On Fri, Jan 08, 2021 at 03:41:05PM +0200, Tony Lindgren wrote:
> We get suspcious RCU usage splats with cpuidle in several places in
> omap_enter_idle_coupled() with the kernel debug options enabled:
>
> RCU used illegally from extended quiescent state!
> ...
> (_raw_spin_lock_irqsave)
> (omap_enter_idle_coupled+0x17c/0x2d8)
> (omap_enter_idle_coupled)
> (cpuidle_enter_state)
> (cpuidle_enter_state_coupled)
> (cpuidle_enter)
>
> Let's use RCU_NONIDLE to suppress these splats. Things got changed around
> with commit 1098582a0f6c ("sched,idle,rcu: Push rcu_idle deeper into the
> idle path") that started triggering these warnings.
>
> For the tick_broadcast related calls, ideally we'd just switch over to
> using CPUIDLE_FLAG_TIMER_STOP for omap_enter_idle_coupled() to have the
> generic cpuidle code handle the tick_broadcast related calls for us and
> then just drop the tick_broadcast calls here.
>
> But we're currently missing the call in the common cpuidle code for
> tick_broadcast_enable() that CPU1 hotplug needs as described in earlier
> commit 50d6b3cf9403 ("ARM: OMAP2+: fix lack of timer interrupts on CPU1
> after hotplug").
>
> Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Cc: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
> Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
>From an RCU viewpoint:
Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> ---
> arch/arm/mach-omap2/cpuidle44xx.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/cpuidle44xx.c b/arch/arm/mach-omap2/cpuidle44xx.c
> --- a/arch/arm/mach-omap2/cpuidle44xx.c
> +++ b/arch/arm/mach-omap2/cpuidle44xx.c
> @@ -151,10 +151,10 @@ static int omap_enter_idle_coupled(struct cpuidle_device *dev,
> (cx->mpu_logic_state == PWRDM_POWER_OFF);
>
> /* Enter broadcast mode for periodic timers */
> - tick_broadcast_enable();
> + RCU_NONIDLE(tick_broadcast_enable());
>
> /* Enter broadcast mode for one-shot timers */
> - tick_broadcast_enter();
> + RCU_NONIDLE(tick_broadcast_enter());
>
> /*
> * Call idle CPU PM enter notifier chain so that
> @@ -166,7 +166,7 @@ static int omap_enter_idle_coupled(struct cpuidle_device *dev,
>
> if (dev->cpu == 0) {
> pwrdm_set_logic_retst(mpu_pd, cx->mpu_logic_state);
> - omap_set_pwrdm_state(mpu_pd, cx->mpu_state);
> + RCU_NONIDLE(omap_set_pwrdm_state(mpu_pd, cx->mpu_state));
>
> /*
> * Call idle CPU cluster PM enter notifier chain
> @@ -179,7 +179,7 @@ static int omap_enter_idle_coupled(struct cpuidle_device *dev,
> index = 1;
> cx = state_ptr + index;
> pwrdm_set_logic_retst(mpu_pd, cx->mpu_logic_state);
> - omap_set_pwrdm_state(mpu_pd, cx->mpu_state);
> + RCU_NONIDLE(omap_set_pwrdm_state(mpu_pd, cx->mpu_state));
> mpuss_can_lose_context = 0;
> }
> }
> @@ -195,9 +195,9 @@ static int omap_enter_idle_coupled(struct cpuidle_device *dev,
> mpuss_can_lose_context)
> gic_dist_disable();
>
> - clkdm_deny_idle(cpu_clkdm[1]);
> - omap_set_pwrdm_state(cpu_pd[1], PWRDM_POWER_ON);
> - clkdm_allow_idle(cpu_clkdm[1]);
> + RCU_NONIDLE(clkdm_deny_idle(cpu_clkdm[1]));
> + RCU_NONIDLE(omap_set_pwrdm_state(cpu_pd[1], PWRDM_POWER_ON));
> + RCU_NONIDLE(clkdm_allow_idle(cpu_clkdm[1]));
>
> if (IS_PM44XX_ERRATUM(PM_OMAP4_ROM_SMP_BOOT_ERRATUM_GICD) &&
> mpuss_can_lose_context) {
> @@ -225,7 +225,7 @@ static int omap_enter_idle_coupled(struct cpuidle_device *dev,
> cpu_pm_exit();
>
> cpu_pm_out:
> - tick_broadcast_exit();
> + RCU_NONIDLE(tick_broadcast_exit());
>
> fail:
> cpuidle_coupled_parallel_barrier(dev, &abort_barrier);
> --
> 2.30.0
