commit 65141832d29824ebfbf26e8af9e6e4b8549518d4
parent f13dc59416afa8fc93bb3d784d1a73e49e1b5b09
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Fri, 7 Aug 2020 14:53:11 -0300
Open upvalues should be gray when entering gen. mode
Open upvalues are never black; so, when entering generational mode,
they must be colored gray, not black.
Diffstat:
2 files changed, 21 insertions(+), 14 deletions(-)
diff --git a/lgc.c b/lgc.c
@@ -267,21 +267,22 @@ GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
** Mark an object. Userdata, strings, and closed upvalues are visited
** and turned black here. Other objects are marked gray and added
** to appropriate list to be visited (and turned black) later. (Open
-** upvalues are already linked in 'headuv' list. They are kept gray
-** to avoid barriers, as their values will be revisited by the thread.)
+** upvalues are already indirectly linked through the 'twups' list. They
+** are kept gray to avoid barriers, as their values will be revisited by
+** the thread or by 'remarkupvals'.)
*/
static void reallymarkobject (global_State *g, GCObject *o) {
white2gray(o);
switch (o->tt) {
case LUA_VSHRSTR:
case LUA_VLNGSTR: {
- gray2black(o);
+ gray2black(o); /* nothing to visit */
break;
}
case LUA_VUPVAL: {
UpVal *uv = gco2upv(o);
if (!upisopen(uv)) /* open upvalues are kept gray */
- gray2black(o);
+ gray2black(o); /* closed upvalues are visited here */
markvalue(g, uv->v); /* mark its content */
break;
}
@@ -296,7 +297,7 @@ static void reallymarkobject (global_State *g, GCObject *o) {
} /* FALLTHROUGH */
case LUA_VLCL: case LUA_VCCL: case LUA_VTABLE:
case LUA_VTHREAD: case LUA_VPROTO: {
- linkobjgclist(o, g->gray);
+ linkobjgclist(o, g->gray); /* to be visited later */
break;
}
default: lua_assert(0); break;
@@ -355,8 +356,10 @@ static int remarkupvals (global_State *g) {
for (uv = thread->openupval; uv != NULL; uv = uv->u.open.next) {
lua_assert(getage(uv) <= getage(thread));
work++;
- if (!iswhite(uv)) /* upvalue already visited? */
+ if (!iswhite(uv)) { /* upvalue already visited? */
+ lua_assert(upisopen(uv) && isgray(uv));
markvalue(g, uv->v); /* mark its value */
+ }
}
}
}
@@ -1028,8 +1031,8 @@ static void setpause (global_State *g);
/*
** 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.
+** 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;
@@ -1047,6 +1050,8 @@ static void sweep2old (lua_State *L, GCObject **p) {
linkgclist(th, g->grayagain); /* insert into 'grayagain' list */
black2gray(th); /* OK if already gray */
}
+ else if (curr->tt == LUA_VUPVAL && upisopen(gco2upv(curr)))
+ black2gray(curr); /* open upvalues are always gray */
else /* everything else is black */
gray2black(curr); /* OK if already black */
p = &curr->next; /* go to next element */
diff --git a/lstate.h b/lstate.h
@@ -63,7 +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 (with one exception explained below):
+** 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.
@@ -75,11 +75,13 @@
** 'ephemeron': ephemeron tables with white->white entries;
** 'allweak': tables with weak keys and/or weak values to be cleared.
**
-** The exception to that "gray rule" is the TOUCHED2 objects in
-** generational mode. Those objects 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).
+** 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.)
*/
