Re: [Xen-devel] [PATCH 1/3] x86/HPET: obtain proper lock for changing IRQ affinity

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.10.12 at 17:41, Keir Fraser <keir.xen@xxxxxxxxx> wrote:
> On 16/10/2012 16:09, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
> 
>> The IRQ descriptor lock should be held while adjusting the affinity of
>> any IRQ; the HPET channel lock isn't sufficient to protect namely
>> against races with moving the IRQ to a different CPU.
>> 
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> Would be more usual for the underscore-prefixed name to be the one that
> doesn't take locks?

Will make the patch bigger, but I can certainly do that. I specifically
picked only a single underscore to distinguish this a little from the
"usual" case.

Jan

>> --- a/xen/arch/x86/hpet.c
>> +++ b/xen/arch/x86/hpet.c
>> @@ -436,6 +436,16 @@ static struct hpet_event_channel *hpet_g
>>      return ch;
>>  }
>>  
>> +static void _hpet_msi_set_affinity(const struct hpet_event_channel *ch)
>> +{
>> +    struct irq_desc *desc = irq_to_desc(ch->irq);
>> +
>> +    ASSERT(!local_irq_is_enabled());
>> +    spin_lock(&desc->lock);
>> +    hpet_msi_set_affinity(desc, cpumask_of(ch->cpu));
>> +    spin_unlock(&desc->lock);
>> +}
>> +
>>  static void hpet_attach_channel(unsigned int cpu,
>>                                  struct hpet_event_channel *ch)
>>  {
>> @@ -450,7 +460,7 @@ static void hpet_attach_channel(unsigned
>>      if ( ch->cpu != cpu )
>>          return;
>>  
>> -    hpet_msi_set_affinity(irq_to_desc(ch->irq), cpumask_of(ch->cpu));
>> +    _hpet_msi_set_affinity(ch);
>>  }
>>  
>>  static void hpet_detach_channel(unsigned int cpu,
>> @@ -472,7 +482,7 @@ static void hpet_detach_channel(unsigned
>>      }
>>  
>>      ch->cpu = cpumask_first(ch->cpumask);
>> -    hpet_msi_set_affinity(irq_to_desc(ch->irq), cpumask_of(ch->cpu));
>> +    _hpet_msi_set_affinity(ch);
>>  }
>>  
>>  #include <asm/mc146818rtc.h>
>> 
>> 
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxx 
>> http://lists.xen.org/xen-devel 




_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel