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toby
*nix forums addict
Joined: 01 Jul 2005
Posts: 87
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 Posted: Thu Feb 16, 2006 5:18 am Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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James Harris wrote:
| Quote: | "Chris Thompson" <cet1@cus.cam.ac.uk> wrote in message
news:dsqct8$q1r$1@gemini.csx.cam.ac.uk...
In article <dsl62m$1hvr$1@gavrilo.mtu.ru>,
Maxim S. Shatskih <maxim@storagecraft.com> wrote:
I'm not sure what 'reentrant' means here. AFAIK a program code
segment
is usually reentrant in that it cannot normally be written to - so
I'm against the whole word of ''reentrant". It is, in fact, something
from the
old time of MS-DOS add-ons which tried to do multitasking from this
pathetic
OS.
MS-DOS? That's practically yesterday! We were talking about
"reeentrant" and
"serially reusable" load modules back in OS/360, and it probably
wasn't a
new term then.
That's where I first came across the term. It was a long time ago. IIRC
it would apply to any module that did not modify part of itself.
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Before stacks became an architectural commonplace, subroutine linkage
conventions (typically of the 'self-modifying' type, such as storing
the link address in a fixed location[1]) often precluded re-entrancy
and recursion by default.
As other posters point out, a stack answers both problems by providing
storage for state and return link that is local to any activation.
[1] e.g. http://www.cs.clemson.edu/~mark/subroutines/pdp8.html |
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toby
*nix forums addict
Joined: 01 Jul 2005
Posts: 87
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| Posted: Thu Feb 16, 2006 5:17 am Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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James Harris wrote:
| Quote: | "Chris Thompson" <cet1@cus.cam.ac.uk> wrote in message
news:dsqct8$q1r$1@gemini.csx.cam.ac.uk...
In article <dsl62m$1hvr$1@gavrilo.mtu.ru>,
Maxim S. Shatskih <maxim@storagecraft.com> wrote:
I'm not sure what 'reentrant' means here. AFAIK a program code
segment
is usually reentrant in that it cannot normally be written to - so
I'm against the whole word of ''reentrant". It is, in fact, something
from the
old time of MS-DOS add-ons which tried to do multitasking from this
pathetic
OS.
MS-DOS? That's practically yesterday! We were talking about
"reeentrant" and
"serially reusable" load modules back in OS/360, and it probably
wasn't a
new term then.
That's where I first came across the term. It was a long time ago. IIRC
it would apply to any module that did not modify part of itself.
|
Before stacks became an architectural commonplace, subroutine linkage
conventions (typically of the 'self-modifying' type, such as storing
the link address in a fixed location[1]) often precluded re-entrancy
and recursion by default.
As other posters point out, a stack answers both problems by providing
storage for state and return link that is local to any activation.
[1] e.g. http://www.cs.clemson.edu/~mark/subroutines/pdp8.html |
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toby
*nix forums addict
Joined: 01 Jul 2005
Posts: 87
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| Posted: Thu Feb 16, 2006 5:07 am Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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James Harris wrote:
| Quote: | "Chris Thompson" <cet1@cus.cam.ac.uk> wrote in message
news:dsqct8$q1r$1@gemini.csx.cam.ac.uk...
In article <dsl62m$1hvr$1@gavrilo.mtu.ru>,
Maxim S. Shatskih <maxim@storagecraft.com> wrote:
I'm not sure what 'reentrant' means here. AFAIK a program code
segment
is usually reentrant in that it cannot normally be written to - so
I'm against the whole word of ''reentrant". It is, in fact, something
from the
old time of MS-DOS add-ons which tried to do multitasking from this
pathetic
OS.
MS-DOS? That's practically yesterday! We were talking about
"reeentrant" and
"serially reusable" load modules back in OS/360, and it probably
wasn't a
new term then.
