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. > > Note that kempld in practice only implements NMI, though the HW can > do more. I can ask Kontron for feedback on their opinion for possible > actions (and why they didn't implement other actions in the driver). I don't have much interest in it really. I was just looking at what other vendors did as reference. NMI makes sense. Though I don't see an NMI handler, so I assume they just use the NMI to force a panic (like the hpwdt does, sortof)? Cheers, Don -- To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
