[GIT pull] timer fixes for 4.10

From: Thomas Gleixner
Date: Sat Feb 18 2017 - 04:31:14 EST


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);
}