OSDev.org

Posted: **Fri Nov 01, 2019 11:36 pm**

I am working with the do_exit() function，

int
do_exit(int error_code) {
    if (current == idleproc) {
        panic("idleproc exit.\n");
    }
    if (current == initproc) {
        panic("initproc exit.\n");
    }
    
    struct mm_struct *mm = current->mm;
    if (mm != NULL) {
        lcr3(boot_cr3);
        if (mm_count_dec(mm) == 0) {
            exit_mmap(mm);
            put_pgdir(mm);
            mm_destroy(mm);
        }
        current->mm = NULL;
    }
    current->state = PROC_ZOMBIE;
    current->exit_code = error_code;
    
    bool intr_flag;
    struct proc_struct *proc;
    local_intr_save(intr_flag);
    {
        proc = current->parent;
        if (proc->wait_state == WT_CHILD) {
            wakeup_proc(proc);
        }
        while (current->cptr != NULL) {
            proc = current->cptr;
            current->cptr = proc->optr;
    
            proc->yptr = NULL;
            if ((proc->optr = initproc->cptr) != NULL) {
                initproc->cptr->yptr = proc;
            }
            proc->parent = initproc;
            initproc->cptr = proc;
            if (proc->state == PROC_ZOMBIE) {
                if (initproc->wait_state == WT_CHILD) {
                    wakeup_proc(initproc);
                }
            }
        }
    }
    local_intr_restore(intr_flag);
    
    schedule();
    panic("do_exit will not return!! %d.\n", current->pid);
}

My question is why the schedule function will not return?????
It always returned in my do_exit function, and prints the panic line. so what's up????

Many thanks, I solved this problem by using switch_to directly.

switch_to(&_current->context,&current->context);

Posted: **Sat Nov 02, 2019 1:09 am**

The schedule() function returns when the process has been scheduled. A process that has exited should not be scheduled.

Posted: **Sat Nov 02, 2019 1:36 am**

Octocontrabass wrote:The schedule() function returns when the process has been scheduled. A process that has exited should not be scheduled.

Thanks for your reply. I do not known how the schedule works within the exit function.
the panic says it will not return, but in my program it always returns at the time that I want it exit.

Posted: **Sat Nov 02, 2019 2:33 am**

Then there is something wrong with your schedule function. (Is it your function or are you cut and pasting someone else's code?)

Posted: **Sat Nov 02, 2019 3:04 am**

You need to make sure that once the thread exits, it gets removed from the running queue or else it will just be rescheduled.
Once removed from the running queue, place it on some sort of a "dead queue" and have a special thread that picks up the dead threads and removes their metadata.

Posted: **Sat Nov 02, 2019 3:11 am**

Isn't that what

Code: Select all

current->state = PROC_ZOMBIE

does? (Providing the unknown schedule() function handles the state correctly.)

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[solved]do_exit function schedule will return

[solved]do_exit function schedule will return

Re: do_exit function schedule will return

Re: do_exit function schedule will return

Re: do_exit function schedule will return

Re: do_exit function schedule will return

Re: do_exit function schedule will return