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To: bde@zeta.org.au
From: "M. Warner Losh" <imp@bsdimp.com>
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Subject: Re: sio: lots of silo overflows on Asus K8V with Moxa Smartio
 C104H/PCI
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In message: <20040502130027.O1806@gamplex.bde.org>
            Bruce Evans <bde@zeta.org.au> writes:
: No, but siointr() doesn't go near the tty layer or almost any other
: layer.  It uses pseudo-dma and schedules a SWI to transfer data between
: its buffers and the tty layer.  Fast interrupt handlers cannot call
: other layers because they cannot reasonable lock other layers or
: vice versa.  (Even the call to the scheduler to schedule a SWI in the
: current implementation is a layering violation.)

So it is also safe to call the tty layer w/o giant held from the SWI?
I guess that was my question.  Or is the SWI wrapped in Giant when I
wasn't looking...

Warner