This is a note to let you know that I've just added the patch titled
sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters
to the 5.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-isolation-allow-isolcpus-to-skip-unknown-sub-p.patch
and it can be found in the queue-5.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 7552d9131edfdf6f2c1f890c36060266c08c6ff2
Author: Peter Xu <peterx@xxxxxxxxxx>
Date: Fri Apr 3 18:35:17 2020 -0400
sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters
[ Upstream commit 3662daf023500dc084fa3b96f68a6f46179ddc73 ]
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@xxxxxxxxxxxxx>
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200403223517.406353-1-peterx@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 008d6ac2342b7..808244f3ddd98 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 */
