Benjamin Herrenschmidt <b...@kernel.crashing.org> writes: > On Thu, 2017-08-03 at 09:45 +0200, Cédric Le Goater wrote: >> On 08/02/2017 11:57 PM, Benjamin Herrenschmidt wrote: >> > On Wed, 2017-08-02 at 18:43 +0200, Cédric Le Goater wrote: >> > > If xive_find_target_in_mask() fails to find a cpu, the fuzz value used >> > > in xive_pick_irq_target() is decremented and reused in the last >> > > returning call to xive_find_target_in_mask(). This can result in such >> > > WARNINGs if the initial fuzz value is zero : >> > >> > Ah indeed ... would have worked better if "fuzz" had been unsigned. >> >> but 'fuzz' is unsigned ! > > Haha right. > >> With a -1, unsigned or not, the 'first' cpu becomes out of range for >> the calculation below : >> >> /* Pick up a starting point CPU in the mask based on fuzz */ >> num = cpumask_weight(mask); >> first = fuzz % num; > > How can it ? fuzz % num should then return something that's > > 0 <= first < num > > Regardless of the value of fuzz.
What if num is 0? Which it would be in the fallback case, if the affinity mask is empty, AFAICS. cheers
