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Bug 723971 - unmark gray for shapes. r=billm

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This commit is contained in:
Andrew McCreight 2012-03-05 18:11:29 -08:00
parent 23e960e8cf
commit 73839b9bd9
1 changed files with 41 additions and 6 deletions
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47
js/xpconnect/src/nsXPConnect.cpp
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@ -699,6 +699,18 @@ xpc_GCThingIsGrayCCThing(void *thing)
xpc_IsGrayGCThing(thing);
}
struct UnmarkGrayTracer : public JSTracer
{
UnmarkGrayTracer() : mTracingShape(false), mPreviousShape(nsnull) {}
UnmarkGrayTracer(JSTracer *trc, bool aTracingShape)
: mTracingShape(aTracingShape), mPreviousShape(nsnull)
{
JS_TracerInit(this, trc->runtime, trc->callback);
}
bool mTracingShape; // true iff we are tracing the immediate children of a shape
void *mPreviousShape; // If mTracingShape, shape child or NULL. Otherwise, NULL.
};
/*
* The GC and CC are run independently. Consequently, the following sequence of
* events can occur:
@ -729,15 +741,38 @@ UnmarkGrayChildren(JSTracer *trc, void **thingp, JSGCTraceKind kind)
return;
}
// If this thing is not a CC-kind or already non-gray then we're done.
if (!AddToCCKind(kind) || !xpc_IsGrayGCThing(thing))
if (!xpc_IsGrayGCThing(thing))
return;
// Unmark.
static_cast<js::gc::Cell *>(thing)->unmark(js::gc::GRAY);
// Trace children.
JS_TraceChildren(trc, thing, kind);
/*
* Trace children of |thing|. If |thing| and its parent are both shapes, |thing| will
* get saved to mPreviousShape without being traced. The parent will later
* trace |thing|. This is done to avoid increasing the stack depth during shape
* tracing. It is safe to do because a shape can only have one child that is a shape.
*/
UnmarkGrayTracer *tracer = static_cast<UnmarkGrayTracer*>(trc);
UnmarkGrayTracer childTracer(tracer, kind == JSTRACE_SHAPE);
if (kind != JSTRACE_SHAPE) {
JS_TraceChildren(&childTracer, thing, kind);
MOZ_ASSERT(!childTracer.mPreviousShape);
return;
}
if (tracer->mTracingShape) {
MOZ_ASSERT(!tracer->mPreviousShape);
tracer->mPreviousShape = thing;
return;
}
do {
MOZ_ASSERT(!xpc_IsGrayGCThing(thing));
JS_TraceChildren(&childTracer, thing, JSTRACE_SHAPE);
thing = childTracer.mPreviousShape;
childTracer.mPreviousShape = nsnull;
} while (thing);
}
void
@ -749,7 +784,7 @@ xpc_UnmarkGrayObjectRecursive(JSObject *obj)
js::gc::AsCell(obj)->unmark(js::gc::GRAY);
// Trace children.
JSTracer trc;
UnmarkGrayTracer trc;
JS_TracerInit(&trc, JS_GetObjectRuntime(obj), UnmarkGrayChildren);
JS_TraceChildren(&trc, obj, JSTRACE_OBJECT);
}