[lkml]   [2020]   [Feb]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters
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 <>
CC: Ingo Molnar <>
CC: Peter Zijlstra <>
CC: Juri Lelli <>
CC: Luiz Capitulino <>
Suggested-by: Thomas Gleixner <>
Signed-off-by: Peter Xu <>
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)

- 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 */
 \ /
  Last update: 2020-02-04 17:17    [W:0.184 / U:0.716 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site