From: "ariga masahiro" <ariga@link-lab.co.jp>
To: "Andrew Lunn" <andrew@lunn.ch>
Cc: <ecos-discuss@ecos.sourceware.org>
Subject: Re: [ECOS] When or on what condition does "deschedule" happen?
Date: Mon, 19 May 2008 05:32:00 -0000 [thread overview]
Message-ID: <001901c8b971$a14202c0$1c0110ac@ariga> (raw)
In-Reply-To: <20080516125053.GA27629@lunn.ch>
Hello everyone,
Thank you,Andrew, for your reply.
There is one unclear point that I would make it clear.
In explaning it ,let me use the scenario that
Anthony J. Massa elaborate in his book
"Embedded Software Development With Ecos".
(supposing since I bought the book I don't infringe its licence)
In case of Multilevel Queue Scheduler,
three threads are created like next.
ThreadC -- priority 30(lower)
ThreadA,B -- priority 0(highest)
- ThreadA - Timeslice - ThreadB -Deschedule - ThreadA -
|
|
Preemption
Deschedule
|
|
ThreadC
ThreadC
Next is Anthony J. Massa's description.
"three threads-Thread A, Thread B, and Thread C-
are configured during creation of the threads at priority levels 0, 0, and
30, respectively.
--- starts with Thread C executing.
Next, Thread A becomes able to run, causing Thread C to be preempted and a
context
switch occurs. During the execution of Thread A, Thread B also becomes able
to run. Thread A
continues until its timeslice period expires. Then, another context switch
occurs allowing Thread
B to run. Thread B completes within its given timeslice period. The
de-scheduling of a thread
can happen for various reasons; for example, by waiting on a mutex that is
not free or delaying
for a specified amount of time. Since Thread A has the highest priority of
tasks waiting to execute,
a context switch occurs and it runs next. After Thread A has completed, a
context switch
takes place allowing Thread C to execute."
My question is last part of Deschedule when ThreadC resumes execution.
Am I correct in assuming that among your conditions, only two conditions
should be fullfiled to make it possible
for ThreadC to resume execution ?
1.When the thread blocks.(How does scheduler recognise this ?)
2.When a thread exits.
If ThreadA does not finish and enter looping state,then isn't there any way
for ThreadC to resume execution ?
Please kindly forgive my ignorance and enlighten me.
Thanks in advance.
Masahiro Ariga
> On Fri, May 16, 2008 at 05:12:30PM +0900, ariga masahiro wrote:
>> Hello everyone,
>>
>> Please teach me about eCos Thread Scheduler.
>> When or on what condition does "deschedule" happen ?
>
> When the thread blocks.
>
> When a higher priority thread becomes runnable.
>
> When a thread uses up its time slice and there is another thread of
> the same priority which is runnable.
>
> When a thread calls yield and there is another thread of the same
> priority which is runnable.
>
> When a thread exits.
>
> There is nothing unusual here. Any good book on operating systems will
> teach you the same.
>
> Andrew
>
> --
> Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
> and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
>
>
>
--
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
next prev parent reply other threads:[~2008-05-19 5:32 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-01-07 23:59 [ECOS] Wrongfully compiled code ariga masahiro
2008-01-08 0:05 ` Gary Thomas
2008-01-08 1:05 ` ariga masahiro
2008-01-17 19:21 ` [ECOS] " Dave Lawrence
2008-01-17 23:50 ` ariga masahiro
2008-01-18 12:16 ` Dave Lawrence
2008-01-18 14:40 ` Gregg Levine
2008-01-18 15:44 ` Dave Lawrence
2008-01-18 15:49 ` Gregg Levine
2008-01-18 16:09 ` Dave Lawrence
2008-01-21 0:34 ` ariga masahiro
2008-02-04 1:49 ` ariga masahiro
2008-02-04 11:38 ` Dave Lawrence
2008-02-12 1:06 ` ariga masahiro
2008-02-12 10:55 ` Dave Lawrence
2008-02-22 4:57 ` [ECOS] How to re-install newly compiled gnutools ariga masahiro
2008-02-22 7:15 ` ariga masahiro
2008-05-16 8:13 ` [ECOS] When or on what condition does "deschedule" happen? ariga masahiro
2008-05-16 15:26 ` Andrew Lunn
2008-05-19 5:32 ` ariga masahiro [this message]
2008-05-19 13:18 ` Andrew Lunn
2008-05-19 13:31 ` Gary Thomas
2008-05-20 1:26 ` ariga masahiro
2008-05-20 12:18 ` Andrew Lunn
2008-05-23 7:38 ` ariga masahiro
2008-05-23 9:35 ` Nick Garnett
[not found] ` <000601c8c165$406e0970$1c0110ac@ariga>
2008-05-29 18:23 ` [ECOS] Re: In trouble of timer operations Andrew Lunn
2008-05-30 2:50 ` ariga masahiro
2008-05-30 3:09 ` Paul D. DeRocco
2008-05-30 4:11 ` ariga masahiro
2008-05-30 4:43 ` Paul D. DeRocco
2008-05-30 7:26 ` ariga masahiro
2008-05-30 7:47 ` Paul D. DeRocco
2008-05-30 8:03 ` ariga masahiro
2008-05-30 8:07 ` Andrew Lunn
2008-06-04 5:25 ` ariga masahiro
2008-06-04 10:06 ` Paul D. DeRocco
2008-06-05 6:14 ` ariga masahiro
2008-06-05 17:39 ` Paul D. DeRocco
2008-05-30 6:35 ` Andrew Lunn
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