* Nicholas Mc Guire | 2014-02-10 16:37:59 [+0100]: >2a) premption induced race in __this_cpu_dec > T1 dec:start > T2 dec > T1 dec:end > >__this_cpu_dec > -> __this_cpu_sub > -> __this_cpu_add > -> __this_cpu_add_# > -> __this_cpu_generic_to_op > -> __this_cpu_ptr += val > > >so we end up with the possibilities of > T1 load > T2 load > T2 store > T1 store >and the increment provided by T2 would be lost. The result of which >is that reaching the buffer_heads_over_limit threshold in recalc_bh_state I don't like this very much. __this_cpu_inc() is not atomic as you say and without the locking that is provided by preempt_disable() it might lose one store in inc or dec direction. This error will never be corrected again. That code path looks very short unless you have 4096 CPUs. Sebastian -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
