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

Yasuaki Ishimatsu
2014-07-23T08:57:18Z

(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@linux.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;
>