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Merge pull request #200 from dibyendumajumdar/lua542-gc

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Lua 5.4.2 gc
pull/201/head
Dibyendu Majumdar 3 years ago committed by GitHub
parent 001dceb996 e9cb48e15c
commit 389c98ee35
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6 changed files with 383 additions and 177 deletions
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29
include/lgc.h
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@ -12,16 +12,16 @@
#include "lstate.h"
/*
** Collectable objects may have one of three colors: white, which
** means the object is not marked; gray, which means the
** object is marked, but its references may be not marked; and
** black, which means that the object and all its references are marked.
** The main invariant of the garbage collector, while marking objects,
** is that a black object can never point to a white one. Moreover,
** any gray object must be in a "gray list" (gray, grayagain, weak,
** allweak, ephemeron) so that it can be visited again before finishing
** the collection cycle. These lists have no meaning when the invariant
** is not being enforced (e.g., sweep phase).
** Collectable objects may have one of three colors: white, which means
** the object is not marked; gray, which means the object is marked, but
** its references may be not marked; and black, which means that the
** object and all its references are marked. The main invariant of the
** garbage collector, while marking objects, is that a black object can
** never point to a white one. Moreover, any gray object must be in a
** "gray list" (gray, grayagain, weak, allweak, ephemeron) so that it
** can be visited again before finishing the collection cycle. (Open
** upvalues are an exception to this rule.) These lists have no meaning
** when the invariant is not being enforced (e.g., sweep phase).
*/
@ -69,14 +69,16 @@
/*
** Layout for bit use in 'marked' field. First three bits are
** used for object "age" in generational mode. Last bit is free
** to be used by respective objects.
** used for object "age" in generational mode. Last bit is used
** by tests.
*/
#define WHITE0BIT 3 /* object is white (type 0) */
#define WHITE1BIT 4 /* object is white (type 1) */
#define BLACKBIT 5 /* object is black */
#define FINALIZEDBIT 6 /* object has been marked for finalization */
#define TESTBIT 7
#define WHITEBITS bit2mask(WHITE0BIT, WHITE1BIT)
@ -94,7 +96,8 @@
#define isdead(g,v) isdeadm(otherwhite(g), (v)->marked)
#define changewhite(x) ((x)->marked ^= WHITEBITS)
#define gray2black(x) l_setbit((x)->marked, BLACKBIT)
#define nw2black(x) \
check_exp(!iswhite(x), l_setbit((x)->marked, BLACKBIT))
#define luaC_white(g) cast_byte((g)->currentwhite & WHITEBITS)

44
include/lstate.h
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@ -15,7 +15,6 @@
#include "lopcodes.h"
