Self restarting property of RTOS-How it works?

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Dear all,
  I was going through the explaination for taskRestart() call in the
vxworks reference manual.I believe such a feature is available for most
of the RTOS in the market.This dicussion talks about vxworks,But it
applies in general for any rtos which offers a restarting facility.I am
looking for replys from a architecture perspective rather then os
specific discussion.

Vxworks reference manual for taskRestart() states the following:
"This routine "restarts" a task. The task is first terminated, and then
reinitialized with the same ID, priority, options, original entry
point, stack size, and parameters it had when it was terminated.
Self-restarting of a calling task is performed by the exception task.
The shell utilizes this routine to restart itself when aborted. "

I have never got a chance to use this call in my application,but
curious to learn how it works.Heres my doubt:

After restarting will the task start executing from the starting point
or will execute from where it left?(that means continue executing,from
the point where its terminated before restarting?).


Incase it starts executing from scratch from the place where its
spawned,will it not cause problems to my application?For eg,I am in
middle of some biomedical application and some task goes for a toss and
I restart it using this call,the task will start performing everything
from scratch which may not be suitable to the current status of
application(In terms of micro heart surgery,typically lets say the task
performing the cutting of tissues goes for a toss after some time,and I
restart,if it again starts cutting the tissues which is not required
for me,because I have already removed it!).

If its otherway around,for eg it starts executing from the point where
it got terminated,how does the task ensure it gets all the resources
like I/O device,semaphores or some other resource,which is required to
execute from the point where it was terminated?Because the time before
it restarts,may be there can be another high priority task which may
own the resources required by the current task and I feel this should
not be possible because it will cause problem to the entire
application.

In precise can someone clarify me how this taskRestart() call
work?Under what situations its preferred to use this call?What are the
pros and cons of using this call in our application?

Looking farward for your replys and advanced thanks for the same,

Regards,
s.subbarayan


Re: Self restarting property of RTOS-How it works?
You wil find an explanation and advices here:
http://www.bluedonkey.org/cgi-bin/twiki/bin/view/Books/VxWorksCookbookTheKernel#Restarting_a_Task
Look for restarting a task


Re: Self restarting property of RTOS-How it works?

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Are you saying that it's acceptable in any way, shape or form for a task
in a biomedical application to "go for a toss"?

--

Tim Wescott
Wescott Design Services
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Re: Self restarting property of RTOS-How it works?

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Oh, is that not acceptable?  I hadn't fully divined your attitude toward
the patients...

Rufus



Re: Self restarting property of RTOS-How it works?
snipped-for-privacy@earthlink.net says...
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And as much (or more) to the point of the original question no thread or
task 'went for a toss' so restarting would have had no effect.

Robert

Re: Self restarting property of RTOS-How it works?
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There were also serious hardware design flaws with the Therac-25.
The whole system design was a disaster, including operator training.

--

  ... Hank

http://home.earthlink.net/~horedson
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Re: Self restarting property of RTOS-How it works?

-- snip --
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True.  I've noticed that one tends to have organizations that are
committed to quality, or organizations that aren't.  This leads to
entire projects that are disasters from a quality standpoint, or ones
that aren't.  I suspect that the only times you're going to have a
really good part A and a really bad part B is either when you have a
project that doesn't have much cross-discipline awareness or if you're
in an organization that just doesn't care and the people doing part A
are personally committed to quality and have the weight or cleverness to
make it happen in spite of the organization.

--

Tim Wescott
Wescott Design Services
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Re: Self restarting property of RTOS-How it works?


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Or, as I found out at Mattel, Part A is designed in the USA and
part B is designed in China.

BTW, fast food eateries are starting to outsource order-taking.
When you pull up in the drive-through, you may be talking to
someone in India.



Re: Self restarting property of RTOS-How it works?
On Wed, 09 Feb 2005 19:01:00 +0000, the renowned Guy Macon

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I was perusing a copy of an ethnic weekly (the _Urdu Times_--
"North America's Largest Urdu Newspaper") over my lunch of Pakistani
halal nan and Korean bip im bap the other day, and they had companies
offering unlimited voice (over IP) to India for something like $30 a
month, retail to consumers. At less than a dime per hour for the
communication link, that could be pretty practical.


Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
snipped-for-privacy@interlog.com             Info for manufacturers: http://www.trexon.com
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Re: Self restarting property of RTOS-How it works?

