Get interrupt counters like /proc/interrupts from code?

Question

Hi,

I may miss the obvious, but how/is it possible to retrieve interrupt counters for a specific interrupt without manually parsing /proc/interrupts from inside a C/C++ program?

Thanks in advance!

Best regards, Martin

Answer 1

On Linux, the text files in /proc are the canonical user-context interface for most of the information they provide. For better or worse, parsing that text file is the way to do it.

Answer 2

I did some quick checking and it doesn't appear this information is mirrored anywhere under /sys, nor are there any listed syscall numbers which look like it would allow access to this information, so the /proc file is probably the only place it is visible.

You should also be aware that the format is architecture and sometimes kernel configuration specific; the lines are produced by the function show_interrupts, which is usually defined in kernel/irq.c within each architecture subdirectory (eg arch/x86/kernel/irq.c, arch/s390/kernel/irq.c). So you'll probably have to be pretty careful with the parsing (or alternately whitelist the check to only parse the file on architectures you've been able to test it on).

Answer 3

/proc/interrupts and /proc/stat obtain their data by calling the kernel function kstat_irqs_cpu(). The only way to read it without opening the files in /proc is, I think, writing your own kernel driver which would call the same function and return the results via ioctl() or some other way.