/*
** Some notes about garbage-collected objects: All objects in Lua must
** be kept somehow accessible until being freed, so all objects always
** belong to one (and only one) of these lists, using field 'next' of
@ -33,13 +32,29 @@
**
** 'allgc' -> 'survival': new objects;
** 'survival' -> 'old': objects that survived one collection;
** 'old' -> 'reallyold': objects that became old in last collection;
** 'old1' -> 'reallyold': objects that became old in last collection;
** 'reallyold' -> NULL: objects old for more than one cycle.
**
** 'finobj' -> 'finobjsur': new objects marked for finalization;
** 'finobjsur' -> 'finobjold': survived """";
** 'finobjold' -> 'finobjrold': just old """";
** 'finobjsur' -> 'finobjold1': survived """";
** 'finobjold1' -> 'finobjrold': just old """";
** 'finobjrold' -> NULL: really old """".
**
** All lists can contain elements older than their main ages, due
** to 'luaC_checkfinalizer' and 'udata2finalize', which move
** objects between the normal lists and the "marked for finalization"
** lists. Moreover, barriers can age young objects in young lists as
** OLD0, which then become OLD1. However, a list never contains
** elements younger than their main ages.
**
** The generational collector also uses a pointer 'firstold1', which
** points to the first OLD1 object in the list. It is used to optimize
** 'markold'. (Potentially OLD1 objects can be anywhere between 'allgc'
** and 'reallyold', but often the list has no OLD1 objects or they are
** after 'old1'.) Note the difference between it and 'old1':
** 'firstold1': no OLD1 objects before this point; there can be all
** ages after it.
** 'old1': no objects younger than OLD1 after this point.
*/
/*
@ -48,7 +63,7 @@
** can become gray have such a field. The field is not the same
** in all objects, but it always has this name.) Any gray object
** must belong to one of these lists, and all objects in these lists
** must be gray:
** must be gray (with two exceptions explained below):
**
** 'gray': regular gray objects, still waiting to be visited.
** 'grayagain': objects that must be revisited at the atomic phase.
@ -59,9 +74,17 @@
** 'weak': tables with weak values to be cleared;
** 'ephemeron': ephemeron tables with white->white entries;
** 'allweak': tables with weak keys and/or weak values to be cleared.
**
** The exceptions to that "gray rule" are:
** - TOUCHED2 objects in generational mode stay in a gray list (because
** they must be visited again at the end of the cycle), but they are
** marked black because assignments to them must activate barriers (to
** move them back to TOUCHED1).
** - Open upvales are kept gray to avoid barriers, but they stay out
** of gray lists. (They don't even have a 'gclist' field.)
*/
*/
struct lua_longjmp; /* defined in ldo.c */
@ -83,6 +106,8 @@ struct lua_longjmp; /* defined in ldo.c */
#define BASIC_STACK_SIZE (2*LUA_MINSTACK)
#define stacksize(th) cast_int((th)->stack_last - (th)->stack)
/* kinds of Garbage Collection */
#define KGC_INC 0 /* incremental gc */
@ -189,10 +214,11 @@ typedef struct global_State {
GCObject *fixedgc; /* list of objects not to be collected */
/* fields for generational collector */
GCObject *survival; /* start of objects that survived one GC cycle */
GCObject *old; /* start of old objects */
GCObject *reallyold; /* old objects with more than one cycle */
GCObject *old1; /* start of old1 objects */
GCObject *reallyold; /* objects more than one cycle old ("really old") */
GCObject *firstold1; /* first OLD1 object in the list (if any) */
GCObject *finobjsur; /* list of survival objects with finalizers */
GCObject *finobjold; /* list of old objects with finalizers */
GCObject *finobjold1; /* list of old1 objects with finalizers */
GCObject *finobjrold; /* list of really old objects with finalizers */
struct lua_State *twups; /* list of threads with open upvalues */
lua_CFunction panic; /* to be called in unprotected errors */

358
src/lgc.c
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@ -60,16 +60,24 @@
#define PAUSEADJ 100
/* mask to erase all color bits (plus gen. related stuff) */
#define maskcolors (~(bitmask(BLACKBIT) | WHITEBITS | AGEBITS))
/* mask with all color bits */
#define maskcolors (bitmask(BLACKBIT) | WHITEBITS)
/* mask with all GC bits */
#define maskgcbits (maskcolors | AGEBITS)
/* macro to erase all color bits then sets only the current white bit */
/* macro to erase all color bits then set only the current white bit */
#define makewhite(g,x) \
(x->marked = cast_byte((x->marked & maskcolors) | luaC_white(g)))
(x->marked = cast_byte((x->marked & ~maskcolors) | luaC_white(g)))
/* make an object gray (neither white nor black) */
#define set2gray(x) resetbits(x->marked, maskcolors)
#define white2gray(x) resetbits(x->marked, WHITEBITS)
#define black2gray(x) resetbit(x->marked, BLACKBIT)
/* make an object black (coming from any color) */
#define set2black(x) \
(x->marked = cast_byte((x->marked & ~WHITEBITS) | bitmask(BLACKBIT)))
#define valiswhite(x) (iscollectable(x) && iswhite(gcvalue(x)))
@ -78,16 +86,13 @@
#define checkdeadkey(n) lua_assert(!ttisdeadkey(gkey(n)) || ttisnil(gval(n)))
#define checkconsistency(obj) \
lua_longassert(!iscollectable(obj) || righttt(obj))
/*
** Protected access to objects in values
*/
#define gcvalueN(o) (iscollectable(o) ? gcvalue(o) : NULL)
#define markvalue(g,o) { checkconsistency(o); \
#define markvalue(g,o) { checkliveness(g->mainthread,o); \
if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); }
#define markkey(g, n) { if keyiswhite(n) reallymarkobject(g,gckey(n)); }
@ -131,15 +136,23 @@ static GCObject **getgclist (GCObject *o) {
/*
** Link a collectable object 'o' with a known type into list pointed by 'p'.
** Link a collectable object 'o' with a known type into the list 'p'.
** (Must be a macro to access the 'gclist' field in different types.)
*/
#define linkgclist(o,p) ((o)->gclist = (p), (p) = obj2gco(o))
#define linkgclist(o,p) linkgclist_(obj2gco(o), &(o)->gclist, &(p))
static void linkgclist_ (GCObject *o, GCObject **pnext, GCObject **list) {
lua_assert(!isgray(o)); /* cannot be in a gray list */
*pnext = *list;
*list = o;
