Messages in this thread | | | Date | Thu, 22 Mar 2012 15:27:58 +0100 | From | Oleg Nesterov <> | Subject | Re: [RFC 4/4] {RFC} kmod.c: Add new call_usermodehelper_timeout() API |
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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@redhat.com> > 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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