>
> >can i allocate dynamic memory in ISR ??
>
> Yes, it's your CPU so you can do anything you want with it. You can can ev=
en
> disable IRQs or dynamic memory altogether if you really want to.
>
> > If yes wat shd be the
> >precautions i need to take care ??
>
> There are many, and this is by no means an exhaustive list but the first
> percautions that come to mind are correct handling of the following scenar=
ios:
>
> - The allocation fails because there is no more dynamic memory available.
> - The allocation takes too long and causes a subsequent IRQ to be missed.
> - The IRQ occurs while the mainline is in the middle of allocating/freeing=
> dynamic memory and your memory manager is non re-entrant.
> - A higher priority IRQ occurs and causes another ISR to start while this =
one
> is in the middle of allocating memory.
>
> Other percautions will depend on whether or not you are using a paged memo=
ry
> architecture, and whether pages are being swapped to secondary storage, et=
c.
> You also might want to search for "deferred procedure call"
>
Nice Explanation :):)
Karthik Balaguru
Reply by Chris H●February 4, 20082008-02-04
In message <479E489E.48BE6473@yahoo.com>, CBFalconer
<cbfalconer@yahoo.com> writes
>Stephen Pelc wrote:
>> David Brown <david@westcontrol.removethisbit.com> wrote:
>>
>>> Before posting again, please learn to type correctly.
>>
>> May I suggest, that for a different view, you read:
>> The Cell Phone: An Anthropology of Communication
>> By Heather A. Horst, Daniel Miller
>
>Let me point out that Usenet is NOT - repeat NOT - a Cell Phone.
It's on my cell phone
or is that the phone in my cell?
:-)
--
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
\/\/\/\/\ Chris Hills Staffs England /\/\/\/\/
/\/\/ chris@phaedsys.org www.phaedsys.org \/\/\
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
Reply by David T. Ashley●February 4, 20082008-02-04
<aleemakhtar1@gmail.com> wrote in message
news:b140416d-2767-40e2-b8f6-d3d8e91ea71f@e6g2000prf.googlegroups.com...
> can i allocate dynamic memory in ISR ?? If yes wat shd be the
> precautions i need to take care ??
In most systems, the answer is NO.
Reasons:
a)Functions such as malloc() are typically not re-entrant.
b)The allocation would take too long (defeats the rationale of an ISR).
Generally, knowing what you may and may not do from within an ISR is one of
the really important design rules of a system ...
--
David T. Ashley (dta@e3ft.com)
http://www.e3ft.com (Consulting Home Page)
http://www.dtashley.com (Personal Home Page)
http://gpl.e3ft.com (GPL Publications and Projects)
Reply by Stephen Pelc●January 30, 20082008-01-30
On Mon, 28 Jan 2008 16:26:54 -0500, CBFalconer <cbfalconer@yahoo.com>
wrote:
>Stephen Pelc wrote:
>> May I suggest, that for a different view, you read:
>> The Cell Phone: An Anthropology of Communication
>> By Heather A. Horst, Daniel Miller
>
>Let me point out that Usenet is NOT - repeat NOT - a Cell Phone.
Let me point out I that I did not say that it was. I merely
pointed out that the way one accesses Usenet may influence
the content.
Stephen
--
Stephen Pelc, stephenXXX@mpeforth.com
MicroProcessor Engineering Ltd - More Real, Less Time
133 Hill Lane, Southampton SO15 5AF, England
tel: +44 (0)23 8063 1441, fax: +44 (0)23 8033 9691
web: http://www.mpeforth.com - free VFX Forth downloads
Reply by Grant Edwards●January 29, 20082008-01-29
On 2008-01-29, Paul Keinanen <keinanen@sci.fi> wrote:
> On Tue, 29 Jan 2008 00:15:59 +0100, David Brown
><david.brown@hesbynett.removethisbit.no> wrote:
>
>>However, I
>>don't really buy your idea that SMS-speak is saving costs. You don't
>>pay per letter for SMS messages (at least, I've never heard of such a
>>scheme) - you pay per message. SMS abbreviations are nothing more than
>>laziness.
>
> If someone is really posting questions using SMS messages, how is that
> person going to receive messages posted by other users ?
Possibly via an SMS<->email gateway?
> If by SMS, that would imply that the sending a single message
> is very expensive but you can receive an unlimited amount SMS
> messages for free. Is there really such a service anywhere in
> the world ?
Not for free, but for a fixed price.
--
Grant Edwards grante Yow! Jesuit priests are
at DATING CAREER DIPLOMATS!!
visi.com
Reply by John Devereux●January 29, 20082008-01-29
David Brown <david@westcontrol.removethisbit.com> writes:
> John Devereux wrote:
>> David Brown <david.brown@hesbynett.removethisbit.no> writes:
> <snip>
>> I think the root of the difference is that usenet is a "one to many"
>> medium, whereas texting or chatrooms are one-one or one-few.