That's where I first came across the term. It was a long time ago. IIRC
it would apply to any module that did not modify part of itself.
|
Before stacks became commonplace, architectural subroutine linkage
conventions (typically of the 'self-modifying' type, such as storing
the link address in a fixed location[1]) often precluded re-entrancy
and recursion except through explicit emulation of a stack.
[1] e.g. http://www.cs.clemson.edu/~mark/subroutines/pdp8.html |
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toby
*nix forums addict
Joined: 01 Jul 2005
Posts: 87
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| Posted: Thu Feb 16, 2006 4:37 am Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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Matthias Bethke wrote:
| Quote: | begin followup to Paul Barker in comp.unix.programmer:
In linux (at least in my kernel) the folder "block" at the
root of the source tree contains all the generic block device stuff.
There may also be some good docs included with the kernel source.
There's a pretty good book by O'Reilly on Linux device drivers from
kernel 2.0 to 2.4, available on dead trees as well as free hypertext:
http://www.xml.com/ldd/chapter/book/
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The 3rd edition covers 2.6: http://lwn.net/Kernel/LDD3/
| Quote: |
cheers!
Matthias
--
end |
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Andrew Gabriel
*nix forums Guru
Joined: 19 Feb 2005
Posts: 454
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| Posted: Wed Feb 15, 2006 11:47 pm Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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In article <43F3B5B7.3080400@acm.org>,
Nick Roberts <nick.roberts@acm.org> writes:
| Quote: |
I am not an expert on pthreads, but my impression is that this facility
is really rather limited. I have heard that you cannot use the semaphore
facility without running as root, and that you are limited to 32 semaphores.
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That might be a feature of some rather sad (and probably
not standards conforming) implementation, but it's certainly
not inherent in pthreads.
--
Andrew Gabriel |
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Maxim S. Shatskih
*nix forums addict
Joined: 02 Apr 2005
Posts: 55
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| Posted: Wed Feb 15, 2006 11:21 pm Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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| Quote: | do you mean situations that might be considered 'overkill' (e.g. a video
game where every moving object has a thread, so requiring hundreds or
thousands of threads)?
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I mean overkill. For instance, using thread instead of the good old nonblocking
socket :)
| Quote: | While I have the attention of Windows expert, I'd also like to ask about
the Win32 memory model.
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Very similar to UNIX one. The kernel even supports fork(), which is used in
Microsoft Interix (UNIX emulation layer for Windows, rather rich).
| Quote: | How should a full (generational) garbage collection scheme be
approached?
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This is .NET, and not Windows. The details of .NET garbage collector can be
found on msdn.microsoft.com - just google for "CLR garbage collector" or such.
| Quote: | reached. Can this be done under Win32?
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Yes it can. No my area of expertise though (it is .NET), but well-documented.
--
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
maxim@storagecraft.com
http://www.storagecraft.com |
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Nick Roberts
*nix forums beginner
Joined: 12 Feb 2006
Posts: 5
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| Posted: Wed Feb 15, 2006 11:14 pm Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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Maxim S. Shatskih wrote:
| Quote: | I'm surprised by your answer. Can you _name the exact Win32 API routines by
Microsoft_ which do not support multithreading?
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Well, no I cannot, and I have to concede defeat as such :-)
| Quote: | Stupid ancient UNIXen - do not. Good UNIXen - do, and have pthreads
implementation mapped to real kernel threads (like modern Linux does).
|
I am not an expert on pthreads, but my impression is that this facility
is really rather limited. I have heard that you cannot use the semaphore
facility without running as root, and that you are limited to 32 semaphores.
| Quote: | Depends on programmer skills in fact. I use threads in Windows in real-world
projects since around 1996, and never had any issues with them, so are the
people I was working with.
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You really never had /any/ issues with them?
| Quote: | Abusing threads (using a thread when there is
no real need in it) - yes, this is a reality 
|
I'm interested in this point. When you say "using a thread when there is
no real need", do you mean something really daft (e.g. thread B cannot
start any of its work until thread A has completed all of its work) or
do you mean situations that might be considered 'overkill' (e.g. a video
game where every moving object has a thread, so requiring hundreds or
thousands of threads)?