set2gray(o); /* now it is */
}
/*
** Link a generic collectable object 'o' into list pointed by 'p'.
** Link a generic collectable object 'o' into the list 'p'.
*/
#define linkobjgclist(o,p) (*getgclist(o) = (p), (p) = obj2gco(o))
#define linkobjgclist(o,p) linkgclist_(obj2gco(o), getgclist(o), &(p))
@ -154,7 +167,7 @@ static GCObject **getgclist (GCObject *o) {
*/
static void removeentry (Node *n) {
lua_assert(ttisnil(gval(n)));
if (valiswhite(gkey(n)))
if (keyiscollectable(n))
setdeadvalue(wgkey(n)); /* unused and unmarked key; remove it */
}
@ -267,7 +280,8 @@ void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) {
}
else { /* sweep phase */
lua_assert(issweepphase(g));
makewhite(g, o); /* mark main obj. as white to avoid other barriers */
if (g->gckind == KGC_INC) /* incremental mode? */
makewhite(g, o); /* mark 'o' as white to avoid other barriers */
}
}
@ -307,18 +321,20 @@ void luaC_upvalbarrier_compat(lua_State* L, UpVal* uv) {
void luaC_barrierback_ (lua_State *L, GCObject *o) {
global_State *g = G(L);
lua_assert(isblack(o) && !isdead(g, o));
lua_assert(g->gckind != KGC_GEN || (isold(o) && getage(o) != G_TOUCHED1));
if (getage(o) != G_TOUCHED2) /* not already in gray list? */
linkobjgclist(o, g->grayagain); /* link it in 'grayagain' */
black2gray(o); /* make object gray (again) */
setage(o, G_TOUCHED1); /* touched in current cycle */
lua_assert((g->gckind == KGC_GEN) == (isold(o) && getage(o) != G_TOUCHED1));
if (getage(o) == G_TOUCHED2) /* already in gray list? */
set2gray(o); /* make it gray to become touched1 */
else /* link it in 'grayagain' and paint it gray */
linkobjgclist(o, g->grayagain);
if (isold(o)) /* generational mode? */
setage(o, G_TOUCHED1); /* touched in current cycle */
}
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 */
set2gray(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 */
@ -361,17 +377,16 @@ GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
*/
static void reallymarkobject (global_State *g, GCObject *o) {
reentry:
white2gray(o);
switch (o->tt) {
case LUA_TSHRSTR:
case LUA_TLNGSTR: {
gray2black(o);
set2black(o); /* nothing to visit */
break;
}
case LUA_TUSERDATA: {
TValue uvalue;
markobjectN(g, gco2u(o)->metatable); /* mark its metatable */
gray2black(o);
set2black(o);
getuservalue(g->mainthread, gco2u(o), &uvalue);
if (valiswhite(&uvalue)) { /* markvalue(g, &uvalue); */
o = gcvalue(&uvalue);
@ -384,7 +399,7 @@ static void reallymarkobject (global_State *g, GCObject *o) {
case RAVI_TFARRAY: {
RaviArray *slice = gco2array(o);
markobjectN(g, gco2array(o)->metatable); /* mark its metatable */
gray2black(o);
set2black(o);
if (slice->flags & RAVI_ARRAY_SLICE) {
lua_assert(slice->parent);
TValue pvalue = {.tt_ = ctb(slice->parent->tt), .value_.gc = obj2gco(slice->parent)}; // FIX we should use appropriate macro
@ -438,14 +453,14 @@ static lu_mem markbeingfnz (global_State *g) {
static int remarkupvals (global_State *g) {
lua_State *thread;
lua_State **p = &g->twups;
int work = 0;
int work = 0; /* estimate of how much work was done here */
while ((thread = *p) != NULL) {
work++;
lua_assert(!isblack(thread)); /* threads are never black */
if (isgray(thread) && thread->openupval != NULL)
if (!iswhite(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;
lua_assert(!isold(thread) || thread->openupval == NULL);
*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) {
@ -461,12 +476,17 @@ static int remarkupvals (global_State *g) {
}
static void cleargraylists (global_State *g) {
g->gray = g->grayagain = NULL;
g->weak = g->allweak = g->ephemeron = NULL;
}
/*
** 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;
cleargraylists(g);
markobject(g, g->mainthread);
markvalue(g, &g->l_registry);
markmt(g);
@ -482,6 +502,26 @@ static void restartcollection (global_State *g) {
** =======================================================
*/
/*
** Check whether object 'o' should be kept in the 'grayagain' list for
** post-processing by 'correctgraylist'. (It could put all old objects
** in the list and leave all the work to 'correctgraylist', but it is
** more efficient to avoid adding elements that will be removed.) Only
** TOUCHED1 objects need to be in the list. TOUCHED2 doesn't need to go
** back to a gray list, but then it must become OLD. (That is what
** 'correctgraylist' does when it finds a TOUCHED2 object.)
*/
static void genlink (global_State *g, GCObject *o) {
lua_assert(isblack(o));
if (getage(o) == G_TOUCHED1) { /* touched in this cycle? */
linkobjgclist(o, g->grayagain); /* link it back in 'grayagain' */
} /* everything else do not need to be linked back */
else if (getage(o) == G_TOUCHED2)
