linux-kernel - [PATCH] timer: nohz: don't disable the timer if we don't have irqwork interrupt

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Date:	Tue, 23 Jun 2015 16:07:43 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	linux-kernel@...r.kernel.org
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH] timer: nohz: don't disable the timer if we don't have irqwork interrupt

The irq work interrupt is optional: If an architecture does not provide
it then the callback will be run from update_process_times(). This does
not work well for nohz_full_kick_work_func() as we learned in commit
76a33061b932 ("irq_work: Force raised irq work to run on irq work
interrupt").

This patch is just a precaution to ensure that that an irq work
interrupt is required and the timer callback is not enough.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 kernel/time/tick-sched.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index c792429e98c6..d9481bebae22 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -176,6 +176,11 @@ static bool can_stop_full_tick(void)
 		return false;
 	}
 
+	if (!arch_irq_work_has_interrupt()) {
+		trace_tick_stop(0, "missing irq work interrupt\n");
+		return false;
+	}
+
 	/* sched_clock_tick() needs us? */
 #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
 	/*
-- 
2.1.4

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