------- Comment From [email protected] 2016-03-08 03:18 EDT------- (In reply to comment #4) > The requests below two keys are currently out of scope, with the generic > kernel config policy for Ubuntu: > CONFIG_PREEMPT_NONE > CONFIG_SCSI_SCAN_ASYNC >
This has been already discussed on the skipper mailing list. So for CONFIG_SCSI_SCAN_ASYNC, I copy this again to this BZ: > > # CONFIG_SCSI_SCAN_ASYNC is not set > > We have been using _ASYNC ordering since at least 14.04 iirc. So far we > have had no issues with that set in our s390x boots, but I would have to > double check if we are using FCP devices to make that meaningful. Please double check if you were already using FCP devices. Of course, this setting does not affect DASDs. > > Is this a real concern for known issues with asynchronous ordering or > just that this has not been the official order in your testing up to > now? Async ordering should not affect ordering of device naming etc. The long-term default "sync" is probably well-tested. Experiences with async are rare. To be more frank here, sync is also used by other Linux distributions on z. For s390, the defconfig as well as our other upstream kernel configurations have or will have this being set to sync (again). Apart from testing, the reason why I suggest to change this setting goes back to a talk with the zfcp device driver maintainer. I stumbled over this setting as trying out FCP devices on a Debian s390 system. Tools are expecting that attached LUNs to an FCP device should be synchronously, that means, the requests should be synchronously processed by the FCP device and the SCSI layer on top. Asynchronous processing might cause problems in tools that expect synchronous behavior. Further, asynchronous handling makes it more harder to wait for the SCSI device becomes available (if it exists at all). Thus, tools have to actively wait for something to happen... and the worst thing is, that there is no tooling at all that waits for asynchronous processing to become completed (udevadm settle is useless here as there are no uevent for LUN attachment requests). -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1543165 Title: kernel: update kernel configuration To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1543165/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
