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    SubjectRe: [PATCH] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters
    On Mon, Mar 09, 2020 at 11:19:17AM -0400, Peter Xu wrote:
    > On Fri, Feb 14, 2020 at 09:28:25PM +0100, Thomas Gleixner wrote:
    > > Peter Xu <peterx@redhat.com> writes:
    > >
    > > > On Tue, Feb 04, 2020 at 11:16:39AM -0500, Peter Xu wrote:
    > > >> The "isolcpus=" parameter allows sub-parameters to exist before the
    > > >> cpulist is specified, and if it sees unknown sub-parameters the whole
    > > >> parameter will be ignored. This design is incompatible with itself
    > > >> when we add more sub-parameters to "isolcpus=", because the old
    > > >> kernels will not recognize the new "isolcpus=" sub-parameters, then it
    > > >> will invalidate the whole parameter so the CPU isolation will not
    > > >> really take effect if we start to use the new sub-parameters while
    > > >> later we reboot into an old kernel. Instead we will see this when
    > > >> booting the old kernel:
    > > >>
    > > >> isolcpus: Error, unknown flag
    > > >>
    > > >> The better and compatible way is to allow "isolcpus=" to skip unknown
    > > >> sub-parameters, so that even if we add new sub-parameters to it the
    > > >> old kernel will still be able to behave as usual even if with the new
    > > >> sub-parameter is specified.
    > > >>
    > > >> Ideally this patch should be there when we introduce the first
    > > >> sub-parameter for "isolcpus=", so it's already a bit late. However
    > > >> late is better than nothing.
    > > >
    > > > Ping - Hi, Thomas, do you have any further comment on this patch?
    > >
    > > Fine with me.
    > >
    > > Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
    >
    > Thanks Thomas!
    >
    > Does anyone like to pick this up, or does this patch needs more
    > review?

    Another gentle ping with the hope that this patch can be picked up.

    It's a very simple patch, but I really hope it can be in asap because
    the latter means the more kernel versions will be affected by this
    isolcpus incompatibility defect (and imo should consider stable too).

    Thanks.

    --
    Peter Xu

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