(linux-vax@pergamentum.com only bcc'ed because it's subscribers only, Lameter addressed because I think he touched the code last, Velikov and Hellwig because they touched the code first.) The current code in __max_index() will shift by a negative amount first and only then fix the situation by ignoring the result if the shift amount would have been negative. This happens to work on almost any architecture despite not being valid C. Chapter and verse from the (draft) ISO C99 standard, "6.5.7 Bitwise shift operators", paragraph 3: "The integer promotions are performed on each of the operands. The type of the result is that of the promoted left operand. If the value of the right operand is negative or is greater than or equal to the width of the promoted left operand, the behavior is undefined." Right-shifting by a negative amount causes a "reserved operand fault" on the VAX with some gcc versions. Applies to 2.6.22. Boot tested lightly on an emulated VAX. (The function is called 7 times on booth with the values 0..6 -- I checked that the return values were the same + that it returns ~0UL for height==6 as was clearly the intention.) -Peter --- lib/radix-tree-old.c 2007-08-25 15:36:40.000000000 +0200 +++ lib/radix-tree.c 2007-08-25 15:36:51.000000000 +0200 @@ -980,12 +980,14 @@ radix_tree_node_ctor(void *node, struct static __init unsigned long __maxindex(unsigned int height) { - unsigned int tmp = height * RADIX_TREE_MAP_SHIFT; - unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1; - - if (tmp >= RADIX_TREE_INDEX_BITS) - index = ~0UL; - return index; + unsigned int tmp = height * RADIX_TREE_MAP_SHIFT; + int shift = RADIX_TREE_INDEX_BITS - tmp; + unsigned long index; + + if (shift < 0) + return ~0UL; + else + return ~0UL >> shift; } static __init void radix_tree_init_maxindex(void) _______________________________________________ Linux-Vax mailing list Linux-Vax@pergamentum.com http://www.pergamentum.com/mailman/listinfo/linux-vax