On 08/19/2014 09:36 AM, Chai Wen wrote: > On 08/19/2014 04:38 AM, Don Zickus wrote: > >> On Mon, Aug 18, 2014 at 09:02:00PM +0200, Ingo Molnar wrote: >>> >>> * Don Zickus <dzickus@xxxxxxxxxx> wrote: >>> >>>>>>> So I agree with the motivation of this improvement, but >>>>>>> is this implementation namespace-safe? >>>>>> >>>>>> What namespace are you worried about colliding with? I >>>>>> thought softlockup_ would provide the safety?? Maybe I >>>>>> am missing something obvious. :-( >>>>> >>>>> I meant PID namespaces - a PID in itself isn't guaranteed >>>>> to be unique across the system. >>>> >>>> Ah, I don't think we thought about that. Is there a better >>>> way to do this? Is there a domain id or something that can >>>> be OR'd with the pid? >>> >>> What is always unique is the task pointer itself. We use pids >>> when we interface with user-space - but we don't really do that >>> here, right? >> >> No, I don't believe so. Ok, so saving 'current' and comparing that should >> be enough, correct? >> > > > I am not sure of the safety about using pid here with namespace. > But as to the pointer of process, is there a chance that we got a 'historical' > address saved in the 'softlockup_warn_pid(or address)_saved' and the current > hogging process happened to get the same task pointer address? > If it never happens, I think the comparing of address is ok. > Hi Ingo what do you think of Don's solution- 'comparing of task pointer' ? Anyway this is just an additional check about some very special cases, so I think the issue that I am concerned above is not a problem at all. And after learning some concepts about PID namespace, I think comparing of task pointer is reliable dealing with PID namespace here. And Don, If you want me to re-post this patch, please let me know that. thanks chai wen > thanks > chai wen > >> Cheers, >> Don >> . >> > > > -- Regards Chai Wen -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
