Re: [Xen-devel] [PATCHv11 2/4] gnttab: introduce maptrack lock

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.06.15 at 15:44, <david.vrabel@xxxxxxxxxx> wrote:
> On 05/06/15 14:35, Jan Beulich wrote:
>>>>> On 02.06.15 at 18:26, <david.vrabel@xxxxxxxxxx> wrote:
>>> --- a/xen/common/grant_table.c
>>> +++ b/xen/common/grant_table.c
>>> @@ -288,10 +288,10 @@ static inline void put_maptrack_handle(
>>>      struct grant_table *t, int handle)
>>>  {
>>> -    spin_lock(&t->lock);
>>> +    spin_lock(&t->maptrack_lock);
>>>      maptrack_entry(t, handle).ref = t->maptrack_head;
>>>      t->maptrack_head = handle;
>>> -    spin_unlock(&t->lock);
>>> +    spin_unlock(&t->maptrack_lock);
>> 
>> Starting with this change it becomes unclear what protects the
>> maptrack entries - the grant table lock or the maptrack one?
> 
> The grant table lock.  The docs aren't very good here -- the maptrack
> lock is only for the maptrack free list.

I don't think the grant table lock serves that purpose, at least not
anymore after being converted to RW. See my reply on patch 3.

Jan


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