I'm curious about this, because there are programming languages that
could be implemented in a way that tends to use lots of threads, even
when sometimes they are not really necessary. For example, a (modified)
Smalltalk implementation might implement every object as a thread, apart
from some optimisation for primitive operations.
While I have the attention of Windows expert, I'd also like to ask about
the Win32 memory model. I have always found it confusing as to which
parts of the map correspond to what, and how efficient memory management
should be achieved (at the machine code level, not C).
How should a full (generational) garbage collection scheme be
approached? Remember that full GC requires that blocks can be moved
around in memory at any time (to make a contiguous space for a new
allocation). It has to be thread-safe, and it has to be able to cope
with lots of small blocks mixed with a few large blocks. It must be 100%
non-leaking, and it must behave gracefully when memory limitations are
reached. Can this be done under Win32?
Sorry to go off topic here, but I'm eager to take the opportunity!
Thanks in advance.
--
Nick Roberts |
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50295@web.de
*nix forums beginner
Joined: 09 Feb 2005
Posts: 32
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| Posted: Wed Feb 15, 2006 2:34 pm Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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Brian Inglis wrote:
| Quote: | No, they would be device commands and responses.
Some organizations (IBM at least) consider any low level code below
the architectural interface (e.g. on an ethernet card or disk drive)
to be microcode, as opposed to the more widespread view of microcode
as hardwired code used to execute architectural instructions within a
CPU.
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Thanks Brian. I'm now of the view that device driver commands to the
controller are not microcode -- at least in the case of memory-mapped
IO, since it by definition does not distinguish between controller
registers and memory locations. |
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Brian Inglis
*nix forums beginner
Joined: 16 Feb 2005
Posts: 22
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| Posted: Wed Feb 15, 2006 11:55 am Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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On 14 Feb 2006 18:07:26 -0800 in comp.unix.internals, "Olumide"
<50295@web.de> wrote:
| Quote: | Rather than start a new thread, I though it better to add a question
here since the thread has already gone a bit OT alteady  (by the
way, thanks to everyone for the naswers).
Just a minor point: I was pondering on the nature of the "conversation"
(or should I say instructions) the driver has with the controller. Is
it correct to term these commands microcode?
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No, they would be device commands and responses.
Some organizations (IBM at least) consider any low level code below
the architectural interface (e.g. on an ethernet card or disk drive)
to be microcode, as opposed to the more widespread view of microcode
as hardwired code used to execute architectural instructions within a
CPU.
--
Thanks. Take care, Brian Inglis Calgary, Alberta, Canada
Brian.Inglis@CSi.com (Brian[dot]Inglis{at}SystematicSW[dot]ab[dot]ca)
fake address use address above to reply |
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50295@web.de
*nix forums beginner
Joined: 09 Feb 2005
Posts: 32
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| Posted: Wed Feb 15, 2006 2:07 am Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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Rather than start a new thread, I though it better to add a question
here since the thread has already gone a bit OT alteady (by the
way, thanks to everyone for the naswers).
Just a minor point: I was pondering on the nature of the "conversation"
(or should I say instructions) the driver has with the controller. Is
it correct to term these commands microcode?
Thanks,
- Olumide |
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Maxim S. Shatskih
*nix forums addict
Joined: 02 Apr 2005
Posts: 55
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| Posted: Wed Feb 15, 2006 1:02 am Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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| Quote: | There are a few, I think, but they're not what I'd call "Core APIs". The
ImageHlp library doesn't support multi-threading.
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Is it documented? Can I use apartment threading there - i.e. many threads, but
the entity is only used by the thread which created it?
