StgClosurePtr stolen;
StgWord b,t;
- ASSERT_SPARK_POOL_INVARIANTS(deque);
+// Can't do this on someone else's spark pool:
+// ASSERT_SPARK_POOL_INVARIANTS(deque);
b = deque->bottom;
t = deque->top;
- if (b - t <= 0 ) {
+
+ // NB. b and t are unsigned; we need a signed value for the test
+ // below.
+ if ((long)b - (long)t <= 0 ) {
return NULL; /* already looks empty, abort */
}
return NULL;
} /* else: OK, top has been incremented by the cas call */
- ASSERT_SPARK_POOL_INVARIANTS(deque);
+// Can't do this on someone else's spark pool:
+// ASSERT_SPARK_POOL_INVARIANTS(deque);
+
/* return stolen element */
return stolen;
}
StgWord t = deque->top;
StgWord b = deque->bottom;
/* try to prefer false negatives by reading top first */
- return (b - t <= 0);
+ return ((long)b - (long)t <= 0);
/* => array is *never* completely filled, always 1 place free! */
}
This is why we do not just call empty(deque) here.
*/
t = deque->topBound;
- if ( b - t >= sz ) { /* nota bene: sz == deque->size - 1, thus ">=" */
+ if ( (StgInt)b - (StgInt)t >= (StgInt)sz ) {
+ /* NB. 1. sz == deque->size - 1, thus ">="
+ 2. signed comparison, it is possible that t > b
+ */
/* could be full, check the real top value in this case */
t = deque->top;
deque->topBound = t;
pool = cap->sparks;
+ // it is possible that top > bottom, indicating an empty pool. We
+ // fix that here; this is only necessary because the loop below
+ // assumes it.
+ if (pool->top > pool->bottom)
+ pool->top = pool->bottom;
+
// Take this opportunity to reset top/bottom modulo the size of
// the array, to avoid overflow. This is only possible because no
// stealing is happening during GC.