Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> writes: > (Adding Chris Metcalf and Rusty Russell.) > > If NR_CPUS == 1 due to CONFIG_SMP=n, for_each_cpu(cpu, &has_work) loop does > not > evaluate "struct cpumask has_work" modified by cpumask_set_cpu(cpu, > &has_work) at > previous for_each_online_cpu() loop. Guenter Roeck found a problem among three > commits listed below. > > Commit 5fbc461636c32efd ("mm: make lru_add_drain_all() selective") > expects that has_work is evaluated by for_each_cpu(). > > Commit 2d3854a37e8b767a ("cpumask: introduce new API, without changing > anything") > assumes that for_each_cpu() does not need to evaluate has_work. > > Commit 4d43d395fed12463 ("workqueue: Try to catch flush_work() without > INIT_WORK().") > expects that has_work is evaluated by for_each_cpu(). > > What should we do? Do we explicitly evaluate has_mask if NR_CPUS == 1 ?
No, fix the API to be least-surprise. Fix 2d3854a37e8b767a too. Doing anything else would be horrible, IMHO. Cheers, Rusty.