[PATCH v3] sched/core: silence a warning in sched_init()

[Qian Cai <cai@lca.pw>]

Compiling a kernel with both FAIR_GROUP_SCHED=n and RT_GROUP_SCHED=n
will generate a compiler warning,

kernel/sched/core.c: In function 'sched_init':
kernel/sched/core.c:5906:32: warning: variable 'ptr' set but not used
[-Wunused-but-set-variable]
  unsigned long alloc_size = 0, ptr;
                                ^~~
Silence it by adding a check in a if statement to actually use it.

Signed-off-by: Qian Cai <cai@lca.pw>
---

v3: Use a different approach to see if Peter will like it.
v2: Incorporate the feedback from Valentin.

 kernel/sched/core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2b037f195473..ae36a1e5b2e4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6371,7 +6371,8 @@ int in_sched_functions(unsigned long addr)
 
 void __init sched_init(void)
 {
-	unsigned long alloc_size = 0, ptr;
+	unsigned long alloc_size = 0;
+	unsigned long ptr = 0;
 	int i;
 
 	wait_bit_init();
@@ -6382,7 +6383,8 @@ void __init sched_init(void)
 #ifdef CONFIG_RT_GROUP_SCHED
 	alloc_size += 2 * nr_cpu_ids * sizeof(void **);
 #endif
-	if (alloc_size) {
+	/* Avoid a -Wunused-but-set-variable warning. */
+	if (alloc_size && !ptr) {
 		ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT);
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
-- 
1.8.3.1