Commit 06862d78 authored by Tony Lindgren's avatar Tony Lindgren
Browse files

ARM: OMAP2+: Fix suspcious RCU usage splats for omap_enter_idle_coupled 



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 1098582a ("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 50d6b3cf ("ARM: OMAP2+: fix lack of timer interrupts on CPU1
after hotplug").

Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarTony Lindgren <tony@atomide.com>
parent 5c8fe583

arch/arm/mach-omap2/cpuidle44xx.c

+8 −8
Original line number Diff line number Diff line
@@ -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
@@ -178,7 +178,7 @@ static int omap_enter_idle_coupled(struct cpuidle_device *dev, 
				index = 0;

				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;

			}

		}
@@ -194,9 +194,9 @@ 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) {
@@ -222,7 +222,7 @@ 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);