On Fri, 27 Jan 2017 15:10:59 +0100 Philippe Gerum <[email protected]> wrote:
> On 01/27/2017 03:04 PM, Henning Schild wrote: > > On Fri, 27 Jan 2017 14:52:22 +0100 > > Henning Schild <[email protected]> wrote: > > > >> Not running the in-kernel FPU tests while Linux might be using the > >> FPU in kernel-mode is a safeguard measure for development versions > >> that might still have issues with FPU context switching. i.e. it > >> prevents data corruption on RAIDs beeing triggered by an FPU Bug. > >> In a bug-free kernel running the switchtest in kernel-mode is not a > >> problem and may be desired for proper test-coverage. > >> > >> This patch introduces a command line option to switchtest to allow > >> overriding the safeguard. > > > > I am not sure i am happy with this solution either. Actually the > > test should always run as part of the unit tests. It is very > > valuable and skipping it "silently" is a really bad idea. > > If it is really just disabled for when it might mess with your raid > > on the machine you do kernel development on, maybe you should not > > use such a machine for that? > > So i am starting to think the test should run by default and the > > conservative version should be opt-in instead of opt-out. > > > > A conservative version can only be opt-out, otherwise people may run > into damages without knowing, which would defeat the intent of picking > the conservative approach. There should at least be a prominent notice that an important test was skipped. The once-printk is just not the right place. Maybe the whole testcase should fail instead so that people have to say --kfpu-may-be-skipped Maybe i still did not fully understand why the test gets skipped. I have seen CONFIG_CIFS_SMB2 trigger the FPU problem in the broken 4.1. Would that be a reason to add that to the list of switches skipping the test? Or is the whole thing really just there to protect devs from messing up their raids? I do not see who does kernel development on a machine so valueable to justify skipping such an important test for everyone. > I'm still pondering whether this test makes sense in 3.x, given that > official support for running fpu ops over rt threads in kernel space > was dropped for that version. Too much of a mess. Ok, i am actually again looking primarily at xenomai-2 and was planning on backporting whatever we come up with. Henning _______________________________________________ Xenomai mailing list [email protected] https://xenomai.org/mailman/listinfo/xenomai
