Make arm, sh, and x86 stop using RCU when idle

RCU's shiny new diagnostics (thank you, Frederic!) for using RCU when idle located a few problems in arm, sh, and x86. This patch series contains alleged fixes for these problems. And they are real problems -- if RCU believes that the CPU is idle, it is ignoring it. Which means that the idle CPU can say "rcu_read_lock()" all it like, but there will be no useful effect.

Quoted 6 lines · Paul E. McKenney

RCU's shiny new diagnostics (thank you, Frederic!) for using RCU when idle located a few problems in arm, sh, and x86. This patch series contains alleged fixes for these problems. And they are real problems -- if RCU believes that the CPU is idle, it is ignoring it. Which means that the idle CPU can say "rcu_read_lock()" all it like, but there will be no useful effect.

Having to put these calls down in every idle driver seems like such an ugly layering violation. Not that I have a better alternative to suggest...

From: "Paul E. McKenney" <[email protected]>

The idle loop is a quiscent state for RCU, which means that RCU ignores CPUs that have told RCU that they are idle via rcu_idle_enter(). There are nevertheless quite a few places where idle CPUs use RCU, most commonly indirectly via tracing. This patch fixes these problems for x86.

Many of these bugs have been in the kernel for quite some time, but Frederic's recent change now gives warnings.

This patch takes the straightforward approach of pushing the rcu_idle_enter()/rcu_idle_exit() pair further down into the core of the idle loop.

Hello!

RCU's shiny new diagnostics (thank you, Frederic!) for using RCU when idle located a few problems in arm, sh, and x86. This patch series contains alleged fixes for these problems. And they are real problems -- if RCU believes that the CPU is idle, it is ignoring it. Which means that the idle CPU can say "rcu_read_lock()" all it like, but there will be no useful effect.

I was tempted to break these up, but doing so is bad for bisectability.

From: "Paul E. McKenney" <[email protected]>

The idle loop is a quiscent state for RCU, which means that RCU ignores CPUs that have told RCU that they are idle via rcu_idle_enter(). There are nevertheless quite a few places where idle CPUs use RCU, most commonly indirectly via tracing. This patch fixes these problems for ARM.

Many of these bugs have been in the kernel for quite some time, but Frederic's recent change now gives warnings.

This patch takes the straightforward approach of pushing the rcu_idle_enter()/rcu_idle_exit() pair further down into the core of the idle loop.

Signed-off-by Paul E. McKenney <[email protected]>

Signed-off-by Paul E. McKenney <[email protected]>

Cc Russell King <[email protected]>

Cc Andrew Victor <[email protected]>

Cc Nicolas Ferre <[email protected]>

Cc Jean-Christophe Plagniol-Villard <[email protected]>

Cc Sekhar Nori <[email protected]>

Cc Kevin Hilman <[email protected]>

Cc Kukjin Kim <[email protected]>

Cc Rob Herring <[email protected]>

Cc Sascha Hauer <[email protected]>

Cc Shawn Guo <[email protected]>

Cc Lennert Buytenhek <[email protected]>

Cc Nicolas Pitre <[email protected]>

Cc Amit Kucheria <[email protected]>

Cc Tony Lindgren <[email protected]>

Cc Barry Song <[email protected]>

Cc Paul Mundt <[email protected]>

Cc Magnus Damm <[email protected]>

Cc Will Deacon <[email protected]>

Cc H Hartley Sweeten <[email protected]>

Cc Trinabh Gupta <[email protected]>

Cc Deepthi Dharwar <[email protected]>

Cc Len Brown <[email protected]>

Cc linux-arm-kernel at lists.infradead.org

Cc linux-samsung-soc at vger.kernel.org

Cc linux-omap at vger.kernel.org

---
 arch/arm/kernel/process.c          |    2 --
 arch/arm/mach-at91/cpuidle.c       |    3 +++
 arch/arm/mach-davinci/cpuidle.c    |    3 +++
 arch/arm/mach-exynos/common.c      |    2 ++
 arch/arm/mach-highbank/pm.c        |   12 ++++++++++++
 arch/arm/mach-imx/mm-imx3.c        |    3 +++
 arch/arm/mach-imx/pm-imx27.c       |    4 ++++
 arch/arm/mach-imx/pm-imx6q.c       |    4 ++++
 arch/arm/mach-kirkwood/cpuidle.c   |    3 +++
 arch/arm/mach-mx5/mm.c             |    3 +++
 arch/arm/mach-mx5/pm-imx5.c        |    3 +++
 arch/arm/mach-mxs/pm.c             |    4 ++++
 arch/arm/mach-omap1/pm.c           |    4 ++++
 arch/arm/mach-omap2/pm24xx.c       |    2 ++
 arch/arm/mach-omap2/pm34xx.c       |    2 ++
 arch/arm/mach-omap2/pm44xx.c       |    3 +++

 arch/arm/mach-pnx4008/pm.c         |    2 ++
 arch/arm/mach-prima2/pm.c          |    4 ++++
 arch/arm/mach-s5p64x0/common.c     |    2 ++
 arch/arm/mach-s5pc100/common.c     |    2 ++
 arch/arm/mach-s5pv210/common.c     |    2 ++
 arch/arm/mach-shmobile/cpuidle.c   |    3 +++
 arch/arm/mach-shmobile/pm-sh7372.c |    8 ++++++++
 23 files changed, 78 insertions(+), 2 deletions(-)

arch/arm/kernel/process.c +0 -1

 		leds_event(led_idle_start);
 		while (!need_resched()) {
 #ifdef CONFIG_HOTPLUG_CPU

@@ -237,7 +236,6 @@ void cpu_idle(void)
 			}
 		}
 		leds_event(led_idle_end);
-		rcu_idle_exit();
 		tick_nohz_idle_exit();
 		preempt_enable_no_resched();
 		schedule();

arch/arm/mach-at91/cpuidle.c +3 -0

index a851e6c..8feff6b 100644
@@ -20,6 +20,7 @@
 #include <asm/proc-fns.h>
 #include <linux/io.h>
 #include <linux/export.h>
+#include <linux/rcupdate.h>
 
 #include "pm.h"
 

@@ -43,6 +44,7 @@ static int at91_enter_idle(struct cpuidle_device *dev,
 
 	local_irq_disable();
 	do_gettimeofday(&before);
+	rcu_idle_enter();
 	if (index == 0)
 		/* Wait for interrupt state */
 		cpu_do_idle();

@@ -53,6 +55,7 @@ static int at91_enter_idle(struct cpuidle_device *dev,
 		cpu_do_idle();
 		sdram_selfrefresh_disable(saved_lpr);
 	}
+	rcu_idle_exit();
 	do_gettimeofday(&after);
 	local_irq_enable();
 	idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +

arch/arm/mach-davinci/cpuidle.c +3 -0

index a30c7c5..6594b7e 100644
@@ -17,6 +17,7 @@
 #include <linux/cpuidle.h>
 #include <linux/io.h>
 #include <linux/export.h>
+#include <linux/rcupdate.h>
 #include <asm/proc-fns.h>
 
 #include <mach/cpuidle.h>

@@ -90,12 +91,14 @@ static int davinci_enter_idle(struct cpuidle_device *dev,
 	local_irq_disable();
 	do_gettimeofday(&before);
 
+	rcu_idle_enter();
 	if (ops && ops->enter)
 		ops->enter(ops->flags);
 	/* Wait for interrupt state */
 	cpu_do_idle();
 	if (ops && ops->exit)
 		ops->exit(ops->flags);
+	rcu_idle_exit();
 
 	do_gettimeofday(&after);
 	local_irq_enable();

arch/arm/mach-exynos/common.c +2 -0

index c59e188..1e5844a 100644
@@ -203,8 +203,10 @@ static struct map_desc exynos4_iodesc1[] __initdata = {
 
 static void exynos_idle(void)
 {
+	rcu_idle_enter();
 	if (!need_resched())
 		cpu_do_idle();
+	rcu_idle_exit();
 
 	local_irq_enable();
 }

arch/arm/mach-highbank/pm.c +12 -0

index 33b3beb..5ecc4bc 100644
@@ -17,6 +17,7 @@
 #include <linux/init.h>
 #include <linux/io.h>
 #include <linux/suspend.h>
+#include <linux/rcupdate.h>
 
 #include <asm/proc-fns.h>
 #include <asm/smp_scu.h>

@@ -33,12 +34,23 @@ static int highbank_suspend_finish(unsigned long val)
 
 static int highbank_pm_enter(suspend_state_t state)
 {
+	/*
+	 * Some of the functions preceding the cpu_suspend() can
+	 * invoke RCU, but only in case of failure to disable preemption
+	 * or preempt_disable() misnesting.  Assume that these errors
+	 * are not committed in the following code, because RCU just
+	 * doesn't want to run on a CPU that has its caches disabled.
+	 */
+	rcu_idle_enter();
+
 	hignbank_set_pwr_suspend();
 	highbank_set_cpu_jump(0, cpu_resume);
 
 	scu_power_mode(scu_base_addr, SCU_PM_POWEROFF);
 	cpu_suspend(0, highbank_suspend_finish);
 
+	rcu_idle_exit();
+
 	return 0;
 }
 

arch/arm/mach-imx/mm-imx3.c +3 -0

index 31807d2..0945b23 100644
@@ -19,6 +19,7 @@
 #include <linux/mm.h>
 #include <linux/init.h>
 #include <linux/err.h>
+#include <linux/rcupdate.h>
 
 #include <asm/pgtable.h>
 #include <asm/hardware/cache-l2x0.h>

@@ -34,6 +35,7 @@ static void imx3_idle(void)
 {
 	unsigned long reg = 0;
 
+	rcu_idle_enter();
 	if (!need_resched())
 		__asm__ __volatile__(
 			/* disable I and D cache */

@@ -58,6 +60,7 @@ static void imx3_idle(void)
 			"orr %0, %0, #0x00000004\n"
 			"mcr p15, 0, %0, c1, c0, 0\n"
 			: "=r" (reg));
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-imx/pm-imx27.c +4 -0

index e455d2f..c4adc05 100644
@@ -10,12 +10,14 @@
 #include <linux/kernel.h>
 #include <linux/suspend.h>
 #include <linux/io.h>
+#include <linux/rcupdate.h>
 #include <mach/system.h>
 #include <mach/hardware.h>
 
 static int mx27_suspend_enter(suspend_state_t state)
 {
 	u32 cscr;
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		/* Clear MPEN and SPEN to disable MPLL/SPLL */

@@ -24,9 +26,11 @@ static int mx27_suspend_enter(suspend_state_t state)
 		__raw_writel(cscr, MX27_IO_ADDRESS(MX27_CCM_BASE_ADDR));
 		/* Executes WFI */
 		arch_idle();
+		rcu_idle_exit();
 		break;
 
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 	return 0;

arch/arm/mach-imx/pm-imx6q.c +4 -0

index f7b0c2b..b9c2589 100644
@@ -14,6 +14,7 @@
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/suspend.h>
+#include <linux/rcupdate.h>
 #include <asm/cacheflush.h>
 #include <asm/proc-fns.h>
 #include <asm/suspend.h>

@@ -31,6 +32,7 @@ static int imx6q_suspend_finish(unsigned long val)
 
 static int imx6q_pm_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		imx6q_set_lpm(STOP_POWER_OFF);

