Re: [PATCH 5/6] kmod: Add new call_usermodehelper_timeout() API

[Oleg Nesterov <oleg@redhat.com>]

On 03/27, Oleg Nesterov wrote:
>
> On 03/26, Boaz Harrosh wrote:
> >
> >  int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
> >  {
> >  	DECLARE_COMPLETION_ONSTACK(done);
> > +	int wait_state;
> >  	int retval = 0;
> >
> >  	helper_lock();
> > @@ -540,19 +541,15 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
> >  	if (wait == UMH_NO_WAIT)	/* task has freed sub_info */
> >  		goto unlock;
> >
> > -	if (wait & UMH_KILLABLE) {
> > -		retval = wait_for_completion_killable(&done);
> > -		if (!retval)
> > -			goto wait_done;
> > -
> > +	wait_state = (wait & UMH_KILLABLE) ? TASK_KILLABLE : 0;
> > +	retval = wait_for_completion_timeout_state(&done, sub_info->timeout,
> > +						   wait_state);
> > +	if (unlikely(retval)) {
> >  		/* umh_complete() will see NULL and free sub_info */
> >  		if (xchg(&sub_info->complete, NULL))
> >  			goto unlock;
> > -		/* fallthrough, umh_complete() was already called */
> >  	}
> >
> > -	wait_for_completion(&done);
>
> at first glance this looks certainly wrong, or I misread the patch.
>
> We can't remove the "fallback to wait_for_completion" logic until
> you move the completion into subprocess_info (the next patch seems
> to do this).

Yes, I think this is true after I re-checked the code.



One more nit. With this patch call_usermodehelper_fns() does

	info = call_usermodehelper_setup(path, argv, envp, gfp_mask);

	call_usermodehelper_setfns(info, init, cleanup, data);

	info->timeout = timeout;

We have 2 (static!) helpers to initialize info, yet we initialize
->timeout by hand. Of course I do not blame this patch, but imho
this looks a bit messy and deserves another minor cleanup.

Oleg.