings are 'values', so are never weak */
|
|
return 0;
|
|
}
|
|
else return iswhite(o);
|
|
}
|
|
|
|
/*
|
|
Following description is taken from:
|
|
http://wiki.luajit.org/New-Garbage-Collector#gc-algorithms_tri-color-incremental-mark-sweep
|
|
|
|
Newly allocated objects are white. The mark phase starts at the GC roots.
|
|
Marking a reachable object means flipping the color of it from white to
|
|
gray and pushing it onto a gray stack (or re-chaining it onto a gray list).
|
|
The gray stack is iteratively processed, removing one gray object at a time.
|
|
A gray object is traversed and all objects reachable from it are marked,
|
|
like above. After an object has been traversed, it's turned from gray to
|
|
black. The sweep phase works just like the two-color algorithm above.
|
|
|
|
This algorithm is incremental: the collector can operate in small steps,
|
|
processing only a couple of objects from the gray stack and then let the
|
|
mutator run again for a while. This spreads out the GC pauses into
|
|
many short intervals, which is important for highly interactive
|
|
workloads (e.g. games or internet servers).
|
|
|
|
But there's one catch: the mutator might get in the way of the collector
|
|
and store a reference to a white (unprocessed) object at a black
|
|
(processed) object. This object would never be marked and will be
|
|
freed by the sweep, even though it's clearly still referenced from a
|
|
reachable object, i.e. it should be kept alive.
|
|
|
|
To avoid this scenario, one has to preserve the tri-color invariant:
|
|
a black object may never hold a reference to a white object. This is
|
|
done with a write barrier, which has to be checked after every write.
|
|
If the invariant has been violated, a fixup step is needed.
|
|
There are two alternatives:
|
|
|
|
1. Either turn the black object gray and push it back onto the gray stack.
|
|
This is moving the barrier "back", because the object has to be reprocessed
|
|
later on. This is beneficial for container objects, because they usually
|
|
receive several stores in succession. This avoids a barrier for the next
|
|
objects that are stored into it (which are likely white, too).
|
|
|
|
2. Or immediately mark the white object, turning it gray and push it onto
|
|
the gray stack. This moves the barrier "forward", because it implicitly
|
|
drives the GC forward. This works best for objects that only receive
|
|
isolated stores.
|
|
|
|
There are many optimizations to turn this into a practical algorithm.
|
|
Here are the most important:
|
|
|
|
* Stacks should always be kept gray and re-traversed just before the
|
|
final sweep phase. This avoids a write barrier for stores to stack slots,
|
|
which are the most common kind of stores.
|
|
|
|
* Objects which have no references to child objects can immediately be
|
|
turned from white to black and don't need to go through the gray stack.
|
|
|
|
* The sweep phase can be made incremental by using two whites and
|
|
flipping between them just before entering the sweep phase. Objects with
|
|
the 'current' white need to be kept. Only objects with the
|
|
'other' white should be freed.
|
|
|
|
In Lua, Tables use backward barriers, all other traversable objects
|
|
use forward barriers.
|
|
*/
|
|
|
|
|
|
/*
|
|
** 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.)
|
|
**
|
|
** Here we have a black object pointing / referencing a white object
|
|
** So to preserve tri-color invariant the white object must
|
|
** be marked and turned gray or black. Userdata, strings and upvalues
|
|
** are turned black, whereas functions, threads, tables and protos are turned
|
|
** gray.
|
|
**
|
|
** Example: userdata o references user value v, or
|
|
** function proto o references newly added constant v
|
|
*/
|
|
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? (not in sweep phase) */
|
|
reallymarkobject(g, v); /* restore invariant - turn white object to gray or black */
|
|
if (isold(o)) {
|
|
lua_assert(!isold(v)); /* white object could not be old */
|
|
setage(v, G_OLD0); /* restore generational 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.
|
|
**
|
|
** Here we have a container (table) being assigned a value, so the
|
|
** table if black must be turned to gray as black objects cannot point
|
|
** to white objects.
|
|
*/
|
|
void luaC_barrierback_ (lua_State *L, Table *t) {
|
|
global_State *g = G(L);
|
|
lua_assert(isblack(t) && !isdead(g, t));
|
|
lua_assert(g->gckind != KGC_GEN || (isold(t) && getage(t) != G_TOUCHED1));
