Messages in this thread Patch in this message | | | Date | Sat, 28 Feb 2015 11:54:23 +0000 | From | Lorenzo Pieralisi <> | Subject | Re: [PATCH 0/2] drivers: cpuidle: minor suspend-to-idle fixes |
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On Fri, Feb 27, 2015 at 10:11:54PM +0000, Rafael J. Wysocki wrote: > On Friday, February 27, 2015 10:00:00 AM Lorenzo Pieralisi wrote: > > [CC'ed Preeti] > > > > On Thu, Feb 26, 2015 at 11:37:54PM +0000, Rafael J. Wysocki wrote: > > > Me versions of the two $subject patches follow. > > > > Thank you. I am testing them and I have run into the following issue. > > > > Starting with: > > > > 3810631 ("PM / sleep: Re-implement suspend-to-idle handling") > > > > the suspend-to-idle code path in the cpuidle_idle_call() bypasses > > the CPUIDLE_FLAG_TIMER_STOP code path entirely. > > Hmm, this looks like a mistake. Sorry about that.
Thank you for looking into this !
> > Now, on most of > > the current ARM platforms, the deepest idle state loses the tick device > > context, therefore this means that going to idle through > > suspend-to-idle becomes a brute force way of nuking the tick, > > unless I am missing something here. > > > > I am experiencing hangs on resume from suspend-to-idle when the broadcast > > timer is the broadast-hrtimer (ie there is no HW broadcast timer in the > > platform) and the deepest idle states lose the tick device context (ie > > they are CPUIDLE_FLAG_TIMER_STOP), I hope Preeti can help me test this on > > Power, still chasing the issue. > > > > I could not reproduce the issue with a HW broadcast timer device. > > > > Platform has deepest idle states that allow CPUs shutdown where the > > local tick device is gone on entry, I am trying to provide you with a > > backtrace, I need time to debug. > > > > The question I have: is it safe to bypass the CPUIDLE_FLAG_TIMER_STOP > > and related broadcast mode entry/exit in the suspend-to-idle path ? > > > > I do not think it is, but I am asking. > > It isn't in general, but it would be OK in the enter_freeze_proper() path > where the tick is suspended anyway.
Entering state through enter_freeze() (ie adding the function pointer in the idle states, on platforms where it is appropriate), therefore freezing the tick solves the issue, so I think we should patch all ARM drivers that can benefit from this interesting new feature.
> > I can "force" tick freeze by initializing the enter_freeze pointer > > in the idle states (that's the next thing I will test), but still, for > > platforms where that's not possible my question above is still valid. > > Right. > > Does the patch below help (on top of the previous ones)?
I need HW to test, I will do that first thing on Monday, and send you the appropriate tags. I already put together a similar patch and tested it yesterday, so I can say already that it solves the problem, I will test your patch on Monday and get back to you (patch 1 and 2 in this series already tested on a platform with no CPUidle driver registered, and they work and fix the NULL drv dereference issue).
Thank you ! Lorenzo
> > Rafael > > > --- > drivers/cpuidle/cpuidle.c | 31 ++++++++++++++++++++++++++----- > kernel/sched/idle.c | 17 ++--------------- > 2 files changed, 28 insertions(+), 20 deletions(-) > > Index: linux-pm/drivers/cpuidle/cpuidle.c > =================================================================== > --- linux-pm.orig/drivers/cpuidle/cpuidle.c > +++ linux-pm/drivers/cpuidle/cpuidle.c > @@ -230,15 +230,36 @@ int cpuidle_select(struct cpuidle_driver > * @dev: the cpuidle device > * @index: the index in the idle state table > * > - * Returns the index in the idle state, < 0 in case of error. > - * The error code depends on the backend driver > + * Returns the index in the idle state, < 0 in case of error. -EBUSY is > + * returned to indicate that the target state was temporarily unavailable. > + * The other error codes depend on the backend driver. > */ > int cpuidle_enter(struct cpuidle_driver *drv, struct cpuidle_device *dev, > int index) > { > - if (cpuidle_state_is_coupled(dev, drv, index)) > - return cpuidle_enter_state_coupled(dev, drv, index); > - return cpuidle_enter_state(dev, drv, index); > + unsigned int broadcast; > + int ret; > + > + broadcast = drv->states[index].flags & CPUIDLE_FLAG_TIMER_STOP; > + > + /* > + * Tell the time framework to switch to a broadcast timer > + * because our local timer will be shutdown. If a local timer > + * is used from another cpu as a broadcast timer, this call may > + * fail if it is not available > + */ > + if (broadcast && > + clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu)) > + return -EBUSY; > + > + ret = cpuidle_state_is_coupled(dev, drv, index) ? > + cpuidle_enter_state_coupled(dev, drv, index) : > + cpuidle_enter_state(dev, drv, index); > + > + if (broadcast) > + clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu); > + > + return ret; > } > > /** > Index: linux-pm/kernel/sched/idle.c > =================================================================== > --- linux-pm.orig/kernel/sched/idle.c > +++ linux-pm/kernel/sched/idle.c > @@ -81,7 +81,6 @@ static void cpuidle_idle_call(void) > struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices); > struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); > int next_state, entered_state; > - unsigned int broadcast; > > /* > * Check if the idle task must be rescheduled. If it is the > @@ -151,18 +150,6 @@ use_default: > goto exit_idle; > } > > - broadcast = drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP; > - > - /* > - * Tell the time framework to switch to a broadcast timer > - * because our local timer will be shutdown. If a local timer > - * is used from another cpu as a broadcast timer, this call may > - * fail if it is not available > - */ > - if (broadcast && > - clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu)) > - goto use_default; > - > /* Take note of the planned idle state. */ > idle_set_state(this_rq(), &drv->states[next_state]); > > @@ -176,8 +163,8 @@ use_default: > /* The cpu is no longer idle or about to enter idle. */ > idle_set_state(this_rq(), NULL); > > - if (broadcast) > - clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu); > + if (entered_state == -EBUSY) > + goto use_default; > > /* > * Give the governor an opportunity to reflect on the outcome > > >
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