--
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
maxim@storagecraft.com
http://www.storagecraft.com |
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James Harris
*nix forums beginner
Joined: 07 Jun 2005
Posts: 8
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| Posted: Tue Feb 14, 2006 10:04 pm Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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"Chris Thompson" <cet1@cus.cam.ac.uk> wrote in message
news:dsqct8$q1r$1@gemini.csx.cam.ac.uk...
| Quote: | In article <dsl62m$1hvr$1@gavrilo.mtu.ru>,
Maxim S. Shatskih <maxim@storagecraft.com> wrote:
I'm not sure what 'reentrant' means here. AFAIK a program code
segment
is usually reentrant in that it cannot normally be written to - so
I'm against the whole word of ''reentrant". It is, in fact, something
from the
old time of MS-DOS add-ons which tried to do multitasking from this
pathetic
OS.
MS-DOS? That's practically yesterday! We were talking about
"reeentrant" and
"serially reusable" load modules back in OS/360, and it probably
wasn't a
new term then.
|
That's where I first came across the term. It was a long time ago. IIRC
it would apply to any module that did not modify part of itself. |
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Nicholas Sherlock
*nix forums addict
Joined: 02 Mar 2005
Posts: 71
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| Posted: Mon Feb 13, 2006 11:31 pm Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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Maxim S. Shatskih wrote:
| Quote: | Please note where and when the Win32 APIs are not thread-safe.
Maxim, I get the impression that you know a lot about the Win32 API, so
I'm surprised by your question.
I'm surprised by your answer. Can you _name the exact Win32 API routines by
Microsoft_ which do not support multithreading?
|
There are a few, I think, but they're not what I'd call "Core APIs". The
ImageHlp library doesn't support multi-threading.
Cheers,
Nicholas Sherlock |
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Chris Thompson
*nix forums addict
Joined: 09 Mar 2005
Posts: 57
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| Posted: Mon Feb 13, 2006 4:42 pm Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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In article <dsl62m$1hvr$1@gavrilo.mtu.ru>,
Maxim S. Shatskih <maxim@storagecraft.com> wrote:
| Quote: | I'm not sure what 'reentrant' means here. AFAIK a program code segment
is usually reentrant in that it cannot normally be written to - so
I'm against the whole word of ''reentrant". It is, in fact, something from the
old time of MS-DOS add-ons which tried to do multitasking from this pathetic
OS.
|
MS-DOS? That's practically yesterday! We were talking about "reeentrant" and
"serially reusable" load modules back in OS/360, and it probably wasn't a
new term then.
--
Chris Thompson
Email: cet1 [at] cam.ac.uk |
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David Schwartz
*nix forums Guru
Joined: 26 Feb 2005
Posts: 914
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| Posted: Mon Feb 13, 2006 10:04 am Post subject:
Re: Are Device Drivers Reentrant -- or Daemons?
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"Alexei A. Frounze" <alexfru@chat.ru> wrote in message
news:45avjbF5pnlhU1@individual.net...
| Quote: | For this reason (together with the fact that Unix doesn't support
threading at all), most Windows programs remain single-threaded;
programmers acquired the impression that multi-threading under Windows
was such a black art it wasn't worth the effort.
I'm not sure about that. To me it seems that some (or many?) people either
don't think about multithreading and continue to write code in the style
of 70s or have hard time understanding the entire concept and its
implications w/o connection to a particular OS.
|
A lot of Windows software sucks because programmers are unwilling to
learn how to correctly program to the modern WIN32 API. The biggest problem
is people who do things the UNIX way with the minimal changes needed to get
it to seem to work on Windows. The second-biggest problem is people who
still do horrible things you had to do back on Windows 3.1 thinking that you
still have to.
Today, the WIN32 API is suprisingly clean and surprisingly friends to
threading. A lot of things you have to go out of your way to get even close
to right on pthreads are trivial to do on Windows. (Not that it doesn't have
its own problems, of course.)
Perhaps as more programmers start to write multi-threaded programs on
UNIXes (since it is now very stable on most UNIXes people still care about),
WIN32 will benefit. If nothing else, multi-core CPUs should force people to
multi-thread because you have to if you want to get what the hardware is
capable of.
DS |
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