|
|
if (getage(t) != G_TOUCHED2) /* not already in gray list? */
|
|
linkgclist(t, g->grayagain); /* link it in 'grayagain' */
|
|
black2gray(t); /* make table gray (again) */
|
|
setage(t, G_TOUCHED1); /* touched in current cycle */
|
|
}
|
|
|
|
|
|
/*
|
|
** Barrier for prototype's cache of closures. For an 'old1'
|
|
** object, making it gray stops it from being visited by 'markold',
|
|
** so it is linked in the 'grayagain' list to ensure it will be
|
|
** visited. Otherwise, it goes to 'protogray', as only its 'cache' field
|
|
** needs to be revisited. (A prototype to be in this barrier must be
|
|
** already finished, so its other fields cannot change and do not need
|
|
** to be revisited.)
|
|
*/
|
|
LUAI_FUNC void luaC_protobarrier_ (lua_State *L, Proto *p) {
|
|
global_State *g = G(L);
|
|
lua_assert(g->gckind != KGC_GEN || isold(p));
|
|
if (getage(p) == G_OLD1) /* still need to be visited? */
|
|
linkgclist(p, g->grayagain); /* link it in 'grayagain' */
|
|
else
|
|
linkgclist(p, g->protogray); /* link it in 'protogray' */
|
|
black2gray(p); /* make prototype gray (to avoid other barriers) */
|
|
}
|
|
|
|
|
|
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 */
|
|
setage(o, G_OLD); /* and old 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 (functions, tables, threads, protos)
|
|
** are marked gray and added
|
|
** to appropriate list to be visited (and turned black) later. (Open
|
|
** upvalues are already linked in 'headuv' list. They are kept gray
|
|
** to avoid barriers, as their values will be revisited by the thread.)
|
|
*/
|
|
static void reallymarkobject (global_State *g, GCObject *o) {
|
|
reentry:
|
|
white2gray(o);
|
|
switch (o->tt) {
|
|
case LUA_TSHRSTR:
|
|
case LUA_TLNGSTR: {
|
|
gray2black(o);
|
|
break;
|
|
}
|
|
case LUA_TUSERDATA: {
|
|
TValue uvalue;
|
|
markobjectN(g, gco2u(o)->metatable); /* mark its metatable */
|
|
gray2black(o);
|
|
getuservalue(g->mainthread, gco2u(o), &uvalue);
|
|
if (valiswhite(&uvalue)) { /* markvalue(g, &uvalue); */
|
|
o = gcvalue(&uvalue);
|
|
goto reentry;
|
|
}
|
|
break;
|
|
}
|
|
case LUA_TUPVAL: {
|
|
UpVal *uv = gco2upv(o);
|
|
if (!upisopen(uv)) /* open upvalues are kept gray */
|
|
gray2black(o);
|
|
markvalue(g, uv->v); /* mark its content */
|
|
break;
|
|
}
|
|
case LUA_TLCL: {
|
|
linkgclist(gco2lcl(o), g->gray);
|
|
break;
|
|
}
|
|
case LUA_TCCL: {
|
|
linkgclist(gco2ccl(o), g->gray);
|
|
break;
|
|
}
|
|
case RAVI_TIARRAY:
|
|
case RAVI_TFARRAY:
|
|
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 lu_mem markbeingfnz (global_State *g) {
|
|
GCObject *o;
|
|
lu_mem count = 0;
|
|
for (o = g->tobefnz; o != NULL; o = o->next) {
|
|
count++;
|
|
markobject(g, o);
|
|
}
|
|
return count;
|
|
}
|
|
|
|
|
|
/*
|
|
** 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 int remarkupvals (global_State *g) {
|
|
lua_State *thread;
|
|
lua_State **p = &g->twups;
|
|
int work = 0;
|
|
while ((thread = *p) != NULL) {
|
|
work++;
|
|
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) {
|
|
work++;
|
|
if (!iswhite(uv)) /* upvalue already visited? */
|
|
markvalue(g, uv->v); /* mark its value */
|
|
}
|
|
}
|
|
}
|
|
return work;
|
|
}
|
|
|
|
|
|
/*
|
|
** 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 = g->protogray = 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 */
|
|
if (ttisnil(gval(n))) /* entry is empty? */
|
|
removeentry(n); /* remove it */
|
|
else {
|
|
lua_assert(!keyisnil(n));
|
|
markkey(g, n);
|
|
if (!hasclears && iscleared(g, gcvalueN(gval(n)))) /* a white value? */
|
|
hasclears = 1; /* table will have to be cleared */
|
|
}
|
|
}
|
|
if (g->gcstate == GCSatomic && hasclears)
