Nothing prevents a programmer from calling clock_nanosleep() with an already elapsed wakeup time in absolute time mode or with a too small delay in relative time mode. Such timers cannot wake up in time and, thus, should be corrected when entered into the missed timers latency histogram (CONFIG_MISSED_TIMERS_HIST).
This patch marks such timers and uses a corrected expiration time. Signed-off-by: Carsten Emde <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> --- include/linux/hrtimer.h | 3 +++ kernel/hrtimer.c | 16 ++++++++++++++-- 2 files changed, 17 insertions(+), 2 deletions(-) Index: linux-3.4.2-rt10-64+/include/linux/hrtimer.h =================================================================== --- linux-3.4.2-rt10-64+.orig/include/linux/hrtimer.h +++ linux-3.4.2-rt10-64+/include/linux/hrtimer.h @@ -113,6 +113,9 @@ struct hrtimer { unsigned long state; struct list_head cb_entry; int irqsafe; +#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST + ktime_t praecox; +#endif #ifdef CONFIG_TIMER_STATS int start_pid; void *start_site; Index: linux-3.4.2-rt10-64+/kernel/hrtimer.c =================================================================== --- linux-3.4.2-rt10-64+.orig/kernel/hrtimer.c +++ linux-3.4.2-rt10-64+/kernel/hrtimer.c @@ -1021,6 +1021,17 @@ int __hrtimer_start_range_ns(struct hrti #endif } +#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST + { + ktime_t now = new_base->get_time(); + + if (ktime_to_ns(tim) < ktime_to_ns(now)) + timer->praecox = now; + else + timer->praecox = ktime_set(0, 0); + } +#endif + hrtimer_set_expires_range_ns(timer, tim, delta_ns); timer_stats_hrtimer_set_start_info(timer); @@ -1458,8 +1469,9 @@ retry: timer = container_of(node, struct hrtimer, node); trace_hrtimer_interrupt(raw_smp_processor_id(), - ktime_to_ns(ktime_sub( - hrtimer_get_expires(timer), basenow)), + ktime_to_ns(ktime_sub(ktime_to_ns(timer->praecox) ? + timer->praecox : hrtimer_get_expires(timer), + basenow)), current, timer->function == hrtimer_wakeup ? container_of(timer, struct hrtimer_sleeper, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
