Merge branch 'clocksource.2022.02.01b' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into timers/core

Pull clocksource watchdog update from Paul McKenney:

 - Add a config option for the maximum skew of the watchdog.

Link: https://lore.kernel.org/r/20220224000718.GA3747431@paulmck-ThinkPad-P17-Gen-1

Author: KAGA-KOKO

kernel/time/Kconfig

@@ -181,5 +181,14 @@ config HIGH_RES_TIMERS
 	  hardware is not capable then this option only increases
 	  the size of the kernel image.
 
+config CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
+	int "Clocksource watchdog maximum allowable skew (in μs)"
+	depends on CLOCKSOURCE_WATCHDOG
+	range 50 1000
+	default 100
+	help
+	  Specify the maximum amount of allowable watchdog skew in
+	  microseconds before reporting the clocksource to be unstable.
+
 endmenu
 endif

kernel/time/clocksource.c

@@ -107,7 +107,13 @@ static u64 suspend_start;
  * This delay could be due to SMIs, NMIs, or to VCPU preemptions.  Used as
  * a lower bound for cs->uncertainty_margin values when registering clocks.
  */
-#define WATCHDOG_MAX_SKEW (100 * NSEC_PER_USEC)
+#ifdef CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
+#define MAX_SKEW_USEC	CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
+#else
+#define MAX_SKEW_USEC	100
+#endif
+
+#define WATCHDOG_MAX_SKEW (MAX_SKEW_USEC * NSEC_PER_USEC)
 
 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
 static void clocksource_watchdog_work(struct work_struct *work);