|
|
linkgclist(h, g->weak); /* has to be cleared later */
|
|
else
|
|
linkgclist(h, g->grayagain); /* must retraverse it in atomic phase */
|
|
}
|
|
|
|
|
|
/*
|
|
** 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). In generational mode, it (like all visited
|
|
** tables) must be kept in some gray list for post-processing.
|
|
*/
|
|
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++) {
|
|
if (ttisnil(gval(n))) /* entry is empty? */
|
|
removeentry(n); /* remove it */
|
|
else if (iscleared(g, gckeyN(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 */
|
|
else if (g->gckind == KGC_GEN)
|
|
linkgclist(h, g->grayagain); /* keep it in some list */
|
|
else
|
|
gray2black(h);
|
|
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 */
|
|
if (ttisnil(gval(n))) /* entry is empty? */
|
|
removeentry(n); /* remove it */
|
|
else {
|
|
lua_assert(!keyisnil(n));
|
|
markkey(g, n);
|
|
markvalue(g, gval(n));
|
|
}
|
|
}
|
|
if (g->gckind == KGC_GEN) {
|
|
linkgclist(h, g->grayagain); /* keep it in some gray list */
|
|
black2gray(h);
|
|
}
|
|
}
|
|
|
|
|
|
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 1 + h->sizearray + 2 * allocsizenode(h);
|
|
}
|
|
|
|
|
|
/*
|
|
** Check the cache of a prototype, to keep invariants. If the
|
|
** cache is white, clear it. (A cache should not prevent the
|
|
** collection of its reference.) Otherwise, if in generational
|
|
** mode, check the generational invariant. If the cache is old,
|
|
** everything is ok. If the prototype is 'old0', everything
|
|
** is ok too. (It will naturally be visited again.) If the
|
|
** prototype is older than 'old0', then its cache (which is new)
|
|
** must be visited again in the next collection, so the prototype
|
|
** goes to the 'protogray' list. (If the prototype has a cache,
|
|
** it is already immutable and does not need other barriers;
|
|
** then, it can become gray without problems for its other fields.)
|
|
*/
|
|
static void checkprotocache (global_State *g, Proto *p) {
|
|
if (p->cache) {
|
|
if (iswhite(p->cache))
|
|
p->cache = NULL; /* allow cache to be collected */
|
|
else if (g->gckind == KGC_GEN && !isold(p->cache) && getage(p) >= G_OLD1) {
|
|
linkgclist(p, g->protogray); /* link it in 'protogray' */
|
|
black2gray(p); /* make prototype gray */
|
|
}
|
|
}
|
|
p->cachemiss = 0; /* restart counting */
|
|
}
|
|
|
|
|
|
/*
|
|
** 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;
|
|
checkprotocache(g, f);
|
|
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 1 + f->sizek + f->sizeupvalues + f->sizep + f->sizelocvars;
|
|
}
|
|
|
|
|
|
static int traverseCclosure (global_State *g, CClosure *cl) {
|
|
int i;
|
|
for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */
|
|
markvalue(g, &cl->upvalue[i]);
|
|
return 1 + cl->nupvalues;
|
|
}
|
|
|
|
/*
|
|
** Traverse a Lua closure, marking its prototype and its upvalues.
|
|
** (Both can be NULL while closure is being created.)
|
|
*/
|
|
static int traverseLclosure (global_State *g, LClosure *cl) {
|
|
int i;
|
|
markobjectN(g, cl->p); /* mark its prototype */
|
|
for (i = 0; i < cl->nupvalues; i++) { /* visit its upvalues */
|
|
UpVal *uv = cl->upvals[i];
|
|
markobjectN(g, uv); /* mark upvalue */
|
|
}
|
|
return 1 + cl->nupvalues;
|
|
}
|
|
|
|
|
|
/*
|
|
** Traverse a thread, marking the elements in the stack up to its top
|
|
** and cleaning the rest of the stack in the final traversal.
|
|
** That ensures that the entire stack have valid (non-dead) objects.
|
|
*/
|
|
static int 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 == GCSatomic ||
|
|
th->openupval == NULL || isintwups(th));
|
|
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);
|
|
/* '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->gcemergency)
|
|
luaD_shrinkstack(th); /* do not change stack in emergency cycle */
|
|
return 1 + th->stacksize;
|
|
}
|
|
|
|
|
|
/*
|
|
** traverse one gray object, turning it to black (except for threads,
|
|
** which are always gray).
|
|
*/
|
|
static lu_mem propagatemark (global_State *g) {
|
|
GCObject *o = g->gray;
|
|
gray2black(o);
|
|
switch (o->tt) {
|
|
case RAVI_TIARRAY:
|
|
case RAVI_TFARRAY:
|
|
case LUA_TTABLE: {
|
|
Table *h = gco2t(o);
|
|
g->gray = h->gclist; /* remove from 'gray' list */
|
|
return traversetable(g, h);
|
|
}
|
|
case LUA_TLCL: {
|
|
LClosure *cl = gco2lcl(o);
|
|
g->gray = cl->gclist; /* remove from 'gray' list */
|
|
return traverseLclosure(g, cl);
|
|
}
|
|
case LUA_TCCL: {
|
|
CClosure *cl = gco2ccl(o);
|
|
g->gray = cl->gclist; /* remove from 'gray' list */
|
|
return traverseCclosure(g, cl);
|
|
}
|
|
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);
|
|
return traversethread(g, th);
|
|
}
|
|
case LUA_TPROTO: {
|
|
Proto *p = gco2p(o);
|
|
g->gray = p->gclist; /* remove from 'gray' list */
|
|
return traverseproto(g, p);
|
|
}
|
|
default: lua_assert(0); return 0;
|
|
}
|
|
}
|
|
|
|
|
|
static lu_mem propagateall (global_State *g) {
|
|
lu_mem tot = 0;
|
|
while (g->gray)
|
|
tot += propagatemark(g);
|
|
return tot;
