Guenter Roeck <li...@roeck-us.net> writes:
> On Thu, May 11, 2017 at 04:25:23PM -0500, Eric W. Biederman wrote:
>> Guenter Roeck <li...@roeck-us.net> writes:
>> > As an add-on to my previous mail: I added a function to count
>> > the number of threads in the pid namespace, using next_pidmap().
>> > Even though nr_hashed == 2, only the hanging thread is still
>> > present.
>>
>> For your testcase? I suspect you copied the code from
>> zap_pid_ns_processes and skipped pid 1. It is going to be pid 1 that is
>> calling zap_pid_ns_processes.
>>
>
> Almost. Something along the line of
>
> count = 0;
> nr = next_pidmap(pid_ns, 0);
> while (nr > 0) {
> count++;
> nr = next_pidmap(pid_ns, nr);
> }
>
> only I also call sched_show_task() for each thread, and the only
> one printed is the one that hangs in zap_pid_ns_processes().
The function sched_show_task() does:
if (!try_get_task_stack(p))
return;
Which won't work on a zombie who has already released it's stack.
Which is exactly what child2 should be at that point.
Eric
