On 2018/11/1 19:34, Russell King - ARM Linux wrote:
> On Thu, Nov 01, 2018 at 07:20:49PM +0800, Wang Yufen wrote:
>> From: Yufen Wang <wangyu...@huawei.com>
>>
>> In case panic() and panic() called at the same time on different CPUS.
>> For example:
>> CPU 0:
>> panic()
>> __crash_kexec
>> machine_crash_shutdown
>> crash_smp_send_stop
>> machine_kexec
>> BUG_ON(num_online_cpus() > 1);
>>
>> CPU 1:
>> panic()
>> local_irq_disable
>> panic_smp_self_stop
>>
>> If CPU 1 calls panic_smp_self_stop() before crash_smp_send_stop(), kdump
>> fails. CPU1 can't receive the ipi irq, CPU1 will be always online.
>> I changed BUG_ON to WARN in kexec crash as arm64 does, kdump also fails.
>> Because num_online_cpus() > 1, can't disable the L2 in _soft_restart.
>> To fix this problem, this patch split out the panic_smp_self_stop()
>> and add set_cpu_online(smp_processor_id(), false).
> Thanks.
>
> I think this may as well go into arch/arm/kernel/smp.c - it won't be
> required for single-CPU systems, since there aren't "other" CPUs.
>
> It's probably also worth a comment above the function as to why we
> have this.
Thanks.
I will send v2.
>> Signed-off-by: Yufen Wang <wangyu...@huawei.com>
>> ---
>> arch/arm/kernel/setup.c | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
>> index 31940bd..151861f 100644
>> --- a/arch/arm/kernel/setup.c
>> +++ b/arch/arm/kernel/setup.c
>> @@ -602,6 +602,16 @@ static void __init smp_build_mpidr_hash(void)
>> }
>> #endif
>>
>> +void panic_smp_self_stop(void)
>> +{
>> + printk(KERN_DEBUG "CPU %u will stop doing anything useful since another
>> CPU has paniced\n",
>> + smp_processor_id());
>> + set_cpu_online(smp_processor_id(), false);
>> + while (1)
>> + cpu_relax();
>> +
>> +}
>> +
>> static void __init setup_processor(void)
>> {
>> struct proc_info_list *list;
>> --
>> 2.7.4
>>
>>
