Re: [PATCH v2 1/2] pid: Replace pid bitmap implementation with IDR API

Gargi Sharma
2017-09-27T15:07:02Z

On Wed, Sep 27, 2017 at 7:36 PM, Oleg Nesterov <oleg@redhat.com> wrote:
> On 09/27, Rik van Riel wrote:
>>
>> > @@ -240,17 +230,18 @@ void zap_pid_ns_processes(struct pid_namespace
>> > *pid_ns)
>> > *
>> > */
>> > read_lock(&tasklist_lock);
>> > - nr = next_pidmap(pid_ns, 1);
>> > - while (nr > 0) {
>> > - rcu_read_lock();
>> > + pid = idr_get_next(&pid_ns->idr, &nr);
>> > + while (pid) {
>> >
>> > - task = pid_task(find_vpid(nr), PIDTYPE_PID);
>> > - if (task && !__fatal_signal_pending(task))
>> > - send_sig_info(SIGKILL, SEND_SIG_FORCED,
>> > task);
>> > + rcu_read_lock();
>> >
>> > + idr_for_each_entry_continue(&pid_ns->idr, pid, nr) {
>> > + task = pid_task(pid, PIDTYPE_PID);
>> > + if (task && !__fatal_signal_pending(task))
>> > + send_sig_info(SIGKILL,
>> > SEND_SIG_FORCED, task);
>> > + }
>> > rcu_read_unlock();
>> >
>> > - nr = next_pidmap(pid_ns, nr);
>> > }
>> > read_unlock(&tasklist_lock);
>> >
>>
>> I believe we should be fine with just the idr_for_each_entry_continue()
>> surrounding the loop,
>
> Yes, and please move "nr = 2" close to idr_for_each_entry_continue() to
> make it clear why do we use _continue (to skip nr == 1).
>
>> and not need the while (pid) around that.
>>
>> That should still iterate over all the pids in the namespace, and
>> simplify the code even more.
>
> And make this patch correct ;)
>
> because currently it is wrong, zap_pid_ns_processes() won't kill the pid
> returned by the first idr_get_next().
Yes, I missed this. I can simply remove the idr_get_next() before the
idr_for_each_continue and that will take care of it.

Thanks!
Gargi
>
> Oleg.
>