cpu_pattern can sepcify exactly 1 cpu in a partition:
"0[0]". That means CPT0 will have CPU 0. CPU 0 can have
hyperthreading enabled. This combination would result in
weight = cfs_cpu_ht_nsiblings(0);
hrp->hrp_nthrs = cfs_cpt_weight(ptlrpc_hr.hr_cpt_table, i);
hrp->hrp_nthrs /= weight;
evaluating to 0

Causing LASSERT(hrp->hrp_nthrs > 0); to trigger

Patch
http://review.whamcloud.com/#/c/19106/

attempts to resolve this issue.