linux-kernel - [GIT pull] timer fix for 4.17

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Date:   Sun, 20 May 2018 10:43:01 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
cc:     LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...nel.org>
Subject: [GIT pull] timer fix for 4.17

Linus,

please pull the latest timers-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers-urgent-for-linus

Address the for_each_cpu() oddity on UP kernels in the tick broadcast code
which causes boot failures because the CPU0 bit is always reported as set
independent of the cpumask content.

Thanks,

	tglx

------------------>
Dexuan Cui (1):
      tick/broadcast: Use for_each_cpu() specially on UP kernels


 kernel/time/tick-broadcast.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index b398c2ea69b2..aa2094d5dd27 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -612,6 +612,14 @@ static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 	now = ktime_get();
 	/* Find all expired events */
 	for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
+		/*
+		 * Required for !SMP because for_each_cpu() reports
+		 * unconditionally CPU0 as set on UP kernels.
+		 */
+		if (!IS_ENABLED(CONFIG_SMP) &&
+		    cpumask_empty(tick_broadcast_oneshot_mask))
+			break;
+
 		td = &per_cpu(tick_cpu_device, cpu);
 		if (td->evtdev->next_event <= now) {
 			cpumask_set_cpu(cpu, tmpmask);