From: "Xavier Wang" <xavierwang@ms19.url.com.tw>
To: "Jesper Skov" <jskov@redhat.com>
Cc: <ecos-discuss@sources.redhat.com>
Subject: Re: [ECOS] nested interrupts
Date: Thu, 18 Jan 2001 04:59:00 -0000 [thread overview]
Message-ID: <002f01c0814d$d618fa80$6f2314ac@realtek.com.tw> (raw)
In-Reply-To: <otitnd9qr0.fsf@thinktwice.zoftcorp.dk>
Thanks, Jesper.
One more question. By looking into the source code, I still can't
figure out that why DSRs can call most kernel functions but
ISRs can't. Is it the stack problem or scheduler locking problem
or something else?
> Xavier> I got confused about nested interrupts. In
> Xavier> http://sources.redhat.com/ecos/docs-latest/porting/hal-interrupts.html
> Xavier> it seems that interrupts are disabled in ISRs, but enabled in
> Xavier> DSRs.
>
> Xavier> But Hugo's description in the same page said that
> Xavier> higher priority interrupts are enabled before calling
> Xavier> ISR. Which is true for nested interrupts?
>
> Both are true, but depending on configuration. There is an option that
> allows nested interrupts - when disabled, the former is valid, when
> enabled, the latter is valid.
>
> Xavier> If it's the former, should I rewrite the 'hal_cpu_int_enable'
> Xavier> macro used in hal_interrupt_stack_call_pending_DSRs (in
> Xavier> vector.S) to enable only higher priority interrupts? If it's
>
> No. All interrupts are allowed when executing DSRs. DSRs are only
> executin when no interrupts are pending.
>
> Xavier> the latter, what should I do to support nested interrupts?
> Xavier> (I'm using TX39/JMR3904 platform, eCos version 1.3.1)
>
> You need code that enabled higher level interrupts depending on the
> state of CYGSEM_HAL_COMMON_INTERRUPTS_ALLOW_NESTING.
>
> The code needs to go either somewhere in vectors.S around the place
> where the hal_cpu_except_enable macro is called. I don't know if a
> variant/platform specific version of that macro would be a suitable
> solution. None of the other MIPS platforms allow nested interrupts.
>
> Xavier> Besides, by looking into the source code, it seems that if
> Xavier> there is any pending DSRs, no thread will be run. So can a
> Xavier> high priority thread be blocked by a low priority interrupt
> Xavier> (DSR)?
>
> Yes.
>
> Xavier> Will it introduce some problems for a real-time application?
>
> I guess that depends on how you program the DSRs/threads. But I don't
> have anything intelligent to say to that, so I won't.
>
> Jesper
next prev parent reply other threads:[~2001-01-18 4:59 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-01-17 23:51 Xavier Wang
2001-01-18 1:03 ` Jesper Skov
2001-01-18 4:15 ` Xavier Wang
2001-01-18 5:00 ` Nick Garnett
2001-01-18 4:59 ` Xavier Wang [this message]
2001-01-18 5:46 ` Nick Garnett
2001-01-18 21:52 ` Xavier Wang
2001-01-18 22:35 ` Jonathan Larmour
2001-01-18 8:26 ` Sergei Slobodov
2001-01-18 20:56 ` Xavier Wang
2001-01-18 22:37 ` Jonathan Larmour
-- strict thread matches above, loose matches on Subject: below --
2000-09-11 0:03 [ECOS] Nested Interrupts Sandeep Rikhi
2000-09-11 7:53 ` Jonathan Larmour
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