Re: [PATCH v5] x86, cpu-hotplug: fix llc shared map unreleased during cpu hotplug

[Ingo Molnar]

* Wanpeng Li <kernellwp@xxxxxxxxx> wrote:

> 
> ä 14-9-23 äå5:37, Borislav Petkov åé:
> >On Wed, Sep 17, 2014 at 03:17:52PM +0800, Wanpeng Li 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
> >>
> >>This bug can be triggered by hot add and remove large number of xen
> >>domain0's vcpus repeatedly.
> >>
> >>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.
> >>
> >>Reviewed-by: Toshi Kani <toshi.kani@xxxxxx>
> >>Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
> >>Tested-by: Linn Crosetto <linn@xxxxxx>
> >>Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>
> >Reviewed-by: Borislav Petkov <bp@xxxxxxx>
> >
> 
> Thanks.
> 
> 
> Ingo, Peter Z, HPA,
> 
> 
> Could this patch catch up with 3.18 merge window?

Please also add the real-hardware reports to the changelog.

Thanks,

	Ingo
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