[ECOS] ref to previous question-'calling path questions, thanks'
Mon Oct 2 15:33:00 GMT 2006
Thanks a lot for your help Bart.
But inside IRQ (vector.s) what does pre-exception mode points to? (Is that
always supervisor mode prior to entering IRQ mode? (if it is supervisor mode
for pre-exception mode, what is difference between saving pre-exception mode
context and what will be saved later on in hal_switch_context function?)
>From: Bart Veer <firstname.lastname@example.org>
>Subject: Re: [ECOS] ref to previous question-'calling path questions,
>Date: 01 Oct 2006 16:59:13 +0100
> >>>>> " " == Qiang Huang <email@example.com> writes:
> > Hi eCOS experts:
> > Maybe my previous question
> > (http://ecos.sourceware.org/ml/ecos-discuss/2006-09/msg00231.html)
> > little confusing, what it really means is the followings:
> > (ARM target)
> > Two thread #1 and #2 exist in system
> > (1) Thread #1 runs first
> > (2) Thread #1 issues SWI instruction
> > (3) Enter SWI ISR and run on thread #1 stack (svc mode)
> > (4) At the time IRQ occurs and preempts SWI ISR
> > (5) Switch SVC and run on thread #1 stack (svc mode)
> > (6) Eventually comes to interrupt_end() and unlock_inner(), which
> > a context switching
> > (7) Thread #2 context is loadded and return with thread #2 running
> > Here seems SWI is preempted by thread #2? Is this correct?
> > (shouldn't all ISR be finished before any thread has the chance to
> > Hope someone can give me some hint, that would be very
> > thankful.
>eCos does not use SWI's. The main purpose of the SWI instruction is to
>provide a controlled mechanism for switching between user mode and
>supervisor mode, but eCos applications always run in supervisor mode
>so there is no need for a switch. If for some obscure reason an
>application does execute a SWI instruction the resulting system
>behaviour is basically undefined.
>Bart Veer eCos Configuration Architect
>http://www.ecoscentric.com/ The eCos and RedBoot experts
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