diff mbox series

[14/36] cpuidle: Fix rcu_idle_*() usage

Message ID 20220608144516.808451191@infradead.org
State New
Headers show
Series cpuidle,rcu: Cleanup the mess | expand

Commit Message

Peter Zijlstra June 8, 2022, 2:27 p.m. UTC 
The whole disable-RCU, enable-IRQS dance is very intricate since
changing IRQ state is traced, which depends on RCU.

Add two helpers for the cpuidle case that mirror the entry code.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/arm/mach-imx/cpuidle-imx6q.c    |    4 +--
 arch/arm/mach-imx/cpuidle-imx6sx.c   |    4 +--
 arch/arm/mach-omap2/cpuidle34xx.c    |    4 +--
 arch/arm/mach-omap2/cpuidle44xx.c    |    8 +++---
 drivers/acpi/processor_idle.c        |   18 ++++++++------
 drivers/cpuidle/cpuidle-big_little.c |    4 +--
 drivers/cpuidle/cpuidle-mvebu-v7.c   |    4 +--
 drivers/cpuidle/cpuidle-psci.c       |    4 +--
 drivers/cpuidle/cpuidle-riscv-sbi.c  |    4 +--
 drivers/cpuidle/cpuidle-tegra.c      |    8 +++---
 drivers/cpuidle/cpuidle.c            |   11 ++++----
 include/linux/cpuidle.h              |   37 +++++++++++++++++++++++++---
 kernel/sched/idle.c                  |   45 ++++++++++-------------------------
 kernel/time/tick-broadcast.c         |    6 +++-
 14 files changed, 90 insertions(+), 71 deletions(-)

Comments

Mark Rutland June 14, 2022, 12:41 p.m. UTC | #1 
On Wed, Jun 08, 2022 at 04:27:37PM +0200, Peter Zijlstra wrote:
> --- a/kernel/time/tick-broadcast.c
> +++ b/kernel/time/tick-broadcast.c
> @@ -622,9 +622,13 @@ struct cpumask *tick_get_broadcast_onesh
>   * to avoid a deep idle transition as we are about to get the
>   * broadcast IPI right away.
>   */
> -int tick_check_broadcast_expired(void)
> +noinstr int tick_check_broadcast_expired(void)
>  {
> +#ifdef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
> +	return arch_test_bit(smp_processor_id(), cpumask_bits(tick_broadcast_force_mask));
> +#else
>  	return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
> +#endif
>  }

This is somewhat not-ideal. :/

Could we unconditionally do the arch_test_bit() variant, with a comment, or
does that not exist in some cases?

Thanks,
Mark.
Peter Zijlstra June 14, 2022, 4:40 p.m. UTC | #2 
On Tue, Jun 14, 2022 at 01:41:13PM +0100, Mark Rutland wrote:
> On Wed, Jun 08, 2022 at 04:27:37PM +0200, Peter Zijlstra wrote:
> > --- a/kernel/time/tick-broadcast.c
> > +++ b/kernel/time/tick-broadcast.c
> > @@ -622,9 +622,13 @@ struct cpumask *tick_get_broadcast_onesh
> >   * to avoid a deep idle transition as we are about to get the
> >   * broadcast IPI right away.
> >   */
> > -int tick_check_broadcast_expired(void)
> > +noinstr int tick_check_broadcast_expired(void)
> >  {
> > +#ifdef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
> > +	return arch_test_bit(smp_processor_id(), cpumask_bits(tick_broadcast_force_mask));
> > +#else
> >  	return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
> > +#endif
> >  }
> 
> This is somewhat not-ideal. :/

I'll say.

> Could we unconditionally do the arch_test_bit() variant, with a comment, or
> does that not exist in some cases?

