?
Solved

looping

Posted on 2012-04-04
9
Medium Priority
?
411 Views
Last Modified: 2012-04-06
Hi I am writing a kernel module.

I need a continuous loop that will look for tcp traffic and read from skb to store each source ip address from ip_hdr->saddr into an array

I can get it to read packets one at a time but I need it to loop, but when I try to implement a continuous loop the system crashes/hangs.

Can anyone offer any advice/possible fixes?

Cheers
0
Comment
Question by:codey-06
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 5
  • 3
9 Comments
 
LVL 8

Expert Comment

by:Anthony2000
ID: 37805980
Here is an example of using a thread in the kernel module.

http://www.scs.ch/~frey/linux/kernelthreads.html

I think your problem might be that your loop is running and using all available kernel/process time. Thus, giving the result of maybe locking up your machine. Is that what is happening?
0
 

Author Comment

by:codey-06
ID: 37806049
Hi yes you are correct, the loop is using up all the kernel resources.  Is there a quick fix?
0
 
LVL 8

Expert Comment

by:Anthony2000
ID: 37806134
Have you tried some kind of sleep (I cannot remember the API call). This may give the OS and other processes time to run.
0
Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 

Author Comment

by:codey-06
ID: 37806580
Thank you. If anyone could offer a bit more help it would be very much appreciated?
0
 
LVL 35

Assisted Solution

by:sarabande
sarabande earned 1000 total points
ID: 37810387
if you added an infinite or time consuming loop into a kernel module that was needed by others you were blocking all those activities dependent on those calls and the system hangs and some processes would crash or fail because of timeouts. so, the first thing you need is to start a thread where you would add the loop and the normal kernel function could proceed. of course you may not create a new thread for every call but use one thread for all requests. in the thread you would run an infinite loop and at end of loop you should add a call to usleep which would make that the thread waits a little and so other processes and threads could be scheduled by the os. the usleep takes microseconds as argument and i would use at least 1000 (1 millisecond) to not slow down the rest of the system cause that also would depend on your other actions made in the loop.

Sara
0
 
LVL 8

Assisted Solution

by:Anthony2000
Anthony2000 earned 1000 total points
ID: 37814353
Here is another related article.

http://www.linuxjournal.com/article/8144
0
 
LVL 8

Accepted Solution

by:
Anthony2000 earned 1000 total points
ID: 37814357
Also, if you are not familiar with this book, its also a good reference.

http://lwn.net/Kernel/LDD3/
0
 
LVL 8

Expert Comment

by:Anthony2000
ID: 37814383
Also, take a look at the functions:
set_current_state(TASK_INTERRUPTIBLE);
schedule_timeout (signed long timeout);

See chapter 7 of the book link I provided.
0
 

Author Closing Comment

by:codey-06
ID: 37815593
Brilliant thank you
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

When we want to run, execute or repeat a statement multiple times, a loop is necessary. This article covers the two types of loops in Python: the while loop and the for loop.
Examines three attack vectors, specifically, the different types of malware used in malicious attacks, web application attacks, and finally, network based attacks.  Concludes by examining the means of securing and protecting critical systems and inf…
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.
This video will show you how to get GIT to work in Eclipse.   It will walk you through how to install the EGit plugin in eclipse and how to checkout an existing repository.
Suggested Courses

770 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question