* Re: [PATCH 2/4] cpuidle: Fix missing need_resched() check after rcu_idle_enter() [not found] ` <20201222013712.15056-3-frederic@kernel.org> @ 2021-01-05 17:25 ` Dmitry Osipenko 2021-01-05 18:10 ` Dmitry Osipenko 0 siblings, 1 reply; 3+ messages in thread From: Dmitry Osipenko @ 2021-01-05 17:25 UTC (permalink / raw) To: Frederic Weisbecker, LKML Cc: Rafael J . Wysocki, Peter Zijlstra, Ingo Molnar, Fabio Estevam, stable, Thomas Gleixner, Paul E . McKenney, Len Brown, Pengutronix Kernel Team, NXP Linux Team, Daniel Lezcano, Shawn Guo, Sascha Hauer, linux-tegra@vger.kernel.org 22.12.2020 04:37, Frederic Weisbecker пишет: > Entering RCU idle mode may cause a deferred wake up of an RCU NOCB_GP > kthread (rcuog) to be serviced. > > Usually a wake up happening while running the idle task is spotted in > one of the need_resched() checks carefully placed within the idle loop > that can break to the scheduler. > > Unfortunately within cpuidle the call to rcu_idle_enter() is already > beyond the last generic need_resched() check. Some drivers may perform > their own checks like with mwait_idle_with_hints() but many others don't > and we may halt the CPU with a resched request unhandled, leaving the > task hanging. > > Fix this with performing a last minute need_resched() check after > calling rcu_idle_enter(). > > Reported-by: Paul E. McKenney <paulmck@kernel.org> > Fixes: 1098582a0f6c (sched,idle,rcu: Push rcu_idle deeper into the idle path) > Cc: stable@vger.kernel.org > Cc: Daniel Lezcano <daniel.lezcano@linaro.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@kernel.org> > Signed-off-by: Frederic Weisbecker <frederic@kernel.org> > --- > drivers/cpuidle/cpuidle.c | 33 +++++++++++++++++++++++++-------- > 1 file changed, 25 insertions(+), 8 deletions(-) > > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c > index ef2ea1b12cd8..4cc1ba49ce05 100644 > --- a/drivers/cpuidle/cpuidle.c > +++ b/drivers/cpuidle/cpuidle.c > @@ -134,8 +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 int enter_s2idle_proper(struct cpuidle_driver *drv, > + struct cpuidle_device *dev, int index) > { > ktime_t time_start, time_end; > struct cpuidle_state *target_state = &drv->states[index]; > @@ -151,7 +151,14 @@ static void enter_s2idle_proper(struct cpuidle_driver *drv, > stop_critical_timings(); > if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) > rcu_idle_enter(); > - target_state->enter_s2idle(dev, drv, index); > + /* > + * Last need_resched() check must come after rcu_idle_enter() > + * which may wake up RCU internal tasks. > + */ > + if (!need_resched()) > + target_state->enter_s2idle(dev, drv, index); > + else > + index = -EBUSY; > if (WARN_ON_ONCE(!irqs_disabled())) > local_irq_disable(); > if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) > @@ -159,10 +166,13 @@ static void enter_s2idle_proper(struct cpuidle_driver *drv, > tick_unfreeze(); > start_critical_timings(); > > - time_end = ns_to_ktime(local_clock()); > + if (index > 0) { index=0 is valid too > + time_end = ns_to_ktime(local_clock()); > + dev->states_usage[index].s2idle_time += ktime_us_delta(time_end, time_start); > + dev->states_usage[index].s2idle_usage++; > + } > > - dev->states_usage[index].s2idle_time += ktime_us_delta(time_end, time_start); > - dev->states_usage[index].s2idle_usage++; > + return index; > } > > /** > @@ -184,7 +194,7 @@ 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); > + index = enter_s2idle_proper(drv, dev, index); > local_irq_enable(); > } > return index; > @@ -234,7 +244,14 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, > stop_critical_timings(); > if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) > rcu_idle_enter(); > - entered_state = target_state->enter(dev, drv, index); > + /* > + * Last need_resched() check must come after rcu_idle_enter() > + * which may wake up RCU internal tasks. > + */ > + if (!need_resched()) > + entered_state = target_state->enter(dev, drv, index); > + else > + entered_state = -EBUSY; > if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) > rcu_idle_exit(); > start_critical_timings(); > This patch causes a hardlock on NVIDIA Tegra using today's linux-next. Disabling coupled idling state helps. Please fix thanks in advance. ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 2/4] cpuidle: Fix missing need_resched() check after rcu_idle_enter() 2021-01-05 17:25 ` [PATCH 2/4] cpuidle: Fix missing need_resched() check after rcu_idle_enter() Dmitry Osipenko @ 2021-01-05 18:10 ` Dmitry Osipenko 2021-01-05 19:17 ` Paul E. McKenney 0 siblings, 1 reply; 3+ messages in thread From: Dmitry Osipenko @ 2021-01-05 18:10 UTC (permalink / raw) To: Frederic Weisbecker, LKML Cc: Rafael J . Wysocki, Peter Zijlstra, Ingo Molnar, Fabio Estevam, stable, Thomas Gleixner, Paul E . McKenney, Len Brown, Pengutronix Kernel Team, NXP Linux Team, Daniel Lezcano, Shawn Guo, Sascha Hauer, linux-tegra@vger.kernel.org 05.01.2021 20:25, Dmitry Osipenko пишет: > 22.12.2020 04:37, Frederic Weisbecker пишет: >> Entering RCU idle mode may cause a deferred wake up of an RCU NOCB_GP >> kthread (rcuog) to be serviced. >> >> Usually a wake up happening while running the idle task is spotted in >> one of the need_resched() checks carefully placed within the idle loop >> that can break to the scheduler. >> >> Unfortunately within cpuidle the call to rcu_idle_enter() is already >> beyond the last generic need_resched() check. Some drivers may perform >> their own checks like with mwait_idle_with_hints() but many others don't >> and we may halt the CPU with a resched request unhandled, leaving the >> task hanging. >> >> Fix this with performing a last minute need_resched() check after >> calling rcu_idle_enter(). >> >> Reported-by: Paul E. McKenney <paulmck@kernel.org> >> Fixes: 1098582a0f6c (sched,idle,rcu: Push rcu_idle deeper into the idle path) >> Cc: stable@vger.kernel.org >> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> >> Cc: Peter Zijlstra <peterz@infradead.org> >> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> >> Cc: Thomas Gleixner <tglx@linutronix.de> >> Cc: Ingo Molnar <mingo@kernel.org> >> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> >> --- >> drivers/cpuidle/cpuidle.c | 33 +++++++++++++++++++++++++-------- >> 1 file changed, 25 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c >> index ef2ea1b12cd8..4cc1ba49ce05 100644 >> --- a/drivers/cpuidle/cpuidle.c >> +++ b/drivers/cpuidle/cpuidle.c >> @@ -134,8 +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 int enter_s2idle_proper(struct cpuidle_driver *drv, >> + struct cpuidle_device *dev, int index) >> { >> ktime_t time_start, time_end; >> struct cpuidle_state *target_state = &drv->states[index]; >> @@ -151,7 +151,14 @@ static void enter_s2idle_proper(struct cpuidle_driver *drv, >> stop_critical_timings(); >> if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) >> rcu_idle_enter(); >> - target_state->enter_s2idle(dev, drv, index); >> + /* >> + * Last need_resched() check must come after rcu_idle_enter() >> + * which may wake up RCU internal tasks. >> + */ >> + if (!need_resched()) >> + target_state->enter_s2idle(dev, drv, index); >> + else >> + index = -EBUSY; >> if (WARN_ON_ONCE(!irqs_disabled())) >> local_irq_disable(); >> if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) >> @@ -159,10 +166,13 @@ static void enter_s2idle_proper(struct cpuidle_driver *drv, >> tick_unfreeze(); >> start_critical_timings(); >> >> - time_end = ns_to_ktime(local_clock()); >> + if (index > 0) { > > index=0 is valid too > >> + time_end = ns_to_ktime(local_clock()); >> + dev->states_usage[index].s2idle_time += ktime_us_delta(time_end, time_start); >> + dev->states_usage[index].s2idle_usage++; >> + } >> >> - dev->states_usage[index].s2idle_time += ktime_us_delta(time_end, time_start); >> - dev->states_usage[index].s2idle_usage++; >> + return index; >> } >> >> /** >> @@ -184,7 +194,7 @@ 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); >> + index = enter_s2idle_proper(drv, dev, index); >> local_irq_enable(); >> } >> return index; >> @@ -234,7 +244,14 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, >> stop_critical_timings(); >> if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) >> rcu_idle_enter(); >> - entered_state = target_state->enter(dev, drv, index); >> + /* >> + * Last need_resched() check must come after rcu_idle_enter() >> + * which may wake up RCU internal tasks. >> + */ >> + if (!need_resched()) >> + entered_state = target_state->enter(dev, drv, index); >> + else >> + entered_state = -EBUSY; >> if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) >> rcu_idle_exit(); >> start_critical_timings(); >> > > This patch causes a hardlock on NVIDIA Tegra using today's linux-next. > Disabling coupled idling state helps. Please fix thanks in advance. > This isn't a proper fix, but it works: diff --git a/drivers/cpuidle/cpuidle-tegra.c b/drivers/cpuidle/cpuidle-tegra.c index 191966dc8d02..ecc5d9b31553 100644 --- a/drivers/cpuidle/cpuidle-tegra.c +++ b/drivers/cpuidle/cpuidle-tegra.c @@ -148,7 +148,7 @@ static int tegra_cpuidle_c7_enter(void) static int tegra_cpuidle_coupled_barrier(struct cpuidle_device *dev) { - if (tegra_pending_sgi()) { + if (tegra_pending_sgi() || need_resched()) { /* * CPU got local interrupt that will be lost after GIC's * shutdown because GIC driver doesn't save/restore the diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 4cc1ba49ce05..2bc52ccc339b 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -248,7 +248,7 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, * Last need_resched() check must come after rcu_idle_enter() * which may wake up RCU internal tasks. */ - if (!need_resched()) + if ((target_state->flags & CPUIDLE_FLAG_COUPLED) || !need_resched()) entered_state = target_state->enter(dev, drv, index); else entered_state = -EBUSY; ^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH 2/4] cpuidle: Fix missing need_resched() check after rcu_idle_enter() 2021-01-05 18:10 ` Dmitry Osipenko @ 2021-01-05 19:17 ` Paul E. McKenney 0 siblings, 0 replies; 3+ messages in thread From: Paul E. McKenney @ 2021-01-05 19:17 UTC (permalink / raw) To: Dmitry Osipenko Cc: Frederic Weisbecker, LKML, Rafael J . Wysocki, Peter Zijlstra, Ingo Molnar, Fabio Estevam, stable, Thomas Gleixner, Len Brown, Pengutronix Kernel Team, NXP Linux Team, Daniel Lezcano, Shawn Guo, Sascha Hauer, linux-tegra@vger.kernel.org On Tue, Jan 05, 2021 at 09:10:30PM +0300, Dmitry Osipenko wrote: > 05.01.2021 20:25, Dmitry Osipenko пишет: > > 22.12.2020 04:37, Frederic Weisbecker пишет: > >> Entering RCU idle mode may cause a deferred wake up of an RCU NOCB_GP > >> kthread (rcuog) to be serviced. > >> > >> Usually a wake up happening while running the idle task is spotted in > >> one of the need_resched() checks carefully placed within the idle loop > >> that can break to the scheduler. > >> > >> Unfortunately within cpuidle the call to rcu_idle_enter() is already > >> beyond the last generic need_resched() check. Some drivers may perform > >> their own checks like with mwait_idle_with_hints() but many others don't > >> and we may halt the CPU with a resched request unhandled, leaving the > >> task hanging. > >> > >> Fix this with performing a last minute need_resched() check after > >> calling rcu_idle_enter(). > >> > >> Reported-by: Paul E. McKenney <paulmck@kernel.org> > >> Fixes: 1098582a0f6c (sched,idle,rcu: Push rcu_idle deeper into the idle path) > >> Cc: stable@vger.kernel.org > >> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> > >> Cc: Peter Zijlstra <peterz@infradead.org> > >> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > >> Cc: Thomas Gleixner <tglx@linutronix.de> > >> Cc: Ingo Molnar <mingo@kernel.org> > >> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> > >> --- > >> drivers/cpuidle/cpuidle.c | 33 +++++++++++++++++++++++++-------- > >> 1 file changed, 25 insertions(+), 8 deletions(-) > >> > >> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c > >> index ef2ea1b12cd8..4cc1ba49ce05 100644 > >> --- a/drivers/cpuidle/cpuidle.c > >> +++ b/drivers/cpuidle/cpuidle.c > >> @@ -134,8 +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 int enter_s2idle_proper(struct cpuidle_driver *drv, > >> + struct cpuidle_device *dev, int index) > >> { > >> ktime_t time_start, time_end; > >> struct cpuidle_state *target_state = &drv->states[index]; > >> @@ -151,7 +151,14 @@ static void enter_s2idle_proper(struct cpuidle_driver *drv, > >> stop_critical_timings(); > >> if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) > >> rcu_idle_enter(); > >> - target_state->enter_s2idle(dev, drv, index); > >> + /* > >> + * Last need_resched() check must come after rcu_idle_enter() > >> + * which may wake up RCU internal tasks. > >> + */ > >> + if (!need_resched()) > >> + target_state->enter_s2idle(dev, drv, index); > >> + else > >> + index = -EBUSY; > >> if (WARN_ON_ONCE(!irqs_disabled())) > >> local_irq_disable(); > >> if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) > >> @@ -159,10 +166,13 @@ static void enter_s2idle_proper(struct cpuidle_driver *drv, > >> tick_unfreeze(); > >> start_critical_timings(); > >> > >> - time_end = ns_to_ktime(local_clock()); > >> + if (index > 0) { > > > > index=0 is valid too > > > >> + time_end = ns_to_ktime(local_clock()); > >> + dev->states_usage[index].s2idle_time += ktime_us_delta(time_end, time_start); > >> + dev->states_usage[index].s2idle_usage++; > >> + } > >> > >> - dev->states_usage[index].s2idle_time += ktime_us_delta(time_end, time_start); > >> - dev->states_usage[index].s2idle_usage++; > >> + return index; > >> } > >> > >> /** > >> @@ -184,7 +194,7 @@ 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); > >> + index = enter_s2idle_proper(drv, dev, index); > >> local_irq_enable(); > >> } > >> return index; > >> @@ -234,7 +244,14 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, > >> stop_critical_timings(); > >> if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) > >> rcu_idle_enter(); > >> - entered_state = target_state->enter(dev, drv, index); > >> + /* > >> + * Last need_resched() check must come after rcu_idle_enter() > >> + * which may wake up RCU internal tasks. > >> + */ > >> + if (!need_resched()) > >> + entered_state = target_state->enter(dev, drv, index); > >> + else > >> + entered_state = -EBUSY; > >> if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) > >> rcu_idle_exit(); > >> start_critical_timings(); > >> > > > > This patch causes a hardlock on NVIDIA Tegra using today's linux-next. > > Disabling coupled idling state helps. Please fix thanks in advance. > > This isn't a proper fix, but it works: There is some ongoing discussion about what an overall proper fix might look like, so in the meantime I am folding you changes below into Frederic's original. ;-) Thanx, Paul > diff --git a/drivers/cpuidle/cpuidle-tegra.c > b/drivers/cpuidle/cpuidle-tegra.c > index 191966dc8d02..ecc5d9b31553 100644 > --- a/drivers/cpuidle/cpuidle-tegra.c > +++ b/drivers/cpuidle/cpuidle-tegra.c > @@ -148,7 +148,7 @@ static int tegra_cpuidle_c7_enter(void) > > static int tegra_cpuidle_coupled_barrier(struct cpuidle_device *dev) > { > - if (tegra_pending_sgi()) { > + if (tegra_pending_sgi() || need_resched()) { > /* > * CPU got local interrupt that will be lost after GIC's > * shutdown because GIC driver doesn't save/restore the > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c > index 4cc1ba49ce05..2bc52ccc339b 100644 > --- a/drivers/cpuidle/cpuidle.c > +++ b/drivers/cpuidle/cpuidle.c > @@ -248,7 +248,7 @@ int cpuidle_enter_state(struct cpuidle_device *dev, > struct cpuidle_driver *drv, > * Last need_resched() check must come after rcu_idle_enter() > * which may wake up RCU internal tasks. > */ > - if (!need_resched()) > + if ((target_state->flags & CPUIDLE_FLAG_COUPLED) || !need_resched()) > entered_state = target_state->enter(dev, drv, index); > else > entered_state = -EBUSY; > ^ permalink raw reply [flat|nested] 3+ messages in thread
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[not found] ` <20201222013712.15056-3-frederic@kernel.org>
2021-01-05 17:25 ` [PATCH 2/4] cpuidle: Fix missing need_resched() check after rcu_idle_enter() Dmitry Osipenko
2021-01-05 18:10 ` Dmitry Osipenko
2021-01-05 19:17 ` Paul E. McKenney
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