linux-kernel - [GIT pull] timer fixes for 4.10

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Date:   Sat, 18 Feb 2017 10:30:31 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
cc:     LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [GIT pull] timer fixes for 4.10

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

Two small fixes::

  - Prevent deadlock on the tick broadcast lock. Found and fixed by Mike.

  - Stop using printk() in the timekeeping debug code to prevent a deadlock
    against the scheduler.

Thanks,

	tglx

------------------>
Mike Galbraith (1):
      tick/broadcast: Prevent deadlock on tick_broadcast_lock

Sergey Senozhatsky (1):
      timekeeping: Use deferred printk() in debug code


 kernel/time/tick-broadcast.c    | 15 +++++++--------
 kernel/time/timekeeping_debug.c |  4 ++--
 2 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 3109204c87cc..17ac99b60ee5 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -347,17 +347,16 @@ static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
  *
  * Called when the system enters a state where affected tick devices
  * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
- *
- * Called with interrupts disabled, so clockevents_lock is not
- * required here because the local clock event device cannot go away
- * under us.
  */
 void tick_broadcast_control(enum tick_broadcast_mode mode)
 {
 	struct clock_event_device *bc, *dev;
 	struct tick_device *td;
 	int cpu, bc_stopped;
+	unsigned long flags;
 
+	/* Protects also the local clockevent device. */
+	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 	td = this_cpu_ptr(&tick_cpu_device);
 	dev = td->evtdev;
 
@@ -365,12 +364,11 @@ void tick_broadcast_control(enum tick_broadcast_mode mode)
 	 * Is the device not affected by the powerstate ?
 	 */
 	if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
-		return;
+		goto out;
 
 	if (!tick_device_is_functional(dev))
-		return;
+		goto out;
 
-	raw_spin_lock(&tick_broadcast_lock);
 	cpu = smp_processor_id();
 	bc = tick_broadcast_device.evtdev;
 	bc_stopped = cpumask_empty(tick_broadcast_mask);
@@ -420,7 +418,8 @@ void tick_broadcast_control(enum tick_broadcast_mode mode)
 				tick_broadcast_setup_oneshot(bc);
 		}
 	}
-	raw_spin_unlock(&tick_broadcast_lock);
+out:
+	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 }
 EXPORT_SYMBOL_GPL(tick_broadcast_control);
 
diff --git a/kernel/time/timekeeping_debug.c b/kernel/time/timekeeping_debug.c
index ca9fb800336b..38bc4d2208e8 100644
--- a/kernel/time/timekeeping_debug.c
+++ b/kernel/time/timekeeping_debug.c
@@ -75,7 +75,7 @@ void tk_debug_account_sleep_time(struct timespec64 *t)
 	int bin = min(fls(t->tv_sec), NUM_BINS-1);
 
 	sleep_time_bin[bin]++;
-	pr_info("Suspended for %lld.%03lu seconds\n", (s64)t->tv_sec,
-			t->tv_nsec / NSEC_PER_MSEC);
+	printk_deferred(KERN_INFO "Suspended for %lld.%03lu seconds\n",
+			(s64)t->tv_sec, t->tv_nsec / NSEC_PER_MSEC);
 }