On 03/21, Boaz Harrosh wrote:
>
> > @@ -258,7 +262,8 @@ static void __call_usermodehelper(struct work_struct *work)
> >
> > switch (wait) {
> > case UMH_NO_WAIT:
> > - call_usermodehelper_freeinfo(sub_info);
> > + kref_put(&sub_info->kref, call_usermodehelper_freeinfo);
> > + kref_put(&sub_info->kref, call_usermodehelper_freeinfo);
> > break;
This doesn't look very nice. If you add the refcounting, it should be
consistent. Imho it is better to change call_usermodehelper_exec() so
that UMH_NO_WAIT does kref_put() too. Just s/goto unlock/goto out/ afaics.
> > @@ -452,22 +459,27 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info,
> >
> > sub_info->complete = &done;
> > sub_info->wait = wait;
> > + if (!sub_info->wait_timeout)
> > + sub_info->wait_timeout = MAX_SCHEDULE_TIMEOUT;
> >
> > + /* Balanced in __call_usermodehelper or wait_for_helper */
> > + kref_get(&sub_info->kref);
> > queue_work(khelper_wq, &sub_info->work);
> > if (wait == UMH_NO_WAIT) /* task has freed sub_info */
> > goto unlock;
> > - wait_for_completion(&done);
> > - retval = sub_info->retval;
> > -
> > + if (likely(wait_for_completion_timeout(&done, sub_info->wait_timeout)))
> > + retval = sub_info->retval;
> > + else
> > + retval = -ETIMEDOUT;
> > out:
> > - call_usermodehelper_freeinfo(sub_info);
> > + kref_put(&sub_info->kref, call_usermodehelper_freeinfo);
> > unlock:
> > helper_unlock();
> > return retval;
> > }
This looks obviously wrong. You also need to move *sub_info->complete
into subprocess_info.
> Author: Oleg Nesterov <oleg@xxxxxxxxxx>
> Date: Wed Mar 21 10:57:41 2012 +1100
>
> usermodehelper: implement UMH_KILLABLE
>
> Implement UMH_KILLABLE, should be used along with UMH_WAIT_EXEC/PROC. The
> caller must ensure that subprocess_info->path/etc can not go away until
> call_usermodehelper_freeinfo().
> ...
>
> I think that my patch above does a much better/cleaner lifetime management of the
> subprocess_info struct, with the use of a kref.
This is subjective, you know ;) I specially tried to avoid the
refcounting.
In any case. I do not know why do we need timeout, but this is
orthogonal to KILLABLE. Please redo your patches on top of -mm
tree? Please note that in this case the change becomes trivial.
And please explain the use-case for the new API.
> Anyway I thought that we are not
> suppose to use xhcg() since it is not portable to all ARCHs. ;-)
Hmm. For example, exit_mm() does xchg().
Oleg.
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