@@ -40,8 +42,10 @@ static int imx6q_pm_enter(suspend_state_t state)
 		cpu_suspend(0, imx6q_suspend_finish);
 		imx_smp_prepare();
 		imx_gpc_post_resume();
+		rcu_idle_exit();
 		break;
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 

arch/arm/mach-kirkwood/cpuidle.c +3 -0

index 7088180..de8e317 100644
@@ -19,6 +19,7 @@
 #include <linux/cpuidle.h>
 #include <linux/io.h>
 #include <linux/export.h>
+#include <linux/rcupdate.h>
 #include <asm/proc-fns.h>
 #include <mach/kirkwood.h>
 

@@ -41,6 +42,7 @@ static int kirkwood_enter_idle(struct cpuidle_device *dev,
 
 	local_irq_disable();
 	do_gettimeofday(&before);
+	rcu_idle_enter();
 	if (index == 0)
 		/* Wait for interrupt state */
 		cpu_do_idle();

@@ -55,6 +57,7 @@ static int kirkwood_enter_idle(struct cpuidle_device *dev,
 		writel(0x7, DDR_OPERATION_BASE);
 		cpu_do_idle();
 	}
+	rcu_idle_exit();
 	do_gettimeofday(&after);
 	local_irq_enable();
 	idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +

arch/arm/mach-mx5/mm.c +3 -0

index bc17dfe..d919648 100644
@@ -14,6 +14,7 @@
 #include <linux/mm.h>
 #include <linux/init.h>
 #include <linux/clk.h>
+#include <linux/rcupdate.h>
 
 #include <asm/mach/map.h>
 

@@ -37,7 +38,9 @@ static void imx5_idle(void)
 		mx5_cpu_lp_set(WAIT_UNCLOCKED_POWER_OFF);
 		if (tzic_enable_wake())
 			goto err1;
+		rcu_idle_enter();  /* No tracing until rcu_idle_exit(). */
 		cpu_do_idle();
+		rcu_idle_exit();
 err1:
 		clk_disable(gpc_dvfs_clk);
 	}

arch/arm/mach-mx5/pm-imx5.c +3 -0

index 98052fc..b4adf42 100644
@@ -12,6 +12,7 @@
 #include <linux/clk.h>
 #include <linux/io.h>
 #include <linux/err.h>
+#include <linux/rcupdate.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 #include <mach/common.h>

@@ -27,6 +28,7 @@ static int mx5_suspend_prepare(void)
 
 static int mx5_suspend_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		mx5_cpu_lp_set(STOP_POWER_OFF);

@@ -47,6 +49,7 @@ static int mx5_suspend_enter(suspend_state_t state)
 		__raw_writel(0, MXC_SRPG_EMPGC1_SRPGCR);
 	}
 	cpu_do_idle();
+	rcu_idle_exit();
 	return 0;
 }
 

arch/arm/mach-mxs/pm.c +4 -0

index fb042da..36a3a57 100644
@@ -15,16 +15,20 @@
 #include <linux/kernel.h>
 #include <linux/suspend.h>
 #include <linux/io.h>
+#include <linux/rcupdate.h>
 #include <mach/system.h>
 
 static int mxs_suspend_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		arch_idle();
+		rcu_idle_exit();
 		break;
 
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 	return 0;

arch/arm/mach-omap1/pm.c +4 -0

index 89ea20c..c661eba 100644
@@ -108,11 +108,13 @@ void omap1_pm_idle(void)
 	__u32 use_idlect1 = arm_idlect1_mask;
 	int do_sleep = 0;
 
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 	if (need_resched()) {
 		local_fiq_enable();
 		local_irq_enable();
+		rcu_idle_exit();
 		return;
 	}
 

@@ -158,6 +160,7 @@ void omap1_pm_idle(void)
 
 		local_fiq_enable();
 		local_irq_enable();
+		rcu_idle_exit();
 		return;
 	}
 	omap_sram_suspend(omap_readl(ARM_IDLECT1),

@@ -165,6 +168,7 @@ void omap1_pm_idle(void)
 
 	local_fiq_enable();
 	local_irq_enable();
+	rcu_idle_exit();
 }
 
 /*

arch/arm/mach-omap2/pm24xx.c +2 -0

index b8822f8..2139e9d 100644
@@ -232,6 +232,7 @@ static int omap2_can_sleep(void)
 
 static void omap2_pm_idle(void)
 {
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 

@@ -250,6 +251,7 @@ static void omap2_pm_idle(void)
 out:
 	local_fiq_enable();
 	local_irq_enable();
+	rcu_idle_exit();
 }
 
 #ifdef CONFIG_SUSPEND

arch/arm/mach-omap2/pm34xx.c +2 -0

index fc69875..58a8689 100644
@@ -427,7 +427,9 @@ static void omap3_pm_idle(void)
 	trace_power_start(POWER_CSTATE, 1, smp_processor_id());
 	trace_cpu_idle(1, smp_processor_id());
 
+	rcu_idle_enter();
 	omap_sram_idle();
+	rcu_idle_exit();
 
 	trace_power_end(smp_processor_id());
 	trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());

arch/arm/mach-omap2/pm44xx.c +3 -0

index c264ef7..038796c 100644
@@ -16,6 +16,7 @@
 #include <linux/list.h>
 #include <linux/err.h>
 #include <linux/slab.h>
+#include <linux/rcupdate.h>
 
 #include "common.h"
 #include "clockdomain.h"

@@ -178,6 +179,7 @@ static int __init pwrdms_setup(struct powerdomain *pwrdm, void *unused)
  */
 static void omap_default_idle(void)
 {
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 

@@ -185,6 +187,7 @@ static void omap_default_idle(void)
 
 	local_fiq_enable();
 	local_irq_enable();
+	rcu_idle_exit();
 }
 
 /**

arch/arm/mach-pnx4008/pm.c +2 -0

index f3e60a0..0b8703f 100644
@@ -102,6 +102,7 @@ static inline void pnx4008_suspend(void)
 
 static int pnx4008_pm_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_STANDBY:
 		pnx4008_standby();

@@ -110,6 +111,7 @@ static int pnx4008_pm_enter(suspend_state_t state)
 		pnx4008_suspend();
 		break;
 	}
+	rcu_idle_exit();
 	return 0;
 }
 

arch/arm/mach-prima2/pm.c +4 -0

index 26ebb57..1e35c8a 100644
@@ -15,6 +15,7 @@
 #include <linux/of_device.h>
 #include <linux/of_platform.h>
 #include <linux/io.h>
+#include <linux/rcupdate.h>
 #include <linux/rtc/sirfsoc_rtciobrg.h>
 #include <asm/suspend.h>
 #include <asm/hardware/cache-l2x0.h>

@@ -64,6 +65,7 @@ static int sirfsoc_pre_suspend_power_off(void)
 
 static int sirfsoc_pm_enter(suspend_state_t state)
 {
+	rcu_idle_enter(); /* No good place for this: locking->lockdep->RCU. */
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		sirfsoc_pre_suspend_power_off();

@@ -73,8 +75,10 @@ static int sirfsoc_pm_enter(suspend_state_t state)
 		/* go zzz */
 		cpu_suspend(0, sirfsoc_finish_suspend);
 		outer_resume();
+		rcu_idle_exit();
 		break;
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 	return 0;

arch/arm/mach-s5p64x0/common.c +2 -0

index 52b89a3..c59a7f2 100644
@@ -146,6 +146,7 @@ static void s5p64x0_idle(void)
 {
 	unsigned long val;
 
+	rcu_idle_enter();
 	if (!need_resched()) {
 		val = __raw_readl(S5P64X0_PWR_CFG);
 		val &= ~(0x3 << 5);

@@ -154,6 +155,7 @@ static void s5p64x0_idle(void)
 
 		cpu_do_idle();
 	}
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-s5pc100/common.c +2 -0

index c909573..7bf02ff 100644
@@ -131,9 +131,11 @@ static struct map_desc s5pc100_iodesc[] __initdata = {
 
 static void s5pc100_idle(void)
 {
+	rcu_idle_enter();
 	if (!need_resched())
 		cpu_do_idle();
 
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-s5pv210/common.c +2 -0

index 9c1bcdc..ccd6b4d 100644
@@ -144,9 +144,11 @@ static struct map_desc s5pv210_iodesc[] __initdata = {
 
 static void s5pv210_idle(void)
 {
+	rcu_idle_enter();
 	if (!need_resched())
 		cpu_do_idle();
 
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-shmobile/cpuidle.c +3 -0

index 1b23342..651e92b 100644
@@ -13,6 +13,7 @@
 #include <linux/suspend.h>
 #include <linux/module.h>
 #include <linux/err.h>
+#include <linux/rcupdate.h>
 #include <asm/system.h>
 #include <asm/io.h>
 

@@ -33,6 +34,7 @@ static int shmobile_cpuidle_enter(struct cpuidle_device *dev,
 
 	before = ktime_get();
 
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 

@@ -40,6 +42,7 @@ static int shmobile_cpuidle_enter(struct cpuidle_device *dev,
 
 	local_irq_enable();
 	local_fiq_enable();
+	rcu_idle_exit();
 
 	after = ktime_get();
 	dev->last_residency = ktime_to_ns(ktime_sub(after, before)) >> 10;

arch/arm/mach-shmobile/pm-sh7372.c +8 -0

index fcf8b17..e11507e 100644
@@ -21,6 +21,7 @@
 #include <linux/irq.h>
 #include <linux/bitrev.h>
 #include <linux/console.h>
+#include <linux/rcupdate.h>
 #include <asm/system.h>
 #include <asm/io.h>
 #include <asm/tlbflush.h>

@@ -520,17 +521,24 @@ static int sh7372_enter_suspend(suspend_state_t suspend_state)
 		    sh7372_a4s.genpd.status == GPD_STATE_POWER_OFF) {
 			/* enter A4S sleep with PLLC0 off */
 			pr_debug("entering A4S\n");
+			rcu_idle_enter();
 			sh7372_enter_a4s_common(0);
+			rcu_idle_exit();
 		} else {
 			/* enter A3SM sleep with PLLC0 off */
 			pr_debug("entering A3SM\n");
+			rcu_idle_enter();
 			sh7372_enter_a3sm_common(0);
+			rcu_idle_exit();
 		}
 	} else {
 		/* default to Core Standby that supports all wakeup sources */
 		pr_debug("entering Core Standby\n");
+		rcu_idle_enter();
 		sh7372_enter_core_standby();
+		rcu_idle_exit();
 	}
+
 	return 0;
 }
 

From: "Paul E. McKenney" <[email protected]>

The idle loop is a quiscent state for RCU, which means that RCU ignores CPUs that have told RCU that they are idle via rcu_idle_enter(). There are nevertheless quite a few places where idle CPUs use RCU, most commonly indirectly via tracing. This patch fixes these problems for ARM.

Many of these bugs have been in the kernel for quite some time, but Frederic's recent change now gives warnings.

This patch takes the straightforward approach of pushing the rcu_idle_enter()/rcu_idle_exit() pair further down into the core of the idle loop.

