Messages in this thread |  | | Date | Wed, 12 Feb 2014 19:06:37 -0500 (EST) | Subject | Re: [PATCH net 1/3] kref: add kref_sub_return | From | David Miller <> |
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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Date: Wed, 12 Feb 2014 08:56:30 -0800
> On Wed, Feb 12, 2014 at 06:38:21PM +0200, Michael S. Tsirkin wrote: >> It is sometimes useful to get the value of the reference count after >> decrement. >> For example, vhost wants to execute some periodic cleanup operations >> once number of references drops below a specific value, before it >> reaches zero (for efficiency). > > You should never care about what the value of the kref is, if you are > using it correctly :)
It isn't being used to determine when to destroy things.
They use it to as a heuristic of when to trigger polling.
Each ubuf attached gets a kref to the higher level virtio_net buffer holding object, they want to trigger polling when that reference drops to 1 or lower.
Right now they are reading the atomic refcount directly, which I think is much worse than this helper.
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