Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Mon, 22 Jun 2020 18:19:35 +0200 | Subject | Re: [PATCH][v2] PM / s2idle: Clear _TIF_POLLING_NRFLAG before suspend to idle |
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On Tue, Jun 16, 2020 at 6:03 AM Chen Yu <yu.c.chen@intel.com> wrote: > > Suspend to idle was found to not work on Goldmont CPU recently. > And the issue was triggered due to: > > 1. On Goldmont the CPU in idle can only be woken up via IPIs, > not POLLING mode: > Commit 08e237fa56a1 ("x86/cpu: Add workaround for MONITOR > instruction erratum on Goldmont based CPUs") > 2. When the CPU is entering suspend to idle process, the > _TIF_POLLING_NRFLAG is kept on, due to cpuidle_enter_s2idle() > doesn't properly match call_cpuidle(). > 3. Commit b2a02fc43a1f ("smp: Optimize send_call_function_single_ipi()") > makes use of _TIF_POLLING_NRFLAG to avoid sending IPIs to > idle CPUs. > 4. As a result, some IPIs related functions might not work > well during suspend to idle on Goldmont. For example, one > suspected victim: > tick_unfreeze() -> timekeeping_resume() -> hrtimers_resume() > -> clock_was_set() -> on_each_cpu() might wait forever, > because the IPIs will not be sent to the CPUs which are > sleeping with _TIF_POLLING_NRFLAG set, and Goldmont CPU > could not be woken up by only setting _TIF_NEED_RESCHED > on the monitor address. > > I don't find a way in Ubuntu to update the firmware of Goldmont > and check if the issue was gone, a fix patch would do no harm. > Clear the _TIF_POLLING_NRFLAG flag before entering suspend to idle, > and let the driver's enter_s2idle() to decide whether to set > _TIF_POLLING_NRFLAG or not. So that to avoid the scenario described > above and keep the context consistent with before. Also adjust > the naming to be consistent with call_cpuidle(). > > Fixes: b2a02fc43a1f ("smp: Optimize send_call_function_single_ipi()") > Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Reported-by: kbuild test robot <lkp@intel.com> > Cc: "Rafael J. Wysocki" <rafael@kernel.org> > Cc: Len Brown <lenb@kernel.org> > Cc: Peter Zijlstra (Intel) <peterz@infradead.org> > Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Peter, any more comments here?
> --- > v2: According to Peter's review, v1 is racy, if someone already > set TIF_NEED_RESCHED this patch just clear POLLING and go to sleep. > Check TIF_NEED_RESCHED before entering suspend to idle and > adjust the naming to be consistent with call_cpuidle(). > -- > drivers/cpuidle/cpuidle.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c > index c149d9e20dfd..b003767abebd 100644 > --- a/drivers/cpuidle/cpuidle.c > +++ b/drivers/cpuidle/cpuidle.c > @@ -13,6 +13,7 @@ > #include <linux/mutex.h> > #include <linux/sched.h> > #include <linux/sched/clock.h> > +#include <linux/sched/idle.h> > #include <linux/notifier.h> > #include <linux/pm_qos.h> > #include <linux/cpu.h> > @@ -133,8 +134,8 @@ int cpuidle_find_deepest_state(struct cpuidle_driver *drv, > } > > #ifdef CONFIG_SUSPEND > -static void enter_s2idle_proper(struct cpuidle_driver *drv, > - struct cpuidle_device *dev, int index) > +static void s2idle_enter(struct cpuidle_driver *drv, > + struct cpuidle_device *dev, int index) > { > ktime_t time_start, time_end; > > @@ -168,6 +169,15 @@ static void enter_s2idle_proper(struct cpuidle_driver *drv, > dev->states_usage[index].s2idle_usage++; > } > > +static int call_s2idle(struct cpuidle_driver *drv, struct cpuidle_device *dev, > + int index) > +{ > + if (!current_clr_polling_and_test()) > + s2idle_enter(drv, dev, index); > + > + return index;
Is the value returned here used at all?
> +} > + > /** > * cpuidle_enter_s2idle - Enter an idle state suitable for suspend-to-idle. > * @drv: cpuidle driver for the given CPU. > @@ -187,7 +197,7 @@ int cpuidle_enter_s2idle(struct cpuidle_driver *drv, struct cpuidle_device *dev) > */ > index = find_deepest_state(drv, dev, U64_MAX, 0, true); > if (index > 0) > - enter_s2idle_proper(drv, dev, index); > + call_s2idle(drv, dev, index);
I'm wondering why this can't be
if (index > 0 && !current_clr_polling_and_test()) enter_s2idle_proper(drv, dev, index);
> return index; > } > --
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