On Wed, 2013-04-03 at 17:32 +0800, Li Zefan wrote:
> On 2013/4/2 15:16, Li Zhong wrote:
> > In cpuset_hotplug_workfn(), partition_sched_domains() is called without
> > hotplug lock held, which is actually needed (stated in the function
> > header of partition_sched_domains()).
> >
> > This patch tries to use rebuild_sched_domains() to solve the above
> > issue, and makes the code looks a little simpler.
> >
Hi Zefan,
Thanks for your quick review.
> I guess you found this just by code inspection, right?
Ah, yes :)
> The change looks fine and safe at a first glance, but we don't have
> time to review the patch for now.
>
> However I don't know why partition_sched_domains() has to be called
> with hotplug lock held.
>
> After a quick scan, seems the only place in partition_sched_domains()
> that might need hotplug lock is arch_update_cpu_topology().
and cpu_attach_domain(), which is called by partition_sched_domains()
also states that it needs hotplug lock be held.
It seems that the code is moved out of hotplug critical section after it
is converted to work functions.
Thanks, Zhong
>
> It would be better if you had CCed the scheduler guys...They may
> know the answer.
>
> > Signed-off-by: Li Zhong <zh...@linux.vnet.ibm.com>
> > ---
> > kernel/cpuset.c | 13 ++-----------
> > 1 files changed, 2 insertions(+), 11 deletions(-)
> >
> > diff --git a/kernel/cpuset.c b/kernel/cpuset.c
> > index 4f9dfe4..515a713 100644
> > --- a/kernel/cpuset.c
> > +++ b/kernel/cpuset.c
> > @@ -2222,17 +2222,8 @@ static void cpuset_hotplug_workfn(struct work_struct
> > *work)
> > flush_workqueue(cpuset_propagate_hotplug_wq);
> >
> > /* rebuild sched domains if cpus_allowed has changed */
> > - if (cpus_updated) {
> > - struct sched_domain_attr *attr;
> > - cpumask_var_t *doms;
> > - int ndoms;
> > -
> > - mutex_lock(&cpuset_mutex);
> > - ndoms = generate_sched_domains(&doms, &attr);
> > - mutex_unlock(&cpuset_mutex);
> > -
> > - partition_sched_domains(ndoms, doms, attr);
> > - }
> > + if (cpus_updated)
> > + rebuild_sched_domains();
> > }
> >
>
>
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