[PATCH] clocksource/i8253: Acquire the lock disabled interrupts.

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On x86 during boot, clockevent_i8253_disable() can be invoked via
x86_late_time_init -> hpet_time_init() -> pit_timer_init() which happens
with enabled interrupts.
If some of the old i8253 hardware is actually used then lockdep will
notice that i8253_lock is used in hardirq context. This causes lockdep
to complain because it observed the lock being acquired with enabled
interrupts and in hardirq context.

Make clockevent_i8253_disable() acquire the lock with disabled
interrupts.

Fixes: c8c4076723dac ("x86/timer: Skip PIT initialization on modern chipsets")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 drivers/clocksource/i8253.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/clocksource/i8253.c b/drivers/clocksource/i8253.c
index 39f7c2d736d16..67dcd9c8f1875 100644
--- a/drivers/clocksource/i8253.c
+++ b/drivers/clocksource/i8253.c
@@ -103,8 +103,9 @@ int __init clocksource_i8253_init(void)
 #ifdef CONFIG_CLKEVT_I8253
 void clockevent_i8253_disable(void)
 {
-	raw_spin_lock(&i8253_lock);
+	unsigned long flags;
 
+	raw_spin_lock_irqsave(&i8253_lock, flags);
 	/*
 	 * Writing the MODE register should stop the counter, according to
 	 * the datasheet. This appears to work on real hardware (well, on
@@ -133,7 +134,7 @@ void clockevent_i8253_disable(void)
 
 	outb_p(0x30, PIT_MODE);
 
-	raw_spin_unlock(&i8253_lock);
+	raw_spin_unlock_irqrestore(&i8253_lock, flags);
 }
 
 static int pit_shutdown(struct clock_event_device *evt)
-- 
2.49.0