From: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: netdev@vger.kernel.org, Max Krasnyansky <maxk@qualcomm.com>,
virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/5] /dev/vring: simple userspace-kernel ringbuffer interface.
Date: Sat, 19 Apr 2008 20:33:22 +0400 [thread overview]
Message-ID: <20080419163322.GA17089@2ka.mipt.ru> (raw)
In-Reply-To: <200804200205.31508.rusty@rustcorp.com.au>
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
next prev parent reply other threads:[~2008-04-19 16:34 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-18 4:33 [PATCH 0/5] High-speed tun receive and xmit Rusty Russell
2008-04-18 4:35 ` [PATCH 1/5] virtio: put last_used and last_avail index into ring itself Rusty Russell
2008-04-18 4:39 ` [PATCH 2/5] /dev/vring: simple userspace-kernel ringbuffer interface Rusty Russell
2008-04-18 4:41 ` [PATCH 3/5] /dev/vring limit and base ioctls Rusty Russell
2008-04-18 4:42 ` [PATCH 4/5] tun: vringfd receive support Rusty Russell
2008-04-18 4:43 ` [PATCH 5/5] tun: vringfd xmit support Rusty Russell
2008-04-18 11:31 ` Andrew Morton
2008-04-18 15:15 ` Rusty Russell
2008-04-18 16:24 ` Ray Lee
2008-04-18 19:06 ` Andrew Morton
2008-04-19 14:41 ` Rusty Russell
2008-04-19 17:51 ` Andrew Morton
2008-04-19 1:54 ` Andrew Morton
2008-04-18 11:46 ` pradeep singh rautela
2008-04-18 14:25 ` Ray Lee
2008-04-18 18:01 ` pradeep singh rautela
2008-04-18 11:18 ` [PATCH 2/5] /dev/vring: simple userspace-kernel ringbuffer interface Andrew Morton
2008-04-18 14:32 ` Rusty Russell
2008-04-18 18:59 ` Andrew Morton
2008-04-18 19:38 ` Michael Kerrisk
2008-04-19 16:41 ` Rusty Russell
2008-04-20 0:16 ` David Miller
2008-04-19 15:02 ` Jonathan Corbet
2008-04-19 10:22 ` Evgeniy Polyakov
2008-04-19 16:05 ` Rusty Russell
2008-04-19 16:33 ` Evgeniy Polyakov [this message]
2008-04-19 16:45 ` Rusty Russell
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