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new way to GC stacks: the entire stack must be correct all the times;

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the 'dead' part of a stack (after the top) must have only nil's, so
that 'top' may go up without cleaning the stack.
This commit is contained in:
Roberto Ierusalimschy
2009-04-28 16:04:36 -03:00
parent 58c3aa8b5f
commit e091a254df
4 changed files with 63 additions and 47 deletions
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70
lgc.c
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@@ -1,5 +1,5 @@
/*
** $Id: lgc.c,v 2.49 2009/03/10 17:14:37 roberto Exp roberto $
** $Id: lgc.c,v 2.50 2009/04/17 14:28:06 roberto Exp roberto $
** Garbage Collector
** See Copyright Notice in lua.h
*/
@@ -379,34 +379,17 @@ static void traverseclosure (global_State *g, Closure *cl) {
}
static void checkstacksize (lua_State *L, StkId max) {
/* should not change the stack during an emergency gc cycle */
if (G(L)->gckind == KGC_EMERGENCY)
return; /* do not touch the stack */
else {
int s_used = cast_int(max - L->stack) + 1; /* part of stack in use */
if (2*s_used < (L->stacksize - EXTRA_STACK))
luaD_reallocstack(L, 2*s_used);
}
}
static void traversestack (global_State *g, lua_State *L) {
StkId o, lim;
CallInfo *ci;
StkId o;
if (L->stack == NULL)
return; /* stack not completely built yet */
markvalue(g, gt(L));
lim = L->top;
for (ci = L->ci; ci != NULL; ci = ci->previous) {
lua_assert(ci->top <= L->stack_last);
if (lim < ci->top) lim = ci->top;
}
markvalue(g, gt(L)); /* mark global table */
for (o = L->stack; o < L->top; o++)
markvalue(g, o);
for (; o <= lim; o++)
setnilvalue(o);
checkstacksize(L, lim);
if (g->gcstate == GCSatomic) { /* final traversal? */
for (; o <= L->stack_last; o++) /* clear not-marked stack slice */
setnilvalue(o);
}
}
@@ -542,7 +525,35 @@ static void freeobj (lua_State *L, GCObject *o) {
}
static int stackinuse (lua_State *L) {
CallInfo *ci;
StkId lim = L->top;
for (ci = L->ci; ci != NULL; ci = ci->previous) {
lua_assert(ci->top <= L->stack_last);
if (lim < ci->top) lim = ci->top;
}
return cast_int(lim - L->stack) + 1; /* part of stack in use */
}
#define sweepwholelist(L,p) sweeplist(L,p,MAX_LUMEM)
static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count);
static void sweepthread (lua_State *L, lua_State *L1, int alive) {
if (L1->stack == NULL) return; /* stack not completely built yet */
sweepwholelist(L, &L1->openupval); /* sweep open upvalues */
if (L1->nci < LUAI_MAXCALLS) /* not handling stack overflow? */
luaE_freeCI(L1); /* free extra CallInfo slots */
/* should not change the stack during an emergency gc cycle */
if (alive && G(L)->gckind != KGC_EMERGENCY) {
int goodsize = 5 * stackinuse(L1) / 4 + LUA_MINSTACK;
if ((L1->stacksize - EXTRA_STACK) > goodsize)
luaD_reallocstack(L1, goodsize);
else
condhardstacktests(luaD_reallocstack(L, L1->stacksize - EXTRA_STACK - 1));
}
}
static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
@@ -550,12 +561,10 @@ static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) {
global_State *g = G(L);
int deadmask = otherwhite(g);
while ((curr = *p) != NULL && count-- > 0) {
if (ttisthread(gch(curr))) {
lua_State *L1 = gco2th(curr);
sweepwholelist(L, &L1->openupval); /* sweep open upvalues */
luaE_freeCI(L1); /* free extra CallInfo slots */
}
if ((gch(curr)->marked ^ WHITEBITS) & deadmask) { /* not dead? */
int alive = (gch(curr)->marked ^ WHITEBITS) & deadmask;
if (ttisthread(gch(curr)))
sweepthread(L, gco2th(curr), alive);
if (alive) {
lua_assert(!isdead(g, curr) || testbit(gch(curr)->marked, FIXEDBIT));
makewhite(g, curr); /* make it white (for next cycle) */
p = &gch(curr)->next;
@@ -704,6 +713,7 @@ static void atomic (lua_State *L) {
global_State *g = G(L);
size_t udsize; /* total size of userdata to be finalized */
/* remark occasional upvalues of (maybe) dead threads */
g->gcstate = GCSatomic;
remarkupvals(g);
/* traverse objects cautch by write barrier and by 'remarkupvals' */
propagateall(g);