Signed-off-by Paul E. McKenney <[email protected]>

Signed-off-by Paul E. McKenney <[email protected]>

Cc Russell King <[email protected]>

Cc Andrew Victor <[email protected]>

Cc Nicolas Ferre <[email protected]>

Cc Jean-Christophe Plagniol-Villard <[email protected]>

Cc Sekhar Nori <[email protected]>

Cc Kevin Hilman <[email protected]>

Cc Kukjin Kim <[email protected]>

Cc Rob Herring <[email protected]>

Cc Sascha Hauer <[email protected]>

Cc Shawn Guo <[email protected]>

Cc Lennert Buytenhek <[email protected]>

Cc Nicolas Pitre <[email protected]>

Cc Amit Kucheria <[email protected]>

Cc Tony Lindgren <[email protected]>

Cc Barry Song <[email protected]>

Cc Paul Mundt <[email protected]>

Cc Magnus Damm <[email protected]>

Cc Will Deacon <[email protected]>

Cc H Hartley Sweeten <[email protected]>

Cc Trinabh Gupta <[email protected]>

Cc Deepthi Dharwar <[email protected]>

Cc Len Brown <[email protected]>

Cc linux-arm-kernel at lists.infradead.org

Cc linux-samsung-soc at vger.kernel.org

Cc linux-omap at vger.kernel.org

---
 arch/arm/kernel/process.c          |    2 --
 arch/arm/mach-at91/cpuidle.c       |    3 +++
 arch/arm/mach-davinci/cpuidle.c    |    3 +++
 arch/arm/mach-exynos/common.c      |    2 ++
 arch/arm/mach-highbank/pm.c        |   12 ++++++++++++
 arch/arm/mach-imx/mm-imx3.c        |    3 +++
 arch/arm/mach-imx/pm-imx27.c       |    4 ++++
 arch/arm/mach-imx/pm-imx6q.c       |    4 ++++
 arch/arm/mach-kirkwood/cpuidle.c   |    3 +++
 arch/arm/mach-mx5/mm.c             |    3 +++
 arch/arm/mach-mx5/pm-imx5.c        |    3 +++
 arch/arm/mach-mxs/pm.c             |    4 ++++
 arch/arm/mach-omap1/pm.c           |    4 ++++
 arch/arm/mach-omap2/pm24xx.c       |    2 ++
 arch/arm/mach-omap2/pm34xx.c       |    2 ++
 arch/arm/mach-omap2/pm44xx.c       |    3 +++
 arch/arm/mach-pnx4008/pm.c         |    2 ++
 arch/arm/mach-prima2/pm.c          |    4 ++++
 arch/arm/mach-s5p64x0/common.c     |    2 ++
 arch/arm/mach-s5pc100/common.c     |    2 ++
 arch/arm/mach-s5pv210/common.c     |    2 ++
 arch/arm/mach-shmobile/cpuidle.c   |    3 +++
 arch/arm/mach-shmobile/pm-sh7372.c |    8 ++++++++
 23 files changed, 78 insertions(+), 2 deletions(-)

arch/arm/kernel/process.c +0 -2

index 971d65c..8241df7 100644
@@ -207,7 +207,6 @@ void cpu_idle(void)
 	/* endless idle loop with no priority at all */
 	while (1) {
 		tick_nohz_idle_enter();
-		rcu_idle_enter();
 		leds_event(led_idle_start);
 		while (!need_resched()) {
 #ifdef CONFIG_HOTPLUG_CPU

@@ -237,7 +236,6 @@ void cpu_idle(void)
 			}
 		}
 		leds_event(led_idle_end);
-		rcu_idle_exit();
 		tick_nohz_idle_exit();
 		preempt_enable_no_resched();
 		schedule();

arch/arm/mach-at91/cpuidle.c +3 -0

index a851e6c..8feff6b 100644
@@ -20,6 +20,7 @@
 #include <asm/proc-fns.h>
 #include <linux/io.h>
 #include <linux/export.h>
+#include <linux/rcupdate.h>
 
 #include "pm.h"
 

@@ -43,6 +44,7 @@ static int at91_enter_idle(struct cpuidle_device *dev,
 
 	local_irq_disable();
 	do_gettimeofday(&before);
+	rcu_idle_enter();
 	if (index == 0)
 		/* Wait for interrupt state */
 		cpu_do_idle();

@@ -53,6 +55,7 @@ static int at91_enter_idle(struct cpuidle_device *dev,
 		cpu_do_idle();
 		sdram_selfrefresh_disable(saved_lpr);
 	}
+	rcu_idle_exit();
 	do_gettimeofday(&after);
 	local_irq_enable();
 	idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +

arch/arm/mach-davinci/cpuidle.c +3 -0

index a30c7c5..6594b7e 100644
@@ -17,6 +17,7 @@
 #include <linux/cpuidle.h>
 #include <linux/io.h>
 #include <linux/export.h>
+#include <linux/rcupdate.h>
 #include <asm/proc-fns.h>
 
 #include <mach/cpuidle.h>

@@ -90,12 +91,14 @@ static int davinci_enter_idle(struct cpuidle_device *dev,
 	local_irq_disable();
 	do_gettimeofday(&before);
 
+	rcu_idle_enter();
 	if (ops && ops->enter)
 		ops->enter(ops->flags);
 	/* Wait for interrupt state */
 	cpu_do_idle();
 	if (ops && ops->exit)
 		ops->exit(ops->flags);
+	rcu_idle_exit();
 
 	do_gettimeofday(&after);
 	local_irq_enable();

arch/arm/mach-exynos/common.c +2 -0

index c59e188..1e5844a 100644
@@ -203,8 +203,10 @@ static struct map_desc exynos4_iodesc1[] __initdata = {
 
 static void exynos_idle(void)
 {
+	rcu_idle_enter();
 	if (!need_resched())
 		cpu_do_idle();
+	rcu_idle_exit();
 
 	local_irq_enable();
 }

arch/arm/mach-highbank/pm.c +12 -0

index 33b3beb..5ecc4bc 100644
@@ -17,6 +17,7 @@
 #include <linux/init.h>
 #include <linux/io.h>
 #include <linux/suspend.h>
+#include <linux/rcupdate.h>
 
 #include <asm/proc-fns.h>
 #include <asm/smp_scu.h>

@@ -33,12 +34,23 @@ static int highbank_suspend_finish(unsigned long val)
 
 static int highbank_pm_enter(suspend_state_t state)
 {
+	/*
+	 * Some of the functions preceding the cpu_suspend() can
+	 * invoke RCU, but only in case of failure to disable preemption
+	 * or preempt_disable() misnesting.  Assume that these errors
+	 * are not committed in the following code, because RCU just
+	 * doesn't want to run on a CPU that has its caches disabled.
+	 */
+	rcu_idle_enter();
+
 	hignbank_set_pwr_suspend();
 	highbank_set_cpu_jump(0, cpu_resume);
 
 	scu_power_mode(scu_base_addr, SCU_PM_POWEROFF);
 	cpu_suspend(0, highbank_suspend_finish);
 
+	rcu_idle_exit();
+
 	return 0;
 }
 

arch/arm/mach-imx/mm-imx3.c +3 -0

index 31807d2..0945b23 100644
@@ -19,6 +19,7 @@
 #include <linux/mm.h>
 #include <linux/init.h>
 #include <linux/err.h>
+#include <linux/rcupdate.h>
 
 #include <asm/pgtable.h>
 #include <asm/hardware/cache-l2x0.h>

@@ -34,6 +35,7 @@ static void imx3_idle(void)
 {
 	unsigned long reg = 0;
 
+	rcu_idle_enter();
 	if (!need_resched())
 		__asm__ __volatile__(
 			/* disable I and D cache */

@@ -58,6 +60,7 @@ static void imx3_idle(void)
 			"orr %0, %0, #0x00000004\n"
 			"mcr p15, 0, %0, c1, c0, 0\n"
 			: "=r" (reg));
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-imx/pm-imx27.c +4 -0

index e455d2f..c4adc05 100644
@@ -10,12 +10,14 @@
 #include <linux/kernel.h>
 #include <linux/suspend.h>
 #include <linux/io.h>
+#include <linux/rcupdate.h>
 #include <mach/system.h>
 #include <mach/hardware.h>
 
 static int mx27_suspend_enter(suspend_state_t state)
 {
 	u32 cscr;
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		/* Clear MPEN and SPEN to disable MPLL/SPLL */

@@ -24,9 +26,11 @@ static int mx27_suspend_enter(suspend_state_t state)
 		__raw_writel(cscr, MX27_IO_ADDRESS(MX27_CCM_BASE_ADDR));
 		/* Executes WFI */
 		arch_idle();
+		rcu_idle_exit();
 		break;
 
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 	return 0;

arch/arm/mach-imx/pm-imx6q.c +4 -0

index f7b0c2b..b9c2589 100644
@@ -14,6 +14,7 @@
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/suspend.h>
+#include <linux/rcupdate.h>
 #include <asm/cacheflush.h>
 #include <asm/proc-fns.h>
 #include <asm/suspend.h>

@@ -31,6 +32,7 @@ static int imx6q_suspend_finish(unsigned long val)
 
 static int imx6q_pm_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		imx6q_set_lpm(STOP_POWER_OFF);

@@ -40,8 +42,10 @@ static int imx6q_pm_enter(suspend_state_t state)
 		cpu_suspend(0, imx6q_suspend_finish);
 		imx_smp_prepare();
 		imx_gpc_post_resume();
+		rcu_idle_exit();
 		break;
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 

arch/arm/mach-kirkwood/cpuidle.c +3 -0

index 7088180..de8e317 100644
@@ -19,6 +19,7 @@
 #include <linux/cpuidle.h>
 #include <linux/io.h>
 #include <linux/export.h>
+#include <linux/rcupdate.h>
 #include <asm/proc-fns.h>
 #include <mach/kirkwood.h>
 

@@ -41,6 +42,7 @@ static int kirkwood_enter_idle(struct cpuidle_device *dev,
 
 	local_irq_disable();
 	do_gettimeofday(&before);
+	rcu_idle_enter();
 	if (index == 0)
 		/* Wait for interrupt state */
 		cpu_do_idle();

@@ -55,6 +57,7 @@ static int kirkwood_enter_idle(struct cpuidle_device *dev,
 		writel(0x7, DDR_OPERATION_BASE);
 		cpu_do_idle();
 	}
+	rcu_idle_exit();
 	do_gettimeofday(&after);
 	local_irq_enable();
 	idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +

arch/arm/mach-mx5/mm.c +3 -0

index bc17dfe..d919648 100644
@@ -14,6 +14,7 @@
 #include <linux/mm.h>
 #include <linux/init.h>
 #include <linux/clk.h>
+#include <linux/rcupdate.h>
 
 #include <asm/mach/map.h>
 

@@ -37,7 +38,9 @@ static void imx5_idle(void)
 		mx5_cpu_lp_set(WAIT_UNCLOCKED_POWER_OFF);
 		if (tzic_enable_wake())
 			goto err1;
+		rcu_idle_enter();  /* No tracing until rcu_idle_exit(). */
 		cpu_do_idle();
+		rcu_idle_exit();
 err1:
 		clk_disable(gpc_dvfs_clk);
 	}

arch/arm/mach-mx5/pm-imx5.c +3 -0

index 98052fc..b4adf42 100644
@@ -12,6 +12,7 @@
 #include <linux/clk.h>
 #include <linux/io.h>
 #include <linux/err.h>
+#include <linux/rcupdate.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 #include <mach/common.h>

@@ -27,6 +28,7 @@ static int mx5_suspend_prepare(void)
 
 static int mx5_suspend_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		mx5_cpu_lp_set(STOP_POWER_OFF);

@@ -47,6 +49,7 @@ static int mx5_suspend_enter(suspend_state_t state)
 		__raw_writel(0, MXC_SRPG_EMPGC1_SRPGCR);
 	}
 	cpu_do_idle();
+	rcu_idle_exit();
 	return 0;
 }
 

arch/arm/mach-mxs/pm.c +4 -0

index fb042da..36a3a57 100644
@@ -15,16 +15,20 @@
 #include <linux/kernel.h>
 #include <linux/suspend.h>
 #include <linux/io.h>
+#include <linux/rcupdate.h>
 #include <mach/system.h>
 
 static int mxs_suspend_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		arch_idle();
+		rcu_idle_exit();
 		break;
 
