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

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Date:	Wed, 23 Jul 2014 17:56:07 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	Wanpeng Li <wanpeng.li@...ux.intel.com>
CC:	<hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>, <x86@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	David Rientjes <rientjes@...gle.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Steven Rostedt <srostedt@...hat.com>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Toshi Kani <toshi.kani@...com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] x86, hotplug: fix llc shared map unreleased during
 cpu hotplug

(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?

Thanks,
Yasuaki Ishimatsu

> Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
> ---
> 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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