linux-kernel - [PATCH] nohz: Fix local_timer_softirq

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Message-Id: <20180731161358.29472-1-anna-maria@linutronix.de>
Date:   Tue, 31 Jul 2018 18:13:58 +0200
From:   Anna-Maria Gleixner <anna-maria@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     bigeasy@...utronix.de, tglx@...utronix.de, frederic@...nel.org,
        bristot@...hat.com, paulmck@...ux.vnet.ibm.com,
        peterz@...radead.org,
        Anna-Maria Gleixner <anna-maria@...utronix.de>
Subject: [PATCH] nohz: Fix local_timer_softirq_pending()

local_timer_softirq_pending() checks whether the timer softirq is
pending with: local_softirq_pending() & TIMER_SOFTIRQ.

This is wrong because TIMER_SOFTIRQ is the softirq number and not a
bitmask. So the test checks for the wrong bit.

Use BIT(TIMER_SOFTIRQ) instead.

Fixes: 5d62c183f9e9 ("nohz: Prevent a timer interrupt storm in tick_nohz_stop_sched_tick()")
Signed-off-by: Anna-Maria Gleixner <anna-maria@...utronix.de>
---
 kernel/time/tick-sched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index da9455a6b42b..5b33e2f5c0ed 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -642,7 +642,7 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
 
 static inline bool local_timer_softirq_pending(void)
 {
-	return local_softirq_pending() & TIMER_SOFTIRQ;
+	return local_softirq_pending() & BIT(TIMER_SOFTIRQ);
 }
 
 static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu)
-- 
2.18.0