|
|
}
|
|
|
|
|
|
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
|
|
** =======================================================
|
|
*/
|
|
|
|
static void clearprotolist (global_State *g) {
|
|
GCObject *p = g->protogray;
|
|
g->protogray = NULL;
|
|
while (p != NULL) {
|
|
Proto *pp = gco2p(p);
|
|
GCObject *next = pp->gclist;
|
|
lua_assert(isgray(pp) && (pp->cache != NULL || pp->cachemiss >= MAXMISS));
|
|
gray2black(pp);
|
|
checkprotocache(g, pp);
|
|
p = next;
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
** clear entries with unmarked keys from all weaktables in list 'l'
|
|
*/
|
|
static void clearkeys (global_State *g, GCObject *l) {
|
|
for (; l; 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, gckeyN(n)))) /* unmarked key? */
|
|
setnilvalue(gval(n)); /* clear value */
|
|
if (ttisnil(gval(n))) /* is entry empty? */
|
|
removeentry(n); /* remove it 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, gcvalueN(o))) /* value was collected? */
|
|
setnilvalue(o); /* remove value */
|
|
}
|
|
for (n = gnode(h, 0); n < limit; n++) {
|
|
if (iscleared(g, gcvalueN(gval(n)))) /* unmarked value? */
|
|
setnilvalue(gval(n)); /* clear value */
|
|
if (ttisnil(gval(n))) /* is entry empty? */
|
|
removeentry(n); /* remove it from table */
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
static void freeupval (lua_State *L, UpVal *uv) {
|
|
if (upisopen(uv))
|
|
luaF_unlinkupval(uv);
|
|
luaM_free(L, uv);
|
|
}
|
|
|
|
|
|
static void freeobj (lua_State *L, GCObject *o) {
|
|
switch (o->tt) {
|
|
case LUA_TPROTO:
|
|
luaF_freeproto(L, gco2p(o));
|
|
break;
|
|
case LUA_TUPVAL:
|
|
freeupval(L, gco2upv(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 RAVI_TFARRAY: case RAVI_TIARRAY:
|
|
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);
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
** sweep at most 'countin' 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. ('*countout' gets the number of elements traversed.)
|
|
*/
|
|
static GCObject **sweeplist (lua_State *L, GCObject **p, int countin,
|
|
int *countout) {
|
|
global_State *g = G(L);
|
|
int ow = otherwhite(g);
|
|
int i;
|
|
int white = luaC_white(g); /* current white */
|
|
for (i = 0; *p != NULL && i < countin; i++) {
|
|
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 */
|
|
}
|
|
}
|
|
if (countout)
|
|
*countout = i; /* number of elements traversed */
|
|
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, NULL);
|
|
} while (p == old);
|
|
return p;
|
|
}
|
|
|
|
/* }====================================================== */
|
|
|
|
|
|
/*
|
|
** {======================================================
|
|
** Finalization
|
|
** =======================================================
|
|
*/
|
|
|
|
/*
|
|
** If possible, shrink string table.
|
|
*/
|
|
static void checkSizes (lua_State *L, global_State *g) {
|
|
if (!g->gcemergency) {
|
|
l_mem olddebt = g->GCdebt;
|
|
if (g->strt.nuse < g->strt.size / 4) /* string table too big? */
|
|
luaS_resize(L, g->strt.size / 2);
|
|
g->GCestimate += g->GCdebt - olddebt; /* correct estimate */
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
** Get the next udata to be finalized from the 'tobefnz' list, and
|
|
** link it back into the 'allgc' list.
|
|
*/
|
|
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 finalizers
|
|
*/
|
|
static int runafewfinalizers (lua_State *L, int n) {
|
|
global_State *g = G(L);
|
|
int i;
|
|
for (i = 0; i < n && g->tobefnz; i++)
|
|
GCTM(L, 1); /* call one finalizer */
|
|
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).
|
|
** (Note that objects after 'finobjold' cannot be white, so they
|
|
** don't need to be traversed. In incremental mode, 'finobjold' is NULL,
|
|
** so the whole list is traversed.)
|
|
*/
|
|
static void separatetobefnz (global_State *g, int all) {
|
|
GCObject *curr;
|
|
GCObject **p = &g->finobj;
|
|
GCObject **lastnext = findlast(&g->tobefnz);
|
|
while ((curr = *p) != g->finobjold) { /* traverse all finalizable objects */
|
|
lua_assert(tofinalize(curr));
|
|
if (!(iswhite(curr) || all)) /* not being collected? */
|
|
p = &curr->next; /* don't bother with it */
|
|
else {
|
|
if (curr == g->finobjsur) /* removing 'finobjsur'? */
|
|
g->finobjsur = curr->next; /* correct it */
|
|
*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' */
|
|
}
|
|
else { /* correct pointers into 'allgc' list, if needed */
|
|
if (o == g->survival)
|
|
g->survival = o->next;
|
|
if (o == g->old)
|
|
g->old = o->next;
|
|
if (o == g->reallyold)
|
|
g->reallyold = o->next;
|
|
}
|
|
/* 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 */
|
|
}
|
|
}
|
|
|
|
/* }====================================================== */
|
|
|
|
|
|
/*
|
|
** {======================================================
|
|
** Generational Collector
|
|
** =======================================================
|
|
*/
|
|
|
|
|
|
/* mask to erase all color bits, not changing gen-related stuff */
|
|
#define maskgencolors (~(bitmask(BLACKBIT) | WHITEBITS))
