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SubjectRe: [PATCH 2/5] /dev/vring: simple userspace-kernel ringbuffer interface.
On Sun, Apr 20, 2008 at 02:05:31AM +1000, Rusty Russell (rusty@rustcorp.com.au) wrote:
> > Should this whole function and vring_used_buffer() be protected with
> > vr->lock mutex?
>
> No; it's up to the caller to make sure that they are serialized. In the case
> of tun that happens naturally.
>
> There are two reasons not to grab the lock. It turns out that if we tried to
> lock here, we'd deadlock, since the callbacks are called under the lock.
> Secondly, it's possible to implement an atomic vring_used_buffer variant,
> which could fail: this would avoid using the thread most of the time.

Yep, I decided that too. But it limits its usage to tun only or any
other system where only single thread picks up results, so no generic
userspace ring buffers?

--
Evgeniy Polyakov


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