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 	return 0;

arch/arm/mach-omap1/pm.c +4 -0

index 89ea20c..c661eba 100644
@@ -108,11 +108,13 @@ void omap1_pm_idle(void)
 	__u32 use_idlect1 = arm_idlect1_mask;
 	int do_sleep = 0;
 
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 	if (need_resched()) {
 		local_fiq_enable();
 		local_irq_enable();
+		rcu_idle_exit();
 		return;
 	}
 

@@ -158,6 +160,7 @@ void omap1_pm_idle(void)
 
 		local_fiq_enable();
 		local_irq_enable();
+		rcu_idle_exit();
 		return;
 	}
 	omap_sram_suspend(omap_readl(ARM_IDLECT1),

@@ -165,6 +168,7 @@ void omap1_pm_idle(void)
 
 	local_fiq_enable();
 	local_irq_enable();
+	rcu_idle_exit();
 }
 
 /*

arch/arm/mach-omap2/pm24xx.c +2 -0

index b8822f8..2139e9d 100644
@@ -232,6 +232,7 @@ static int omap2_can_sleep(void)
 
 static void omap2_pm_idle(void)
 {
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 

@@ -250,6 +251,7 @@ static void omap2_pm_idle(void)
 out:
 	local_fiq_enable();
 	local_irq_enable();
+	rcu_idle_exit();
 }
 
 #ifdef CONFIG_SUSPEND

arch/arm/mach-omap2/pm34xx.c +2 -0

index fc69875..58a8689 100644
@@ -427,7 +427,9 @@ static void omap3_pm_idle(void)
 	trace_power_start(POWER_CSTATE, 1, smp_processor_id());
 	trace_cpu_idle(1, smp_processor_id());
 
+	rcu_idle_enter();
 	omap_sram_idle();
+	rcu_idle_exit();
 
 	trace_power_end(smp_processor_id());
 	trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());

arch/arm/mach-omap2/pm44xx.c +3 -0

index c264ef7..038796c 100644
@@ -16,6 +16,7 @@
 #include <linux/list.h>
 #include <linux/err.h>
 #include <linux/slab.h>
+#include <linux/rcupdate.h>
 
 #include "common.h"
 #include "clockdomain.h"

@@ -178,6 +179,7 @@ static int __init pwrdms_setup(struct powerdomain *pwrdm, void *unused)
  */
 static void omap_default_idle(void)
 {
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 

@@ -185,6 +187,7 @@ static void omap_default_idle(void)
 
 	local_fiq_enable();
 	local_irq_enable();
+	rcu_idle_exit();
 }
 
 /**

arch/arm/mach-pnx4008/pm.c +2 -0

index f3e60a0..0b8703f 100644
@@ -102,6 +102,7 @@ static inline void pnx4008_suspend(void)
 
 static int pnx4008_pm_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_STANDBY:
 		pnx4008_standby();

@@ -110,6 +111,7 @@ static int pnx4008_pm_enter(suspend_state_t state)
 		pnx4008_suspend();
 		break;
 	}
+	rcu_idle_exit();
 	return 0;
 }
 

arch/arm/mach-prima2/pm.c +4 -0

index 26ebb57..1e35c8a 100644
@@ -15,6 +15,7 @@
 #include <linux/of_device.h>
 #include <linux/of_platform.h>
 #include <linux/io.h>
+#include <linux/rcupdate.h>
 #include <linux/rtc/sirfsoc_rtciobrg.h>
 #include <asm/suspend.h>
 #include <asm/hardware/cache-l2x0.h>

@@ -64,6 +65,7 @@ static int sirfsoc_pre_suspend_power_off(void)
 
 static int sirfsoc_pm_enter(suspend_state_t state)
 {
+	rcu_idle_enter(); /* No good place for this: locking->lockdep->RCU. */
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		sirfsoc_pre_suspend_power_off();

@@ -73,8 +75,10 @@ static int sirfsoc_pm_enter(suspend_state_t state)
 		/* go zzz */
 		cpu_suspend(0, sirfsoc_finish_suspend);
 		outer_resume();
+		rcu_idle_exit();
 		break;
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 	return 0;

arch/arm/mach-s5p64x0/common.c +2 -0

index 52b89a3..c59a7f2 100644
@@ -146,6 +146,7 @@ static void s5p64x0_idle(void)
 {
 	unsigned long val;
 
+	rcu_idle_enter();
 	if (!need_resched()) {
 		val = __raw_readl(S5P64X0_PWR_CFG);
 		val &= ~(0x3 << 5);

@@ -154,6 +155,7 @@ static void s5p64x0_idle(void)
 
 		cpu_do_idle();
 	}
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-s5pc100/common.c +2 -0

index c909573..7bf02ff 100644
@@ -131,9 +131,11 @@ static struct map_desc s5pc100_iodesc[] __initdata = {
 
 static void s5pc100_idle(void)
 {
+	rcu_idle_enter();
 	if (!need_resched())
 		cpu_do_idle();
 
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-s5pv210/common.c +2 -0

index 9c1bcdc..ccd6b4d 100644
@@ -144,9 +144,11 @@ static struct map_desc s5pv210_iodesc[] __initdata = {
 
 static void s5pv210_idle(void)
 {
+	rcu_idle_enter();
 	if (!need_resched())
 		cpu_do_idle();
 
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-shmobile/cpuidle.c +3 -0

index 1b23342..651e92b 100644
@@ -13,6 +13,7 @@
 #include <linux/suspend.h>
 #include <linux/module.h>
 #include <linux/err.h>
+#include <linux/rcupdate.h>
 #include <asm/system.h>
 #include <asm/io.h>
 

@@ -33,6 +34,7 @@ static int shmobile_cpuidle_enter(struct cpuidle_device *dev,
 
 	before = ktime_get();
 
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 

@@ -40,6 +42,7 @@ static int shmobile_cpuidle_enter(struct cpuidle_device *dev,
 
 	local_irq_enable();
 	local_fiq_enable();
+	rcu_idle_exit();
 
 	after = ktime_get();
 	dev->last_residency = ktime_to_ns(ktime_sub(after, before)) >> 10;

arch/arm/mach-shmobile/pm-sh7372.c +8 -0

index fcf8b17..e11507e 100644
@@ -21,6 +21,7 @@
 #include <linux/irq.h>
 #include <linux/bitrev.h>
 #include <linux/console.h>
+#include <linux/rcupdate.h>
 #include <asm/system.h>
 #include <asm/io.h>
 #include <asm/tlbflush.h>

@@ -520,17 +521,24 @@ static int sh7372_enter_suspend(suspend_state_t suspend_state)
 		    sh7372_a4s.genpd.status == GPD_STATE_POWER_OFF) {
 			/* enter A4S sleep with PLLC0 off */
 			pr_debug("entering A4S\n");
+			rcu_idle_enter();
 			sh7372_enter_a4s_common(0);
+			rcu_idle_exit();
 		} else {
 			/* enter A3SM sleep with PLLC0 off */
 			pr_debug("entering A3SM\n");
+			rcu_idle_enter();
 			sh7372_enter_a3sm_common(0);
+			rcu_idle_exit();
 		}
 	} else {
 		/* default to Core Standby that supports all wakeup sources */
 		pr_debug("entering Core Standby\n");
+		rcu_idle_enter();
 		sh7372_enter_core_standby();
+		rcu_idle_exit();
 	}
+
 	return 0;
 }
 

Signature · 1 line

1.7.8

Paul,

Quoted 6 lines · Paul E. McKenney

From: "Paul E. McKenney" <[email protected]>

The idle loop is a quiscent state for RCU, which means that RCU ignores CPUs that have told RCU that they are idle via rcu_idle_enter(). There are nevertheless quite a few places where idle CPUs use RCU, most commonly indirectly via tracing. This patch fixes these problems for ARM.

Do you have some specific examples of actual problems? It's not possible to restrict tracing at this low level?

This really seems like the wrong direction as we are trying to pull common pieces up out of platform specific code.

Quoted 51 lines

Many of these bugs have been in the kernel for quite some time, but Frederic's recent change now gives warnings.

This patch takes the straightforward approach of pushing the rcu_idle_enter()/rcu_idle_exit() pair further down into the core of the idle loop.

Signed-off-by Paul E. McKenney <[email protected]>

Signed-off-by Paul E. McKenney <[email protected]>

Cc Russell King <[email protected]>

Cc Andrew Victor <[email protected]>

Cc Nicolas Ferre <[email protected]>

Cc Jean-Christophe Plagniol-Villard <[email protected]>

Cc Sekhar Nori <[email protected]>

Cc Kevin Hilman <[email protected]>

Cc Kukjin Kim <[email protected]>

Cc Rob Herring <[email protected]>

Cc Sascha Hauer <[email protected]>

Cc Shawn Guo <[email protected]>

Cc Lennert Buytenhek <[email protected]>

Cc Nicolas Pitre <[email protected]>

Cc Amit Kucheria <[email protected]>

Cc Tony Lindgren <[email protected]>

Cc Barry Song <[email protected]>

Cc Paul Mundt <[email protected]>

Cc Magnus Damm <[email protected]>

Cc Will Deacon <[email protected]>

Cc H Hartley Sweeten <[email protected]>

Cc Trinabh Gupta <[email protected]>

Cc Deepthi Dharwar <[email protected]>

Cc Len Brown <[email protected]>

Cc linux-arm-kernel at lists.infradead.org

Cc linux-samsung-soc at vger.kernel.org

Cc linux-omap at vger.kernel.org

---
 arch/arm/kernel/process.c          |    2 --
 arch/arm/mach-at91/cpuidle.c       |    3 +++
 arch/arm/mach-davinci/cpuidle.c    |    3 +++
 arch/arm/mach-exynos/common.c      |    2 ++
 arch/arm/mach-highbank/pm.c        |   12 ++++++++++++
 arch/arm/mach-imx/mm-imx3.c        |    3 +++
 arch/arm/mach-imx/pm-imx27.c       |    4 ++++
 arch/arm/mach-imx/pm-imx6q.c       |    4 ++++
 arch/arm/mach-kirkwood/cpuidle.c   |    3 +++
 arch/arm/mach-mx5/mm.c             |    3 +++
 arch/arm/mach-mx5/pm-imx5.c        |    3 +++
 arch/arm/mach-mxs/pm.c             |    4 ++++
 arch/arm/mach-omap1/pm.c           |    4 ++++
 arch/arm/mach-omap2/pm24xx.c       |    2 ++
 arch/arm/mach-omap2/pm34xx.c       |    2 ++
 arch/arm/mach-omap2/pm44xx.c       |    3 +++

Quoted 9 lines

 arch/arm/mach-pnx4008/pm.c         |    2 ++
 arch/arm/mach-prima2/pm.c          |    4 ++++
 arch/arm/mach-s5p64x0/common.c     |    2 ++
 arch/arm/mach-s5pc100/common.c     |    2 ++
 arch/arm/mach-s5pv210/common.c     |    2 ++
 arch/arm/mach-shmobile/cpuidle.c   |    3 +++
 arch/arm/mach-shmobile/pm-sh7372.c |    8 ++++++++
 23 files changed, 78 insertions(+), 2 deletions(-)

This is clearly not all platforms and you're missing some cpuidle drivers like omap. Some platform's idle code don't need this?

