Messages in this thread Patch in this message | | | From | Andi Kleen <> | Subject | [PATCH x86] [1/16] Make clocksource watchdog cycle through online CPUs | Date | Thu, 3 Jan 2008 16:42:14 +0100 (CET) |
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This way it checks if the clocks are synchronized between CPUs too. This might be able to detect slowly drifting TSCs which only go wrong over longer time.
Cc: tglx@linutronix.de
Signed-off-by: Andi Kleen <ak@suse.de>
--- kernel/time/clocksource.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-)
Index: linux/kernel/time/clocksource.c =================================================================== --- linux.orig/kernel/time/clocksource.c +++ linux/kernel/time/clocksource.c @@ -142,8 +142,13 @@ static void clocksource_watchdog(unsigne } if (!list_empty(&watchdog_list)) { - __mod_timer(&watchdog_timer, - watchdog_timer.expires + WATCHDOG_INTERVAL); + /* Cycle through CPUs to check if the CPUs stay synchronized to + * each other. */ + int next_cpu = next_cpu(raw_smp_processor_id(), cpu_online_map); + if (next_cpu >= NR_CPUS) + next_cpu = first_cpu(cpu_online_map); + watchdog_timer.expires += WATCHDOG_INTERVAL; + add_timer_on(&watchdog_timer, next_cpu); } spin_unlock(&watchdog_lock); } @@ -165,7 +170,7 @@ static void clocksource_check_watchdog(s if (!started && watchdog) { watchdog_last = watchdog->read(); watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; - add_timer(&watchdog_timer); + add_timer_on(&watchdog_timer, first_cpu(cpu_online_map)); } } else { if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) @@ -186,7 +191,8 @@ static void clocksource_check_watchdog(s watchdog_last = watchdog->read(); watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; - add_timer(&watchdog_timer); + add_timer_on(&watchdog_timer, + first_cpu(cpu_online_map)); } } }
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