Messages in this thread |  | | From | Thomas Gleixner <> | Subject | Re: [PATCH V4] sched/isolation: isolate from handling managed interrupt | Date | Mon, 03 Feb 2020 23:15:50 +0000 |
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Peter Xu <peterx@redhat.com> writes: > The new "managed_irq" works for us, thanks for both of your work! > > However I just noticed that this new sub-parameter might break users > if applied incorrectly to old kernels, because iiuc "isolcpus=" > parameter will not apply at all when there's unknown sub-parameters: > > static int __init housekeeping_isolcpus_setup(char *str) > { > unsigned int flags = 0; > > while (isalpha(*str)) { > ... > pr_warn("isolcpus: Error, unknown flag\n"); > return 0; > } > ... > } > > Then the same kernel parameter will break isolcpus= if the user > reboots and switches to an older kernel. > > A solution to this could be that we introduce an isolated parameter > for "managed_irq", then on the old kernels only the new parameter will > be ignored rather than the whole "isolcpus=" parameter, so nothing > will break. > > I'm not sure whether it's already too late for this, or if there's any > better alternative. Just raise this question up to see whether we > still have chance to fix this up.
No, really. The basic guarantee is that your new kernel is going to work fine with the previous command line, but making a guarantee that new command line options still work on an old kernel are just creating a horrible mess. So if that command line interface was not designed to handle unknown arguments in the first place, you better fix that.
Thanks,
tglx
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