| Message ID | 20200915103806.411374792@infradead.org (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
| Series | Fix up ACPI processor idle vs RCU | expand |
On Tue, 15 Sep 2020 at 12:44, Peter Zijlstra <peterz@infradead.org> wrote: > > Some drivers have to do significant work, some of which relies on RCU > still being active. Instead of using RCU_NONIDLE in the drivers and > flipping RCU back on, allow drivers to take over RCU-idle duty. > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> Kind regards Uffe > --- > drivers/cpuidle/cpuidle.c | 15 ++++++++++----- > include/linux/cpuidle.h | 1 + > 2 files changed, 11 insertions(+), 5 deletions(-) > > --- a/drivers/cpuidle/cpuidle.c > +++ b/drivers/cpuidle/cpuidle.c > @@ -138,6 +138,7 @@ static void enter_s2idle_proper(struct c > struct cpuidle_device *dev, int index) > { > ktime_t time_start, time_end; > + struct cpuidle_state *target_state = &drv->states[index]; > > time_start = ns_to_ktime(local_clock()); > > @@ -153,8 +154,9 @@ static void enter_s2idle_proper(struct c > * suspended is generally unsafe. > */ > stop_critical_timings(); > - rcu_idle_enter(); > - drv->states[index].enter_s2idle(dev, drv, index); > + if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) > + rcu_idle_enter(); > + target_state->enter_s2idle(dev, drv, index); > if (WARN_ON_ONCE(!irqs_disabled())) > local_irq_disable(); > /* > @@ -162,7 +164,8 @@ static void enter_s2idle_proper(struct c > * first CPU executing it calls functions containing RCU read-side > * critical sections, so tell RCU about that. > */ > - rcu_idle_exit(); > + if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) > + rcu_idle_exit(); > tick_unfreeze(); > start_critical_timings(); > > @@ -239,9 +242,11 @@ int cpuidle_enter_state(struct cpuidle_d > time_start = ns_to_ktime(local_clock()); > > stop_critical_timings(); > - rcu_idle_enter(); > + if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) > + rcu_idle_enter(); > entered_state = target_state->enter(dev, drv, index); > - rcu_idle_exit(); > + if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) > + rcu_idle_exit(); > start_critical_timings(); > > sched_clock_idle_wakeup_event(); > --- a/include/linux/cpuidle.h > +++ b/include/linux/cpuidle.h > @@ -82,6 +82,7 @@ struct cpuidle_state { > #define CPUIDLE_FLAG_UNUSABLE BIT(3) /* avoid using this state */ > #define CPUIDLE_FLAG_OFF BIT(4) /* disable this state by default */ > #define CPUIDLE_FLAG_TLB_FLUSHED BIT(5) /* idle-state flushes TLBs */ > +#define CPUIDLE_FLAG_RCU_IDLE BIT(6) /* idle-state takes care of RCU */ > > struct cpuidle_device_kobj; > struct cpuidle_state_kobj; > >
--- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -138,6 +138,7 @@ static void enter_s2idle_proper(struct c struct cpuidle_device *dev, int index) { ktime_t time_start, time_end; + struct cpuidle_state *target_state = &drv->states[index]; time_start = ns_to_ktime(local_clock()); @@ -153,8 +154,9 @@ static void enter_s2idle_proper(struct c * suspended is generally unsafe. */ stop_critical_timings(); - rcu_idle_enter(); - drv->states[index].enter_s2idle(dev, drv, index); + if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) + rcu_idle_enter(); + target_state->enter_s2idle(dev, drv, index); if (WARN_ON_ONCE(!irqs_disabled())) local_irq_disable(); /* @@ -162,7 +164,8 @@ static void enter_s2idle_proper(struct c * first CPU executing it calls functions containing RCU read-side * critical sections, so tell RCU about that. */ - rcu_idle_exit(); + if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) + rcu_idle_exit(); tick_unfreeze(); start_critical_timings(); @@ -239,9 +242,11 @@ int cpuidle_enter_state(struct cpuidle_d time_start = ns_to_ktime(local_clock()); stop_critical_timings(); - rcu_idle_enter(); + if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) + rcu_idle_enter(); entered_state = target_state->enter(dev, drv, index); - rcu_idle_exit(); + if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE)) + rcu_idle_exit(); start_critical_timings(); sched_clock_idle_wakeup_event(); --- a/include/linux/cpuidle.h +++ b/include/linux/cpuidle.h @@ -82,6 +82,7 @@ struct cpuidle_state { #define CPUIDLE_FLAG_UNUSABLE BIT(3) /* avoid using this state */ #define CPUIDLE_FLAG_OFF BIT(4) /* disable this state by default */ #define CPUIDLE_FLAG_TLB_FLUSHED BIT(5) /* idle-state flushes TLBs */ +#define CPUIDLE_FLAG_RCU_IDLE BIT(6) /* idle-state takes care of RCU */ struct cpuidle_device_kobj; struct cpuidle_state_kobj;
Some drivers have to do significant work, some of which relies on RCU still being active. Instead of using RCU_NONIDLE in the drivers and flipping RCU back on, allow drivers to take over RCU-idle duty. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- drivers/cpuidle/cpuidle.c | 15 ++++++++++----- include/linux/cpuidle.h | 1 + 2 files changed, 11 insertions(+), 5 deletions(-)