Loads of build errors ensued, which is how I ended up with this mess ...
Mark Rutland June 14, 2022, 4:59 p.m. UTC | #3 
On Tue, Jun 14, 2022 at 06:40:53PM +0200, Peter Zijlstra wrote:
> On Tue, Jun 14, 2022 at 01:41:13PM +0100, Mark Rutland wrote:
> > On Wed, Jun 08, 2022 at 04:27:37PM +0200, Peter Zijlstra wrote:
> > > --- a/kernel/time/tick-broadcast.c
> > > +++ b/kernel/time/tick-broadcast.c
> > > @@ -622,9 +622,13 @@ struct cpumask *tick_get_broadcast_onesh
> > >   * to avoid a deep idle transition as we are about to get the
> > >   * broadcast IPI right away.
> > >   */
> > > -int tick_check_broadcast_expired(void)
> > > +noinstr int tick_check_broadcast_expired(void)
> > >  {
> > > +#ifdef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
> > > +	return arch_test_bit(smp_processor_id(), cpumask_bits(tick_broadcast_force_mask));
> > > +#else
> > >  	return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
> > > +#endif
> > >  }
> > 
> > This is somewhat not-ideal. :/
> 
> I'll say.
> 
> > Could we unconditionally do the arch_test_bit() variant, with a comment, or
> > does that not exist in some cases?
> 
> Loads of build errors ensued, which is how I ended up with this mess ...

Yaey :(

I see the same is true for the thread flag manipulation too.

I'll take a look and see if we can layer things so that we can use the arch_*()
helpers and wrap those consistently so that we don't have to check the CPP
guard.

Ideally we'd have a a better language that allows us to make some
context-senstive decisions, then we could hide all this gunk in the lower
levels with somethin like:

	if (!THIS_IS_A_NOINSTR_FUNCTION()) {
		explicit_instrumentation(...);
	}

... ho hum.

Mark.
diff mbox series

Patch

--- a/arch/arm/mach-imx/cpuidle-imx6q.c
+++ b/arch/arm/mach-imx/cpuidle-imx6q.c
@@ -24,9 +24,9 @@  static int imx6q_enter_wait(struct cpuid
 		imx6_set_lpm(WAIT_UNCLOCKED);
 	raw_spin_unlock(&cpuidle_lock);
 
-	rcu_idle_enter();
+	cpuidle_rcu_enter();
 	cpu_do_idle();
-	rcu_idle_exit();
+	cpuidle_rcu_exit();
 
 	raw_spin_lock(&cpuidle_lock);
 	if (num_idle_cpus-- == num_online_cpus())
--- a/arch/arm/mach-imx/cpuidle-imx6sx.c
+++ b/arch/arm/mach-imx/cpuidle-imx6sx.c
@@ -47,9 +47,9 @@  static int imx6sx_enter_wait(struct cpui
 		cpu_pm_enter();
 		cpu_cluster_pm_enter();
 
-		rcu_idle_enter();
+		cpuidle_rcu_enter();
 		cpu_suspend(0, imx6sx_idle_finish);
-		rcu_idle_exit();
+		cpuidle_rcu_exit();
 
 		cpu_cluster_pm_exit();
 		cpu_pm_exit();
--- a/arch/arm/mach-omap2/cpuidle34xx.c
+++ b/arch/arm/mach-omap2/cpuidle34xx.c
@@ -133,9 +133,9 @@  static int omap3_enter_idle(struct cpuid
 	}
 
 	/* Execute ARM wfi */
-	rcu_idle_enter();
+	cpuidle_rcu_enter();
 	omap_sram_idle();
-	rcu_idle_exit();
+	cpuidle_rcu_exit();
 
 	/*
 	 * Call idle CPU PM enter notifier chain to restore
--- a/arch/arm/mach-omap2/cpuidle44xx.c
+++ b/arch/arm/mach-omap2/cpuidle44xx.c
@@ -105,9 +105,9 @@  static int omap_enter_idle_smp(struct cp
 	}
 	raw_spin_unlock_irqrestore(&mpu_lock, flag);
 
-	rcu_idle_enter();
+	cpuidle_rcu_enter();
 	omap4_enter_lowpower(dev->cpu, cx->cpu_state);
-	rcu_idle_exit();
+	cpuidle_rcu_exit();
 
 	raw_spin_lock_irqsave(&mpu_lock, flag);
 	if (cx->mpu_state_vote == num_online_cpus())
@@ -186,10 +186,10 @@  static int omap_enter_idle_coupled(struc
 		}
 	}
 
-	rcu_idle_enter();
+	cpuidle_rcu_enter();
 	omap4_enter_lowpower(dev->cpu, cx->cpu_state);
 	cpu_done[dev->cpu] = true;
-	rcu_idle_exit();
+	cpuidle_rcu_exit();
 
