-------- Original Message --------
Subject: Re: PATCH: Fusion PPC thread switching
Date: Sun, 20 Mar 2005 23:02:28 +0100
From: Philippe Gerum <[EMAIL PROTECTED]>
Organization: Xenomai
To: Heikki Lindholm <[EMAIL PROTECTED]>
References: <[EMAIL PROTECTED]>
<[EMAIL PROTECTED]> <[EMAIL PROTECTED]>
Heikki Lindholm wrote:
Philippe Gerum kirjoitti:
Heikki Lindholm wrote:
Hello,
There is a problem in Fusion (PPC) that enabling ALTIVEC triggers.
The problem is that fusion uses _switch from Linux, which expects to
have "current" task (r2) in valid state. If I'm not horribly mistaken
--- also an option, I know next to nothing about Fusion --- "current"
is not valid when in other domains than root(=Linux). The attached
patch should fix the problem.
Ah. Ok, I definitely thought that r2 would not be altered while
switching domains. I'm going to test this patch asap (likely
tomorrow) and let you know of the outcome here. Thanks.
I didn't care trace exactly where r2 gets toasted, I'd guess the first
domain switch. I thought of this more generally: in a domain other than
Linux, r2 could be anything, so don't trust it there. One could, of
course, copy _switch function over to fusion and take out r2 references,
but that doesn't seem like worth the effort.
Ack. Seeing r2 set in _switch for the incoming thread made me think that
unless somebody trashes it, it should always point to "current" as Linux
defined it, but I was wrong. Indeed, assuming that no code from non-root
domains would reuse r2 for its own purpose sounds rather optimistic to
me now...
-- Heikki Lindholm
--
Philippe.
--
Philippe.