changeage(o, G_TOUCHED2, G_OLD); /* advance age */
}
/*
** 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
@ -519,8 +559,9 @@ static void traverseweakvalue (global_State *g, Table *h) {
** 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.
** (in the atomic phase). In generational mode, some tables
** must be kept in some gray list for post-processing; this is done
** by 'genlink'.
*/
static int traverseephemeron (global_State *g, Table *h, int inv) {
int marked = 0; /* true if an object is marked in this traversal */
@ -556,10 +597,8 @@ static int traverseephemeron (global_State *g, Table *h, int inv) {
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);
genlink(g, obj2gco(h)); /* check whether collector still needs to see it */
return marked;
}
@ -578,10 +617,7 @@ static void traversestrongtable (global_State *g, Table *h) {
markvalue(g, gval(n)); /* mark value */
}
}
if (g->gckind == KGC_GEN) {
linkgclist(h, g->grayagain); /* keep it in some gray list */
black2gray(h);
}
genlink(g, obj2gco(h));
}
@ -593,7 +629,6 @@ static lu_mem traversetable (global_State *g, Table *h) {
(cast_void(weakkey = strchr(svalue(mode), 'k')),
cast_void(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? */
@ -666,12 +701,21 @@ static int traverseLclosure (global_State *g, LClosure *cl) {
/*
** 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 lu_mem traversethread (global_State *g, lua_State *th) {
** and cleaning the rest of the stack in the final traversal. That
** ensures that the entire stack have valid (non-dead) objects.
** Threads have no barriers. In gen. mode, old threads must be visited
** at every cycle, because they might point to young objects. In inc.
** mode, the thread can still be modified before the end of the cycle,
** and therefore it must be visited again in the atomic phase. To ensure
** these visits, threads must return to a gray list if they are not new
** (which can only happen in generational mode) or if the traverse is in
** the propagate phase (which can only happen in incremental mode).
*/
static int traversethread (global_State *g, lua_State *th) {
UpVal *uv;
StkId o = th->stack;
if (isold(th) || g->gcstate == GCSpropagate)
linkgclist(th, g->grayagain); /* insert into 'grayagain' list */
if (o == NULL)
return 1; /* stack not completely built yet */
lua_assert(g->gcstate == GCSatomic ||
@ -681,8 +725,7 @@ static lu_mem traversethread (global_State *g, lua_State *th) {
for (uv = th->openupval; uv != NULL; uv = uv->u.open.next)
markvalue(g, uv->v); /* open upvalues cannot be collected */
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 */
for (; o < th->stack_last + EXTRA_STACK; o++)
setnilvalue(o);
/* 'remarkupvals' may have removed thread from 'twups' list */
if (!isintwups(th) && th->openupval != NULL) {
@ -697,24 +740,18 @@ static lu_mem traversethread (global_State *g, lua_State *th) {
/*
** traverse one gray object, turning it to black (except for threads,
** which are always gray).
** traverse one gray object, turning it to black.
*/
static lu_mem propagatemark (global_State *g) {
GCObject *o = g->gray;
gray2black(o);
nw2black(o);
g->gray = *getgclist(o); /* remove from 'gray' list */
switch (o->tt) {
case LUA_TTABLE: return traversetable(g, gco2t(o));
case LUA_TLCL: return traverseLclosure(g, gco2lcl(o));
case LUA_TCCL: return traverseCclosure(g, gco2ccl(o));
case LUA_TPROTO: return traverseproto(g, gco2p(o));
case LUA_TTHREAD: {
lua_State *th = gco2th(o);
linkgclist(th, g->grayagain); /* insert into 'grayagain' list */
black2gray(o);
return traversethread(g, th);
}
case LUA_TTHREAD: return traversethread(g, gco2th(o));
default: lua_assert(0); return 0;
}
}
@ -744,8 +781,10 @@ static void convergeephemerons (global_State *g) {
g->ephemeron = NULL; /* tables may return to this list when traversed */
changed = 0;
while ((w = next) != NULL) { /* for each ephemeron table */
next = gco2t(w)->gclist; /* list is rebuilt during loop */
if (traverseephemeron(g, gco2t(w), dir)) { /* marked some value? */
Table *h = gco2t(w);
next = h->gclist; /* list is rebuilt during loop */
nw2black(h); /* out of the list (for now) */
if (traverseephemeron(g, h, dir)) { /* marked some value? */
propagateall(g); /* propagate changes */
changed = 1; /* will have to revisit all ephemeron tables */
}
@ -888,7 +927,7 @@ static GCObject **sweeplist (lua_State *L, GCObject **p, int countin,
freeobj(L, curr); /* erase 'curr' */
}
else { /* change mark to 'white' */
curr->marked = cast_byte((marked & maskcolors) | white);
curr->marked = cast_byte((marked & ~maskgcbits) | white);
p = &curr->next; /* go to next element */
}
}
@ -945,6 +984,8 @@ static GCObject *udata2finalize (global_State *g) {
resetbit(o->marked, FINALIZEDBIT); /* object is "normal" again */
if (issweepphase(g))
makewhite(g, o); /* "sweep" object */
else if (getage(o) == G_OLD1)
g->firstold1 = o; /* it is the first OLD1 object in the list */
return o;
}
@ -1018,15 +1059,15 @@ static GCObject **findlast (GCObject **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,
** (Note that objects after 'finobjold1' cannot be white, so they
** don't need to be traversed. In incremental mode, 'finobjold1' 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 */
while ((curr = *p) != g->finobjold1) { /* traverse all finalizable objects */
lua_assert(tofinalize(curr));
