Messages in this thread | | | Subject | Re: [RFC 4/4] {RFC} kmod.c: Add new call_usermodehelper_timeout()API | From | Tetsuo Handa <> | Date | Thu, 22 Mar 2012 20:48:31 +0900 |
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Boaz Harrosh wrote: > > @@ -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;
This patch is incomplete because sub_info->complete refers on-stack variable. Returning without waiting for completion will overwrite stack memory later.
> Anyway I thought that we are not > suppose to use xhcg() since it is not portable to all ARCHs. ;-)
Don't worry. xchg() is used in many places. ;-) http://tomoyo.sourceforge.jp/cgi-bin/lxr/ident?i=xchg
> But basically we both need support for the waiter to be returning before > the child has completed.
I think basically we should not give up unless fatal events (e.g. SIGKILL or TIF_MEMDIE) occur. Thus, I feel UMH_KILLABLE is sufficient.
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