>>
>> In texts and chatrooms, it is generally good to be able to express
>> something as quickly as possible, to make it like a face to face
>> "real-time" conversation. It takes more effort to write a message than
>> to read it, so you can argue it is not worth putting much work into
>> the writing side, that would just slow things down.
>>
>> But with usenet, there are hundreds of readers reading the post. So it
>> is worthwhile putting effort in to the writing side, since even a
>> small increase in "readability" is multiplied by the number of
>> readers. Also usenet is less of a "real-time" medium than texts and
>> chatrooms are.
>>
>
> I think there is a lot in what you say here. People often don't seem
> to understand Usenet - they think in terms of posting a question and
> getting an answer, rather than having a discussion for the benefit of
> many. They also often fail to realise that newsgroup archives are an
> important resource for the future - when you've solved a problem, and
> post the answer here, it's available for others searching the
> archives.
Good point about the archives - that's another factor I had intended
to mention, too. The difference between writing a "txt" that will be
deleted on reading, and a Usenet article that will likely remain
archived and searchable until the end of time.
--
John Devereux
Reply by David Brown●January 29, 20082008-01-29
John Devereux wrote:
> David Brown <david.brown@hesbynett.removethisbit.no> writes:
<snip>
> I think the root of the difference is that usenet is a "one to many"
> medium, whereas texting or chatrooms are one-one or one-few.
>
> In texts and chatrooms, it is generally good to be able to express
> something as quickly as possible, to make it like a face to face
> "real-time" conversation. It takes more effort to write a message than
> to read it, so you can argue it is not worth putting much work into
> the writing side, that would just slow things down.
>
> But with usenet, there are hundreds of readers reading the post. So it
> is worthwhile putting effort in to the writing side, since even a
> small increase in "readability" is multiplied by the number of
> readers. Also usenet is less of a "real-time" medium than texts and
> chatrooms are.
>
I think there is a lot in what you say here. People often don't seem to
understand Usenet - they think in terms of posting a question and
getting an answer, rather than having a discussion for the benefit of
many. They also often fail to realise that newsgroup archives are an
important resource for the future - when you've solved a problem, and
post the answer here, it's available for others searching the archives.
Reply by David Brown●January 29, 20082008-01-29
Paul Keinanen wrote:
> On Tue, 29 Jan 2008 00:15:59 +0100, David Brown
> <david.brown@hesbynett.removethisbit.no> wrote:
>
>> However, I
>> don't really buy your idea that SMS-speak is saving costs. You don't
>> pay per letter for SMS messages (at least, I've never heard of such a
>> scheme) - you pay per message. SMS abbreviations are nothing more than
>> laziness.
>
> If someone is really posting questions using SMS messages, how is that
> person going to receive messages posted by other users ?
>
> If by SMS, that would imply that the sending a single message is very
> expensive but you can receive an unlimited amount SMS messages for
> free. Is there really such a service anywhere in the world ?
>
I don't think anyone is actually posting to Usenet via SMS (I'm sure
it's possible - after all, someone actually implemented RFC1149,
although they did not bother trying out Usenet). Stephen was suggesting
that a reason for people posting in SMS-speak is that they are used to
using SMS, and simply carry the same "language" over to Usenet.
Reply by Paul Keinanen●January 29, 20082008-01-29
On Tue, 29 Jan 2008 00:15:59 +0100, David Brown
<david.brown@hesbynett.removethisbit.no> wrote:
>However, I
>don't really buy your idea that SMS-speak is saving costs. You don't
>pay per letter for SMS messages (at least, I've never heard of such a
>scheme) - you pay per message. SMS abbreviations are nothing more than
>laziness.
If someone is really posting questions using SMS messages, how is that
person going to receive messages posted by other users ?
If by SMS, that would imply that the sending a single message is very
expensive but you can receive an unlimited amount SMS messages for
free. Is there really such a service anywhere in the world ?
Paul
Reply by Tom●January 28, 20082008-01-28
In article <b140416d-2767-40e2-b8f6-d3d8e91ea71f@e6g2000prf.googlegroups.com>, "aleemakhtar1@gmail.com" <aleemakhtar1@gmail.com> wrote:
>can i allocate dynamic memory in ISR ??
Yes, it's your CPU so you can do anything you want with it. You can can even
disable IRQs or dynamic memory altogether if you really want to.
> If yes wat shd be the
>precautions i need to take care ??
There are many, and this is by no means an exhaustive list but the first
percautions that come to mind are correct handling of the following scenarios:
- The allocation fails because there is no more dynamic memory available.
- The allocation takes too long and causes a subsequent IRQ to be missed.
- The IRQ occurs while the mainline is in the middle of allocating/freeing
dynamic memory and your memory manager is non re-entrant.
- A higher priority IRQ occurs and causes another ISR to start while this one
is in the middle of allocating memory.
Other percautions will depend on whether or not you are using a paged memory
architecture, and whether pages are being swapped to secondary storage, etc.
You also might want to search for "deferred procedure call"
--Tom.