if (!(iswhite(curr) || all)) /* not being collected? */
p = &curr->next; /* don't bother with it */
@ -1042,6 +1083,27 @@ static void separatetobefnz (global_State *g, int all) {
}
/*
** If pointer 'p' points to 'o', move it to the next element.
*/
static void checkpointer (GCObject **p, GCObject *o) {
if (o == *p)
*p = o->next;
}
/*
** Correct pointers to objects inside 'allgc' list when
** object 'o' is being removed from the list.
*/
static void correctpointers (global_State *g, GCObject *o) {
checkpointer(&g->survival, o);
checkpointer(&g->old1, o);
checkpointer(&g->reallyold, o);
checkpointer(&g->firstold1, o);
}
/*
** if object 'o' has a finalizer, remove it from 'allgc' list (must
** search the list to find it) and link it in 'finobj' list.
@ -1058,14 +1120,8 @@ void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
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;
}
else
correctpointers(g, o);
/* search for pointer pointing to 'o' */
for (p = &g->allgc; *p != o; p = &(*p)->next) { /* empty */ }
*p = o->next; /* remove 'o' from 'allgc' list */
@ -1087,24 +1143,29 @@ void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
static void setpause (global_State *g);
/* 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).
** Sweep a list of objects to enter generational mode. Deletes dead
** objects and turns the non dead to old. All non-dead threads---which
** are now old---must be in a gray list. Everything else is not in a
** gray list. Open upvalues are also kept gray.
*/
static void sweep2old (lua_State *L, GCObject **p) {
GCObject *curr;
global_State *g = G(L);
while ((curr = *p) != NULL) {
if (iswhite(curr)) { /* is 'curr' dead? */
lua_assert(isdead(G(L), curr));
lua_assert(isdead(g, curr));
*p = curr->next; /* remove 'curr' from list */
freeobj(L, curr); /* erase 'curr' */
}
else { /* all surviving objects become old */
setage(curr, G_OLD);
if (curr->tt == LUA_TTHREAD) { /* threads must be watched */
lua_State *th = gco2th(curr);
linkgclist(th, g->grayagain); /* insert into 'grayagain' list */
}
else /* everything else is black */
nw2black(curr);
p = &curr->next; /* go to next element */
}
}
@ -1117,9 +1178,13 @@ static void sweep2old (lua_State *L, GCObject **p) {
** 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.)
** The ages of G_TOUCHED1 and G_TOUCHED2 objects cannot be advanced
** here, because these old-generation objects are usually not swept
** here. They will all be advanced in 'correctgraylist'. That function
** will also remove objects turned white here from any gray list.
*/
static GCObject **sweepgen (lua_State *L, global_State *g, GCObject **p,
GCObject *limit) {
GCObject *limit, GCObject **pfirstold1) {
static const lu_byte nextage[] = {
G_SURVIVAL, /* from G_NEW */
G_OLD1, /* from G_SURVIVAL */
@ -1138,9 +1203,15 @@ static GCObject **sweepgen (lua_State *L, global_State *g, GCObject **p,
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)]);
if (getage(curr) == G_NEW) { /* new objects go back to white */
int marked = curr->marked & ~maskgcbits; /* erase GC bits */
curr->marked = cast_byte(marked | G_SURVIVAL | white);
}
else { /* all other objects will be old, and so keep their color */
setage(curr, nextage[getage(curr)]);
if (getage(curr) == G_OLD1 && *pfirstold1 == NULL)
*pfirstold1 = curr; /* first OLD1 object in the list */
}
p = &curr->next; /* go to next element */
}
}
@ -1150,58 +1221,50 @@ static GCObject **sweepgen (lua_State *L, global_State *g, GCObject **p,
/*
** Traverse a list making all its elements white and clearing their
** age.
** age. In incremental mode, all objects are 'new' all the time,
** except for fixed strings (which are always old).
*/
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);
p->marked = cast_byte((p->marked & ~maskgcbits) | white);
