clockevents: Add module refcount

We want to be able to remove clockevent modules as well. Add a
refcount so we don't remove a module with an active clock event
device.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130425143436.307435149@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

4 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
index 2f498f66c1bb..ae1193bcf074 100644
--- a/include/linux/clockchips.h
+++ b/include/linux/clockchips.h
@@ -30,6 +30,7 @@ enum clock_event_nofitiers {
 #include <linux/notifier.h>
 
 struct clock_event_device;
+struct module;
 
 /* Clock event mode commands */
 enum clock_event_mode {
@@ -83,6 +84,7 @@ enum clock_event_mode {
  * @irq:                IRQ number (only for non CPU local devices)
  * @cpumask:            cpumask to indicate for which CPUs this device works
  * @list:               list head for the management code
+ * @owner:              module reference
  */
 struct clock_event_device {
         void                    (*event_handler)(struct clock_event_device *);
@@ -112,6 +114,7 @@ struct clock_event_device {
         int                     irq;
         const struct cpumask    *cpumask;
         struct list_head        list;
+        struct module           *owner;
 } ____cacheline_aligned;
 
 /*
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 0e3a8448e115..89e394caa769 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -357,6 +357,7 @@ void clockevents_exchange_device(struct clock_event_device *old,
          * released list and do a notify add later.
          */
         if (old) {
+                module_put(old->owner);
                 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
                 list_del(&old->list);
                 list_add(&old->list, &clockevents_released);
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 3500caaa0bfd..0e374cd2e0ef 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -19,6 +19,7 @@
 #include <linux/profile.h>
 #include <linux/sched.h>
 #include <linux/smp.h>
+#include <linux/module.h>
 
 #include "tick-internal.h"
 
@@ -73,6 +74,8 @@ void tick_install_broadcast_device(struct clock_event_device *dev)
              tick_broadcast_device.evtdev->rating >= dev->rating) ||
              (dev->features & CLOCK_EVT_FEAT_C3STOP))
                 return;
+        if (!try_module_get(dev->owner))
+                return;
 
         clockevents_exchange_device(tick_broadcast_device.evtdev, dev);
         if (cur)
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 84c7cfca4d7d..433a1e11d13b 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -18,6 +18,7 @@
 #include <linux/percpu.h>
 #include <linux/profile.h>
 #include <linux/sched.h>
+#include <linux/module.h>
 
 #include <asm/irq_regs.h>
 
@@ -257,6 +258,9 @@ void tick_check_new_device(struct clock_event_device *newdev)
                         goto out_bc;
         }
 
+        if (!try_module_get(newdev->owner))
+                return;
+
         /*
          * Replace the eventually existing device by the new
          * device. If the current device is the broadcast device, do