Messages in this thread | | | Date | Wed, 10 Apr 2013 17:23:37 +0200 | Subject | Re: [PATCH Resend v5] sched: fix init NOHZ_IDLE flag | From | Vincent Guittot <> |
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On 9 April 2013 14:45, Frederic Weisbecker <fweisbec@gmail.com> wrote: > 2013/4/4 Vincent Guittot <vincent.guittot@linaro.org>: >> On 4 April 2013 19:07, Frederic Weisbecker <fweisbec@gmail.com> wrote: >>> Is it possible that we can be dealing here with a >>> sched_group/sched_group_power that is used on another CPU (from that >>> CPU's rq->rq_sd->sd) concurrently? >>> When we call build_sched_groups(), we might reuse an exisiting struct >>> sched_group used elsewhere right? If so, is there a race with the >>> above initialization? >> >> No we are not reusing an existing struct, the >> sched_group/sched_group_power that is initialized here, has just been >> created by __visit_domain_allocation_hell in build_sched_domains. The >> sched_group/sched_group_power is not already attached to any CPU > > I see. Yeah the group allocations/initialization is done per domain > found in ndoms_new[]. And there is no further reuse of these groups > once these are attached. > > Looking at the code it seems we can make some symetric conclusion with > group release? When we destroy a per cpu domain hierarchy and then put > our references to the struct sched_group, all the other per cpu > domains that reference these sched_group are about to put their > reference soon too, right? Because IIUC we always destroy these per > cpu domains per highest level partition (those found in doms_cur[])?
Yes
> > I'm just asking to make sure we don't need some > atomic_dec(nr_busy_cpus) on per cpu domain release, which is not > necessary the sched group is getting released soon.
yes, it's not needed
> > Thanks for your patience :)
That's fine.
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