}
/*
** Correct a list of gray objects.
** Correct a list of gray objects. Return pointer to where rest of the
** list should be linked.
** Because this correction is done after sweeping, young objects might
** be turned white and still be in the list. They are only removed.
** For tables and userdata, advance 'touched1' to 'touched2'; 'touched2'
** objects become regular old and are removed from the list.
** For threads, just remove white ones from the list.
** 'TOUCHED1' objects are advanced to 'TOUCHED2' and remain on the list;
** Non-white threads also remain on the list; 'TOUCHED2' objects become
** regular old; they and anything else are removed from the list.
*/
static GCObject **correctgraylist (GCObject **p) {
GCObject *curr;
while ((curr = *p) != NULL) {
switch (curr->tt) {
case LUA_TTABLE: {
GCObject **next = getgclist(curr);
if (getage(curr) == G_TOUCHED1) { /* touched in this cycle? */
lua_assert(isgray(curr));
gray2black(curr); /* make it black, for next barrier */
changeage(curr, G_TOUCHED1, G_TOUCHED2);
p = next; /* go to next element */
}
else { /* not touched in this cycle */
if (!iswhite(curr)) { /* not white? */
lua_assert(isold(curr));
if (getage(curr) == G_TOUCHED2) /* advance from G_TOUCHED2... */
changeage(curr, G_TOUCHED2, G_OLD); /* ... to G_OLD */
gray2black(curr); /* make it black */
}
/* else, object is white: just remove it from this list */
*p = *next; /* 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 */
GCObject **next = getgclist(curr);
if (iswhite(curr))
goto remove; /* remove all white objects */
else if (getage(curr) == G_TOUCHED1) { /* touched in this cycle? */
lua_assert(isgray(curr));
nw2black(curr); /* make it black, for next barrier */
changeage(curr, G_TOUCHED1, G_TOUCHED2);
goto remain; /* keep it in the list and go to next element */
}
else if (curr->tt == LUA_TTHREAD) {
lua_assert(isgray(curr));
goto remain; /* keep non-white threads on the list */
}
else { /* everything else is removed */
lua_assert(isold(curr)); /* young objects should be white here */
if (getage(curr) == G_TOUCHED2) /* advance from TOUCHED2... */
changeage(curr, G_TOUCHED2, G_OLD); /* ... to OLD */
nw2black(curr); /* make object black (to be removed) */
goto remove;
}
remove: *p = *next; continue;
remain: p = next; continue;
}
return p;
}
@ -1231,10 +1294,9 @@ static void markold (global_State *g, GCObject *from, GCObject *to) {
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 */
changeage(p, G_OLD1, G_OLD); /* now they are old */
if (isblack(p))
reallymarkobject(g, p);
}
}
}
}
@ -1259,42 +1321,57 @@ static void finishgencycle (lua_State *L, global_State *g) {
*/
static void youngcollection (lua_State *L, global_State *g) {
GCObject **psurvival; /* to point to first non-dead survival object */
GCObject *dummy; /* dummy out parameter to 'sweepgen' */
lua_assert(g->gcstate == GCSpropagate);
markold(g, g->allgc, g->reallyold);
if (g->firstold1) { /* are there regular OLD1 objects? */
markold(g, g->firstold1, g->reallyold); /* mark them */
g->firstold1 = NULL; /* no more OLD1 objects (for now) */
}
markold(g, g->finobj, g->finobjrold);
markold(g, g->tobefnz, NULL);
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->gcstate = GCSswpallgc;
psurvival = sweepgen(L, g, &g->allgc, g->survival, &g->firstold1);
/* sweep 'survival' */
sweepgen(L, g, psurvival, g->old1, &g->firstold1);
g->reallyold = g->old1;
g->old1 = *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 */
dummy = NULL; /* no 'firstold1' optimization for 'finobj' lists */
psurvival = sweepgen(L, g, &g->finobj, g->finobjsur, &dummy);
/* sweep 'survival' */
sweepgen(L, g, psurvival, g->finobjold1, &dummy);
g->finobjrold = g->finobjold1;
g->finobjold1 = *psurvival; /* 'survival' survivals are old now */
g->finobjsur = g->finobj; /* all news are survivals */
sweepgen(L, g, &g->tobefnz, NULL);
sweepgen(L, g, &g->tobefnz, NULL, &dummy);
finishgencycle(L, g);
}
/*
** Clears all gray lists, sweeps objects, and prepare sublists to enter
** generational mode. The sweeps remove dead objects and turn all
** surviving objects to old. Threads go back to 'grayagain'; everything
** else is turned black (not in any gray list).
*/
static void atomic2gen (lua_State *L, global_State *g) {
cleargraylists(g);
/* sweep all elements making them old */
g->gcstate = GCSswpallgc;
sweep2old(L, &g->allgc);
/* everything alive now is old */
g->reallyold = g->old = g->survival = g->allgc;
g->reallyold = g->old1 = g->survival = g->allgc;
g->firstold1 = NULL; /* there are no OLD1 objects anywhere */
/* repeat for 'finobj' lists */
sweep2old(L, &g->finobj);
g->finobjrold = g->finobjold = g->finobjsur = g->finobj;
g->finobjrold = g->finobjold1 = g->finobjsur = g->finobj;
sweep2old(L, &g->tobefnz);
