On 2 April 2015 at 19:04, Peter Zijlstra peterz@infradead.org wrote:
On Fri, Mar 27, 2015 at 10:44:28PM +0530, Viresh Kumar wrote:
+++ b/kernel/time/hrtimer.c @@ -566,6 +566,7 @@ static int hrtimer_reprogram(struct hrtimer *timer, {
/* Switchback to ONESHOT state */if (unlikely(dev->state == CLOCK_EVT_STATE_ONESHOT_STOPPED))clockevents_set_state(dev, CLOCK_EVT_STATE_ONESHOT);/* * Clockevents returns -ETIME, when the event was in the past. */Should we not do this in tick_program_event() instead? Note that there are a few more places that call that, the two in the hrtimer_interrupt() should be safe because if we're handling the interrupt its cannot be stopped anyhow.
hrtimer_force_reprogram() seems to need the annotation regardless.
Do you mean that we need the same modification here as well? In order to save myself against any bugs, I have added following to clockevents_program_event():
+ /* We must be in ONESHOT state here */ + WARN_ONCE(dev->state != CLOCK_EVT_STATE_ONESHOT, "Current state: %d\n", + dev->state);
And I never faced this WARN, or any such reports from Fengguang. So probably after all the hrtimers are gone, we will always call hrtimer_reprogram().
Furthermore, by putting it in tick_program_event() you also don't need to fixup tick_nohz_restart().
Or am I completely missing something?
So yes, if we would have done that in tick_program_event(), it would have been a single place for doing this change..
But, when Thomas ranted [1] at me on this earlier, he said:
" No, we are not doing a state change behind the scene and a magic restore.
2B) Implement the ONESHOT_STOPPED logic and make sure all of the core code is aware of it. "
And so I did it explicitly, wherever it is required.
-- viresh