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clocksource: Add a Kconfig option for WATCHDOG_MAX_SKEW
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A watchdog maximum skew of 100us may still be too small for
some systems or archs. It may also be too small when some kernel
debug config options are enabled.  So add a new Kconfig option
CLOCKSOURCE_WATCHDOG_MAX_SKEW_US to allow kernel builders to have more
control on the threshold for marking clocksource as unstable.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Waiman Long authored and Paul E. McKenney committed Feb 2, 2022
1 parent da12301 commit fc153c1
Showing 2 changed files with 16 additions and 1 deletion.
9 changes: 9 additions & 0 deletions kernel/time/Kconfig
Original file line number Diff line number Diff line change
@@ -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
8 changes: 7 additions & 1 deletion kernel/time/clocksource.c
Original file line number Diff line number Diff line change
@@ -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);

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