[PATCH] sched, output warning when isolcpus kernel parameter is invalid

[Prarit Bhargava]

The isolcpus kernel parameter restricts userspace from scheduling on the
specified cpus.  If a cpu is specified that is outside the range of 0 to
nr_cpu_ids, cpulist_parse() will return -ERANGE, return an empty cpulist,
and fail silently.

This patch adds an error message to isolated_cpu_setup() to indicate to
the user that something has gone awry, and returns 0 on error.

Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
---
 kernel/sched/core.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9503d59..bce37ca 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6173,8 +6173,15 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
 /* Setup the mask of cpus configured for isolated domains */
 static int __init isolated_cpu_setup(char *str)
 {
+	int ret;
+
 	alloc_bootmem_cpumask_var(&cpu_isolated_map);
-	cpulist_parse(str, cpu_isolated_map);
+	ret = cpulist_parse(str, cpu_isolated_map);
+	if (ret) {
+		pr_err("Error: kernel parameter isolcpus values must be between 0 and %d\n",
+		       nr_cpu_ids);
+		return 0;
+	}
 	return 1;
 }
 
-- 
1.7.9.3