[PATCH v4 6/8] sched: Replace strncmp with str_has_prefix

[Chuhong Yuan]

strncmp(str, const, len) is error-prone because len
is easy to have typo.
The example is the hard-coded len has counting error
or sizeof(const) forgets - 1.
So we prefer using newly introduced str_has_prefix()
to substitute such strncmp to make code better.

Signed-off-by: Chuhong Yuan <hslester96@xxxxxxxxx>
---
Changes in v4:
  - Eliminate assignments in if conditions.

 kernel/sched/debug.c     |  6 ++++--
 kernel/sched/isolation.c | 11 +++++++----
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index f7e4579e746c..a03900523e5d 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -102,10 +102,12 @@ static int sched_feat_set(char *cmp)
 {
 	int i;
 	int neg = 0;
+	size_t len;
 
-	if (strncmp(cmp, "NO_", 3) == 0) {
+	len = str_has_prefix(cmp, "NO_");
+	if (len) {
 		neg = 1;
-		cmp += 3;
+		cmp += len;
 	}
 
 	i = match_string(sched_feat_names, __SCHED_FEAT_NR, cmp);
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index ccb28085b114..ea2ead4b1906 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -141,16 +141,19 @@ __setup("nohz_full=", housekeeping_nohz_full_setup);
 static int __init housekeeping_isolcpus_setup(char *str)
 {
 	unsigned int flags = 0;
+	size_t len;
 
 	while (isalpha(*str)) {
-		if (!strncmp(str, "nohz,", 5)) {
-			str += 5;
+		len = str_has_prefix(str, "nohz,");
+		if (len) {
+			str += len;
 			flags |= HK_FLAG_TICK;
 			continue;
 		}
 
-		if (!strncmp(str, "domain,", 7)) {
-			str += 7;
+		len = str_has_prefix(str, "domain,");
+		if (len) {
+			str += len;
 			flags |= HK_FLAG_DOMAIN;
 			continue;
 		}
-- 
2.20.1