Messages in this thread | | | Date | Mon, 10 Dec 2012 11:48:13 -0500 | From | Don Zickus <> | Subject | Re: [RFC][PATCH] pstore: Skip spinlock when just one cpu is online |
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On Fri, Dec 07, 2012 at 11:43:03PM +0000, Seiji Aguchi wrote: > > Can all these things really happen (did you run into this problem on a real system?). Or is this just a theoretical problem. Ugly (but > > practical) hacks might be OK to solve real problems. > > It is a theoretical problem right now. > But it is a timing issue and there is a possibility to happen actually. > > > But do we really want them to fix problems that actually never happen? > > If we find a problem (even if it is theoretical), we can't say "It actually never happen.". > > I have some reasons to submit this patch before reproducing actually. > > 1) > It is too late if we fix a problem after it actually happened in case where we apply Linux, including pstore, > to mission critical systems, because the failure of those systems has a great impact on a whole society. > Customers in this area ask us to fix a problem as soon as possible. > On the other hand, this kind of timing issue is hard to reproduce. > So, our support service engineers often work all night to reproduce it. > It is a nightmare for us. > > If we can fix it with a small patch in adance, it is really helpful for us.
As I said in my email I just sent, it may not help you without testing it. As there are probably other problems in that un-tested theoretical scenario.
> > 2) > In the long term, I plan to add a kmsg_dump to a kexec path because kdump may fail in the real world. > In that case, we need another troubleshooting material like pstore to detect a root cause of failure.
But you are assuming that kmsg_dump is perfect and it isn't, in which case by putting kmsg_dump in the kdump path, you actually may be blocking kdump from working.
That is the biggest hold up for those guys from including it I believe.
Cheers, Don
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