From: Sergei Slobodov <sslobodov@caracal-tech.com>
To: ecos-discuss@sources.redhat.com
Subject: Re: [ECOS] nested interrupts
Date: Thu, 18 Jan 2001 08:26:00 -0000 [thread overview]
Message-ID: <3A671913.9090209@caracal-tech.com> (raw)
In-Reply-To: <otitnd9qr0.fsf@thinktwice.zoftcorp.dk>
>
> 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?
>
> Interrupts are always higher priority than tasks (threads), and DSRs
> are all at the same priority, higher than any thread and lower than
> any interrupt. When designing a real-time system, it is a good idea to
> include the total time of all possible interrupts (and their DSRs)
> when calculating thread response time
>
> As I was explained here, a main purpose of a DSR is to avoid
> scheduler's ready list manipulation from an interrupt. DSR mechanism
> serializes access to the scheduler (to suspend or resume a thread, or
> to send a message), thus completely avoiding disabling interrupts when
> posting. Quite neat. There is a price to pay, however, since DSR
> mechanism nearly doubles the time between posting interrupt and thread
> resumption. Bearing this in mind, the only thing DSR absolutely has to
> do is to notify the scheduler. All the rest ought to be done either in
> an ISR or in a thread.
>
Regards,
Sergei Slobodov
next prev parent reply other threads:[~2001-01-18 8:26 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
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 [this message]
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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