On 05/08/2015 02:20 AM, Rafael J. Wysocki wrote: > 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.
Agreed. Makes the patch a lot simpler as well. I have sent out V3 doing this. Thank you Regards Preeti U Murthy > > -- 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/
