How to finding all runnable processes - linux

Question

I'm learning about the scheduler and trying to print all runnable proceeses. So I have written a kernel module that uses the for_each_process macro to iterate over all processes, and prints the ones at "runnable" state. But this seems like a stupid (and inefficient) way of doing this. So I thought about getting a reference to all running queues and use their Red-Black-Tree to go over the runnable processes, but couldn't find a way to do this.
I have found out that there is a list of sched_classs for each CPU which are stop_sched_class->rt_sched_class->fair_sched_class->idle_sched_class and each one of them has it's own running queue. But couldn't find a way to reach them all.
I have used the module that uses the tasks_timeline to find all runnable processes, to print the address of the running queues - seems I have 3 running queues (while having only two processors).
The module:
#include <linux/module.h> /* Needed by all modules */
#include <linux/kernel.h> /* Needed for KERN_INFO */
#include <linux/sched.h>
MODULE_LICENSE("GPL");
struct cfs_rq {
struct load_weight load;
unsigned int nr_running, h_nr_running;
};
void printList(void){
int count;
struct task_struct * tsk;
count = 0;
for_each_process(tsk){
if(tsk->state)
continue;
printk("pid: %d rq: %p (%d)\n", tsk->pid, tsk->se.cfs_rq, tsk->se.cfs_rq->nr_running);
count++;
}
printk("count is: %d\n", count);
}
int init_module(void)
{
printList();
return 0;
}
void cleanup_module(void)
{
printk(KERN_INFO "Goodbye world proc.\n");
}
The output:
[ 8215.627038] pid: 9147 ffff88007bbe9200 (3)
[ 8215.627043] pid: 9148 ffff8800369b0200 (2)
[ 8215.627045] pid: 9149 ffff8800369b0200 (2)
[ 8215.627047] pid: 9150 ffff88007bbe9200 (3)
[ 8215.627049] pid: 9151 ffff88007bbe9200 (3)
[ 8215.627051] pid: 9154 ffff8800a46d4600 (1)
[ 8215.627053] count is: 6
[ 8215.653741] Goodbye world proc.
About the computer:
$ uname -a
Linux k 3.13.0-39-generic #66-Ubuntu SMP Tue Oct 28 13:30:27 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
$ cat /proc/cpuinfo | grep 'processor' | wc -l
2
So my questions are:
How can I print all runnable processes in a nicer way?
How are running queues made and managed?
Are the running queues somehow linked each other? (How?)

Answer 1

$ps -A -l and find the instance where both the process state (R) and the Process Flags (1) are as mentioned.

Answer 2

You can try this below cmd.
Sample output.
127:~$ ps -A -l | grep -e R -e D
F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD
1 S 0 1367 2 0 80 0 - 0 - ? 00:00:01 SEPDRV_ABNORMAL
4 R 1000 2634 2569 2 80 0 - 794239 - ? 00:25:06 Web Content
1 D 0 20091 2 0 80 0 - 0 - ? 00:00:00 kworker/3:2
4 R 1000 21077 9361 0 80 0 - 7229 - pts/17 00:00:00 ps