linux-kernel - Re: [PATCH resend] virtio_console: Free buffers from out-queue upon close

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Message-ID: <87sj8l2cea.fsf@rustcorp.com.au>
Date:	Thu, 08 Nov 2012 10:28:53 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	sjur.brandeland@...ricsson.com, Amit Shah <amit.shah@...hat.com>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org, sjur@...ndeland.net,
	Sjur Brændeland <sjur.brandeland@...ricsson.com>
Subject: Re: [PATCH resend] virtio_console: Free buffers from out-queue upon close

sjur.brandeland@...ricsson.com writes:

> From: Sjur Brændeland <sjur.brandeland@...ricsson.com>
>
> Free pending output buffers from the virtio out-queue when
> host has acknowledged port_close. Also removed WARN_ON()
> in remove_port_data().
>
> Signed-off-by: Sjur Brændeland <sjur.brandeland@...ricsson.com>
> ---
>
> Resending, this time including a proper "Subject"...
> --
>
> Hi Amit,
>
> Note: This patch is compile tested only. I have done the removal
> of buffers from out-queue in handle_control_message()
> when host has acked the close request. This seems less
> racy than doing it in the release function.

This confuses me... why are we doing this in case
VIRTIO_CONSOLE_PORT_OPEN:?

We can't pull unconsumed buffers out of the ring when the other side may
still access it, and this seems to be doing that.

Thanks,
Rusty.
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