From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <4D63D6D4.5040808@bouyapop.org>
Date: Tue, 22 Feb 2011 16:31:32 +0100
From: Philippe Anel <xigh@bouyapop.org>
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To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
References: <20110222151218.4A02965D3E@server.hemiola.co.uk>
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Subject: Re: [9fans] usb ohci question
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Hello,

A 'page-in' occurs on page fault exception, which cannot be masked.

Phil;


Le 22/02/2011 16:10, rod@hemiola.co.uk a �crit :
> 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
>
>