From mboxrd@z Thu Jan  1 00:00:00 1970
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In-Reply-To: <20110222151218.4A02965D3E@server.hemiola.co.uk>
References: <20110222151218.4A02965D3E@server.hemiola.co.uk>
Date: Tue, 22 Feb 2011 16:30:10 +0100
Message-ID: <AANLkTinnsrwtXyLmakRdCvaToQfAs=CbR40wf_fZtu_W@mail.gmail.com>
From: Francisco J Ballesteros <nemo@lsub.org>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Subject: Re: [9fans] usb ohci question
Topicbox-Message-UUID: b2d14e94-ead6-11e9-9d60-3106f5b1d025

I'll look again (just did).
But I think you found a bug.

On Tue, Feb 22, 2011 at 4:10 PM,  <rod@hemiola.co.uk> wrote:
> I'm struggling to understand the ins and outs of the usb ohci driver
> (usbohci.c) and have a question (well, several).
>
> If one writes to an endpoint, then "epio" gets called. This in turn
> does ilock(ctrl) which disables interrupts on my single-processor
> machine. Then "epgettd" is called several times to allocate transfer
> descriptors. Each call to epgettd copies a portion from the user space
> buffer which was passed as a parameter to "epio".
>
> What happens here if the user space buffer is in a page which is not
> present? Is it possible for a page-in to happen even when interrupts
> are disabled by the ilock?
>
> Thanks for any insight.
>
> rod
>
>