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

From: Peter Zijlstra
Date: Wed Jun 08 2022 - 10:51:20 EST

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@xxxxxxxxxxxxx>
---
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(-)

--- 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
}

/*