From: Peter Xu <peterx@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: peterx@redhat.com, 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>,
Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters
Date: Tue, 4 Feb 2020 11:16:39 -0500 [thread overview]
Message-ID: <20200204161639.267026-1-peterx@redhat.com> (raw)
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
next reply other threads:[~2020-02-04 16:16 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-04 16:16 Peter Xu [this message]
2020-02-05 12:27 ` [PATCH] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters 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
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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