On 2013/6/6 4:51, Tejun Heo wrote: > Hello, Li. > > On Wed, Jun 05, 2013 at 05:16:59PM +0800, Li Zefan wrote: >> @@ -2092,11 +2183,13 @@ static void cpuset_propagate_hotplug_workfn(struct >> work_struct *work) >> mutex_unlock(&cpuset_mutex); >> >> /* >> - * If @cs became empty, move tasks to the nearest ancestor with >> - * execution resources. This is full cgroup operation which will >> + * If sane_behavior flag is set, we'll keep tasks in empty cpusets. >> + * >> + * Otherwise move tasks to the nearest ancestor with execution >> + * resources. This is full cgroup operation which will >> * also call back into cpuset. Should be done outside any lock. >> */ >> - if (is_empty) >> + if (!sane && is_empty) >> remove_tasks_in_empty_cpuset(cs); >> >> /* the following may free @cs, should be the last operation */ >> @@ -2171,6 +2264,7 @@ static void cpuset_hotplug_workfn(struct work_struct >> *work) >> cpumask_copy(top_cpuset.cpus_allowed, &new_cpus); >> mutex_unlock(&callback_mutex); >> /* we don't mess with cpumasks of tasks in top_cpuset */ >> + update_tasks_cpumask_hier(&top_cpuset, false, NULL); >> } > > I'm a little confused by the order of operation. We now have two > different hierarchical walks for hotplug propagation, right? I > suppose the above one is added because we now also need to update the > mask when cpus are being brought online? >
The first one will only update tasks in empty cpusets (no matter online or offline), and the second one will only update tasks in non-empty cpusets (only when offline). > I wonder whether it'd be possible to merge the two paths. My > suspicion is that we probably don't need propagate_hotplug_work > anymore now that we can drop RCU read lock while doing the pre-order > walk. What do you think? > It indeed can be confusing. I'll see if we can make the code clearer. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
