Re: [PATCH v4] x86, hotplug: fix llc shared map unreleased during cpu hotplug

[Wanpeng Li]

Ping Ingo, HPA, PeterZ
ä 14-9-4 äå5:34, Wanpeng Li åé:
> Hi Ingo,
> On Thu, Sep 04, 2014 at 04:56:41PM +0800, Wanpeng Li wrote:
> > On Thu, Sep 04, 2014 at 07:20:34AM +0200, Ingo Molnar wrote:
> > > * Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx> wrote:
> > >
> > > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000004
> > > > IP: [..] find_busiest_group
> > > > PGD 5a9d5067 PUD 13067 PMD 0
> > > > Oops: 0000 [#3] SMP
> > > > [...]
> > > > Call Trace:
> > > > load_balance
> > > > ? _raw_spin_unlock_irqrestore
> > > > idle_balance
> > > > __schedule
> > > > schedule
> > > > schedule_timeout
> > > > ? lock_timer_base
> > > > schedule_timeout_uninterruptible
> > > > msleep
> > > > lock_device_hotplug_sysfs
> > > > online_store
> > > > dev_attr_store
> > > > sysfs_write_file
> > > > vfs_write
> > > > SyS_write
> > > > system_call_fastpath
> > > >
> > > > Last level cache shared map is built during cpu up and build sched domain
> > > > routine takes advantage of it to setup sched domain cpu topology, however,
> > > > llc shared map is unreleased during cpu disable which lead to invalid sched
> > > > domain cpu topology. This patch fix it by release llc shared map correctly
> > > > during cpu disable.
> > > Very little is said in this changelog about how the bug was
> > > found, how likely it is to occur for others, what systems are
> > > affected, etc.
> > This bug can be triggered by hot add and remove large number of xen
> > domain0's vcpus repeated.
> If I need to send a new version of the patch or you can pick the patch
> w/ the updated changelog for me? ;-)
>
> Regards,
> Wanpeng Li
>
> > Regards,
> > Wanpeng Li
> >
> > > Thanks,
> > >
> > > 	Ingo
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