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So does that mean I can order saag ghosht at
MacDonalds :-)

Re: Self restarting property of RTOS-How it works?
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... snip ...
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I was building software that could kill people 10 years before
that.  I was aware of it, and it didn't.  By the late '70s my
software was almost all implemented in Pascal (real ISO standard
Pascal, with full range checking etc. - not the Borland mixture)
with everything from the naked board up under my control.  Yes,
there were failures, usually hardware, but the effect was to stop
and scream for human help.

It doesn't take a genius to recognize potential pitfalls.  People
have been building fail-safe mechanisms for centuries.

--
"If you want to post a followup via groups.google.com, don't use
 the broken "Reply" link at the bottom of the article.  Click on
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Re: Self restarting property of RTOS-How it works?

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It was nearly 1:00AM, and I left out the "in the medical industry".
Just out of curiosity what industry were you working in?

I have noticed that there is a strong tendency for people to view the
software engineering process as somehow fundamentally different from
mechanical, electrical or other "old-line" engineering processes -- so
where there will be significant controls and reviews on mechanical and
electrical assemblies, a software engineer may be allowed to compile
something, test it for two minutes, and ship product.

--

Tim Wescott
Wescott Design Services
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Re: Self restarting property of RTOS-How it works?
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I attended a lecture by Jack Ganssle on ESC last September in which he
talked about a software engineer whose software error rate was way lower
than their co-workers'. The guy was formerly a hardware engineer. When
asked about it, the guy said nobody told him he was allowed to err. The
pervasive "bugs are unavoidable" attitude of software engineering
professionals has perhaps established a tolerance for errors much higher
than it would be acceptable. The fact "it's just software, please add
this and this last minute feature and fix" doesn't help at all.

Just my EU0.02

Elder.

Re: Self restarting property of RTOS-How it works?

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the
so
and
lower
The
higher

Like hardware doesn't have bugs or "errata".  Go check Intel's web site.

Especially new hardware.
sheesh



Re: Self restarting property of RTOS-How it works?


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Yeah, let the software guys figure out how to work around it :-)

It does point to one thing: hardware errors are really hard to fix
you need to ship new, physical, product.  Software can be fixed
after it was shipped at little extra expense for the manufacturer
(but potentially a lot for the customer).


Casper
--
Expressed in this posting are my opinions.  They are in no way related
to opinions held by my employer, Sun Microsystems.
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Re: Self restarting property of RTOS-How it works?
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Therefore, it would be foolish, from a business point of view, to
build software to the same standards of correctness as hardware.
And sure enough, it doesn't happen.

Whether software companies are getting the cost/quality balance
right is debatable, but the idea that they should aim for the same
balance point as hardware companies is surely wrong.



Re: Self restarting property of RTOS-How it works?

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I disagree on both counts.  Software *on a PC* can be fixed after
it ships, but PCs are only a small but visible part of the total
worldwide production of computer hardware/software.  I have produced
toys that sold more units per year than all the PC manufacturers
combined, and the software was in masked ROM.  It was also built
to the same standards of correctness as the hardware.  Over on the
other end of the price/quality spectrum, I have worked on aircraft
parts, and here too the software was built to the same standards
of correctness as the hardware.  This is true of nearly all embedded
systems.

--
Guy Macon <http://www.guymacon.com/


Re: Self restarting property of RTOS-How it works?
Guy Macon <http://www.guymacon.com/ writes:

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There's no proof that embedded systems are not engineered to
a higher standard; I'm certain they are (well, not for small
household electronics things or not even cars; I've encountered
bugs in all of my embedded electronics devices, including
my car, tvs, dvd player, etc)

Casper
--
Expressed in this posting are my opinions.  They are in no way related
to opinions held by my employer, Sun Microsystems.
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Re: Self restarting property of RTOS-How it works?
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That's why the historical succession from masked ROMS to PROMS,
EPROMS, EEPROMS, flash, etc. is important.  They all eased the
fixing process.  Another similar area is PLAs replacing random
wired logic.

--
"If you want to post a followup via groups.google.com, don't use
 the broken "Reply" link at the bottom of the article.  Click on
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Re: Self restarting property of RTOS-How it works?
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First of all, I dare to say this kind of hardware is mostly if not
totaly software as these processors are synthesized from (Verilog?
VHDL?) building blocks. Therefore some or most of software engineering
applies I guess.

I think Ganssle meant much more the mindset than the knowledge/expertise
area itself. Hardware design and development also carries its own set of
"bugs" and bad practices though (I wonder how many engineers design
based only on components typical figures.)

Regards.

Elder.


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