From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: [PATCH RT 02/11] Latency histograms: Adjust timer, if already elapsed when programmed Date: Mon, 16 Jul 2012 14:43:12 -0400 Message-ID: <20120716184353.853883147@goodmis.org> References: <20120716184310.223095720@goodmis.org> Cc: Thomas Gleixner , Carsten Emde , John Kacur To: linux-kernel@vger.kernel.org, linux-rt-users Return-path: Content-Disposition: inline; filename=0002-Latency-histograms-Adjust-timer-if-already-elapsed-w.patch Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org From: Carsten Emde 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 Signed-off-by: Thomas Gleixner Signed-off-by: Steven Rostedt --- include/linux/hrtimer.h | 3 +++ kernel/hrtimer.c | 16 ++++++++++++++-- 2 files changed, 17 insertions(+), 2 deletions(-) diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index 0e37086..7408760 100644 --- a/include/linux/hrtimer.h +++ b/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; diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index 3991464..a080e62 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -1021,6 +1021,17 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim, #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, -- 1.7.10.4