How do you get the set of available CPUs in a Linux kernel module?

Question

I would like to start one kernel thread per CPU with kthread_create()/kthread_bind(). However, I can't for the life of me figure out how to query the number of available CPUs. I did find the CPU_SET man page but that didn't help either.

Any thoughts?

Answer 1

You can use num_online_cpus() to get the number of available cpus. This may be different from things like nr_cpu_ids if the system was booted using a maxcpus setting that is not the same as the number of cpus in the system.

Answer 2

See following link, cpuinfo.c, proc.c, may be help you. And at line 143, you can use two functions for traversing cpus, cpumask_first, cpumask_next. I think, by try and error, you can find the solutions.