Search icon CANCEL
Subscription
0
Cart icon
Cart
Close icon
You have no products in your basket yet
Save more on your purchases!
Savings automatically calculated. No voucher code required
Arrow left icon
All Products
Best Sellers
New Releases
Books
Videos
Audiobooks
Learning Hub
Newsletters
Free Learning
Arrow right icon
Arrow up icon
GO TO TOP
Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization

You're reading from  Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization

Product type Book
Published in Mar 2021
Publisher Packt
ISBN-13 9781801079518
Pages 452 pages
Edition 1st Edition
Languages
Author (1):
Kaiwan N. Billimoria Kaiwan N. Billimoria
Profile icon Kaiwan N. Billimoria
Toc

Table of Contents (11) Chapters close

Preface 1. Section 1: Character Device Driver Basics
2. Writing a Simple misc Character Device Driver 3. User-Kernel Communication Pathways 4. Working with Hardware I/O Memory 5. Handling Hardware Interrupts 6. Working with Kernel Timers, Threads, and Workqueues 7. Section 2: Delving Deeper
8. Kernel Synchronization - Part 1 9. Kernel Synchronization - Part 2 10. Other Books You May Enjoy

Our simple kernel timer module running it

Now, let's test our kernel timer module. On our x86_64 Ubuntu VM, we will use our lkm convenience script to load up the kernel module. The following screenshot shows a partial view of this and the kernel log:

Figure 5.2 – A partial screenshot of running our timer_simple.ko kernel module

Study the dmesg (kernel log) output shown here. Since we've set the initial value of our private structure's data member to 3, the kernel timer expires three times (just as our logic demands). Check out the timestamps in the left-most column; you can see that the second timer expiry occurred at 4234.289334 (sec.us) and the third at 4234.737346; a quick subtraction reveals that the time difference is 448,012 microseconds; that is, about 448 milliseconds. This is reasonable since we asked for a 420 ms timeout (its a bit over that; the overheads of the printks do matter as well).

The PRINT_CTX() macro's...

lock icon The rest of the chapter is locked
Register for a free Packt account to unlock a world of extra content!
A free Packt account unlocks extra newsletters, articles, discounted offers, and much more. Start advancing your knowledge today.
Unlock this book and the full library FREE for 7 days
Get unlimited access to 7000+ expert-authored eBooks and videos courses covering every tech area you can think of
Renews at €14.99/month. Cancel anytime}