Messages in this thread | | | From | Hoang-Nam Nguyen <> | Subject | Re: idr_get_new_above() limitation? | Date | Wed, 4 Jul 2007 16:11:29 +0200 |
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On Tuesday 03 July 2007 02:31, Jim Houston wrote: > The problem is in idr_get_new_above_int() in the loop which > adds new layers to the top of the radix tree. It is failing > the "layers < (MAX_LEVEL - 1)" test. It doesn't allocate the > new layer but still calls sub_alloc() which relies on having > the new layer properly constructed. I believe that it is > allocating the slot which corresponds to id = 0. Hi Jim, Thanks for your quick reply. Yes, I realized that while condition too and have tried with a tiny change like (layers < MAX_LEVEL), but without success with idr_find(), even though 6 layers were created and the object was added at proper location. After several debug cycles I think to find the root cause in the if-condition in idr_find(): void *idr_find(struct idr *idp, int id) { int n; struct idr_layer *p;
n = idp->layers * IDR_BITS; p = idp->top;
/* Mask off upper bits we don't use for the search. */ id &= MAX_ID_MASK;
if (id >= (1 << n)) return NULL; ... } Since idp->layers is now 6, n is equal 36, ie out of 32-bit-range, and therefore (1 << n) = (1 << 36) = 0 causing that if-cond to be true ie idr_find() fails. Replacing that if-line by if ((long)id >= (1L << n)) makes idr_find() working properly until MAX_ID_MASK. Since there are other places to be changed like above as well eg. idr_replace() and because you're creating a patch too, I'm waiting first for your comment. Let me know if you prefer me to send a patch. Regards Nam
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