Messages in this thread Patch in this message |  | | From | Peter Xu <> | Subject | [PATCH] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters | Date | Tue, 4 Feb 2020 11:16:39 -0500 |
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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; } /* Default behaviour for isolcpus without flags */ -- 2.24.1
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