 	/* Wakeup CPU1 only if it is not offlined */
 	if (dev->cpu == 0 && cpumask_test_cpu(1, cpu_online_mask)) {
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -607,7 +607,7 @@  static DEFINE_RAW_SPINLOCK(c3_lock);
  * @cx: Target state context
  * @index: index of target state
  */
-static int acpi_idle_enter_bm(struct cpuidle_driver *drv,
+static noinstr int acpi_idle_enter_bm(struct cpuidle_driver *drv,
 			       struct acpi_processor *pr,
 			       struct acpi_processor_cx *cx,
 			       int index)
@@ -626,6 +626,8 @@  static int acpi_idle_enter_bm(struct cpu
 	 */
 	bool dis_bm = pr->flags.bm_control;
 
+	instrumentation_begin();
+
 	/* If we can skip BM, demote to a safe state. */
 	if (!cx->bm_sts_skip && acpi_idle_bm_check()) {
 		dis_bm = false;
@@ -647,11 +649,11 @@  static int acpi_idle_enter_bm(struct cpu
 		raw_spin_unlock(&c3_lock);
 	}
 
-	rcu_idle_enter();
+	cpuidle_rcu_enter();
 
 	acpi_idle_do_entry(cx);
 
-	rcu_idle_exit();
+	cpuidle_rcu_exit();
 
 	/* Re-enable bus master arbitration */
 	if (dis_bm) {
@@ -661,11 +663,13 @@  static int acpi_idle_enter_bm(struct cpu
 		raw_spin_unlock(&c3_lock);
 	}
 
+	instrumentation_end();
+
 	return index;
 }
 
-static int acpi_idle_enter(struct cpuidle_device *dev,
-			   struct cpuidle_driver *drv, int index)
+static noinstr int acpi_idle_enter(struct cpuidle_device *dev,
+				   struct cpuidle_driver *drv, int index)
 {
 	struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);
 	struct acpi_processor *pr;
@@ -693,8 +697,8 @@  static int acpi_idle_enter(struct cpuidl
 	return index;
 }
 
-static int acpi_idle_enter_s2idle(struct cpuidle_device *dev,
-				  struct cpuidle_driver *drv, int index)
+static noinstr int acpi_idle_enter_s2idle(struct cpuidle_device *dev,
+					  struct cpuidle_driver *drv, int index)
 {
 	struct acpi_processor_cx *cx = per_cpu(acpi_cstate[index], dev->cpu);
 
--- a/drivers/cpuidle/cpuidle-big_little.c
+++ b/drivers/cpuidle/cpuidle-big_little.c
@@ -126,13 +126,13 @@  static int bl_enter_powerdown(struct cpu
 				struct cpuidle_driver *drv, int idx)
 {
 	cpu_pm_enter();
-	rcu_idle_enter();
+	cpuidle_rcu_enter();
 
 	cpu_suspend(0, bl_powerdown_finisher);
 
 	/* signals the MCPM core that CPU is out of low power state */
 	mcpm_cpu_powered_up();
-	rcu_idle_exit();
+	cpuidle_rcu_exit();
 
 	cpu_pm_exit();
 
--- a/drivers/cpuidle/cpuidle-mvebu-v7.c
+++ b/drivers/cpuidle/cpuidle-mvebu-v7.c
@@ -36,9 +36,9 @@  static int mvebu_v7_enter_idle(struct cp
 	if (drv->states[index].flags & MVEBU_V7_FLAG_DEEP_IDLE)
 		deepidle = true;
 
-	rcu_idle_enter();
+	cpuidle_rcu_enter();
 	ret = mvebu_v7_cpu_suspend(deepidle);
-	rcu_idle_exit();
+	cpuidle_rcu_exit();
 
 	cpu_pm_exit();
 
--- a/drivers/cpuidle/cpuidle-psci.c
+++ b/drivers/cpuidle/cpuidle-psci.c
@@ -74,7 +74,7 @@  static int __psci_enter_domain_idle_stat
 	else
 		pm_runtime_put_sync_suspend(pd_dev);
 
-	rcu_idle_enter();
+	cpuidle_rcu_enter();
 
 	state = psci_get_domain_state();
 	if (!state)
@@ -82,7 +82,7 @@  static int __psci_enter_domain_idle_stat
 
 	ret = psci_cpu_suspend_enter(state) ? -1 : idx;
 
