Re: [PATCH v2] x86, hotplug: fix llc shared map unreleased during cpu hotplug

[Yasuaki Ishimatsu]

Hi Wanpeng,

(2014/07/29 16:06), Wanpeng Li wrote:
> Hi Yasuaki,
> On Wed, Jul 23, 2014 at 05:56:07PM +0900, Yasuaki Ishimatsu wrote:
> > (2014/07/22 17:04), Wanpeng Li wrote:
> > > [  220.262093] BUG: unable to handle kernel NULL pointer dereference at 0000000000000004
> > > [  220.262104] IP: [<ffffffff810e7ac9>] find_busiest_group+0x2b9/0xa30
> > > [  220.262111] PGD 5a9d5067 PUD 13067 PMD 0
> > > [  220.262117] Oops: 0000 [#3] SMP
> > > [...]
> > > [  220.262245] Call Trace:
> > > [  220.262252]  [<ffffffff810e8396>] load_balance+0x156/0x980
> > > [  220.262259]  [<ffffffff816eeffe>] ? _raw_spin_unlock_irqrestore+0x2e/0xa0
> > > [  220.262266]  [<ffffffff810e9aa3>] idle_balance+0xe3/0x150
> > > [  220.262270]  [<ffffffff816ec4e7>] __schedule+0x797/0x8d0
> > > [  220.262277]  [<ffffffff816ec934>] schedule+0x24/0x70
> > > [  220.262283]  [<ffffffff816e9cd9>] schedule_timeout+0x119/0x1f0
> > > [  220.262294]  [<ffffffff810bb6e0>] ? lock_timer_base+0x70/0x70
> > > [  220.262301]  [<ffffffff816e9dc9>] schedule_timeout_uninterruptible+0x19/0x20
> > > [  220.262308]  [<ffffffff810bd3e8>] msleep+0x18/0x20
> > > [  220.262317]  [<ffffffff813aa11a>] lock_device_hotplug_sysfs+0x2a/0x50
> > > [  220.262323]  [<ffffffff813aa16e>] online_store+0x2e/0x80
> > > [  220.262358]  [<ffffffff813a873b>] dev_attr_store+0x1b/0x20
> > > [  220.262366]  [<ffffffff812292fd>] sysfs_write_file+0xdd/0x160
> > > [  220.262377]  [<ffffffff811b7e78>] vfs_write+0xc8/0x170
> > > [  220.262384]  [<ffffffff811b83ca>] SyS_write+0x5a/0xa0
> > > [  220.262388]  [<ffffffff816f76b9>] system_call_fastpath+0x16/0x1b
> > >
> > > 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.
> >
> > I posted a latest patch as follows:
> > https://lkml.org/lkml/2014/7/22/1018
> >
> > Could you confirm the patch fixes your issue?
>
> Sorry for the late, there is still call trace w/ your patch applied. The
> call trace is in attachment.

Thank you for reporting the result. As Borislav said, your v2 patch
is necessary for fixing your issue.

> Regards,
> Wanpeng Li
>
> > Thanks,
> > Yasuaki Ishimatsu
> >
> > > Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>

Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>

Thanks,
Yasuaki Ishimatsu

> > > ---
> > > v1 -> v2:
> > >    * fix subject line
> > >
> > >    arch/x86/kernel/smpboot.c | 3 +++
> > >    1 file changed, 3 insertions(+)
> > >
> > > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> > > index 5492798..0134ec7 100644
> > > --- a/arch/x86/kernel/smpboot.c
> > > +++ b/arch/x86/kernel/smpboot.c
> > > @@ -1292,6 +1292,9 @@ static void remove_siblinginfo(int cpu)
> > >
> > >    	for_each_cpu(sibling, cpu_sibling_mask(cpu))
> > >    		cpumask_clear_cpu(cpu, cpu_sibling_mask(sibling));
> > > +	for_each_cpu(sibling, cpu_llc_shared_mask(cpu))
> > > +		cpumask_clear_cpu(cpu, cpu_llc_shared_mask(sibling));
> > > +	cpumask_clear(cpu_llc_shared_mask(cpu));
> > >    	cpumask_clear(cpu_sibling_mask(cpu));
> > >    	cpumask_clear(cpu_core_mask(cpu));
> > >    	c->phys_proc_id = 0;


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