On Fri, Oct 02, 2015 at 04:46:14PM +0900, [email protected] wrote: > From: Byungchul Park <[email protected]> > > in hrtimer_interrupt(), the first tick_program_event() can be failed > because the next timer could be already expired due to, > (see the comment in hrtimer_interrupt()) > > - tracing > - long lasting callbacks
If anything keeps interrupts disabled for longer than 1 tick, you'd better go fix that. > - being scheduled away when running in a VM Not sure how much I should care about that, and this patch is completely wrong for that anyhow. And this case in hrtimer_interrupt() is basically a fail case, if you hit that, you've got bigger problems. The solution is to rework things so you don't get there. > in the case that the first tick_program_event() is failed, the second > tick_program_event() set the expired time to more than one tick later. > then next tick can happen after more than one tick, even though tick is > not stopped by e.g. NOHZ. > > when the next tick occurs, update_process_times() -> scheduler_tick() > -> update_cpu_load_active() is performed, assuming the distance between > last tick and current tick is 1 tick! it's wrong in this case. thus, > this abnormal case should be considered in update_cpu_load_active(). Everything in update_process_times() assumes 1 tick, just fixing up one function inside that callchain is wrong -- I've already told you that. -- 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/
