Subject: Re: spl naming etc
To: Arne H. Juul <arnej@pvv.unit.no>
From: Jason Thorpe <thorpej@nas.nasa.gov>
List: tech-kern
Date: 01/02/1996 16:52:47
On Wed, 3 Jan 1996 01:39:03 +0100
"Arne H. Juul" <arnej@pvv.unit.no> wrote:
> But in NetBSD the current spl() structure is not strictly hierarchic;
> splnet() can block just network interrupts, splbio() just disk interrupts,
> spltty() just serial interrupts and so on. [This is a simplified picture
> of course, ignoring parallel ports etc...] At least this is my current
> understanding of the NetBSD source code. Of course many machines must
> have the spl() routines in a hierarchy anyway, because of the hardware
> construction.
Actually, this is problably machine-dependent. For example, if you have
an HP-IB controller at ipl3 and a SCSI controller at ipl5 on an hp300,
blocking HP-IB "disk" interrupts does not block SCSI "disk" interrupts.
However, some architecures may have interrupt "bitmasks" where each type
of interrupt (network, disk, serial line) corresponds to a "bit" in the
mask ... This is guesswork on my part. I'm not about to say I
completely understand how interrupts work on the i386, alpha, or pmax.
> Now what about another (maybe stupid) idea: Most boxes doesn't
> necessarily run slip or ppp at all. What about making splimp() not
> block tty interrupts if slip/ppp is not configured? This *might*
> be a huge win on many machines for serial port reliability, which
> would be nice for driving printers / terminals. [Of course, you need
> serial port reliability when using slip/ppp too!]
Which boxes won't run SLIP or PPP? (Actually, do some ports change
splimp() if PPP and SLIP are both not present? I thought so...)
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