Question

I am writing a system call which should store some info for the process that called it,for its oldest children process and for its oldest sibling process.

I know that the information i want is kept in sched.h in the task_struct and i have managed to store info for the process that called the system call from the fields i wanted from the struct task_struct.

My problem with the oldest children and the oldest sibling is that in the struct task_struct there are two lists which have all the children and all the siblings (if i have understood right).I assume that i have to iterate through those lists and find the last element.But if i find the last element on those lists how can i access their task_struct?

Thank you in advance.

Answer 1

task_struct has pointers to youngest child, younger sibling and older sibling. These pointers points to the respective task_struct s . *p_cptr, *p_ysptr, *p_osptr in task_struct points to youngest child, younger sibling and older sibling respectively. For example current->p_cptr simply points to the youngest child,where current is the pointer to the task_struct of the process currently running.