Hi! On 09/14/2018 09:59 AM, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > There is a difference in behavior between suspend-to-idle and > suspend-to-RAM in the timekeeping handling that leads to functional > issues. Namely, every iteration of the loop in s2idle_loop() > increases the monotinic clock somewhat, even if timekeeping_suspend() > and timekeeping_resume() are invoked from s2idle_enter(), and if > many of them are carried out in a row, the monotonic clock can grow > significantly while the system is regarded as suspended, which > doesn't happen during suspend-to-RAM and so it is unexpected and > leads to confusion and misbehavior in user space (similar to what > ensued when we tried to combine the boottime and monotonic clocks). > > To avoid that, count all iterations of the loop in s2idle_loop() > as "sleep time" and adjust the clock for that on exit from > suspend-to-idle. > > [That also covers systems on which timekeeping is not suspended > by by s2idle_enter().] > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > --- > > This is a replacement for https://patchwork.kernel.org/patch/10599209/ > > I decided to count the entire loop in s2idle_loop() as "sleep time" as the > patch is then simpler and it also covers systems where timekeeping is not > suspended in the final step of suspend-to-idle. > > I dropped the "Fixes:" tag, because the monotonic clock delta problem > has been present on the latter since the very introduction of "freeze" > (as suspend-to-idle was referred to previously) and so this doesn't fix > any particular later commits. > > --- > kernel/power/suspend.c | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > Index: linux-pm/kernel/power/suspend.c > =================================================================== > --- linux-pm.orig/kernel/power/suspend.c > +++ linux-pm/kernel/power/suspend.c > @@ -109,8 +109,12 @@ static void s2idle_enter(void) > > static void s2idle_loop(void) > { > + ktime_t start, delta; > + > pm_pr_dbg("suspend-to-idle\n"); > > + start = ktime_get(); > + > for (;;) { > int error; > > @@ -150,6 +154,20 @@ static void s2idle_loop(void) > pm_wakeup_clear(false); > } > > + /* > + * If the monotonic clock difference between the start of the loop and > + * this point is too large, user space may get confused about whether or > + * not the system has been suspended and tasks may get killed by > + * watchdogs etc., so count the loop as "sleep time" to compensate for > + * that. > + */ > + delta = ktime_sub(ktime_get(), start); > + if (ktime_to_ns(delta) > 0) { > + struct timespec64 timespec64_delta = ktime_to_timespec64(delta); > + > + timekeeping_inject_sleeptime64(×pec64_delta); > + } But doesn't injecting sleep time here make monotonic clock too large by the amount of sleeptime? tick_freeze() / tick_unfreeze() already injects the sleeptime (otherwise delta would be 0). > + > pm_pr_dbg("resume from suspend-to-idle\n"); > } > >