|
|
|
|
|
|
/*
|
|
** Sweep a list of objects, deleting dead ones and turning
|
|
** the non dead to old (without changing their colors).
|
|
*/
|
|
static void sweep2old (lua_State *L, GCObject **p) {
|
|
GCObject *curr;
|
|
while ((curr = *p) != NULL) {
|
|
if (iswhite(curr)) { /* is 'curr' dead? */
|
|
lua_assert(isdead(G(L), curr));
|
|
*p = curr->next; /* remove 'curr' from list */
|
|
freeobj(L, curr); /* erase 'curr' */
|
|
}
|
|
else { /* all surviving objects become old */
|
|
setage(curr, G_OLD);
|
|
p = &curr->next; /* go to next element */
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
** Sweep for generational mode. Delete dead objects. (Because the
|
|
** collection is not incremental, there are no "new white" objects
|
|
** during the sweep. So, any white object must be dead.) For
|
|
** non-dead objects, advance their ages and clear the color of
|
|
** new objects. (Old objects keep their colors.)
|
|
*/
|
|
static GCObject **sweepgen (lua_State *L, global_State *g, GCObject **p,
|
|
GCObject *limit) {
|
|
static lu_byte nextage[] = {
|
|
G_SURVIVAL, /* from G_NEW */
|
|
G_OLD1, /* from G_SURVIVAL */
|
|
G_OLD1, /* from G_OLD0 */
|
|
G_OLD, /* from G_OLD1 */
|
|
G_OLD, /* from G_OLD (do not change) */
|
|
G_TOUCHED1, /* from G_TOUCHED1 (do not change) */
|
|
G_TOUCHED2 /* from G_TOUCHED2 (do not change) */
|
|
};
|
|
int white = luaC_white(g);
|
|
GCObject *curr;
|
|
while ((curr = *p) != limit) {
|
|
if (iswhite(curr)) { /* is 'curr' dead? */
|
|
lua_assert(!isold(curr) && isdead(g, curr));
|
|
*p = curr->next; /* remove 'curr' from list */
|
|
freeobj(L, curr); /* erase 'curr' */
|
|
}
|
|
else { /* correct mark and age */
|
|
if (getage(curr) == G_NEW)
|
|
curr->marked = cast_byte((curr->marked & maskgencolors) | white);
|
|
setage(curr, nextage[getage(curr)]);
|
|
p = &curr->next; /* go to next element */
|
|
}
|
|
}
|
|
return p;
|
|
}
|
|
|
|
|
|
/*
|
|
** Traverse a list making all its elements white and clearing their
|
|
** age.
|
|
*/
|
|
static void whitelist (global_State *g, GCObject *p) {
|
|
int white = luaC_white(g);
|
|
for (; p != NULL; p = p->next)
|
|
p->marked = cast_byte((p->marked & maskcolors) | white);
|
|
}
|
|
|
|
|
|
/*
|
|
** Correct a list of gray objects. Because this correction is
|
|
** done after sweeping, young objects can be white and still
|
|
** be in the list. They are only removed.
|
|
** For tables, advance 'touched1' to 'touched2'; 'touched2' objects
|
|
** become regular old and are removed from the list.
|
|
** For threads, just remove white ones from the list.
|
|
*/
|
|
static GCObject **correctgraylist (GCObject **p) {
|
|
GCObject *curr;
|
|
while ((curr = *p) != NULL) {
|
|
switch (curr->tt) {
|
|
case RAVI_TIARRAY:
|
|
case RAVI_TFARRAY:
|
|
case LUA_TTABLE: {
|
|
Table *h = gco2t(curr);
|
|
if (getage(h) == G_TOUCHED1) { /* touched in this cycle? */
|
|
lua_assert(isgray(h));
|
|
gray2black(h); /* make it black, for next barrier */
|
|
changeage(h, G_TOUCHED1, G_TOUCHED2);
|
|
p = &h->gclist; /* go to next element */
|
|
}
|
|
else {
|
|
if (!iswhite(h)) {
|
|
lua_assert(isold(h));
|
|
if (getage(h) == G_TOUCHED2)
|
|
changeage(h, G_TOUCHED2, G_OLD);
|
|
gray2black(h); /* make it black */
|
|
}
|
|
*p = h->gclist; /* remove 'curr' from gray list */
|
|
}
|
|
break;
|
|
}
|
|
case LUA_TTHREAD: {
|
|
lua_State *th = gco2th(curr);
|
|
lua_assert(!isblack(th));
|
|
if (iswhite(th)) /* new object? */
|
|
*p = th->gclist; /* remove from gray list */
|
|
else /* old threads remain gray */
|
|
p = &th->gclist; /* go to next element */
|
|
break;
|
|
}
|
|
default: lua_assert(0); /* nothing more could be gray here */
|
|
}
|
|
}
|
|
return p;
