In tick_do_update_jiffies64() we are processing ticks only if delta is greater than tick_period. This is what we are supposed to do here and it broke a bit with this patch:
commit 47a1b796306356f358e515149d86baf0cc6bf007 Author: John Stultz john.stultz@linaro.org Date: Thu Dec 12 13:10:55 2013 -0800
tick/timekeeping: Call update_wall_time outside the jiffies lock
With above patch, we might end up calling update_wall_time() even if delta is found to be smaller that tick_period. Fix this by reversing the check and returning early.
Cc: John Stultz john.stultz@linaro.org Signed-off-by: Viresh Kumar viresh.kumar@linaro.org --- kernel/time/tick-sched.c | 32 +++++++++++++++++--------------- 1 file changed, 17 insertions(+), 15 deletions(-)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index b7b09b9..bff7f97 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -65,26 +65,28 @@ static void tick_do_update_jiffies64(ktime_t now) write_seqlock(&jiffies_lock);
delta = ktime_sub(now, last_jiffies_update); - if (delta.tv64 >= tick_period.tv64) { - - delta = ktime_sub(delta, tick_period); - last_jiffies_update = ktime_add(last_jiffies_update, - tick_period); + if (delta.tv64 < tick_period.tv64) { + write_sequnlock(&jiffies_lock); + return; + }
- /* Slow path for long timeouts */ - if (unlikely(delta.tv64 >= tick_period.tv64)) { - s64 incr = ktime_to_ns(tick_period); + delta = ktime_sub(delta, tick_period); + last_jiffies_update = ktime_add(last_jiffies_update, tick_period);
- ticks = ktime_divns(delta, incr); + /* Slow path for long timeouts */ + if (unlikely(delta.tv64 >= tick_period.tv64)) { + s64 incr = ktime_to_ns(tick_period);
- last_jiffies_update = ktime_add_ns(last_jiffies_update, - incr * ticks); - } - do_timer(++ticks); + ticks = ktime_divns(delta, incr);
- /* Keep the tick_next_period variable up to date */ - tick_next_period = ktime_add(last_jiffies_update, tick_period); + last_jiffies_update = ktime_add_ns(last_jiffies_update, + incr * ticks); } + do_timer(++ticks); + + /* Keep the tick_next_period variable up to date */ + tick_next_period = ktime_add(last_jiffies_update, tick_period); + write_sequnlock(&jiffies_lock); update_wall_time(); }