I'd guess this conflicts with Nico's idle clean-up which is in Russell's for-next branch now.

arch/arm/kernel/process.c void cpu_idle(void) · line 210

Quoted 9 lines

arch/arm/kernel/process.c +0 -1

index 971d65c..8241df7 100644
@@ -207,7 +207,6 @@ void cpu_idle(void)
 	/* endless idle loop with no priority at all */
 	while (1) {
 		tick_nohz_idle_enter();
-		rcu_idle_enter();

In some cases with the clean-up, there is no platform specific idle code, so rcu_idle_enter would never be called.

Rob

Quoted 574 lines

arch/arm/kernel/process.c +0 -1

 		leds_event(led_idle_start);
 		while (!need_resched()) {
 #ifdef CONFIG_HOTPLUG_CPU

@@ -237,7 +236,6 @@ void cpu_idle(void)
 			}
 		}
 		leds_event(led_idle_end);
-		rcu_idle_exit();
 		tick_nohz_idle_exit();
 		preempt_enable_no_resched();
 		schedule();

arch/arm/mach-at91/cpuidle.c +3 -0

index a851e6c..8feff6b 100644
@@ -20,6 +20,7 @@
 #include <asm/proc-fns.h>
 #include <linux/io.h>
 #include <linux/export.h>
+#include <linux/rcupdate.h>
 
 #include "pm.h"
 

@@ -43,6 +44,7 @@ static int at91_enter_idle(struct cpuidle_device *dev,
 
 	local_irq_disable();
 	do_gettimeofday(&before);
+	rcu_idle_enter();
 	if (index == 0)
 		/* Wait for interrupt state */
 		cpu_do_idle();

@@ -53,6 +55,7 @@ static int at91_enter_idle(struct cpuidle_device *dev,
 		cpu_do_idle();
 		sdram_selfrefresh_disable(saved_lpr);
 	}
+	rcu_idle_exit();
 	do_gettimeofday(&after);
 	local_irq_enable();
 	idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +

arch/arm/mach-davinci/cpuidle.c +3 -0

index a30c7c5..6594b7e 100644
@@ -17,6 +17,7 @@
 #include <linux/cpuidle.h>
 #include <linux/io.h>
 #include <linux/export.h>
+#include <linux/rcupdate.h>
 #include <asm/proc-fns.h>
 
 #include <mach/cpuidle.h>

@@ -90,12 +91,14 @@ static int davinci_enter_idle(struct cpuidle_device *dev,
 	local_irq_disable();
 	do_gettimeofday(&before);
 
+	rcu_idle_enter();
 	if (ops && ops->enter)
 		ops->enter(ops->flags);
 	/* Wait for interrupt state */
 	cpu_do_idle();
 	if (ops && ops->exit)
 		ops->exit(ops->flags);
+	rcu_idle_exit();
 
 	do_gettimeofday(&after);
 	local_irq_enable();

arch/arm/mach-exynos/common.c +2 -0

index c59e188..1e5844a 100644
@@ -203,8 +203,10 @@ static struct map_desc exynos4_iodesc1[] __initdata = {
 
 static void exynos_idle(void)
 {
+	rcu_idle_enter();
 	if (!need_resched())
 		cpu_do_idle();
+	rcu_idle_exit();
 
 	local_irq_enable();
 }

arch/arm/mach-highbank/pm.c +12 -0

index 33b3beb..5ecc4bc 100644
@@ -17,6 +17,7 @@
 #include <linux/init.h>
 #include <linux/io.h>
 #include <linux/suspend.h>
+#include <linux/rcupdate.h>
 
 #include <asm/proc-fns.h>
 #include <asm/smp_scu.h>

@@ -33,12 +34,23 @@ static int highbank_suspend_finish(unsigned long val)
 
 static int highbank_pm_enter(suspend_state_t state)
 {
+	/*
+	 * Some of the functions preceding the cpu_suspend() can
+	 * invoke RCU, but only in case of failure to disable preemption
+	 * or preempt_disable() misnesting.  Assume that these errors
+	 * are not committed in the following code, because RCU just
+	 * doesn't want to run on a CPU that has its caches disabled.
+	 */
+	rcu_idle_enter();
+
 	hignbank_set_pwr_suspend();
 	highbank_set_cpu_jump(0, cpu_resume);
 
 	scu_power_mode(scu_base_addr, SCU_PM_POWEROFF);
 	cpu_suspend(0, highbank_suspend_finish);
 
+	rcu_idle_exit();
+
 	return 0;
 }
 

arch/arm/mach-imx/mm-imx3.c +3 -0

index 31807d2..0945b23 100644
@@ -19,6 +19,7 @@
 #include <linux/mm.h>
 #include <linux/init.h>
 #include <linux/err.h>
+#include <linux/rcupdate.h>
 
 #include <asm/pgtable.h>
 #include <asm/hardware/cache-l2x0.h>

@@ -34,6 +35,7 @@ static void imx3_idle(void)
 {
 	unsigned long reg = 0;
 
+	rcu_idle_enter();
 	if (!need_resched())
 		__asm__ __volatile__(
 			/* disable I and D cache */

@@ -58,6 +60,7 @@ static void imx3_idle(void)
 			"orr %0, %0, #0x00000004\n"
 			"mcr p15, 0, %0, c1, c0, 0\n"
 			: "=r" (reg));
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-imx/pm-imx27.c +4 -0

index e455d2f..c4adc05 100644
@@ -10,12 +10,14 @@
 #include <linux/kernel.h>
 #include <linux/suspend.h>
 #include <linux/io.h>
+#include <linux/rcupdate.h>
 #include <mach/system.h>
 #include <mach/hardware.h>
 
 static int mx27_suspend_enter(suspend_state_t state)
 {
 	u32 cscr;
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		/* Clear MPEN and SPEN to disable MPLL/SPLL */

@@ -24,9 +26,11 @@ static int mx27_suspend_enter(suspend_state_t state)
 		__raw_writel(cscr, MX27_IO_ADDRESS(MX27_CCM_BASE_ADDR));
 		/* Executes WFI */
 		arch_idle();
+		rcu_idle_exit();
 		break;
 
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 	return 0;

arch/arm/mach-imx/pm-imx6q.c +4 -0

index f7b0c2b..b9c2589 100644
@@ -14,6 +14,7 @@
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/suspend.h>
+#include <linux/rcupdate.h>
 #include <asm/cacheflush.h>
 #include <asm/proc-fns.h>
 #include <asm/suspend.h>

@@ -31,6 +32,7 @@ static int imx6q_suspend_finish(unsigned long val)
 
 static int imx6q_pm_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		imx6q_set_lpm(STOP_POWER_OFF);

@@ -40,8 +42,10 @@ static int imx6q_pm_enter(suspend_state_t state)
 		cpu_suspend(0, imx6q_suspend_finish);
 		imx_smp_prepare();
 		imx_gpc_post_resume();
+		rcu_idle_exit();
 		break;
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 

arch/arm/mach-kirkwood/cpuidle.c +3 -0

index 7088180..de8e317 100644
@@ -19,6 +19,7 @@
 #include <linux/cpuidle.h>
 #include <linux/io.h>
 #include <linux/export.h>
+#include <linux/rcupdate.h>
 #include <asm/proc-fns.h>
 #include <mach/kirkwood.h>
 

@@ -41,6 +42,7 @@ static int kirkwood_enter_idle(struct cpuidle_device *dev,
 
 	local_irq_disable();
 	do_gettimeofday(&before);
+	rcu_idle_enter();
 	if (index == 0)
 		/* Wait for interrupt state */
 		cpu_do_idle();

@@ -55,6 +57,7 @@ static int kirkwood_enter_idle(struct cpuidle_device *dev,
 		writel(0x7, DDR_OPERATION_BASE);
 		cpu_do_idle();
 	}
+	rcu_idle_exit();
 	do_gettimeofday(&after);
 	local_irq_enable();
 	idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +

arch/arm/mach-mx5/mm.c +3 -0

index bc17dfe..d919648 100644
@@ -14,6 +14,7 @@
 #include <linux/mm.h>
 #include <linux/init.h>
 #include <linux/clk.h>
+#include <linux/rcupdate.h>
 
 #include <asm/mach/map.h>
 

@@ -37,7 +38,9 @@ static void imx5_idle(void)
 		mx5_cpu_lp_set(WAIT_UNCLOCKED_POWER_OFF);
 		if (tzic_enable_wake())
 			goto err1;
+		rcu_idle_enter();  /* No tracing until rcu_idle_exit(). */
 		cpu_do_idle();
+		rcu_idle_exit();
 err1:
 		clk_disable(gpc_dvfs_clk);
 	}

arch/arm/mach-mx5/pm-imx5.c +3 -0

index 98052fc..b4adf42 100644
@@ -12,6 +12,7 @@
 #include <linux/clk.h>
 #include <linux/io.h>
 #include <linux/err.h>
+#include <linux/rcupdate.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 #include <mach/common.h>

@@ -27,6 +28,7 @@ static int mx5_suspend_prepare(void)
 
 static int mx5_suspend_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		mx5_cpu_lp_set(STOP_POWER_OFF);

@@ -47,6 +49,7 @@ static int mx5_suspend_enter(suspend_state_t state)
 		__raw_writel(0, MXC_SRPG_EMPGC1_SRPGCR);
 	}
 	cpu_do_idle();
+	rcu_idle_exit();
 	return 0;
 }
 

arch/arm/mach-mxs/pm.c +4 -0

index fb042da..36a3a57 100644
@@ -15,16 +15,20 @@
 #include <linux/kernel.h>
 #include <linux/suspend.h>
 #include <linux/io.h>
+#include <linux/rcupdate.h>
 #include <mach/system.h>
 
 static int mxs_suspend_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		arch_idle();
+		rcu_idle_exit();
 		break;
 
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 	return 0;

arch/arm/mach-omap1/pm.c +4 -0

index 89ea20c..c661eba 100644
@@ -108,11 +108,13 @@ void omap1_pm_idle(void)
 	__u32 use_idlect1 = arm_idlect1_mask;
 	int do_sleep = 0;
 
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 	if (need_resched()) {
 		local_fiq_enable();
 		local_irq_enable();
+		rcu_idle_exit();
 		return;
 	}
 

@@ -158,6 +160,7 @@ void omap1_pm_idle(void)
 
 		local_fiq_enable();
 		local_irq_enable();
+		rcu_idle_exit();
 		return;
 	}
 	omap_sram_suspend(omap_readl(ARM_IDLECT1),

@@ -165,6 +168,7 @@ void omap1_pm_idle(void)
 
 	local_fiq_enable();
 	local_irq_enable();
+	rcu_idle_exit();
 }
 
 /*

arch/arm/mach-omap2/pm24xx.c +2 -0

index b8822f8..2139e9d 100644
@@ -232,6 +232,7 @@ static int omap2_can_sleep(void)
 
 static void omap2_pm_idle(void)
 {
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 

@@ -250,6 +251,7 @@ static void omap2_pm_idle(void)
 out:
 	local_fiq_enable();
 	local_irq_enable();
+	rcu_idle_exit();
 }
 
 #ifdef CONFIG_SUSPEND

arch/arm/mach-omap2/pm34xx.c +2 -0

index fc69875..58a8689 100644
@@ -427,7 +427,9 @@ static void omap3_pm_idle(void)
 	trace_power_start(POWER_CSTATE, 1, smp_processor_id());
 	trace_cpu_idle(1, smp_processor_id());
 
