clocksource: Remove kthread

The clocksource watchdog uses a work to spawn a kthread to run the
watchdog. That is about as silly as it sounds, run the watchdog
directly from the work.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: len.brown@intel.com
Cc: rjw@rjwysocki.net
Cc: diego.viola@gmail.com
Cc: rui.zhang@intel.com
Link: https://lkml.kernel.org/r/20180430100344.713862818@infradead.org

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 84f37420fcf544c09e12f730f05a8a85411b36f1..56fd2239674f7c522df07fc095bfc6e0b8f0965c 100644 (file)
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -129,31 +129,19 @@ static void inline clocksource_watchdog_unlock(unsigned long *flags)
        spin_unlock_irqrestore(&watchdog_lock, *flags);
 }
 
-static int clocksource_watchdog_kthread(void *data);
-static void __clocksource_change_rating(struct clocksource *cs, int rating);
-
 /*
  * Interval: 0.5sec Threshold: 0.0625s
  */
 #define WATCHDOG_INTERVAL (HZ >> 1)
 #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
 
-static void clocksource_watchdog_work(struct work_struct *work)
-{
-       /*
-        * If kthread_run fails the next watchdog scan over the
-        * watchdog_list will find the unstable clock again.
-        */
-       kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
-}
-
 static void __clocksource_unstable(struct clocksource *cs)
 {
        cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
        cs->flags |= CLOCK_SOURCE_UNSTABLE;
 
        /*
-        * If the clocksource is registered clocksource_watchdog_kthread() will
+        * If the clocksource is registered clocksource_watchdog_work() will
         * re-rate and re-select.
         */
        if (list_empty(&cs->list)) {
@@ -164,7 +152,7 @@ static void __clocksource_unstable(struct clocksource *cs)
        if (cs->mark_unstable)
                cs->mark_unstable(cs);
 
-       /* kick clocksource_watchdog_kthread() */
+       /* kick clocksource_watchdog_work() */
        if (finished_booting)
                schedule_work(&watchdog_work);
 }
@@ -174,7 +162,7 @@ static void __clocksource_unstable(struct clocksource *cs)
  * @cs:                clocksource to be marked unstable
  *
  * This function is called by the x86 TSC code to mark clocksources as unstable;
- * it defers demotion and re-selection to a kthread.
+ * it defers demotion and re-selection to a work.
  */
 void clocksource_mark_unstable(struct clocksource *cs)
 {
@@ -399,7 +387,9 @@ static void clocksource_dequeue_watchdog(struct clocksource *cs)
        }
 }
 
-static int __clocksource_watchdog_kthread(void)
+static void __clocksource_change_rating(struct clocksource *cs, int rating);
+
+static int __clocksource_watchdog_work(void)
 {
        struct clocksource *cs, *tmp;
        unsigned long flags;
@@ -424,13 +414,12 @@ static int __clocksource_watchdog_kthread(void)
        return select;
 }
 
-static int clocksource_watchdog_kthread(void *data)
+static void clocksource_watchdog_work(struct work_struct *work)
 {
        mutex_lock(&clocksource_mutex);
-       if (__clocksource_watchdog_kthread())
+       if (__clocksource_watchdog_work())
                clocksource_select();
        mutex_unlock(&clocksource_mutex);
-       return 0;
 }
 
 static bool clocksource_is_watchdog(struct clocksource *cs)
@@ -449,7 +438,7 @@ static void clocksource_enqueue_watchdog(struct clocksource *cs)
 static void clocksource_select_watchdog(bool fallback) { }
 static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
 static inline void clocksource_resume_watchdog(void) { }
-static inline int __clocksource_watchdog_kthread(void) { return 0; }
+static inline int __clocksource_watchdog_work(void) { return 0; }
 static bool clocksource_is_watchdog(struct clocksource *cs) { return false; }
 void clocksource_mark_unstable(struct clocksource *cs) { }
 
@@ -683,7 +672,7 @@ static int __init clocksource_done_booting(void)
        /*
         * Run the watchdog first to eliminate unstable clock sources
         */
-       __clocksource_watchdog_kthread();
+       __clocksource_watchdog_work();
        clocksource_select();
        mutex_unlock(&clocksource_mutex);
        return 0;