1 files changed, 29 insertions, 5 deletions

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index d422c7b2236b..1f663d23e85e 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -343,7 +343,19 @@ static void clocksource_resume_watchdog(void)
 {
         unsigned long flags;
 
-        spin_lock_irqsave(&watchdog_lock, flags);
+        /*
+         * We use trylock here to avoid a potential dead lock when
+         * kgdb calls this code after the kernel has been stopped with
+         * watchdog_lock held. When watchdog_lock is held we just
+         * return and accept, that the watchdog might trigger and mark
+         * the monitored clock source (usually TSC) unstable.
+         *
+         * This does not affect the other caller clocksource_resume()
+         * because at this point the kernel is UP, interrupts are
+         * disabled and nothing can hold watchdog_lock.
+         */
+        if (!spin_trylock_irqsave(&watchdog_lock, flags))
+                return;
         clocksource_reset_watchdog();
         spin_unlock_irqrestore(&watchdog_lock, flags);
 }
@@ -441,6 +453,18 @@ static inline int clocksource_watchdog_kthread(void *data) { return 0; }
 #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
 
 /**
+ * clocksource_suspend - suspend the clocksource(s)
+ */
+void clocksource_suspend(void)
+{
+        struct clocksource *cs;
+
+        list_for_each_entry_reverse(cs, &clocksource_list, list)
+                if (cs->suspend)
+                        cs->suspend(cs);
+}
+
+/**
  * clocksource_resume - resume the clocksource(s)
  */
 void clocksource_resume(void)
@@ -449,7 +473,7 @@ void clocksource_resume(void)
 
         list_for_each_entry(cs, &clocksource_list, list)
                 if (cs->resume)
-                        cs->resume();
+                        cs->resume(cs);
 
         clocksource_resume_watchdog();
 }
@@ -458,8 +482,8 @@ void clocksource_resume(void)
  * clocksource_touch_watchdog - Update watchdog
  *
  * Update the watchdog after exception contexts such as kgdb so as not
- * to incorrectly trip the watchdog.
- *
+ * to incorrectly trip the watchdog. This might fail when the kernel
+ * was stopped in code which holds watchdog_lock.
  */
 void clocksource_touch_watchdog(void)
 {
@@ -677,7 +701,7 @@ sysfs_show_current_clocksources(struct sys_device *dev,
  * @count:      length of buffer
  *
  * Takes input from sysfs interface for manually overriding the default
- * clocksource selction.
+ * clocksource selection.
  */
 static ssize_t sysfs_override_clocksource(struct sys_device *dev,
                                           struct sysdev_attribute *attr,