+	rcu_idle_enter();
 	omap_sram_idle();
+	rcu_idle_exit();
 
 	trace_power_end(smp_processor_id());
 	trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());

arch/arm/mach-omap2/pm44xx.c +3 -0

index c264ef7..038796c 100644
@@ -16,6 +16,7 @@
 #include <linux/list.h>
 #include <linux/err.h>
 #include <linux/slab.h>
+#include <linux/rcupdate.h>
 
 #include "common.h"
 #include "clockdomain.h"

@@ -178,6 +179,7 @@ static int __init pwrdms_setup(struct powerdomain *pwrdm, void *unused)
  */
 static void omap_default_idle(void)
 {
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 

@@ -185,6 +187,7 @@ static void omap_default_idle(void)
 
 	local_fiq_enable();
 	local_irq_enable();
+	rcu_idle_exit();
 }
 
 /**

arch/arm/mach-pnx4008/pm.c +2 -0

index f3e60a0..0b8703f 100644
@@ -102,6 +102,7 @@ static inline void pnx4008_suspend(void)
 
 static int pnx4008_pm_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_STANDBY:
 		pnx4008_standby();

@@ -110,6 +111,7 @@ static int pnx4008_pm_enter(suspend_state_t state)
 		pnx4008_suspend();
 		break;
 	}
+	rcu_idle_exit();
 	return 0;
 }
 

arch/arm/mach-prima2/pm.c +4 -0

index 26ebb57..1e35c8a 100644
@@ -15,6 +15,7 @@
 #include <linux/of_device.h>
 #include <linux/of_platform.h>
 #include <linux/io.h>
+#include <linux/rcupdate.h>
 #include <linux/rtc/sirfsoc_rtciobrg.h>
 #include <asm/suspend.h>
 #include <asm/hardware/cache-l2x0.h>

@@ -64,6 +65,7 @@ static int sirfsoc_pre_suspend_power_off(void)
 
 static int sirfsoc_pm_enter(suspend_state_t state)
 {
+	rcu_idle_enter(); /* No good place for this: locking->lockdep->RCU. */
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		sirfsoc_pre_suspend_power_off();

@@ -73,8 +75,10 @@ static int sirfsoc_pm_enter(suspend_state_t state)
 		/* go zzz */
 		cpu_suspend(0, sirfsoc_finish_suspend);
 		outer_resume();
+		rcu_idle_exit();
 		break;
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 	return 0;

arch/arm/mach-s5p64x0/common.c +2 -0

index 52b89a3..c59a7f2 100644
@@ -146,6 +146,7 @@ static void s5p64x0_idle(void)
 {
 	unsigned long val;
 
+	rcu_idle_enter();
 	if (!need_resched()) {
 		val = __raw_readl(S5P64X0_PWR_CFG);
 		val &= ~(0x3 << 5);

@@ -154,6 +155,7 @@ static void s5p64x0_idle(void)
 
 		cpu_do_idle();
 	}
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-s5pc100/common.c +2 -0

index c909573..7bf02ff 100644
@@ -131,9 +131,11 @@ static struct map_desc s5pc100_iodesc[] __initdata = {
 
 static void s5pc100_idle(void)
 {
+	rcu_idle_enter();
 	if (!need_resched())
 		cpu_do_idle();
 
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-s5pv210/common.c +2 -0

index 9c1bcdc..ccd6b4d 100644
@@ -144,9 +144,11 @@ static struct map_desc s5pv210_iodesc[] __initdata = {
 
 static void s5pv210_idle(void)
 {
+	rcu_idle_enter();
 	if (!need_resched())
 		cpu_do_idle();
 
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-shmobile/cpuidle.c +3 -0

index 1b23342..651e92b 100644
@@ -13,6 +13,7 @@
 #include <linux/suspend.h>
 #include <linux/module.h>
 #include <linux/err.h>
+#include <linux/rcupdate.h>
 #include <asm/system.h>
 #include <asm/io.h>
 

@@ -33,6 +34,7 @@ static int shmobile_cpuidle_enter(struct cpuidle_device *dev,
 
 	before = ktime_get();
 
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 

@@ -40,6 +42,7 @@ static int shmobile_cpuidle_enter(struct cpuidle_device *dev,
 
 	local_irq_enable();
 	local_fiq_enable();
+	rcu_idle_exit();
 
 	after = ktime_get();
 	dev->last_residency = ktime_to_ns(ktime_sub(after, before)) >> 10;

arch/arm/mach-shmobile/pm-sh7372.c +8 -0

index fcf8b17..e11507e 100644
@@ -21,6 +21,7 @@
 #include <linux/irq.h>
 #include <linux/bitrev.h>
 #include <linux/console.h>
+#include <linux/rcupdate.h>
 #include <asm/system.h>
 #include <asm/io.h>
 #include <asm/tlbflush.h>

@@ -520,17 +521,24 @@ static int sh7372_enter_suspend(suspend_state_t suspend_state)
 		    sh7372_a4s.genpd.status == GPD_STATE_POWER_OFF) {
 			/* enter A4S sleep with PLLC0 off */
 			pr_debug("entering A4S\n");
+			rcu_idle_enter();
 			sh7372_enter_a4s_common(0);
+			rcu_idle_exit();
 		} else {
 			/* enter A3SM sleep with PLLC0 off */
 			pr_debug("entering A3SM\n");
+			rcu_idle_enter();
 			sh7372_enter_a3sm_common(0);
+			rcu_idle_exit();
 		}
 	} else {
 		/* default to Core Standby that supports all wakeup sources */
 		pr_debug("entering Core Standby\n");
+		rcu_idle_enter();
 		sh7372_enter_core_standby();
+		rcu_idle_exit();
 	}
+
 	return 0;
 }
 

Quoted 7 lines · Paul E. McKenney

From: "Paul E. McKenney" <[email protected]>

The idle loop is a quiscent state for RCU, which means that RCU ignores CPUs that have told RCU that they are idle via rcu_idle_enter(). There are nevertheless quite a few places where idle CPUs use RCU, most commonly indirectly via tracing. This patch fixes these problems for ARM.

Quoted 6 lines

Many of these bugs have been in the kernel for quite some time, but Frederic's recent change now gives warnings.

This patch takes the straightforward approach of pushing the rcu_idle_enter()/rcu_idle_exit() pair further down into the core of the idle loop.

NAK.

1) This is going to conflict with a patch series I've pushed to RMK already. You can see its result in linux-next.

2) The purpose of (1) is to do precisely the very opposite i.e. move as much common knowledge as possible up the idle call paths and leave the platform specific quirks as bare as possible, if any.

So I'd much prefer if this change was constrained to be inside cpu_idle(), or at least in its close vicinity.

Quoted 639 lines

Signed-off-by Paul E. McKenney <[email protected]>

Signed-off-by Paul E. McKenney <[email protected]>

Cc Russell King <[email protected]>

Cc Andrew Victor <[email protected]>

Cc Nicolas Ferre <[email protected]>

Cc Jean-Christophe Plagniol-Villard <[email protected]>

Cc Sekhar Nori <[email protected]>

Cc Kevin Hilman <[email protected]>

Cc Kukjin Kim <[email protected]>

Cc Rob Herring <[email protected]>

Cc Sascha Hauer <[email protected]>

Cc Shawn Guo <[email protected]>

Cc Lennert Buytenhek <[email protected]>

Cc Nicolas Pitre <[email protected]>

Cc Amit Kucheria <[email protected]>

Cc Tony Lindgren <[email protected]>

Cc Barry Song <[email protected]>

Cc Paul Mundt <[email protected]>

Cc Magnus Damm <[email protected]>

Cc Will Deacon <[email protected]>

Cc H Hartley Sweeten <[email protected]>

Cc Trinabh Gupta <[email protected]>

Cc Deepthi Dharwar <[email protected]>

Cc Len Brown <[email protected]>

Cc linux-arm-kernel at lists.infradead.org

Cc linux-samsung-soc at vger.kernel.org

Cc linux-omap at vger.kernel.org

---
 arch/arm/kernel/process.c          |    2 --
 arch/arm/mach-at91/cpuidle.c       |    3 +++
 arch/arm/mach-davinci/cpuidle.c    |    3 +++
 arch/arm/mach-exynos/common.c      |    2 ++
 arch/arm/mach-highbank/pm.c        |   12 ++++++++++++
 arch/arm/mach-imx/mm-imx3.c        |    3 +++
 arch/arm/mach-imx/pm-imx27.c       |    4 ++++
 arch/arm/mach-imx/pm-imx6q.c       |    4 ++++
 arch/arm/mach-kirkwood/cpuidle.c   |    3 +++
 arch/arm/mach-mx5/mm.c             |    3 +++
 arch/arm/mach-mx5/pm-imx5.c        |    3 +++
 arch/arm/mach-mxs/pm.c             |    4 ++++
 arch/arm/mach-omap1/pm.c           |    4 ++++
 arch/arm/mach-omap2/pm24xx.c       |    2 ++
 arch/arm/mach-omap2/pm34xx.c       |    2 ++
 arch/arm/mach-omap2/pm44xx.c       |    3 +++
 arch/arm/mach-pnx4008/pm.c         |    2 ++
 arch/arm/mach-prima2/pm.c          |    4 ++++
 arch/arm/mach-s5p64x0/common.c     |    2 ++
 arch/arm/mach-s5pc100/common.c     |    2 ++
 arch/arm/mach-s5pv210/common.c     |    2 ++
 arch/arm/mach-shmobile/cpuidle.c   |    3 +++
 arch/arm/mach-shmobile/pm-sh7372.c |    8 ++++++++
 23 files changed, 78 insertions(+), 2 deletions(-)

arch/arm/kernel/process.c +0 -2

index 971d65c..8241df7 100644
@@ -207,7 +207,6 @@ void cpu_idle(void)
 	/* endless idle loop with no priority at all */
 	while (1) {
 		tick_nohz_idle_enter();
-		rcu_idle_enter();
 		leds_event(led_idle_start);
 		while (!need_resched()) {
 #ifdef CONFIG_HOTPLUG_CPU

@@ -237,7 +236,6 @@ void cpu_idle(void)
 			}
 		}
 		leds_event(led_idle_end);
-		rcu_idle_exit();
 		tick_nohz_idle_exit();
 		preempt_enable_no_resched();
 		schedule();

arch/arm/mach-at91/cpuidle.c +3 -0

index a851e6c..8feff6b 100644
@@ -20,6 +20,7 @@
 #include <asm/proc-fns.h>
 #include <linux/io.h>
 #include <linux/export.h>
+#include <linux/rcupdate.h>
 
 #include "pm.h"
 

@@ -43,6 +44,7 @@ static int at91_enter_idle(struct cpuidle_device *dev,
 
 	local_irq_disable();
 	do_gettimeofday(&before);
+	rcu_idle_enter();
 	if (index == 0)
 		/* Wait for interrupt state */
 		cpu_do_idle();

@@ -53,6 +55,7 @@ static int at91_enter_idle(struct cpuidle_device *dev,
 		cpu_do_idle();
 		sdram_selfrefresh_disable(saved_lpr);
 	}
+	rcu_idle_exit();
 	do_gettimeofday(&after);
 	local_irq_enable();
 	idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +

arch/arm/mach-davinci/cpuidle.c +3 -0

index a30c7c5..6594b7e 100644
@@ -17,6 +17,7 @@
 #include <linux/cpuidle.h>
 #include <linux/io.h>
 #include <linux/export.h>
+#include <linux/rcupdate.h>
 #include <asm/proc-fns.h>
 
