| Message ID | 20200616040442.21515-1-yu.c.chen@intel.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | [v2] PM / s2idle: Clear _TIF_POLLING_NRFLAG before suspend to idle | expand |
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; > } > --
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) <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? 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 <yu.c.chen@intel.com> 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 <yu.c.chen@intel.com> 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
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; }
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> --- 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(-)