@ -1307,8 +1384,9 @@ static void atomic2gen (lua_State *L, global_State *g) {
/*
** Enter generational mode. Must go until the end of an atomic cycle
** to ensure that all threads and weak tables are in the gray lists.
** Then, turn all objects into old and finishes the collection.
** to ensure that all objects are correctly marked and weak tables
** are cleared. Then, turn all objects into old and finishes the
** collection.
*/
static lu_mem entergen (lua_State *L, global_State *g) {
lu_mem numobjs;
@ -1327,10 +1405,10 @@ static lu_mem entergen (lua_State *L, global_State *g) {
*/
static void enterinc (global_State *g) {
whitelist(g, g->allgc);
g->reallyold = g->old = g->survival = NULL;
g->reallyold = g->old1 = g->survival = NULL;
whitelist(g, g->finobj);
whitelist(g, g->tobefnz);
g->finobjrold = g->finobjold = g->finobjsur = NULL;
g->finobjrold = g->finobjold1 = g->finobjsur = NULL;
g->gcstate = GCSpause;
g->gckind = KGC_INC;
g->lastatomic = 0;

4
src/lstate.c
Unescape View File

@ -393,8 +393,8 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
g->gckind = KGC_INC;
g->gcemergency = 0;
g->finobj = g->tobefnz = g->fixedgc = NULL;
g->survival = g->old = g->reallyold = NULL;
g->finobjsur = g->finobjold = g->finobjrold = NULL;
g->firstold1 = g->survival = g->old1 = g->reallyold = NULL;
g->finobjsur = g->finobjold1 = g->finobjrold = NULL;
g->sweepgc = NULL;
g->gray = g->grayagain = NULL;
g->weak = g->ephemeron = g->allweak = NULL;

64
src/ltests.c
Unescape View File

@ -428,10 +428,15 @@ static void checkobject (global_State *g, GCObject *o, int maybedead,
}
static void checkgraylist (global_State *g, GCObject *o) {
static lu_mem checkgraylist (global_State *g, GCObject *o) {
int total = 0; /* count number of elements in the list */
((void)g); /* better to keep it available if we need to print an object */
while (o) {
lua_assert(isgray(o) || getage(o) == G_TOUCHED2);
lua_assert(!!isgray(o) ^ (getage(o) == G_TOUCHED2));
lua_assert(!testbit(o->marked, TESTBIT));
if (keepinvariant(g))
l_setbit(o->marked, TESTBIT); /* mark that object is in a gray list */
total++;
switch (o->tt) {
case LUA_TTABLE: o = gco2t(o)->gclist; break;
case LUA_TLCL: o = gco2lcl(o)->gclist; break;
@ -441,40 +446,68 @@ static void checkgraylist (global_State *g, GCObject *o) {
default: lua_assert(0); /* other objects cannot be gray */
}
}
return total;
}
/*
** Check objects in gray lists.
*/
static void checkgrays (global_State *g) {
if (!keepinvariant(g)) return;
checkgraylist(g, g->gray);
checkgraylist(g, g->grayagain);
checkgraylist(g, g->weak);
checkgraylist(g, g->ephemeron);
static lu_mem checkgrays (global_State *g) {
int total = 0; /* count number of elements in all lists */
if (!keepinvariant(g)) return total;
total += checkgraylist(g, g->gray);
total += checkgraylist(g, g->grayagain);
total += checkgraylist(g, g->weak);
total += checkgraylist(g, g->allweak);
total += checkgraylist(g, g->ephemeron);
return total;
}
static void checklist (global_State *g, int maybedead, int tof,
/*
** Check whether 'o' should be in a gray list. If so, increment
** 'count' and check its TESTBIT. (It must have been previously set by
** 'checkgraylist'.)
*/
static void incifingray (global_State *g, GCObject *o, lu_mem *count) {
if (!keepinvariant(g))
return; /* gray lists not being kept in these phases */
/* these are the ones that must be in gray lists */
if (isgray(o) || getage(o) == G_TOUCHED2) {
(*count)++;
lua_assert(testbit(o->marked, TESTBIT));
resetbit(o->marked, TESTBIT); /* prepare for next cycle */
}
}
static lu_mem checklist (global_State *g, int maybedead, int tof,
GCObject *newl, GCObject *survival, GCObject *old, GCObject *reallyold) {
GCObject *o;
lu_mem total = 0; /* number of object that should be in gray lists */
for (o = newl; o != survival; o = o->next) {
checkobject(g, o, maybedead, G_NEW);
incifingray(g, o, &total);
lua_assert(!tof == !tofinalize(o));
}
for (o = survival; o != old; o = o->next) {
checkobject(g, o, 0, G_SURVIVAL);
incifingray(g, o, &total);
lua_assert(!tof == !tofinalize(o));
}
for (o = old; o != reallyold; o = o->next) {
checkobject(g, o, 0, G_OLD1);
incifingray(g, o, &total);
lua_assert(!tof == !tofinalize(o));
}
for (o = reallyold; o != NULL; o = o->next) {
checkobject(g, o, 0, G_OLD);