|
|
}
|
|
|
|
|
|
/*
|
|
** Correct all gray lists, coalescing them into 'grayagain'.
|
|
*/
|
|
static void correctgraylists (global_State *g) {
|
|
GCObject **list = correctgraylist(&g->grayagain);
|
|
*list = g->weak; g->weak = NULL;
|
|
list = correctgraylist(list);
|
|
*list = g->allweak; g->allweak = NULL;
|
|
list = correctgraylist(list);
|
|
*list = g->ephemeron; g->ephemeron = NULL;
|
|
correctgraylist(list);
|
|
}
|
|
|
|
|
|
/*
|
|
** Mark 'old1' objects when starting a new young collection.
|
|
** Gray objects are already in some gray list, and so will be visited
|
|
** in the atomic step.
|
|
*/
|
|
static void markold (global_State *g, GCObject *from, GCObject *to) {
|
|
GCObject *p;
|
|
for (p = from; p != to; p = p->next) {
|
|
if (getage(p) == G_OLD1) {
|
|
lua_assert(!iswhite(p));
|
|
if (isblack(p)) {
|
|
black2gray(p); /* should be '2white', but gray works too */
|
|
reallymarkobject(g, p);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
** Finish a young-generation collection.
|
|
*/
|
|
static void finishgencycle (lua_State *L, global_State *g) {
|
|
correctgraylists(g);
|
|
checkSizes(L, g);
|
|
g->gcstate = GCSpropagate; /* skip restart */
|
|
callallpendingfinalizers(L);
|
|
}
|
|
|
|
|
|
/*
|
|
** Does a young collection. First, mark 'old1' objects. (Only survival
|
|
** and "recent old" lists can contain 'old1' objects. New lists cannot
|
|
** contain 'old1' objects, at most 'old0' objects that were already
|
|
** visited when marked old.) Then does the atomic step. Then,
|
|
** sweep all lists and advance pointers. Finally, finish the collection.
|
|
*/
|
|
static void youngcollection (lua_State *L, global_State *g) {
|
|
GCObject **psurvival; /* to point to first non-dead survival object */
|
|
lua_assert(g->gcstate == GCSpropagate);
|
|
markold(g, g->survival, g->reallyold);
|
|
markold(g, g->finobj, g->finobjrold);
|
|
atomic(L);
|
|
|
|
/* sweep nursery and get a pointer to its last live element */
|
|
psurvival = sweepgen(L, g, &g->allgc, g->survival);
|
|
/* sweep 'survival' and 'old' */
|
|
sweepgen(L, g, psurvival, g->reallyold);
|
|
g->reallyold = g->old;
|
|
g->old = *psurvival; /* 'survival' survivals are old now */
|
|
g->survival = g->allgc; /* all news are survivals */
|
|
|
|
/* repeat for 'finobj' lists */
|
|
psurvival = sweepgen(L, g, &g->finobj, g->finobjsur);
|
|
/* sweep 'survival' and 'old' */
|
|
sweepgen(L, g, psurvival, g->finobjrold);
|
|
g->finobjrold = g->finobjold;
|
|
g->finobjold = *psurvival; /* 'survival' survivals are old now */
|
|
g->finobjsur = g->finobj; /* all news are survivals */
|
|
|
|
sweepgen(L, g, &g->tobefnz, NULL);
|
|
|
|
finishgencycle(L, g);
|
|
}
|
|
|
|
|
|
/*
|
|
** Enter generational mode. Must go until the end of an atomic cycle
|
|
** to ensure that all threads are in the gray list. Then, turn all
|
|
** objects into old and finishes the collection.
|
|
*/
|
|
static void entergen (lua_State *L, global_State *g) {
|
|
luaC_runtilstate(L, bitmask(GCSpause)); /* prepare to start a new cycle */
|
|
luaC_runtilstate(L, bitmask(GCSpropagate)); /* start new cycle */
|
|
atomic(L);
|
|
/* sweep all elements making them old */
|
|
sweep2old(L, &g->allgc);
|
|
/* everything alive now is old */
|
|
g->reallyold = g->old = g->survival = g->allgc;
|
|
|
|
/* repeat for 'finobj' lists */
|
|
sweep2old(L, &g->finobj);
|
|
g->finobjrold = g->finobjold = g->finobjsur = g->finobj;
|
|
|
|
sweep2old(L, &g->tobefnz);
|
|
|
|
finishgencycle(L, g);
|
|
g->gckind = KGC_GEN;
