clocksource: Defer override invalidation unless clock is unstable
PATCH 1/1 clocksource: Defer override invalidation unless clock is unstable
The clock_select() operation will attempt to use the clocksource override to apply the desired clocksource when the "clocksource=" boot parameter is supplied. However, in the event that "clocksource=tsc" is used on a system where there is a more desireable clocksource available, the boot parameter fails. This is due to the TSC clocksource being installed unvalidated, but the override being invalidated during the initial run through clocksource_done_booting().
To address this condition, the override_name is only invalidated for unstable clocksources. Otherwise, the override is left intact until after the watchdog has validated the clocksource as stable/unstable.
Signed-off-by Kyle Walker <[email protected]>
Cc John Stultz <[email protected]>
Cc Thomas Gleixner <[email protected]>
--- kernel/time/clocksource.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
kernel/time/clocksource.c +12 -3
@@ -600,9 +600,18 @@ static void __clocksource_select(bool skipcur)*/ if (!(cs->flags &CLOCK_SOURCE_VALID_FOR_HRES ) && oneshot) {/* Override clocksource cannot be used. */ -pr_warn ("Override clocksource %s is not HRT compatible - cannot switch while in HRT/NOHZ mode\n" , - cs->name); - override_name[0 ] =0 ; +if (cs->flags &CLOCK_SOURCE_UNSTABLE ) { +pr_warn ("Override clocksource %s is unstable and not HRT compatible - cannot switch while in HRT/NOHZ mode\n" , + cs->name); + override_name[0 ] =0 ; + }else { +/* +* The override cannot be currently verified. +* Deferring to let the watchdog check. +*/ +pr_info ("Override clocksource %s is not currently HRT compatible - deferring\n" , + cs->name); + } }else /* Override clocksource can be used. */ best = cs;
Signature · 1 line
2.5.5