Hello, Glauber. On Mon, Apr 09, 2012 at 10:59:56AM -0300, Glauber Costa wrote: > During your cgroup refactor, I was wondering if you have any plans > to get rid of the bind() callback that is called when hierarchies > are moved? > > At least in tree, there seems to be no users for that. I don't have any current plan for the callback but if it doesn't have in-kernel user, I'd prefer to remove it. > I actually planned to use it myself, to start or remove a jump label > when cpuacct and cpu cgroups were comounted. I see. > Problem is, because we have some calls in the cpuset cgroup from > inside the cpu hotplug handler, we end up taking the almighty > cgroup_mutex from inside the cpu_hotplug.lock. Yeah, those two are pretty big locks. > jump labels take it in most arches through the get_online_cpus() > function call. This means we effectively can't apply jump labels > with the cgroup_mutex held, which is the case throughout the whole > bind() call. > > All that explained, I figured I might as well ask before I attempted > a solution to that myself: as much as populate(), bind seems to be > one of the overly complicated callbacks, designed for a scenario in > which everything can come and go at will, which is something we're > trying to fix. I haven't read the code so this could be completely off but if this is jump label optimization which can be made to work w/o it immediately applied, maybe just punt it to a work item from the callback? Note that if cancellation is necessary for e.g. unbinding, it may re-introduce locking dependency through flushing. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
