Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.arch.embedded > #29087
| From | Niklas Holsti <niklas.holsti@tidorum.invalid> |
|---|---|
| Newsgroups | comp.arch.embedded |
| Subject | Re: From cooperative to preemptive scheduler: a real example |
| Date | 2020-01-09 14:03 +0200 |
| Organization | Tidorum Ltd |
| Message-ID | <h7oj3sFcrvnU1@mid.individual.net> (permalink) |
| References | <qv0lmu$up1$1@dont-email.me> <h7iqr4F6k9uU1@mid.individual.net> <qv32lj$ko6$1@dont-email.me> <h7n4tfF3sqmU1@mid.individual.net> <qv7286$8cb$1@dont-email.me> |
On 2020-01-09 13:19, pozz wrote:
> Il 08/01/2020 23:54, Niklas Holsti ha scritto:
>> On 2020-01-08 1:02, pozz wrote:
>>> Il 07/01/2020 08:38, Niklas Holsti ha scritto:
[snip]
>>>> Let's assume these requirements and properties of the environment:
>>>>
>>>> A. The function "serial_rx" polls the one-character reception buffer
>>>> of the serial line once, and returns the received character, if any,
>>>> and EOF otherwise. It must be called at least as often as characters
>>>> arrive (that is, depending on baud rate) to avoid overrun and loss
>>>> of some characters.
>>
>> You asked about possible advantages of pre-emption; I made my
>> assumptions, above, such that the (incomplete) example you gave shows
>> this advantage, under these assumptions (which could be true for
>> other, otherwise similar example applications).
>>
>>> No, serial driver works in interrupt mode and already use a FIFO
>>> buffer, sufficiently big. serial_rx() pop a single element from the
>>> FIFO, if any.
>>
>> Ah, then your *system* is intrinsically pre-emptive (the interrupts
>> pre-empt the tasks), even if the *code you showed* does not show this
>> pre-emption.
>
> Ah yes, interrupts are preemptive and I use them a lot, but they are
> confined in their works, they are very lightweight and fast.
That's a design decision. Some systems do most of their work in
interrupt handlers, and use "background" processing only for some
non-critical housekeeping tasks.
> The discussion here regards medium to high complexity tasks.
I don't recall you saying so, and your example (perhaps naturally, for
an example) did not have such tasks. Many interrupt handlers are more
complex than the tasks in your example.
In a pre-emptive system there is no logical difference between
interrupts and tasks. The only practical difference is that interrupts
are "tasks" that are scheduled by the processor HW (moderated by SW
control of interrupt masking and disabling) while the tasks are
scheduled by the RTOS.
The advantages (and complications) of pre-emptive scheduling are mostly
the same for tasks as for interrupts.
--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .
Back to comp.arch.embedded | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
From cooperative to preemptive scheduler: a real example pozz <pozzugno@gmail.com> - 2020-01-07 02:08 +0100
Re: From cooperative to preemptive scheduler: a real example Don Y <blockedofcourse@foo.invalid> - 2020-01-06 19:37 -0700
Re: From cooperative to preemptive scheduler: a real example pozz <pozzugno@gmail.com> - 2020-01-07 10:11 +0100
Re: From cooperative to preemptive scheduler: a real example Don Y <blockedofcourse@foo.invalid> - 2020-01-07 07:51 -0700
Re: From cooperative to preemptive scheduler: a real example pozz <pozzugno@gmail.com> - 2020-01-07 23:51 +0100
Re: From cooperative to preemptive scheduler: a real example Niklas Holsti <niklas.holsti@tidorum.invalid> - 2020-01-09 01:39 +0200
Re: From cooperative to preemptive scheduler: a real example pozz <pozzugno@gmail.com> - 2020-01-10 00:42 +0100
Re: From cooperative to preemptive scheduler: a real example Niklas Holsti <niklas.holsti@tidorum.invalid> - 2020-01-15 18:39 +0200
Re: From cooperative to preemptive scheduler: a real example Don Y <blockedofcourse@foo.invalid> - 2020-01-08 23:12 -0700
Re: From cooperative to preemptive scheduler: a real example pozz <pozzugno@gmail.com> - 2020-01-10 00:49 +0100
Re: From cooperative to preemptive scheduler: a real example Don Y <blockedofcourse@foo.invalid> - 2020-01-08 23:12 -0700
Re: From cooperative to preemptive scheduler: a real example Don Y <blockedofcourse@foo.invalid> - 2020-01-09 01:33 -0700
Re: From cooperative to preemptive scheduler: a real example Niklas Holsti <niklas.holsti@tidorum.invalid> - 2020-01-07 09:38 +0200
Re: From cooperative to preemptive scheduler: a real example pozz <pozzugno@gmail.com> - 2020-01-08 00:02 +0100
Re: From cooperative to preemptive scheduler: a real example Niklas Holsti <niklas.holsti@tidorum.invalid> - 2020-01-09 00:54 +0200
Re: From cooperative to preemptive scheduler: a real example pozz <pozzugno@gmail.com> - 2020-01-09 12:19 +0100
Re: From cooperative to preemptive scheduler: a real example Niklas Holsti <niklas.holsti@tidorum.invalid> - 2020-01-09 14:03 +0200
Re: From cooperative to preemptive scheduler: a real example pozz <pozzugno@gmail.com> - 2020-01-10 00:32 +0100
Re: From cooperative to preemptive scheduler: a real example Niklas Holsti <niklas.holsti@tidorum.invalid> - 2020-01-15 18:53 +0200
Re: From cooperative to preemptive scheduler: a real example pozz <pozzugno@gmail.com> - 2020-01-16 14:48 +0100
Re: From cooperative to preemptive scheduler: a real example upsidedown@downunder.com - 2020-01-16 21:04 +0200
Re: From cooperative to preemptive scheduler: a real example Niklas Holsti <niklas.holsti@tidorum.invalid> - 2020-01-16 22:24 +0200
Re: From cooperative to preemptive scheduler: a real example pozz <pozzugno@gmail.com> - 2020-01-17 02:05 +0100
Re: From cooperative to preemptive scheduler: a real example Niklas Holsti <niklas.holsti@tidorum.invalid> - 2020-01-18 23:03 +0200
Re: From cooperative to preemptive scheduler [Stack] pozz <pozzugno@gmail.com> - 2020-01-14 13:27 +0100
Re: From cooperative to preemptive scheduler [Stack] Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2020-01-14 20:10 +0100
Re: From cooperative to preemptive scheduler [Stack] pozz <pozzugno@gmail.com> - 2020-01-15 09:36 +0100
Re: From cooperative to preemptive scheduler [Stack] Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2020-01-15 11:30 +0100
Re: From cooperative to preemptive scheduler [Stack] pozz <pozzugno@gmail.com> - 2020-01-15 11:51 +0100
Re: From cooperative to preemptive scheduler [Stack] Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2020-01-15 21:51 +0100
Re: From cooperative to preemptive scheduler [Stack] Niklas Holsti <niklas.holsti@tidorum.invalid> - 2020-01-15 21:26 +0200
Re: From cooperative to preemptive scheduler [Stack] Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2020-01-15 22:12 +0100
Re: From cooperative to preemptive scheduler [Stack] Niklas Holsti <niklas.holsti@tidorum.invalid> - 2020-01-15 23:30 +0200
csiph-web