On Tue, Jun 20, 2000 at 05:25:08PM -0400, Olivier Galibert wrote:
> > Now, can't this be done by setting up a direct communication channel
> > between two userspace processes? With a semaphore you can check on
> > incoming messages, etc. This way you only need to do a context-switch if
> > you ask the kernel to set up a direct message-channel.
>
> Bzzt wrong. Going userspace->kernel and back does not involve any
> context switch. It's going userspace->another userspace that does.
Really? I thought I remembered Tanenbaum's book "Modern Operating
Systems" saying that this was one of the problems with drivers in
Userspace. It's been a while since I've read it, so I might be wrong. =)
--
"It is easy to be blinded to the essential uselessness of computers by
the sense of accomplishment you get from getting them to work at all."
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