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

[Wanpeng Li]

Ping

于 14-7-29 下午5:24, Wanpeng Li 写道:
> 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.
>
> Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>
> ---
> v1 -> v2:
>  * fix subject line
> v2 -> v3:
>  * simplify backtrace 
>
>  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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