Re: [PATCH v2] mm/kmemleak: avoid soft lockup when scanning task stacks

[Oleg Nesterov <oleg@redhat.com>]

On 06/12, Catalin Marinas wrote:
>
> Yet anther variant below, untested. Basically, it follows the
> next_tgid() or task_seq_get_next() approach (we might as well move this
> to a separate function to avoid excessive indentation):
>
> 	if (kmemleak_stack_scan) {
> 		struct pid *pid;
> 		int nr = 1;
>
> 		do {
> 			struct task_struct *p = NULL;
>
> 			rcu_read_lock();
> 			pid = find_ge_pid(nr, &init_pid_ns);
> 			if (pid) {
> 				nr = pid_nr(pid) + 1;
> 				p = pid_task(pid, PIDTYPE_PID);
> 				if (p)
> 					get_task_struct(p);
> 			}
> 			rcu_read_unlock();

I don't think we need get_task_struct(p), the code above can just do

				if (p)
					stack = try_get_task_stack(p);

Oleg.