On Tue, Jun 15, 2010 at 13:20, Tejun Heo <tj@xxxxxxxxxx> wrote: > On 06/15/2010 12:30 PM, Kay Sievers wrote: >>> Hmm... maybe what we can do is generating an uevent when an IRQ is >>> confirmed to be bad and then let udev notify the user. That way we'll >>> probably have better chance of getting bug reports and users have >>> whiny but working system. >> >> Not really, uevents are not picked up by anything that could report an >> error to userspace, they are just seen by udev. Also uevents are >> usually not the proper passing method. They are not meant to ever >> transport higher frequency events, or structured data. They cause to >> run the entire udev rule matching machine, and update symlinks and >> permissions with every event. > > Oh, these will be very low frequency event. At most once per > irq_expect or irqaction. e.g. on a machine with four hard drives, it > can only happen four times after boot unless the driver is unloaded > and reloaded, so from frequency standpoint it should be okay. > >> We will need some better error reporting facility. On Linux you don't >> even get notified when the kernel mounts your filesystem read-only >> because of an error. It will only end up in 'dmesg' as a pretty much >> undefined bunch of words. :) > > That one is a very low frequency too. > >> We will need some generic error reporting facility, with structured >> data exported, and where userspace stuff can subscribe to. >> Uevents/udev can not really properly provide such infrastructure. >> Maybe that can be extended somehow, but using kobject_uevent() and >> trigger the usual udev rule engine is not what we are looking for, for >> sane error reporting. > > It's true that there are higher frequency events which will be > horrible to report via kobject_uevent(). Hmmm... but the thing is > that events which should annoy the user by userland notification can't > be definition high freq. There's only so many users can recognize and > respond, so the frequency limitation of uevent might actually fit here > although it would be nice to have some kind of safety mechanism. > Still no go for uevent? Yeah, I'm pretty sure that's not what we want. We want structured data, and a generic channel to pass all sort of errors through, and a userspace part to handle it in a sane way. Many error sources may also not have a device path in /sys, and therefore no uevent to send. Uevents/udev just seem so convinient because it's already there, but I think, has too many limitations to provide the needed functionality. Besides the fact that nothing listens to these events in userspace today -- it's a lot more to think through and work on than passing things through uevents, especially some generic classification and structured data passing, which is needed, instead of the current free-text 'dmsg' or the property-based stuff in uevents. I'm very sure it's the wrong facility to use. Kay -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
