linux-kernel - [PATCH] kernel/sched/core.c: Avoid unused variable on non-SMP configs

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Date:   Sat, 8 Sep 2018 21:05:53 +0200
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] kernel/sched/core.c: Avoid unused variable on non-SMP configs

On non-SMP configs, when only one of CONFIG_{PARAVIRT,IRQ_TIME}_ACCOUNTING
is defined, we are declaring a variable (irq_delta or steal) which
is not used:

    kernel/sched/core.c: In function ‘update_rq_clock_task’:
    kernel/sched/core.c:139:17: warning: unused variable ‘irq_delta’ [-Wunused-variable]
      s64 steal = 0, irq_delta = 0;

The reason is that CONFIG_SMP guards HAVE_SCHED_AVG_IRQ, which in turn
disables the code guarded by HAVE_SCHED_AVG_IRQ.

Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
---
 kernel/sched/core.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 625bc9897f62..d662d1e11843 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -135,8 +135,11 @@ static void update_rq_clock_task(struct rq *rq, s64 delta)
  * In theory, the compile should just see 0 here, and optimize out the call
  * to sched_rt_avg_update. But I don't trust it...
  */
-#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
-	s64 steal = 0, irq_delta = 0;
+#if defined(HAVE_SCHED_AVG_IRQ) || defined(CONFIG_IRQ_TIME_ACCOUNTING)
+	s64 irq_delta = 0;
+#endif
+#if defined(HAVE_SCHED_AVG_IRQ) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
+	s64 steal = 0;
 #endif
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
 	irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
-- 
2.17.1