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

[Ming Lei]

On Mon, Dec 12, 2011 at 4:54 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Mon, 2011-12-12 at 11:48 +0800, Ming Lei wrote:
>> For kref, maybe it is still multiple operations done on one cpu vs them
>> being visible on another, but seems a bit implicit, see the common kref
>> usage below:
>>
>> CPU0                            CPU1
>>                                         A:kref_init(&obj->ref)
>
> how does CPU0 get a ref to obj?

Suppose open/close/read/.. context is run on CPU0, and driver .probe/.release
context(hotplug context) is run on CPU1. There are a few examples on
usb driver(eg. usb-skeleton.c, ...)

>
>> B:kref_get(&obj->ref)
>> C:access obj                    E:access obj
>>                                         F:kref_put(&ojb->ref)
>> D:kref_put(obj->ref)


thanks,
-- 
Ming Lei
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