On 02/12/2013 06:14 PM, Peter Zijlstra wrote: > On Thu, 2013-01-24 at 11:06 +0800, Alex Shi wrote: >> It is impossible to miss a task allowed cpu in a eligible group. > > I suppose your reasoning goes like: tsk->cpus_allowed is protected by > ->pi_lock, we hold this, therefore it cannot change and > find_idlest_group() dtrt?
yes. > > We can then state that this is due to adding proper serialization to > tsk->cpus_allowed. > >> And since find_idlest_group only return a different group which >> excludes old cpu, it's also impossible to find a new cpu same as old >> cpu. > > Sounds plausible, but I'm not convinced, do we have hard serialization > against hotplug? Any caller of select_task_rq will check if returned dst_cpu is still working. So there is nothing need worry about. > > > -- Thanks Alex -- 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/