|
|
g->GCestimate = gettotalbytes(g); /* base for memory control */
|
|
}
|
|
|
|
|
|
/*
|
|
** Enter incremental mode. Turn all objects white, make all
|
|
** intermediate lists point to NULL (to avoid invalid pointers),
|
|
** and go to pause state.
|
|
*/
|
|
static void enterinc (global_State *g) {
|
|
whitelist(g, g->allgc);
|
|
g->reallyold = g->old = g->survival = NULL;
|
|
whitelist(g, g->finobj);
|
|
g->finobjrold = g->finobjold = g->finobjsur = NULL;
|
|
lua_assert(g->tobefnz == NULL); /* no need to sweep */
|
|
g->gcstate = GCSpause;
|
|
g->gckind = KGC_INC;
|
|
}
|
|
|
|
|
|
/*
|
|
** Change collector mode to 'newmode'.
|
|
*/
|
|
void luaC_changemode (lua_State *L, int newmode) {
|
|
global_State *g = G(L);
|
|
if (newmode != g->gckind) {
|
|
if (newmode == KGC_GEN) /* entering generational mode? */
|
|
entergen(L, g);
|
|
else
|
|
enterinc(g); /* entering incremental mode */
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
** Does a full collection in generational mode.
|
|
*/
|
|
static void fullgen (lua_State *L, global_State *g) {
|
|
enterinc(g);
|
|
entergen(L, g);
|
|
}
|
|
|
|
|
|
/*
|
|
** Does a generational "step". If memory grows 'genmajormul'% larger
|
|
** than last major collection (kept in 'g->GCestimate'), does a major
|
|
** collection. Otherwise, does a minor collection and set debt to make
|
|
** another collection when memory grows 'genminormul'% larger.
|
|
** 'GCdebt <= 0' means an explicit call to GC step with "size" zero;
|
|
** in that case, always do a minor collection.
|
|
*/
|
|
static void genstep (lua_State *L, global_State *g) {
|
|
lu_mem majorbase = g->GCestimate;
|
|
int majormul = getgcparam(g->genmajormul);
|
|
if (g->GCdebt > 0 &&
|
|
gettotalbytes(g) > (majorbase / 100) * (100 + majormul)) {
|
|
fullgen(L, g);
|
|
}
|
|
else {
|
|
lu_mem mem;
|
|
youngcollection(L, g);
|
|
mem = gettotalbytes(g);
|
|
luaE_setdebt(g, -(cast(l_mem, (mem / 100)) * g->genminormul));
|
|
g->GCestimate = majorbase; /* preserve base value */
|
|
}
|
|
}
|
|
|
|
/* }====================================================== */
|
|
|
|
|
|
/*
|
|
** {======================================================
|
|
** GC control
|
|
** =======================================================
|
|
*/
|
|
|
|
|
|
/*
|
|
** Set the "time" to wait before starting a new GC cycle; cycle will
|
|
** start when memory use hits the threshold of ('estimate' * pause /
|
|
** PAUSEADJ). (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;
|
|
int pause = getgcparam(g->gcpause);
|
|
l_mem estimate = g->GCestimate / PAUSEADJ; /* adjust 'estimate' */
|
|
lua_assert(estimate > 0);
|
|
threshold = (pause < MAX_LMEM / estimate) /* overflow? */
|
|
? estimate * pause /* no overflow */
|
|
: MAX_LMEM; /* overflow; truncate to maximum */
|
|
debt = gettotalbytes(g) - threshold;
|
|
if (debt > 0) debt = 0;
|
|
luaE_setdebt(g, debt);
|
|
}
|
|
|
|
|
|
/*
|
|
** Enter first sweep phase.
|
|
** The call to 'sweeptolive' makes the 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 = sweeptolive(L, &g->allgc);
|
|
}
|
|
|
|
|
|
/*
|
|
** Delete all objects in list 'p' until (but not including) object
|
|
** 'limit'.
|
|
*/
|
|
static void deletelist (lua_State *L, GCObject *p, GCObject *limit) {
|
|
while (p != limit) {
|
|
GCObject *next = p->next;
|
|
freeobj(L, p);
|
|
p = next;
