| Date | Wed, 13 Feb 2013 22:44:12 +0800 | From | Alex Shi <> | Subject | Re: [patch v4 02/18] sched: select_task_rq_fair clean up |
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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
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