On Fri, May 02, 2014 at 10:10:02PM -0400, Don Zickus wrote: > On Fri, May 02, 2014 at 04:52:12PM -0500, Corey Minyard wrote: > > On 05/02/2014 12:46 PM, Don Zickus wrote: > > > On Fri, May 02, 2014 at 10:18:03AM -0700, Guenter Roeck wrote: > > >>>>> That isn't enough to be able to report the pretimeout to the user. > > >>>>> You > > >>>>> can set it and get it with those calls, but it also needs poll, > > >>>>> fasync, > > >>>>> and read to be able to select on a pretimeout or block on a read. > > >>>>> > > >>>> Ah, but now you are talking about a specific implementation, which is > > >>>> a bit > > >>>> different. The question here is what you expect to occur when a > > >>>> pretimeout > > >>>> happens, and you have a certain set of expectations. Personally I > > >>>> don't know > > >>>> what the best solution is; maybe a sysfs attribute or, yes, some > > >>>> activity > > >>>> on the watchdog device entry. Why don't you (or Don) suggest something > > >>>> and come up with a patch set for review ? > > >>> I look through the only other two watchdogs that I could find with > > >>> pretimeouts (kempld and hpwdt). hpwdt uses NMI as its pretimeout > > >>> notification, while kempld uses a low level configured action (nmi, smi, > > >>> sci, delay). I think ipmi is the only one that chooses a user space > > >>> implementation (which raises another question[1]). > > >>> > > >>> I can try to respectfully copy the ipmi implementation to watchdog_dev.c > > >>> and set a wdd->option to indicate its use and in addition add the > > >>> pretimeout ioctls to watchdog_dev.c (and struct watchdog_device). > > >>> > > >>> Otherwise I am not sure if adding read, fasync, and poll wrappers to > > >>> watchdog_dev.c looks like a dirty hack. > > >>> > > >>> Cheers, > > >>> Don > > >>> > > >>> [1] if the system is stuck such that the pretimeout goes off, is it even > > >>> possible for userspace to run? Or guaranteed that it could run > > >>> reliably? > > >>> Just curious behind the history for this addition. > > >>> > > >> I would guess it depends. In most cases, I would assume it reflects that > > >> the > > >> watchdog daemon did not run. This in turn may suggest that userspace is, > > >> for all practical purposes, unable to run. Given that, I would suspect > > >> that > > >> a solution which depends on user space to act will in most cases not be > > >> able > > >> to fulfil its purpose, and I would not want to depend on it. > > > I am sure Corey ran into one vendor who wanted it, hence why he > > > implemented it. But yeah, I am not sure I would depend on it either. > > > > The driver hardware can do an NMI or an indication through an IPMI > > interrupt/signal, and the driver can either panic or try to give > > information to the user. > > > > I don't exactly remember the reason for giving a pretimeout to the > > user. I think there were some older implementations that did this, so I > > kept the function. You can't depend on it, of course, but if it can work > > then debugging a problem with the watchdog daemon (or something else in > > userland) would be a lot easier with an option like this. I have no > > idea if anyone uses it. > > > > I do agree that the driver should be moved over to use the framework. > > Implementing read/poll should be easy in the framework. > > > > Don, are you interested in working on this? i won't be able to get to > > it for a bit. > > I don't mind doing the work, as long as we agree on an implementation. :-) > > Just throwing an idea out there based on Guenter's reply, should I just > create a new file ipmi_wdt in the drivers/watchdog area that is ported to > the new watchdog framework? > I would suggest to move it in the 1st patch, then implement the wd framework in the next patch. That makes it easier to identify the changes.
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