Re: [PATCH 1/2] kref: add kref_test_and_get

From: Greg KH
Date: Tue Jan 04 2011 - 16:00:27 EST

On Tue, Jan 04, 2011 at 04:52:26PM +0100, Jerome Marchand wrote:
> Add kref_test_and_get() function, which atomically add a reference only if
> refcount is not zero. This prevent to add a reference to an object that is
> already being removed.

We just removed a function like this recently as it really isn't the
solution for what you need here at all.

Please use a lock that protects the desctruction of the kref, like the
rest of the kernel, to keep someone from grabing a reference while the
device could be going away. That's the only way to safely do this.

See the archives for why this overall, isn't a good idea for a kref to
have this type of function.


greg k-h
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