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
** Call all finalizers of the objects in the given Lua state, and
|
|
** then free all objects, except for the main thread.
|
|
*/
|
|
void luaC_freeallobjects (lua_State *L) {
|
|
global_State *g = G(L);
|
|
luaC_changemode(L, KGC_INC);
|
|
separatetobefnz(g, 1); /* separate all objects with finalizers */
|
|
lua_assert(g->finobj == NULL);
|
|
callallpendingfinalizers(L);
|
|
deletelist(L, g->allgc, obj2gco(g->mainthread));
|
|
deletelist(L, g->finobj, NULL);
|
|
deletelist(L, g->fixedgc, NULL); /* collect fixed objects */
|
|
lua_assert(g->strt.nuse == 0);
|
|
}
|
|
|
|
|
|
static lu_mem atomic (lua_State *L) {
|
|
global_State *g = G(L);
|
|
lu_mem work = 0;
|
|
GCObject *origweak, *origall;
|
|
GCObject *grayagain = g->grayagain; /* save original list */
|
|
g->grayagain = NULL;
|
|
lua_assert(g->ephemeron == NULL && g->weak == NULL);
|
|
lua_assert(!iswhite(g->mainthread));
|
|
g->gcstate = GCSatomic;
|
|
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 */
|
|
work += remarkupvals(g);
|
|
work += propagateall(g); /* propagate changes */
|
|
g->gray = grayagain;
|
|
work += propagateall(g); /* traverse 'grayagain' list */
|
|
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;
|
|
separatetobefnz(g, 0); /* separate objects to be finalized */
|
|
work += markbeingfnz(g); /* mark objects that will be finalized */
|
|
work += propagateall(g); /* remark, to propagate 'resurrection' */
|
|
convergeephemerons(g);
|
|
/* at this point, all resurrected objects are marked. */
|
|
/* remove dead objects from weak tables */
|
|
clearkeys(g, g->ephemeron); /* clear keys from all ephemeron tables */
|
|
clearkeys(g, g->allweak); /* 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);
|
|
clearprotolist(g);
|
|
g->currentwhite = cast_byte(otherwhite(g)); /* flip current white */
|
|
lua_assert(g->gray == NULL);
|
|
return work; /* estimate of slots marked by 'atomic' */
|
|
}
|
|
|
|
|
|
static int sweepstep (lua_State *L, global_State *g,
|
|
int nextstate, GCObject **nextlist) {
|
|
if (g->sweepgc) {
|
|
l_mem olddebt = g->GCdebt;
|
|
int count;
|
|
g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX, &count);
|
|
g->GCestimate += g->GCdebt - olddebt; /* update estimate */
|
|
return count;
|
|
}
|
|
else { /* enter next state */
|
|
g->gcstate = nextstate;
|
|
g->sweepgc = nextlist;
|
|
return 0; /* no work done */
|
|
}
|
|
}
|
|
|
|
|
|
static lu_mem singlestep (lua_State *L) {
|
|
global_State *g = G(L);
|
|
switch (g->gcstate) {
|
|
case GCSpause: {
|
|
restartcollection(g);
|
|
g->gcstate = GCSpropagate;
|
|
return 1;
|
|
}
|
|
case GCSpropagate: {
|
|
if (g->gray == NULL) { /* no more gray objects? */
|
|
g->gcstate = GCSenteratomic; /* finish propagate phase */
|
|
return 0;
|
|
}
|
|
else
|
|
return propagatemark(g); /* traverse one gray object */
|
|
}
|
|
case GCSenteratomic: {
|
|
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 */
|
|
checkSizes(L, g);
|
|
g->gcstate = GCScallfin;
|
|
return 0;
|
|
}
|
|
case GCScallfin: { /* call remaining finalizers */
|
|
if (g->tobefnz && !g->gcemergency) {
|
|
int n = runafewfinalizers(L, GCFINMAX);
|
|
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);
|
|
}
|
|
|
|
|
|
/*
|
|
** Performs a basic incremental step. The debt and step size are
|
|
** converted from bytes to "units of work"; then the function loops
|
|
** running single steps until adding that many units of work or
|
|
** finishing a cycle (pause state). Finally, it sets the debt that
|
|
** controls when next step will be performed.
|
|
*/
|
|
static void incstep (lua_State *L, global_State *g) {
|
|
int stepmul = (getgcparam(g->gcstepmul) | 1); /* avoid division by 0 */
|
|
l_mem debt = (g->GCdebt / WORK2MEM) * stepmul;
|
|
l_mem stepsize = (g->gcstepsize <= log2maxs(l_mem))
|
|
? ((cast(l_mem, 1) << g->gcstepsize) / WORK2MEM) * stepmul
|
|
: MAX_LMEM; /* overflow; keep maximum value */
|
|
do { /* repeat until pause or enough "credit" (negative debt) */
|
|
lu_mem work = singlestep(L); /* perform one single step */
|
|
debt -= work;
|
|
} while (debt > -stepsize && g->gcstate != GCSpause);
|
|
if (g->gcstate == GCSpause)
|
|
setpause(g); /* pause until next cycle */
|
|
else {
|
|
debt = (debt / stepmul) * WORK2MEM; /* convert 'work units' to bytes */
|
|
luaE_setdebt(g, debt);
|
|
}
|
|
}
|
|
|
|
/*
|
|
** performs a basic GC step if collector is running
|
|
*/
|
|
void luaC_step (lua_State *L) {
|
|
global_State *g = G(L);
|
|
if (g->gcrunning) { /* running? */
|
|
if (g->gckind == KGC_INC)
|
|
incstep(L, g);
|
|
else
|
|
genstep(L, g);
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
** Perform a full collection in incremental mode.
|
|
** 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).
|
|
*/
|
|
static void fullinc (lua_State *L, global_State *g) {
|
|
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(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 */
|
|
setpause(g);
|
|
}
|
|
|
|
|
|
/*
|
|
** 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).
|
|
*/
|
|
void luaC_fullgc (lua_State *L, int isemergency) {
|
|
global_State *g = G(L);
|
|
lua_assert(!g->gcemergency);
|
|
g->gcemergency = isemergency; /* set flag */
|
|
if (g->gckind == KGC_INC)
|
|
fullinc(L, g);
|
|
else
|
|
fullgen(L, g);
|
|
g->gcemergency = 0;
|
|
}
|
|
|
|
/* }====================================================== */
|
|
|
|
|