 #include <mach/cpuidle.h>

@@ -90,12 +91,14 @@ static int davinci_enter_idle(struct cpuidle_device *dev,
 	local_irq_disable();
 	do_gettimeofday(&before);
 
+	rcu_idle_enter();
 	if (ops && ops->enter)
 		ops->enter(ops->flags);
 	/* Wait for interrupt state */
 	cpu_do_idle();
 	if (ops && ops->exit)
 		ops->exit(ops->flags);
+	rcu_idle_exit();
 
 	do_gettimeofday(&after);
 	local_irq_enable();

arch/arm/mach-exynos/common.c +2 -0

index c59e188..1e5844a 100644
@@ -203,8 +203,10 @@ static struct map_desc exynos4_iodesc1[] __initdata = {
 
 static void exynos_idle(void)
 {
+	rcu_idle_enter();
 	if (!need_resched())
 		cpu_do_idle();
+	rcu_idle_exit();
 
 	local_irq_enable();
 }

arch/arm/mach-highbank/pm.c +12 -0

index 33b3beb..5ecc4bc 100644
@@ -17,6 +17,7 @@
 #include <linux/init.h>
 #include <linux/io.h>
 #include <linux/suspend.h>
+#include <linux/rcupdate.h>
 
 #include <asm/proc-fns.h>
 #include <asm/smp_scu.h>

@@ -33,12 +34,23 @@ static int highbank_suspend_finish(unsigned long val)
 
 static int highbank_pm_enter(suspend_state_t state)
 {
+	/*
+	 * Some of the functions preceding the cpu_suspend() can
+	 * invoke RCU, but only in case of failure to disable preemption
+	 * or preempt_disable() misnesting.  Assume that these errors
+	 * are not committed in the following code, because RCU just
+	 * doesn't want to run on a CPU that has its caches disabled.
+	 */
+	rcu_idle_enter();
+
 	hignbank_set_pwr_suspend();
 	highbank_set_cpu_jump(0, cpu_resume);
 
 	scu_power_mode(scu_base_addr, SCU_PM_POWEROFF);
 	cpu_suspend(0, highbank_suspend_finish);
 
+	rcu_idle_exit();
+
 	return 0;
 }
 

arch/arm/mach-imx/mm-imx3.c +3 -0

index 31807d2..0945b23 100644
@@ -19,6 +19,7 @@
 #include <linux/mm.h>
 #include <linux/init.h>
 #include <linux/err.h>
+#include <linux/rcupdate.h>
 
 #include <asm/pgtable.h>
 #include <asm/hardware/cache-l2x0.h>

@@ -34,6 +35,7 @@ static void imx3_idle(void)
 {
 	unsigned long reg = 0;
 
+	rcu_idle_enter();
 	if (!need_resched())
 		__asm__ __volatile__(
 			/* disable I and D cache */

@@ -58,6 +60,7 @@ static void imx3_idle(void)
 			"orr %0, %0, #0x00000004\n"
 			"mcr p15, 0, %0, c1, c0, 0\n"
 			: "=r" (reg));
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-imx/pm-imx27.c +4 -0

index e455d2f..c4adc05 100644
@@ -10,12 +10,14 @@
 #include <linux/kernel.h>
 #include <linux/suspend.h>
 #include <linux/io.h>
+#include <linux/rcupdate.h>
 #include <mach/system.h>
 #include <mach/hardware.h>
 
 static int mx27_suspend_enter(suspend_state_t state)
 {
 	u32 cscr;
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		/* Clear MPEN and SPEN to disable MPLL/SPLL */

@@ -24,9 +26,11 @@ static int mx27_suspend_enter(suspend_state_t state)
 		__raw_writel(cscr, MX27_IO_ADDRESS(MX27_CCM_BASE_ADDR));
 		/* Executes WFI */
 		arch_idle();
+		rcu_idle_exit();
 		break;
 
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 	return 0;

arch/arm/mach-imx/pm-imx6q.c +4 -0

index f7b0c2b..b9c2589 100644
@@ -14,6 +14,7 @@
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/suspend.h>
+#include <linux/rcupdate.h>
 #include <asm/cacheflush.h>
 #include <asm/proc-fns.h>
 #include <asm/suspend.h>

@@ -31,6 +32,7 @@ static int imx6q_suspend_finish(unsigned long val)
 
 static int imx6q_pm_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		imx6q_set_lpm(STOP_POWER_OFF);

@@ -40,8 +42,10 @@ static int imx6q_pm_enter(suspend_state_t state)
 		cpu_suspend(0, imx6q_suspend_finish);
 		imx_smp_prepare();
 		imx_gpc_post_resume();
+		rcu_idle_exit();
 		break;
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 

arch/arm/mach-kirkwood/cpuidle.c +3 -0

index 7088180..de8e317 100644
@@ -19,6 +19,7 @@
 #include <linux/cpuidle.h>
 #include <linux/io.h>
 #include <linux/export.h>
+#include <linux/rcupdate.h>
 #include <asm/proc-fns.h>
 #include <mach/kirkwood.h>
 

@@ -41,6 +42,7 @@ static int kirkwood_enter_idle(struct cpuidle_device *dev,
 
 	local_irq_disable();
 	do_gettimeofday(&before);
+	rcu_idle_enter();
 	if (index == 0)
 		/* Wait for interrupt state */
 		cpu_do_idle();

@@ -55,6 +57,7 @@ static int kirkwood_enter_idle(struct cpuidle_device *dev,
 		writel(0x7, DDR_OPERATION_BASE);
 		cpu_do_idle();
 	}
+	rcu_idle_exit();
 	do_gettimeofday(&after);
 	local_irq_enable();
 	idle_time = (after.tv_sec - before.tv_sec) * USEC_PER_SEC +

arch/arm/mach-mx5/mm.c +3 -0

index bc17dfe..d919648 100644
@@ -14,6 +14,7 @@
 #include <linux/mm.h>
 #include <linux/init.h>
 #include <linux/clk.h>
+#include <linux/rcupdate.h>
 
 #include <asm/mach/map.h>
 

@@ -37,7 +38,9 @@ static void imx5_idle(void)
 		mx5_cpu_lp_set(WAIT_UNCLOCKED_POWER_OFF);
 		if (tzic_enable_wake())
 			goto err1;
+		rcu_idle_enter();  /* No tracing until rcu_idle_exit(). */
 		cpu_do_idle();
+		rcu_idle_exit();
 err1:
 		clk_disable(gpc_dvfs_clk);
 	}

arch/arm/mach-mx5/pm-imx5.c +3 -0

index 98052fc..b4adf42 100644
@@ -12,6 +12,7 @@
 #include <linux/clk.h>
 #include <linux/io.h>
 #include <linux/err.h>
+#include <linux/rcupdate.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 #include <mach/common.h>

@@ -27,6 +28,7 @@ static int mx5_suspend_prepare(void)
 
 static int mx5_suspend_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		mx5_cpu_lp_set(STOP_POWER_OFF);

@@ -47,6 +49,7 @@ static int mx5_suspend_enter(suspend_state_t state)
 		__raw_writel(0, MXC_SRPG_EMPGC1_SRPGCR);
 	}
 	cpu_do_idle();
+	rcu_idle_exit();
 	return 0;
 }
 

arch/arm/mach-mxs/pm.c +4 -0

index fb042da..36a3a57 100644
@@ -15,16 +15,20 @@
 #include <linux/kernel.h>
 #include <linux/suspend.h>
 #include <linux/io.h>
+#include <linux/rcupdate.h>
 #include <mach/system.h>
 
 static int mxs_suspend_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		arch_idle();
+		rcu_idle_exit();
 		break;
 
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 	return 0;

arch/arm/mach-omap1/pm.c +4 -0

index 89ea20c..c661eba 100644
@@ -108,11 +108,13 @@ void omap1_pm_idle(void)
 	__u32 use_idlect1 = arm_idlect1_mask;
 	int do_sleep = 0;
 
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 	if (need_resched()) {
 		local_fiq_enable();
 		local_irq_enable();
+		rcu_idle_exit();
 		return;
 	}
 

@@ -158,6 +160,7 @@ void omap1_pm_idle(void)
 
 		local_fiq_enable();
 		local_irq_enable();
+		rcu_idle_exit();
 		return;
 	}
 	omap_sram_suspend(omap_readl(ARM_IDLECT1),

@@ -165,6 +168,7 @@ void omap1_pm_idle(void)
 
 	local_fiq_enable();
 	local_irq_enable();
+	rcu_idle_exit();
 }
 
 /*

arch/arm/mach-omap2/pm24xx.c +2 -0

index b8822f8..2139e9d 100644
@@ -232,6 +232,7 @@ static int omap2_can_sleep(void)
 
 static void omap2_pm_idle(void)
 {
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 

@@ -250,6 +251,7 @@ static void omap2_pm_idle(void)
 out:
 	local_fiq_enable();
 	local_irq_enable();
+	rcu_idle_exit();
 }
 
 #ifdef CONFIG_SUSPEND

arch/arm/mach-omap2/pm34xx.c +2 -0

index fc69875..58a8689 100644
@@ -427,7 +427,9 @@ static void omap3_pm_idle(void)
 	trace_power_start(POWER_CSTATE, 1, smp_processor_id());
 	trace_cpu_idle(1, smp_processor_id());
 
+	rcu_idle_enter();
 	omap_sram_idle();
+	rcu_idle_exit();
 
 	trace_power_end(smp_processor_id());
 	trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());

arch/arm/mach-omap2/pm44xx.c +3 -0

index c264ef7..038796c 100644
@@ -16,6 +16,7 @@
 #include <linux/list.h>
 #include <linux/err.h>
 #include <linux/slab.h>
+#include <linux/rcupdate.h>
 
 #include "common.h"
 #include "clockdomain.h"

@@ -178,6 +179,7 @@ static int __init pwrdms_setup(struct powerdomain *pwrdm, void *unused)
  */
 static void omap_default_idle(void)
 {
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 

@@ -185,6 +187,7 @@ static void omap_default_idle(void)
 
 	local_fiq_enable();
 	local_irq_enable();
+	rcu_idle_exit();
 }
 
 /**

arch/arm/mach-pnx4008/pm.c +2 -0

index f3e60a0..0b8703f 100644
@@ -102,6 +102,7 @@ static inline void pnx4008_suspend(void)
 
 static int pnx4008_pm_enter(suspend_state_t state)
 {
+	rcu_idle_enter();
 	switch (state) {
 	case PM_SUSPEND_STANDBY:
 		pnx4008_standby();

@@ -110,6 +111,7 @@ static int pnx4008_pm_enter(suspend_state_t state)
 		pnx4008_suspend();
 		break;
 	}
+	rcu_idle_exit();
 	return 0;
 }
 

arch/arm/mach-prima2/pm.c +4 -0

index 26ebb57..1e35c8a 100644
@@ -15,6 +15,7 @@
 #include <linux/of_device.h>
 #include <linux/of_platform.h>
 #include <linux/io.h>
+#include <linux/rcupdate.h>
 #include <linux/rtc/sirfsoc_rtciobrg.h>
 #include <asm/suspend.h>
 #include <asm/hardware/cache-l2x0.h>

@@ -64,6 +65,7 @@ static int sirfsoc_pre_suspend_power_off(void)
 
 static int sirfsoc_pm_enter(suspend_state_t state)
 {
+	rcu_idle_enter(); /* No good place for this: locking->lockdep->RCU. */
 	switch (state) {
 	case PM_SUSPEND_MEM:
 		sirfsoc_pre_suspend_power_off();

