Doubly-linked lists ("chains") in RTEMS have a "control" block that
looks like the next/prev link pair in an element. The list elements
link both ways to this control block.
_Chain_Is_first and _Chain_Is_last only probed if the link to the
next element - which would be the control block - is non-NULL.
Telling by the function description and given that there are already
functions called _Chain_Is_head and _Chain_Is_tail (which could be
simplified), this is probably not the intended behaviour.
This also affects the aliases rtems_chain_is_first and
rtems_chain_is_last.
These functions are not used a lot and I haven't seen any immediate
effect on M1 after changing them, so I can't say whether this patch
may unearth other problems.
- Werner
Index: cpukit/score/inline/rtems/score/chain.inl
===================================================================
RCS file: /usr1/CVS/rtems/cpukit/score/inline/rtems/score/chain.inl,v
retrieving revision 1.23
diff -U 4 -r1.23 chain.inl
--- cpukit/score/inline/rtems/score/chain.inl 25 Nov 2010 11:48:11 -0000
1.23
+++ cpukit/score/inline/rtems/score/chain.inl 9 Nov 2011 19:42:13 -0000
@@ -296,9 +296,9 @@
RTEMS_INLINE_ROUTINE bool _Chain_Is_first(
const Chain_Node *the_node
)
{
- return (the_node->previous == NULL);
+ return the_node->previous->previous == NULL;
}
/** @brief Is this the Last Node on the Chain
*
@@ -313,9 +313,9 @@
RTEMS_INLINE_ROUTINE bool _Chain_Is_last(
const Chain_Node *the_node
)
{
- return (the_node->next == NULL);
+ return the_node->next->next == NULL;
}
/** @brief Does this Chain have only One Node
*
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