Messages in this thread | | | Date | Wed, 5 Feb 2020 20:27:54 +0800 | From | Ming Lei <> | Subject | Re: [PATCH] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters |
| |
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. > > CC: Ming Lei <ming.lei@redhat.com> > CC: Ingo Molnar <mingo@redhat.com> > CC: Peter Zijlstra <peterz@infradead.org> > CC: Juri Lelli <juri.lelli@redhat.com> > CC: Luiz Capitulino <lcapitulino@redhat.com> > Suggested-by: Thomas Gleixner <tglx@linutronix.de> > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > kernel/sched/isolation.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c > index 008d6ac2342b..d5defb667bbc 100644 > --- a/kernel/sched/isolation.c > +++ b/kernel/sched/isolation.c > @@ -169,8 +169,12 @@ static int __init housekeeping_isolcpus_setup(char *str) > continue; > } > > - pr_warn("isolcpus: Error, unknown flag\n"); > - return 0; > + str = strchr(str, ','); > + if (str) > + /* Skip unknown sub-parameter */ > + str++; > + else > + return 0;
Looks fine, even though the 'old' kernel has to apply this patch.
Reviewed-by: Ming Lei <ming.lei@redhat.com>
thanks, Ming
| |