Summary
Good going! You've just completed the first of many techniques for debugging the kernel. Instrumentation, though deceptively simple, almost always proves to be a useful and powerful debugging technique.
In this chapter, you began by learning the basics regarding the ubiquitous kernel printk(), pr_*(), and dev_*() routines and macros. We then went into more detail about the specific use of these routines to help in debug situations and tips and tricks that will prove useful in debugging your (driver) modules... This included leveraging the kernel's ability to rate-limit printks, often a necessity on high-volume code paths.
The kernel's elegant and powerful dynamic debug framework was the highlight of this chapter. Here, you learned about it, and how to leverage it to be able to toggle your (and indeed the kernel's) debug prints even on production systems, with virtually no performance degradation when turned off.
We finished this chapter with a...
