diff options
| -rw-r--r-- | kernel/time/jiffies.c | 1 | ||||
| -rw-r--r-- | kernel/time/timekeeping.c | 28 | ||||
| -rw-r--r-- | lib/Kconfig.debug | 13 |
3 files changed, 42 insertions, 0 deletions
diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c index a6a5bf53e86d..7e413902aa6a 100644 --- a/kernel/time/jiffies.c +++ b/kernel/time/jiffies.c @@ -71,6 +71,7 @@ static struct clocksource clocksource_jiffies = { .mask = 0xffffffff, /*32bits*/ .mult = NSEC_PER_JIFFY << JIFFIES_SHIFT, /* details above */ .shift = JIFFIES_SHIFT, + .max_cycles = 10, }; __cacheline_aligned_in_smp DEFINE_SEQLOCK(jiffies_lock); diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 91db94136c10..acf049144cf6 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -118,6 +118,31 @@ static inline void tk_update_sleep_time(struct timekeeper *tk, ktime_t delta) tk->offs_boot = ktime_add(tk->offs_boot, delta); } +#ifdef CONFIG_DEBUG_TIMEKEEPING +static void timekeeping_check_update(struct timekeeper *tk, cycle_t offset) +{ + + cycle_t max_cycles = tk->tkr.clock->max_cycles; + const char *name = tk->tkr.clock->name; + + if (offset > max_cycles) { + printk_deferred("WARNING: timekeeping: Cycle offset (%lld) is larger than allowed by the '%s' clock's max_cycles value (%lld): time overflow\n", + offset, name, max_cycles); + printk_deferred(" timekeeping: Your kernel is sick, but tries to cope\n"); + } else { + if (offset > (max_cycles >> 1)) { + printk_deferred("INFO: timekeeping: Cycle offset (%lld) is larger than the the '%s' clock's 50%% safety margin (%lld)\n", + offset, name, max_cycles >> 1); + printk_deferred(" timekeeping: Your kernel is still fine, but is feeling a bit nervous\n"); + } + } +} +#else +static inline void timekeeping_check_update(struct timekeeper *tk, cycle_t offset) +{ +} +#endif + /** * tk_setup_internals - Set up internals to use clocksource clock. * @@ -1630,6 +1655,9 @@ void update_wall_time(void) if (offset < real_tk->cycle_interval) goto out; + /* Do some additional sanity checking */ + timekeeping_check_update(real_tk, offset); + /* * With NO_HZ we may have to accumulate many cycle_intervals * (think "ticks") worth of time at once. To do this efficiently, diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index c5cefb3c009c..36b6fa88ce5b 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -865,6 +865,19 @@ config SCHED_STACK_END_CHECK data corruption or a sporadic crash at a later stage once the region is examined. The runtime overhead introduced is minimal. +config DEBUG_TIMEKEEPING + bool "Enable extra timekeeping sanity checking" + help + This option will enable additional timekeeping sanity checks + which may be helpful when diagnosing issues where timekeeping + problems are suspected. + + This may include checks in the timekeeping hotpaths, so this + option may have a (very small) performance impact to some + workloads. + + If unsure, say N. + config TIMER_STATS bool "Collect kernel timers statistics" depends on DEBUG_KERNEL && PROC_FS |