linux-kernel - [PATCH 4.17 09/18] nohz: Fix local_timer_softirq

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Date:   Tue,  7 Aug 2018 20:51:12 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        bigeasy@...utronix.de, peterz@...radead.org
Subject: [PATCH 4.17 09/18] nohz: Fix local_timer_softirq_pending()

4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Anna-Maria Gleixner <anna-maria@...utronix.de>

commit 80d20d35af1edd632a5e7a3b9c0ab7ceff92769e upstream.

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>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Reviewed-by: Daniel Bristot de Oliveira <bristot@...hat.com>
Acked-by: Frederic Weisbecker <frederic@...nel.org>
Cc: bigeasy@...utronix.de
Cc: peterz@...radead.org
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/20180731161358.29472-1-anna-maria@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/time/tick-sched.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -642,7 +642,7 @@ static void tick_nohz_restart(struct tic

 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)