On 05/02/2014 09:44 AM, Don Zickus wrote: > On Fri, May 02, 2014 at 06:17:51AM -0700, Guenter Roeck wrote: >> On 05/01/2014 09:38 PM, Corey Minyard wrote: >>> On 05/01/2014 08:11 PM, Guenter Roeck wrote: >>>> On 05/01/2014 05:38 PM, Corey Minyard wrote: >>>>> On 05/01/2014 08:58 AM, Don Zickus wrote: >>>>>> Hi Corey, >>>>>> >>>>>> I stumbled upon an issue with a partner of ours, where they booted >>>>>> their >>>>>> machine and tried to load the ipmi_watchdog module by hand and it >>>>>> failed. >>>>>> >>>>>> The reason it failed was that the iTCO watchdog driver was already >>>>>> loaded >>>>>> and it registered the misc device /dev/watchdog first. >>>>>> >>>>>> I looked at the ipmi watchdog driver and realized it was never >>>>>> converted >>>>>> to the new watchdog framework where the watchdog_core module manages >>>>>> the >>>>>> '/dev/watchdog' misc device. >>>>>> >>>>>> So being naive and not knowing much about IPMI, I decided to follow the >>>>>> helpful document >>>>>> Documentation/watchdog/convert_drivers_to_kernel_api.txt >>>>>> and convert the ipmi_watchdog to use the new watchdog framework. >>>>>> >>>>>> I ran into a few issues and then realized the driver itself never >>>>>> really >>>>>> binds to any hardware, so it makes the conversion process a little more >>>>>> challenging. >>>>>> >>>>>> So a few questions to you before I waste my time in this area: >>>>>> >>>>>> - Is there any prior history about why the ipmi_watchdog was never >>>>>> converted to the new watchdog framework? Lack of interest? >>>>>> Technical >>>>>> hurdles? >>>>> >>>>> Mostly lack of interest, but there are some technical hurdles. >>>>> >>>>> It would be hard to implement some things. The watchdog framework has >>>>> no concept of pretimeouts. And IPMI is message based, you send a >>>> >>>> Are you saying that WDIOC_SETPRETIMEOUT and WDIOC_GETPRETIMEOUT don't >>>> work >>>> for ipmi ? If so, can you explain ? >>>> >>> >>> 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. 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). Guenter ------------------------------------------------------------------------------ "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE Instantly run your Selenium tests across 300+ browser/OS combos. Get unparalleled scalability from the best Selenium testing platform available. Simple to use. Nothing to install. Get started now for free." http://p.sf.net/sfu/SauceLabs _______________________________________________ Openipmi-developer mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/openipmi-developer
