Linux Kernel generic question (procedure queue)

Linux Kernel generic question (procedure queue)

[None Atall]

 Hello everybody,
 Is it possible to insert
a specific procedure (among with it's args) to the
kernel scheduler? I know that we can just call
schedule(); when we wait for an asychronus input or
we can even insert an interrupt to the kernel queue,
but is it possible to queue a procedure?
 Just for understanding the problem better, I have
a function write_buff that calls write_byte.
Write_byte
function uses PPC gpio for implementing something like
an SPI interface. When we write a big file (e.x 1M),
the system will not respond to anything until the
transfer is done. I inserted "schedule();" every time
the write_byte is called so that the system will
accually perform some other tasks. So my question is
if I could insert write_byte function to the scheduler
queue in such a way to prevent this problem.

                           Thanks in advance
                                  Dimitrios.

=====
------------------------------------------------------------
-Dhmhtrios Meidanis
-Degree in Mathematics, University of the Aegean.
-Master in Computer Architecture and Digital
 Systems, University of Crete.
 Greece.
------------------------------------------------------------


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Re: Linux Kernel generic question (procedure queue)

[Der Herr Hofrat]

>
>  Hello everybody,
>  Is it possible to insert
> a specific procedure (among with it's args) to the
> kernel scheduler? I know that we can just call
> schedule(); when we wait for an asychronus input or
> we can even insert an interrupt to the kernel queue,
> but is it possible to queue a procedure?

not realy the same effect but you could use a tasklet and call
tasklet_schedule(&write_byte_tasklet);
where the  write_bytee tasklet is nothing else but your write_byte function.

>  Just for understanding the problem better, I have
> a function write_buff that calls write_byte.
> Write_byte
> function uses PPC gpio for implementing something like
> an SPI interface. When we write a big file (e.x 1M),
> the system will not respond to anything until the
> transfer is done. I inserted "schedule();" every time
> the write_byte is called so that the system will
> accually perform some other tasks. So my question is
> if I could insert write_byte function to the scheduler
> queue in such a way to prevent this problem.

hofrat

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Re: Linux Kernel generic question (procedure queue)

[Vladimir Gurevich]

Hello Dimitrios,

There are a number of mechanisms in the Linux kernel
that allow you to schedule execution of some code at
a later time as well as to wait for something to
happen. Wait queues, tasklets, kernel timers are
the most important ones.

The problem is that to choose and to use them properly
you need to know how they work, how they differ from
each other and how they are supposed to be used (because
they can easily be misused and this usually leads to
disasters). It is definitely not possible to go over
it in an email, so I'd refer you to the excellent book
by Rubini and Corbet that discusses all these (and many
other) issues.

As for your question goes, there are two main mechanisms
you should look at:
   -- wait queues are usually used in drivers to
      return the control to the scheduler until the
      HW operation is finished. Look for
      interruptible_sleep_on() and wake_up_interruptible()

   -- I don't know exactly how do you plan to use your GPIOs
      to implement SPI, but if you plan to use interrupts
      you might be better of by using the write_buff()
      function to fill your driver's buffer, submit
      the first byte to the device via write_byte() and then go
      to sleep on a wait queue. Then use the interrupt handler
      to drain the buffer and wake up the process after
      you have finished sending data (you can also use kernel
      timers to wake it up in case there was a timeout).

But my main advise will be to get yourself a copy of
"Linux Device Drivers" by Rubini and Corbet first.

Happy hacking,
Vladimir Gurevich


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Re: Linux Kernel generic question (procedure queue)

[Steven Rothweiler]

>
> But my main advice will be to get yourself a copy of
> "Linux Device Drivers" by Rubini and Corbet first.
>

After purchasing the book on Vladmir's great advice, I realized
that I could download the PDF version of the entire book at
http://www.xml.com/ldd/chapter/book/bookindexpdf.html .

Is there any reason the PDF version of this book is (seemingly)
free?  I don't feel bad about downloading it, since I've already
purchased the book, but I think it's not fair to the authors.

Unless, of course, they *want* to give it away...
--
STeve

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Re: Linux Kernel generic question (procedure queue)

[Gary Thomas]

On Tue, 2003-05-06 at 06:40, Steven Rothweiler wrote:
> >
> > But my main advice will be to get yourself a copy of
> > "Linux Device Drivers" by Rubini and Corbet first.
> >
>
> After purchasing the book on Vladmir's great advice, I realized
> that I could download the PDF version of the entire book at
> http://www.xml.com/ldd/chapter/book/bookindexpdf.html .
>
> Is there any reason the PDF version of this book is (seemingly)
> free?  I don't feel bad about downloading it, since I've already
> purchased the book, but I think it's not fair to the authors.
>
> Unless, of course, they *want* to give it away...

Read page 'xvii':
  Online Version and License
  The authors have chosen to make this book freely available under
  the GNU Free Documentation License, version 1.1.

--
Gary Thomas <gary@mlbassoc.com>
MLB Associates


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Re: Linux Kernel generic question (procedure queue)

[Steven Rothweiler]

Thanks, Gary, I didn't know there was such a thing...

>
> Read page 'xvii':
>   Online Version and License
>   The authors have chosen to make this book freely available under
>   the GNU Free Documentation License, version 1.1.
>

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