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Date: Fri, 30 Sep 2005 10:31:18 -0600 (MDT)
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To: kerndev@yahoo.com
From: "M. Warner Losh" <imp@bsdimp.com>
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	Fri, 30 Sep 2005 10:30:37 -0600 (MDT)
Cc: hackers@freebsd.org
Subject: Re: using fast interrupts with em(4)
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In message: <20050930010434.67727.qmail@web35003.mail.mud.yahoo.com>
            Kernel Dev <kerndev@yahoo.com> writes:
: Hello All. For a project, I am looking into making the em(4) driver use fast interrupts. Has someone done this or are there other driver references that could help me in this?
:  
: I understand that the main problems are:
:  
: 1. Sharing of interrupts.
: 2. Blocking (memory and mutexes).
:  
: Are there any other issues I might have missed?

You can share fast interrupts, but it isn't a good idea...

You can't block in a fast interrupt.  You must use spin locks.  You
cannot call anything that will sleep in a fast interrupt.  Ideally,
you'd not modify anything that isn't covered by your own spin locks,
leaving that for a taskqueue or similar queueing strategy.

Warner