Re: [Xen-devel] [PATCH 2 of 7] KEXEC BUG: nmi_shootdown_cpus doesn't look after the interrupt flag

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 14/06/2011 09:46, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>>>> On 13.06.11 at 19:02, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>> nmi_shootdown_cpus is part of the kexec path, coming from a panic, and
>> as such can be called both with interrupts enabled or disabled. We
>> really dont want to accidentally set IF.
> 
> Can interrupts really be enabled when entering this function?
> 
>> Therefore, use save/restore in preference to disable/enable.
> 
> I.e. wouldn't just removing the stray local_irq_enable() suffice?

I'd say that the caller should local_irq_disable(). The function itself
should at most BUG_ON(local_irq_is_enabled()).

 -- Keir

> Jan
> 
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> 
>> diff -r 076c3034c8c7 -r 1c3d2e4d06fe xen/arch/x86/crash.c
>> --- a/xen/arch/x86/crash.c Mon Jun 13 17:45:43 2011 +0100
>> +++ b/xen/arch/x86/crash.c Mon Jun 13 17:45:43 2011 +0100
>> @@ -55,9 +55,9 @@ static int crash_nmi_callback(struct cpu
>>  
>>  static void nmi_shootdown_cpus(void)
>>  {
>> -    unsigned long msecs;
>> +    unsigned long msecs, flags;
>>  
>> -    local_irq_disable();
>> +    local_irq_save(flags);
>>  
>>      crashing_cpu = smp_processor_id();
>>      local_irq_count(crashing_cpu) = 0;
>> @@ -80,7 +80,7 @@ static void nmi_shootdown_cpus(void)
>>      __stop_this_cpu();
>>      disable_IO_APIC();
>>  
>> -    local_irq_enable();
>> +    local_irq_restore(flags);
>>  }
>>  
>>  void machine_crash_shutdown(void)
>> 
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> 
> 
> 
> 
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