incifingray(g, o, &total);
lua_assert(!tof == !tofinalize(o));
}
return total;
}
@ -482,13 +515,15 @@ int lua_checkmemory (lua_State *L) {
global_State *g = G(L);
GCObject *o;
int maybedead;
lu_mem totalin; /* total of objects that are in gray lists */
lu_mem totalshould; /* total of objects that should be in gray lists */
if (keepinvariant(g)) {
lua_assert(!iswhite(g->mainthread));
lua_assert(!iswhite(gcvalue(&g->l_registry)));
}
lua_assert(!isdead(g, gcvalue(&g->l_registry)));
lua_assert(g->sweepgc == NULL || issweepphase(g));
checkgrays(g);
totalin = checkgrays(g);
/* check 'fixedgc' list */
for (o = g->fixedgc; o != NULL; o = o->next) {
@ -497,17 +532,22 @@ int lua_checkmemory (lua_State *L) {
/* check 'allgc' list */
maybedead = (GCSatomic < g->gcstate && g->gcstate <= GCSswpallgc);
checklist(g, maybedead, 0, g->allgc, g->survival, g->old, g->reallyold);
totalshould = checklist(g, maybedead, 0, g->allgc,
g->survival, g->old1, g->reallyold);
/* check 'finobj' list */
checklist(g, 0, 1, g->finobj, g->finobjsur, g->finobjold, g->finobjrold);
totalshould += checklist(g, 0, 1, g->finobj,
g->finobjsur, g->finobjold1, g->finobjrold);
/* check 'tobefnz' list */
for (o = g->tobefnz; o != NULL; o = o->next) {
checkobject(g, o, 0, G_NEW);
incifingray(g, o, &totalshould);
lua_assert(tofinalize(o));
lua_assert(o->tt == LUA_TUSERDATA || o->tt == LUA_TTABLE);
}
if (keepinvariant(g))
lua_assert(totalin == totalshould);
return 0;
}

61
tests/lua53/gengc.lua
Unescape View File

@ -37,6 +37,22 @@ do
end
do
-- ensure that 'firstold1' is corrected when object is removed from
-- the 'allgc' list
local function foo () end
local old = {10}
collectgarbage() -- make 'old' old
assert(not T or T.gcage(old) == "old")
setmetatable(old, {}) -- new table becomes OLD0 (barrier)
assert(not T or T.gcage(getmetatable(old)) == "old0")
collectgarbage("step", 0) -- new table becomes OLD1 and firstold1
assert(not T or T.gcage(getmetatable(old)) == "old1")
setmetatable(getmetatable(old), {__gc = foo}) -- get it out of allgc list
collectgarbage("step", 0) -- should not seg. fault
end
do -- bug in 5.4.0
-- When an object aged OLD1 is finalized, it is moved from the list
-- 'finobj' to the *beginning* of the list 'allgc', but that part of the
@ -57,13 +73,56 @@ do -- bug in 5.4.0
local obj = {} -- create a new object
collectgarbage("step", 0) -- make it a survival
assert(not T or T.gcage(obj) == "survival")
setmetatable(obj, {__gc = gcf, x = "ok"}) -- create its metatable
setmetatable(obj, {__gc = gcf, x = "+"}) -- create its metatable
assert(not T or T.gcage(getmetatable(obj)) == "new")
obj = nil -- clear object
collectgarbage("step", 0) -- will call obj's finalizer
end
do -- another bug in 5.4.0
local old = {10}
collectgarbage() -- make 'old' old
local co = coroutine.create(
function ()
local x = nil
local f = function ()
return x[1]
end
x = coroutine.yield(f)
coroutine.yield()
end
)
local _, f = coroutine.resume(co) -- create closure over 'x' in coroutine
collectgarbage("step", 0) -- make upvalue a survival
old[1] = {"hello"} -- 'old' go to grayagain as 'touched1'
coroutine.resume(co, {123}) -- its value will be new
co = nil
collectgarbage("step", 0) -- hit the barrier
assert(f() == 123 and old[1][1] == "hello")
collectgarbage("step", 0) -- run the collector once more
-- make sure old[1] was not collected
assert(f() == 123 and old[1][1] == "hello")
end
do -- bug introduced in commit 9cf3299fa
local t = setmetatable({}, {__mode = "kv"}) -- all-weak table
collectgarbage() -- full collection
assert(not T or T.gcage(t) == "old")
t[1] = {10}
assert(not T or (T.gcage(t) == "touched1" and T.gccolor(t) == "gray"))
collectgarbage("step", 0) -- minor collection
assert(not T or (T.gcage(t) == "touched2" and T.gccolor(t) == "black"))
collectgarbage("step", 0) -- minor collection
assert(not T or T.gcage(t) == "old") -- t should be black, but it was gray
t[1] = {10} -- no barrier here, so t was still old
collectgarbage("step", 0) -- minor collection
-- t, being old, is ignored by the collection, so it is not cleared
assert(t[1] == nil) -- fails with the bug
end
if T == nil then
(Message or print)('\n >>> testC not active: \z
skipping some generational tests <<<\n')

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