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) <[email protected]>
Reported-by: kbuild test robot <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Len Brown <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Chen Yu <[email protected]>
---
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;
+}
+
/**
* 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);
return index;
}
--
2.17.1
On Tue, Jun 16, 2020 at 6:03 AM Chen Yu <[email protected]> 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) <[email protected]>
> Reported-by: kbuild test robot <[email protected]>
> Cc: "Rafael J. Wysocki" <[email protected]>
> Cc: Len Brown <[email protected]>
> Cc: Peter Zijlstra (Intel) <[email protected]>
> Signed-off-by: Chen Yu <[email protected]>
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;
> }
> --
Hi Rafael,
On Mon, Jun 22, 2020 at 06:19:35PM +0200, Rafael J. Wysocki wrote:
[cut]
> > +{
> > + if (!current_clr_polling_and_test())
> > + s2idle_enter(drv, dev, index);
> > +
> > + return index;
>
> Is the value returned here used at all?
>
It is not used for now IMO.
> > */
> > 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);
>
Yes, it should be simpler, but I guess Peter was trying to
make call_s2idle() consistent with call_cpuidle(),
and also s2idle_enter() is analogous to cpuidle_enter().
Thanks,
Chenyu
On Mon, Jun 22, 2020 at 06:19:35PM +0200, Rafael J. Wysocki wrote:
> > Fixes: b2a02fc43a1f ("smp: Optimize send_call_function_single_ipi()")
> > Suggested-by: Peter Zijlstra (Intel) <[email protected]>
> > Reported-by: kbuild test robot <[email protected]>
> > Cc: "Rafael J. Wysocki" <[email protected]>
> > Cc: Len Brown <[email protected]>
> > Cc: Peter Zijlstra (Intel) <[email protected]>
> > Signed-off-by: Chen Yu <[email protected]>
>
> Peter, any more comments here?
Only that the whole s2idle stuff could do with a cleanup :-)
> > +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);
Works for me. Some Wysocki guy wrote much of it, best ask him :-)
The thing that confused me is that all this is way different from the
normal idle path and didn't keep the invariants.
Ideally; much of that gets folded back into the normal patch somehow.
On Mon, Jun 22, 2020 at 7:16 PM Chen Yu <[email protected]> wrote:
>
> Hi Rafael,
> On Mon, Jun 22, 2020 at 06:19:35PM +0200, Rafael J. Wysocki wrote:
> [cut]
> > > +{
> > > + if (!current_clr_polling_and_test())
> > > + s2idle_enter(drv, dev, index);
> > > +
> > > + return index;
> >
> > Is the value returned here used at all?
> >
> It is not used for now IMO.
> > > */
> > > 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);
> >
> Yes, it should be simpler, but I guess Peter was trying to
> make call_s2idle() consistent with call_cpuidle(),
> and also s2idle_enter() is analogous to cpuidle_enter().
So IMO it would be better to do the simplest fix first and then do the
cleanup on top of it.
Thanks!
On Mon, Jun 22, 2020 at 09:45:35PM +0200, Rafael J. Wysocki wrote:
> On Mon, Jun 22, 2020 at 7:16 PM Chen Yu <[email protected]> wrote:
> >
> > Hi Rafael,
> > On Mon, Jun 22, 2020 at 06:19:35PM +0200, Rafael J. Wysocki wrote:
> > [cut]
> > > > +{
> > > > + if (!current_clr_polling_and_test())
> > > > + s2idle_enter(drv, dev, index);
> > > > +
> > > > + return index;
> > >
> > > Is the value returned here used at all?
> > >
> > It is not used for now IMO.
> > > > */
> > > > 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);
> > >
> > Yes, it should be simpler, but I guess Peter was trying to
> > make call_s2idle() consistent with call_cpuidle(),
> > and also s2idle_enter() is analogous to cpuidle_enter().
>
> So IMO it would be better to do the simplest fix first and then do the
> cleanup on top of it.
>
Okay, I'll do that.
Thanks,
Chenyu