clocksource: Resolve cpu hotplug dead lock with TSC unstable

[pandora-kernel.git] / kernel / time / clocksource.c

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index e0c86ad..a0af4ff 100644 (file)
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -149,15 +149,42 @@ static void clocksource_watchdog_work(struct work_struct *work)
        kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
 }
 
-static void clocksource_unstable(struct clocksource *cs, int64_t delta)
+static void __clocksource_unstable(struct clocksource *cs)
 {
-       printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
-              cs->name, delta);
        cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
        cs->flags |= CLOCK_SOURCE_UNSTABLE;
        schedule_work(&watchdog_work);
 }
 
+static void clocksource_unstable(struct clocksource *cs, int64_t delta)
+{
+       printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
+              cs->name, delta);
+       __clocksource_unstable(cs);
+}
+
+/**
+ * clocksource_mark_unstable - mark clocksource unstable via watchdog
+ * @cs:                clocksource to be marked unstable
+ *
+ * This function is called instead of clocksource_change_rating from
+ * cpu hotplug code to avoid a deadlock between the clocksource mutex
+ * and the cpu hotplug mutex. It defers the update of the clocksource
+ * to the watchdog thread.
+ */
+void clocksource_mark_unstable(struct clocksource *cs)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&watchdog_lock, flags);
+       if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) {
+               if (list_empty(&cs->wd_list))
+                       list_add(&cs->wd_list, &watchdog_list);
+               __clocksource_unstable(cs);
+       }
+       spin_unlock_irqrestore(&watchdog_lock, flags);
+}
+
 static void clocksource_watchdog(unsigned long data)
 {
        struct clocksource *cs;