-	rcu_idle_exit();
+	cpuidle_rcu_exit();
 
 	if (s2idle)
 		dev_pm_genpd_resume(pd_dev);
--- a/drivers/cpuidle/cpuidle-riscv-sbi.c
+++ b/drivers/cpuidle/cpuidle-riscv-sbi.c
@@ -121,7 +121,7 @@  static int __sbi_enter_domain_idle_state
 	else
 		pm_runtime_put_sync_suspend(pd_dev);
 
-	rcu_idle_enter();
+	cpuidle_rcu_enter();
 
 	if (sbi_is_domain_state_available())
 		state = sbi_get_domain_state();
@@ -130,7 +130,7 @@  static int __sbi_enter_domain_idle_state
 
 	ret = sbi_suspend(state) ? -1 : idx;
 
-	rcu_idle_exit();
+	cpuidle_rcu_exit();
 
 	if (s2idle)
 		dev_pm_genpd_resume(pd_dev);
--- a/drivers/cpuidle/cpuidle-tegra.c
+++ b/drivers/cpuidle/cpuidle-tegra.c
@@ -183,7 +183,7 @@  static int tegra_cpuidle_state_enter(str
 	tegra_pm_set_cpu_in_lp2();
 	cpu_pm_enter();
 
-	rcu_idle_enter();
+	cpuidle_rcu_enter();
 
 	switch (index) {
 	case TEGRA_C7:
@@ -199,7 +199,7 @@  static int tegra_cpuidle_state_enter(str
 		break;
 	}
 
-	rcu_idle_exit();
+	cpuidle_rcu_exit();
 
 	cpu_pm_exit();
 	tegra_pm_clear_cpu_in_lp2();
@@ -240,10 +240,10 @@  static int tegra_cpuidle_enter(struct cp
 
 	if (index == TEGRA_C1) {
 		if (do_rcu)
-			rcu_idle_enter();
+			cpuidle_rcu_enter();
 		ret = arm_cpuidle_simple_enter(dev, drv, index);
 		if (do_rcu)
-			rcu_idle_exit();
+			cpuidle_rcu_exit();
 	} else
 		ret = tegra_cpuidle_state_enter(dev, index, cpu);
 
--- 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>
@@ -150,12 +151,12 @@  static void enter_s2idle_proper(struct c
 	 */
 	stop_critical_timings();
 	if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
-		rcu_idle_enter();
+		cpuidle_rcu_enter();
 	target_state->enter_s2idle(dev, drv, index);
 	if (WARN_ON_ONCE(!irqs_disabled()))
-		local_irq_disable();
+		raw_local_irq_disable();
 	if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
-		rcu_idle_exit();
+		cpuidle_rcu_exit();
 	tick_unfreeze();
 	start_critical_timings();
 
@@ -233,14 +234,14 @@  int cpuidle_enter_state(struct cpuidle_d
 
 	stop_critical_timings();
 	if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
-		rcu_idle_enter();
+		cpuidle_rcu_enter();
 
 	entered_state = target_state->enter(dev, drv, index);
 	if (WARN_ONCE(!irqs_disabled(), "%ps leaked IRQ state", target_state->enter))
 		raw_local_irq_disable();
 
 	if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
-		rcu_idle_exit();
+		cpuidle_rcu_exit();
 	start_critical_timings();
 
 	sched_clock_idle_wakeup_event();
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -115,6 +115,35 @@  struct cpuidle_device {
 DECLARE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
 DECLARE_PER_CPU(struct cpuidle_device, cpuidle_dev);
 
