linux-kernel - [PATCH] x86/apic: Implement set_state_oneshot

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Message-Id: <1483029949-6925-1-git-send-email-fweisbec@gmail.com>
Date:   Thu, 29 Dec 2016 17:45:49 +0100
From:   Frederic Weisbecker <fweisbec@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Ingo Molnar <mingo@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>
Subject: [PATCH] x86/apic: Implement set_state_oneshot_stopped() callback

When clock_event_device::set_state_oneshot_stopped() is not implemented,
hrtimer_cancel() can't stop the clock when there is no more timer in
the queue. So the ghost of the freshly cancelled hrtimer haunts us back
later with an extra interrupt:

          <idle>-0     [002] d..2  2248.557659: hrtimer_cancel: hrtimer=ffff88021fa92d80
          <idle>-0     [002] d.h1  2249.303659: local_timer_entry: vector=239

So let's implement this missing callback for the lapic clock. This
consist in calling its set_state_shutdown() callback. There don't seem
to be a lighter way to stop the clock. Simply writing 0 to APIC_TMICT
won't be enough to stop the clock and avoid the extra interrupt, as
opposed to what is specified in the specs. We must also mask the
timer interrupt in the device.

Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Wanpeng Li <wanpeng.li@...mail.com>
Cc: Viresh Kumar <viresh.kumar@...aro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
 arch/x86/kernel/apic/apic.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 5b7e43e..a8e90db 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -529,18 +529,19 @@ static void lapic_timer_broadcast(const struct cpumask *mask)
  * The local apic timer can be used for any function which is CPU local.
  */
 static struct clock_event_device lapic_clockevent = {
-	.name			= "lapic",
-	.features		= CLOCK_EVT_FEAT_PERIODIC |
-				  CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP
-				  | CLOCK_EVT_FEAT_DUMMY,
-	.shift			= 32,
-	.set_state_shutdown	= lapic_timer_shutdown,
-	.set_state_periodic	= lapic_timer_set_periodic,
-	.set_state_oneshot	= lapic_timer_set_oneshot,
-	.set_next_event		= lapic_next_event,
-	.broadcast		= lapic_timer_broadcast,
-	.rating			= 100,
-	.irq			= -1,
+	.name				= "lapic",
+	.features			= CLOCK_EVT_FEAT_PERIODIC |
+					  CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP
+					  | CLOCK_EVT_FEAT_DUMMY,
+	.shift				= 32,
+	.set_state_shutdown		= lapic_timer_shutdown,
+	.set_state_periodic		= lapic_timer_set_periodic,
+	.set_state_oneshot		= lapic_timer_set_oneshot,
+	.set_state_oneshot_stopped	= lapic_timer_shutdown,
+	.set_next_event			= lapic_next_event,
+	.broadcast			= lapic_timer_broadcast,
+	.rating				= 100,
+	.irq				= -1,
 };
 static DEFINE_PER_CPU(struct clock_event_device, lapic_events);
 
-- 
2.7.4