On 07/18/2014 03:38 PM, Stephen Boyd wrote: > On 07/18/14 15:25, John Stultz wrote: >> On 07/18/2014 03:09 PM, Stephen Boyd wrote: >>> During suspend we call sched_clock_poll() to update the epoch and >>> accumulated time and reprogram the sched_clock_timer to fire >>> before the next wrap-around time. Unfortunately, >>> sched_clock_poll() doesn't restart the timer, instead it relies >>> on the hrtimer layer to do that and during suspend we aren't >>> calling that function from the hrtimer layer. Instead, we're >>> reprogramming the expires time while the hrtimer is enqueued, >>> which can cause the hrtimer tree to be corrupted. Fix this >>> problem by updating the state via update_sched_clock() and >>> properly restarting the timer via hrtimer_start(). >>> >>> Fixes: a08ca5d1089d "sched_clock: Use an hrtimer instead of timer" >>> Signed-off-by: Stephen Boyd <sb...@codeaurora.org> >>> --- >>> >>> I also wonder if we should be restarting the timer during resume >>> instead of suspend given that the resume path modifies the epoch. >>> At that point timers can't run because interrupts are disabled and >>> we don't really care if the timer fires earlier than it's supposed >>> to anyway because it's just there to avoid rollover events, but >>> does it seem better to do it that way? I didn't send that version >>> because this patch is to fix the code intention, but I'm curious >>> if anyone else feels like it should be changed. >> Yea, starting the timer on suspend seems unintuitive to me. >> >> Is this something you were hoping to get in for 3.17 or is this a urgent >> 3.16 item? > Ok I'll send a follow up patch to cancel during suspend and start during > resume, unless you want that to be part of this fix? It's a regression > back to v3.13 so I would think it's urgent, although I haven't seen any > reports on the mailing list, just reports on some of our android kernels.
If its a regression (and needs -stable backports) it needs to go in via tip/timers/urgent, and not via the regular merge window. Whats the additional risk -stable wise for canceling the timer during suspend and starting it back up during resume? thanks -john -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
