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 v3] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters
Date: Fri, 3 Apr 2020 18:35:17 -0400 [thread overview]
Message-ID: <20200403223517.406353-1-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>
---
v3:
- add brackets for for loop
- move "illegal" a bit higher, which may look tiny bit nicer
- also allow '_'
v2:
- only allow isalpha() for sub-parameters [tglx]
---
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 008d6ac2342b..808244f3ddd9 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 */
--
2.24.1
next reply other threads:[~2020-04-03 22:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-03 22:35 Peter Xu [this message]
2020-04-14 21:57 ` [PATCH v3] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters Peter Xu
2020-04-15 8:44 ` [tip: sched/core] " tip-bot2 for Peter Xu
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