+static __always_inline void cpuidle_rcu_enter(void)
+{
+	lockdep_assert_irqs_disabled();
+	/*
+	 * Idle is allowed to (temporary) enable IRQs. It
+	 * will return with IRQs disabled.
+	 *
+	 * Trace IRQs enable here, then switch off RCU, and have
+	 * arch_cpu_idle() use raw_local_irq_enable(). Note that
+	 * rcu_idle_enter() relies on lockdep IRQ state, so switch that
+	 * last -- this is very similar to the entry code.
+	 */
+	trace_hardirqs_on_prepare();
+	lockdep_hardirqs_on_prepare();
+	instrumentation_end();
+	rcu_idle_enter();
+	lockdep_hardirqs_on(_THIS_IP_);
+}
+
+static __always_inline void cpuidle_rcu_exit(void)
+{
+	/*
+	 * Carefully undo the above.
+	 */
+	lockdep_hardirqs_off(_THIS_IP_);
+	rcu_idle_exit();
+	instrumentation_begin();
+}
+
 /****************************
  * CPUIDLE DRIVER INTERFACE *
  ****************************/
@@ -282,18 +311,18 @@  extern s64 cpuidle_governor_latency_req(
 	int __ret = 0;							\
 									\
 	if (!idx) {							\
-		rcu_idle_enter();					\
+		cpuidle_rcu_enter();					\
 		cpu_do_idle();						\
-		rcu_idle_exit();					\
+		cpuidle_rcu_exit();					\
 		return idx;						\
 	}								\
 									\
 	if (!is_retention)						\
 		__ret =  cpu_pm_enter();				\
 	if (!__ret) {							\
-		rcu_idle_enter();					\
+		cpuidle_rcu_enter();					\
 		__ret = low_level_idle_enter(state);			\
-		rcu_idle_exit();					\
+		cpuidle_rcu_exit();					\
 		if (!is_retention)					\
 			cpu_pm_exit();					\
 	}								\
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -51,18 +51,22 @@  __setup("hlt", cpu_idle_nopoll_setup);
 
 static noinline int __cpuidle cpu_idle_poll(void)
 {
+	instrumentation_begin();
 	trace_cpu_idle(0, smp_processor_id());
 	stop_critical_timings();
-	rcu_idle_enter();
-	local_irq_enable();
+	cpuidle_rcu_enter();
 
+	raw_local_irq_enable();
 	while (!tif_need_resched() &&
 	       (cpu_idle_force_poll || tick_check_broadcast_expired()))
 		cpu_relax();
+	raw_local_irq_disable();
 
-	rcu_idle_exit();
+	cpuidle_rcu_exit();
 	start_critical_timings();
 	trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
+	local_irq_enable();
+	instrumentation_end();
 
 	return 1;
 }
@@ -85,44 +89,21 @@  void __weak arch_cpu_idle(void)
  */
 void __cpuidle default_idle_call(void)
 {
-	if (current_clr_polling_and_test()) {
-		local_irq_enable();
-	} else {
-
+	instrumentation_begin();
+	if (!current_clr_polling_and_test()) {
 		trace_cpu_idle(1, smp_processor_id());
 		stop_critical_timings();
 
-		/*
-		 * arch_cpu_idle() is supposed to enable IRQs, however
-		 * we can't do that because of RCU and tracing.
-		 *
-		 * Trace IRQs enable here, then switch off RCU, and have
-		 * arch_cpu_idle() use raw_local_irq_enable(). Note that
-		 * rcu_idle_enter() relies on lockdep IRQ state, so switch that
-		 * last -- this is very similar to the entry code.
-		 */
-		trace_hardirqs_on_prepare();
-		lockdep_hardirqs_on_prepare();
-		rcu_idle_enter();
-		lockdep_hardirqs_on(_THIS_IP_);
-
+		cpuidle_rcu_enter();
 		arch_cpu_idle();
-
-		/*
-		 * OK, so IRQs are enabled here, but RCU needs them disabled to
-		 * turn itself back on.. funny thing is that disabling IRQs
-		 * will cause tracing, which needs RCU. Jump through hoops to
-		 * make it 'work'.
-		 */
 		raw_local_irq_disable();
-		lockdep_hardirqs_off(_THIS_IP_);
-		rcu_idle_exit();
-		lockdep_hardirqs_on(_THIS_IP_);
-		raw_local_irq_enable();
+		cpuidle_rcu_exit();
 
 		start_critical_timings();
 		trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
 	}
+	local_irq_enable();
+	instrumentation_end();
 }
 
 static int call_cpuidle_s2idle(struct cpuidle_driver *drv,
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -622,9 +622,13 @@  struct cpumask *tick_get_broadcast_onesh
  * to avoid a deep idle transition as we are about to get the
  * broadcast IPI right away.
  */
-int tick_check_broadcast_expired(void)
+noinstr int tick_check_broadcast_expired(void)
 {
+#ifdef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
+	return arch_test_bit(smp_processor_id(), cpumask_bits(tick_broadcast_force_mask));
+#else
 	return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
+#endif
 }
 
 /*