@@ -73,8 +75,10 @@ static int sirfsoc_pm_enter(suspend_state_t state)
 		/* go zzz */
 		cpu_suspend(0, sirfsoc_finish_suspend);
 		outer_resume();
+		rcu_idle_exit();
 		break;
 	default:
+		rcu_idle_exit();
 		return -EINVAL;
 	}
 	return 0;

arch/arm/mach-s5p64x0/common.c +2 -0

index 52b89a3..c59a7f2 100644
@@ -146,6 +146,7 @@ static void s5p64x0_idle(void)
 {
 	unsigned long val;
 
+	rcu_idle_enter();
 	if (!need_resched()) {
 		val = __raw_readl(S5P64X0_PWR_CFG);
 		val &= ~(0x3 << 5);

@@ -154,6 +155,7 @@ static void s5p64x0_idle(void)
 
 		cpu_do_idle();
 	}
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-s5pc100/common.c +2 -0

index c909573..7bf02ff 100644
@@ -131,9 +131,11 @@ static struct map_desc s5pc100_iodesc[] __initdata = {
 
 static void s5pc100_idle(void)
 {
+	rcu_idle_enter();
 	if (!need_resched())
 		cpu_do_idle();
 
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-s5pv210/common.c +2 -0

index 9c1bcdc..ccd6b4d 100644
@@ -144,9 +144,11 @@ static struct map_desc s5pv210_iodesc[] __initdata = {
 
 static void s5pv210_idle(void)
 {
+	rcu_idle_enter();
 	if (!need_resched())
 		cpu_do_idle();
 
+	rcu_idle_exit();
 	local_irq_enable();
 }
 

arch/arm/mach-shmobile/cpuidle.c +3 -0

index 1b23342..651e92b 100644
@@ -13,6 +13,7 @@
 #include <linux/suspend.h>
 #include <linux/module.h>
 #include <linux/err.h>
+#include <linux/rcupdate.h>
 #include <asm/system.h>
 #include <asm/io.h>
 

@@ -33,6 +34,7 @@ static int shmobile_cpuidle_enter(struct cpuidle_device *dev,
 
 	before = ktime_get();
 
+	rcu_idle_enter();
 	local_irq_disable();
 	local_fiq_disable();
 

@@ -40,6 +42,7 @@ static int shmobile_cpuidle_enter(struct cpuidle_device *dev,
 
 	local_irq_enable();
 	local_fiq_enable();
+	rcu_idle_exit();
 
 	after = ktime_get();
 	dev->last_residency = ktime_to_ns(ktime_sub(after, before)) >> 10;

arch/arm/mach-shmobile/pm-sh7372.c +8 -0

index fcf8b17..e11507e 100644
@@ -21,6 +21,7 @@
 #include <linux/irq.h>
 #include <linux/bitrev.h>
 #include <linux/console.h>
+#include <linux/rcupdate.h>
 #include <asm/system.h>
 #include <asm/io.h>
 #include <asm/tlbflush.h>

@@ -520,17 +521,24 @@ static int sh7372_enter_suspend(suspend_state_t suspend_state)
 		    sh7372_a4s.genpd.status == GPD_STATE_POWER_OFF) {
 			/* enter A4S sleep with PLLC0 off */
 			pr_debug("entering A4S\n");
+			rcu_idle_enter();
 			sh7372_enter_a4s_common(0);
+			rcu_idle_exit();
 		} else {
 			/* enter A3SM sleep with PLLC0 off */
 			pr_debug("entering A3SM\n");
+			rcu_idle_enter();
 			sh7372_enter_a3sm_common(0);
+			rcu_idle_exit();
 		}
 	} else {
 		/* default to Core Standby that supports all wakeup sources */
 		pr_debug("entering Core Standby\n");
+		rcu_idle_enter();
 		sh7372_enter_core_standby();
+		rcu_idle_exit();
 	}
+
 	return 0;
 }
 

Signature · 1 line

1.7.8

Quoted 7 lines · Paul E. McKenney

From: "Paul E. McKenney" <[email protected]>

The idle loop is a quiscent state for RCU, which means that RCU ignores CPUs that have told RCU that they are idle via rcu_idle_enter(). There are nevertheless quite a few places where idle CPUs use RCU, most commonly indirectly via tracing. This patch fixes these problems for x86.

Quoted 6 lines

Many of these bugs have been in the kernel for quite some time, but Frederic's recent change now gives warnings.

This patch takes the straightforward approach of pushing the rcu_idle_enter()/rcu_idle_exit() pair further down into the core of the idle loop.

I guess this is about the trace_power_*() things, right?

Acked-by Frederic Weisbecker <[email protected]>

Thanks.

Quoted 9 lines · Paul E. McKenney

Hello!

RCU's shiny new diagnostics (thank you, Frederic!) for using RCU when idle located a few problems in arm, sh, and x86. This patch series contains alleged fixes for these problems. And they are real problems -- if RCU believes that the CPU is idle, it is ignoring it. Which means that the idle CPU can say "rcu_read_lock()" all it like, but there will be no useful effect.

Quoted 2 lines

I was tempted to break these up, but doing so is bad for bisectability.

Presumably the same changes will also need to be reflected in cpuidle?

If so, here's a start:

Signed-off-by Paul Mundt <[email protected]>

---

drivers/cpuidle/cpuidle.c +7 -1

index 59f4261..97adcd4 100644
@@ -18,6 +18,7 @@
 #include <linux/ktime.h>
 #include <linux/hrtimer.h>
 #include <linux/module.h>
+#include <linux/rcupdate.h>
 #include <trace/events/power.h>
 
 #include "cpuidle.h"

@@ -89,6 +90,8 @@ int cpuidle_idle_call(void)
 	next_state = cpuidle_curr_governor->select(drv, dev);
 	if (need_resched()) {
 		local_irq_enable();
+		rcu_idle_enter();
+		rcu_idle_exit();
 		return 0;
 	}
 

@@ -96,9 +99,11 @@ int cpuidle_idle_call(void)
 
 	trace_power_start(POWER_CSTATE, next_state, dev->cpu);
 	trace_cpu_idle(next_state, dev->cpu);
+	rcu_idle_enter();
 
 	entered_state = target_state->enter(dev, drv, next_state);
 
+	rcu_idle_exit();
 	trace_power_end(dev->cpu);
 	trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu);
 

@@ -173,8 +178,10 @@ static int poll_idle(struct cpuidle_device *dev,
 
 	t1 = ktime_get();
 	local_irq_enable();
+	rcu_idle_enter();
 	while (!need_resched())
 		cpu_relax();
+	rcu_idle_exit();
 
 	t2 = ktime_get();
 	diff = ktime_to_us(ktime_sub(t2, t1));
--

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Quoted 25 lines · Nicolas Pitre

Quoted 7 lines · Paul E. McKenney

From: "Paul E. McKenney" <[email protected]>

The idle loop is a quiscent state for RCU, which means that RCU ignores CPUs that have told RCU that they are idle via rcu_idle_enter(). There are nevertheless quite a few places where idle CPUs use RCU, most commonly indirectly via tracing. This patch fixes these problems for ARM.

Quoted 6 lines

Many of these bugs have been in the kernel for quite some time, but Frederic's recent change now gives warnings.

This patch takes the straightforward approach of pushing the rcu_idle_enter()/rcu_idle_exit() pair further down into the core of the idle loop.

NAK.

1) This is going to conflict with a patch series I've pushed to RMK already. You can see its result in linux-next.

2) The purpose of (1) is to do precisely the very opposite i.e. move as much common knowledge as possible up the idle call paths and leave the platform specific quirks as bare as possible, if any.

Quoted 2 lines

So I'd much prefer if this change was constrained to be inside cpu_idle(), or at least in its close vicinity.

OK. Then the tracing in the inner idle loop needs to go. Other restructuring might be required as well.

The long and short of it is that you absolutely cannot use RCU between the time you invoke rcu_idle_enter() and the time you invoke rcu_idle_exit(). The ARM idle code currently does just that and therefore must change.

Whatever change you choose that causes the code to meet that constraint is met is fine by me.

But that constraint absolutely must be met.

Quoted 26 lines · Paul E. McKenney

Quoted 25 lines · Nicolas Pitre

Quoted 7 lines · Paul E. McKenney

From: "Paul E. McKenney" <[email protected]>

The idle loop is a quiscent state for RCU, which means that RCU ignores CPUs that have told RCU that they are idle via rcu_idle_enter(). There are nevertheless quite a few places where idle CPUs use RCU, most commonly indirectly via tracing. This patch fixes these problems for ARM.

Quoted 6 lines

Many of these bugs have been in the kernel for quite some time, but Frederic's recent change now gives warnings.

This patch takes the straightforward approach of pushing the rcu_idle_enter()/rcu_idle_exit() pair further down into the core of the idle loop.

NAK.

1) This is going to conflict with a patch series I've pushed to RMK already. You can see its result in linux-next.

2) The purpose of (1) is to do precisely the very opposite i.e. move as much common knowledge as possible up the idle call paths and leave the platform specific quirks as bare as possible, if any.

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So I'd much prefer if this change was constrained to be inside cpu_idle(), or at least in its close vicinity.

OK. Then the tracing in the inner idle loop needs to go. Other restructuring might be required as well.

Let me expand a bit more on the "if any" in my #2 above. Most ARM sub-architectures don't have any special idle drivers and they simply rely on the default cpu_do_idle call. What this proposed patch is doing is to move the rcu_idle_enter()/rcu_idle_exit() pair down into the few subarchs with an existing cpu-idle callback. This means in practice that rcu_idle_enter()/rcu_idle_exit() wouldn't be called at all anymore on most ARM targets. Is that appropriate?

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The long and short of it is that you absolutely cannot use RCU between the time you invoke rcu_idle_enter() and the time you invoke rcu_idle_exit(). The ARM idle code currently does just that and therefore must change.

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Whatever change you choose that causes the code to meet that constraint is met is fine by me.

But that constraint absolutely must be met.

I would have to know more about what the rcu_idle_*() calls imply before suggesting an alternative.

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I would have to know more about what the rcu_idle_*() calls imply before suggesting an alternative.

After a call to rcu_idle_enter(), RCU ignores the CPU completely until the next call to rcu_idle_exit(). This means that in the interval between rcu_idle_enter() and rcu_idle_exit(), you can say rcu_read_lock() all you want, but your data structures will get absolutely no RCU protection. This will result in random memory corruption, and for all I know might already be resultin in random memory corruption. So a fix is required.

So why does RCU need to ignore idle CPUs? Because otherwise, RCU needs to periodically wake them up to check their status. Waking them up periodically defeats CONFIG_NO_HZ's attempts to conserve power. Avoiding waking them up and avoiding ignoring them extended RCU grace periods, eventually OOMing the systems.

Why this new imposition? It is not new. It has always been illegal to use RCU in the idle loop from the beginning. But people happily ignored that restriction, partly because it is not always immediately obvious what is using RCU. Event tracing does, but unless you know that...

So we added diagnostics to check for illegal uses of RCU in the idle loop, and also separated rcu_idle_enter() and rcu_idle_exit() from tick_nohz_stop_sched_tick(), so that things like idle notifiers can work. The diagnostics promptly located all sorts of problems, including these.

The two options I see are:

1. Rip tracing out of the inner idle loops and everything that
they invoke.

2. Push rcu_idle_enter() and rcu_idle_exit() further down into
the idle loops. As you say, -all- of them.

My patch set was an attempt at #2, but clearly a very poorly conceived attempt. But I had to start somewhere.

Other ideas?