On Thursday, May 07, 2015 11:17:21 PM Preeti U Murthy wrote: > When a CPU has to enter an idle state where tick stops, it makes a call > to tick_broadcast_enter(). The call will fail if this CPU is the > broadcast CPU. Today, under such a circumstance, the arch cpuidle code > handles this CPU. This is not convincing because not only are we not > aware what the arch cpuidle code does, but we also do not account for > the idle state residency time and usage of such a CPU. > > This scenario can be handled better by simply asking the cpuidle > governor to choose an idle state where in ticks do not stop. To > accommodate this change move the setting of runqueue idle state from the > core to the cpuidle driver, else the rq->idle_state will be set wrong. > > Signed-off-by: Preeti U Murthy <pre...@linux.vnet.ibm.com> > --- > Changes from V1: https://lkml.org/lkml/2015/5/7/24 > Rebased on the latest linux-pm/bleeding-edge > > drivers/cpuidle/cpuidle.c | 21 +++++++++++++++++---- > drivers/cpuidle/governors/ladder.c | 13 ++++++++++--- > drivers/cpuidle/governors/menu.c | 6 +++++- > include/linux/cpuidle.h | 6 +++--- > include/linux/sched.h | 16 ++++++++++++++++ > kernel/sched/core.c | 17 +++++++++++++++++ > kernel/sched/fair.c | 2 +- > kernel/sched/idle.c | 8 +------- > kernel/sched/sched.h | 24 ------------------------ > 9 files changed, 70 insertions(+), 43 deletions(-) > > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c > index 8c24f95..b7e86f4 100644 > --- a/drivers/cpuidle/cpuidle.c > +++ b/drivers/cpuidle/cpuidle.c > @@ -21,6 +21,7 @@ > #include <linux/module.h> > #include <linux/suspend.h> > #include <linux/tick.h> > +#include <linux/sched.h> > #include <trace/events/power.h> > > #include "cpuidle.h" > @@ -168,10 +169,17 @@ int cpuidle_enter_state(struct cpuidle_device *dev, > struct cpuidle_driver *drv, > * CPU as a broadcast timer, this call may fail if it is not available. > */ > if (broadcast && tick_broadcast_enter()) { > - default_idle_call(); > - return -EBUSY; > + index = cpuidle_select(drv, dev, !broadcast);
No, you can't do that. This code path may be used by suspend-to-idle and that should not call cpuidle_select(). What's needed here seems to be a fallback mechanism like "choose the deepest state shallower than X and such that it won't stop the tick". You don't really need to run a full governor for that. -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
