lkml.org 
[lkml]   [2020]   [Apr]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip: sched/core] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters
The following commit has been merged into the sched/core branch of tip:

Commit-ID: 3662daf023500dc084fa3b96f68a6f46179ddc73
Gitweb: https://git.kernel.org/tip/3662daf023500dc084fa3b96f68a6f46179ddc73
Author: Peter Xu <peterx@redhat.com>
AuthorDate: Fri, 03 Apr 2020 18:35:17 -04:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Wed, 15 Apr 2020 10:38:26 +02:00

sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters

The "isolcpus=" parameter allows sub-parameters before the cpulist is
specified, and if the parser detects an unknown sub-parameters the whole
parameter will be ignored.

This design is incompatible with itself when new sub-parameters are added.
An older kernel will not recognize the new sub-parameter and will
invalidate the whole parameter so the CPU isolation will not take
effect. It emits a warning:

isolcpus: Error, unknown flag

The better and compatible way is to allow "isolcpus=" to skip unknown
sub-parameters, so that even if new sub-parameters are added an older
kernel will still be able to behave as usual even if with the new
sub-parameter specified on the command line.

Ideally this should have been there when the first sub-parameter for
"isolcpus=" was introduced.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200403223517.406353-1-peterx@redhat.com

---
kernel/sched/isolation.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 008d6ac..808244f 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -149,6 +149,9 @@ __setup("nohz_full=", housekeeping_nohz_full_setup);
static int __init housekeeping_isolcpus_setup(char *str)
{
unsigned int flags = 0;
+ bool illegal = false;
+ char *par;
+ int len;

while (isalpha(*str)) {
if (!strncmp(str, "nohz,", 5)) {
@@ -169,8 +172,22 @@ static int __init housekeeping_isolcpus_setup(char *str)
continue;
}

- pr_warn("isolcpus: Error, unknown flag\n");
- return 0;
+ /*
+ * Skip unknown sub-parameter and validate that it is not
+ * containing an invalid character.
+ */
+ for (par = str, len = 0; *str && *str != ','; str++, len++) {
+ if (!isalpha(*str) && *str != '_')
+ illegal = true;
+ }
+
+ if (illegal) {
+ pr_warn("isolcpus: Invalid flag %.*s\n", len, par);
+ return 0;
+ }
+
+ pr_info("isolcpus: Skipped unknown flag %.*s\n", len, par);
+ str++;
}

/* Default behaviour for isolcpus without flags */
\
 
 \ /
  Last update: 2020-04-15 10:45    [W:0.057 / U:0.256 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site