From: Peter Xu <peterx@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org, Ming Lei <ming.lei@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Luiz Capitulino <lcapitulino@redhat.com>
Subject: Re: [PATCH] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters
Date: Tue, 31 Mar 2020 16:57:59 -0400 [thread overview]
Message-ID: <20200331205759.GA648829@xz-x1> (raw)
In-Reply-To: <20200309151917.GB4206@xz-x1>
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
next prev parent reply other threads:[~2020-03-31 20:58 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-04 16:16 [PATCH] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters Peter Xu
2020-02-05 12:27 ` Ming Lei
2020-02-05 13:34 ` Peter Xu
2020-02-14 19:40 ` Peter Xu
2020-02-14 20:28 ` Thomas Gleixner
2020-03-09 15:19 ` Peter Xu
2020-03-31 20:57 ` Peter Xu [this message]
2020-04-01 20:30 ` Thomas Gleixner
2020-04-01 23:01 ` Peter Xu
2020-04-01 23:29 ` Thomas Gleixner
2020-04-02 0:50 ` Peter Xu
2020-04-02 8:40 ` Thomas Gleixner
2020-04-02 13:14 ` Peter Xu
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