Iterating over the task list III – the code

Now let's see the (relevant) code of our thrd_showall kernel module:

// ch6/foreach/thrd_showall/thrd_showall.c */
[...]
#include <linux/sched.h>     /* current */
#include <linux/version.h>
#if LINUX_VERSION_CODE > KERNEL_VERSION(4, 10, 0)
#include <linux/sched/signal.h>
#endif
[...]

static int showthrds(void)
{
    struct task_struct *g, *t;      // 'g' : process ptr; 't': thread ptr
    [...]
#if 0
    /* the tasklist_lock reader-writer spinlock for the task list 'should'
     * be used here, but, it's not exported, hence unavailable to our 
     * kernel module */
    read_lock(&tasklist_lock);
#endif
    disp_idle_thread();

A few points to note regarding the preceding code:

• We use the LINUX_VERSION_CODE() macro to conditionally include a header, as required.
• Please ignore the locking work for now – usage (or the lack thereof) of the tasklist_lock() ...