Re: about reference counter

[lml@xxxxxxxxxxxxxxxx]

Hi, Greg,

On Fri, Oct 01, 2004 at 01:14:56PM -0700, Greg KH wrote:
> On Fri, Oct 01, 2004 at 03:50:56PM -0400, lml@xxxxxxxxxxxxxxxx wrote:
> > Hi,
> > 
> > I am not sure how the reference counter can protect the data by just
> > checking the number of usage. For example, one thread gets the object
> > and increases the counter, while another can get the same object at
> > the same time. If there is no locking, how can the reference counter
> > solve the race contention.
> > 
> > Or may be I missed some important part.
> 
> You did.  Your reference count needs to be an atomic value.  Just use a
> struct kref, it handles all of the logic for you.

Yes, I know the reference counter is usually atomic_t, but two threads can "get" the object and this "get" only increases the atomic value. After that, they canread/write the object at the same time, right? It sounds like only the reference counter is atomic, while the content of the object is not protected. Please correct me if I am wrong.

I am still using 2.4 kernel so there is no struct kref, but the principle, which I am not clear, should be the same.

Thanks,

LML

> 
> greg k-h

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