Re: [PATCH 3/3] kref: Remove the memory barriers

[Ming Lei]

On Mon, Dec 12, 2011 at 4:56 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Mon, 2011-12-12 at 11:48 +0800, Ming Lei wrote:
>> >  LOCK
>> >  obj = lookup(); /* lets assume obj != NULL */
>> >  kref_get(&obj->ref);
>> >  UNLOCK
>> >
>> >  value = obj->member;
>> >
>> >  kref_put(&obj->ref);
>> >
>> > Now, under our memory model, the read from obj->member can both happen,
>> > or be observed to happen before the increment from kref_get() is
>> > processed.
>>
>> It should be the problem if another CPU observed that write/read obj
>> is done before kref_get.
>
> WHY?!?!?!

I did't say the reason because it is same with the example I explained in
the same reply. So if you can make me enlightened on this example,
all will be OK, :-)

thanks,
-- 
Ming Lei
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