On Tue, Aug 25, 2009 at 06:52:44PM +0200, Oleg Nesterov wrote:
...
> void exit_ptrace(struct task_struct *tracer)
> {
> - struct task_struct *p, *n;
> - LIST_HEAD(ptrace_dead);
> -
> - write_lock_irq(&tasklist_lock);
> - list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {
> - if (__ptrace_detach(tracer, p))
> - list_add(&p->ptrace_entry, &ptrace_dead);
> - }
> - write_unlock_irq(&tasklist_lock);
> + for (;;) {
> + struct task_struct *tracee = NULL;
>
> - BUG_ON(!list_empty(&tracer->ptraced));
> + read_lock(&tasklist_lock);
> + if (!list_empty(&tracer->ptraced)) {
> + tracee = list_first_entry(&tracer->ptraced,
> + struct task_struct, ptrace_entry);
> + get_task_struct(tracee);
> + }
> + read_unlock(&tasklist_lock);
> + if (!tracee)
> + break;
Can tracee be NULL? If so, get_task_struct() shouldn't be called
unconditionally above.
Ananth
