From 3ad1c8ef083bef96ec922688966484be1039e6b5 Mon Sep 17 00:00:00 2001
From: Borislav Petkov <bp@suse.de>
Date: Mon, 21 Sep 2020 12:31:36 +0200
Subject: [PATCH 1/4] rcu/tree: Export rcu_idle_{enter,exit} to modules
Fix this link error:
ERROR: modpost: "rcu_idle_enter" [drivers/acpi/processor.ko] undefined!
ERROR: modpost: "rcu_idle_exit" [drivers/acpi/processor.ko] undefined!
when CONFIG_ACPI_PROCESSOR is built as module. PeterZ says that in light
of ARM needing those soon too, they should simply be exported.
Fixes: 1fecfdbb7acc ("ACPI: processor: Take over RCU-idle for C3-BM idle")
Reported-by: Sven Joachim <svenjoac@gmx.de>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Paul E. McKenney <paulmckrcu@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
kernel/rcu/tree.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8ce77d9ac716c..f78ee759af9cb 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -673,6 +673,7 @@ void rcu_idle_enter(void)
lockdep_assert_irqs_disabled();
rcu_eqs_enter(false);
}
+EXPORT_SYMBOL_GPL(rcu_idle_enter);
#ifdef CONFIG_NO_HZ_FULL
/**
@@ -886,6 +887,7 @@ void rcu_idle_exit(void)
rcu_eqs_exit(false);
local_irq_restore(flags);
}
+EXPORT_SYMBOL_GPL(rcu_idle_exit);
#ifdef CONFIG_NO_HZ_FULL
/**
From 36050d8984ab743f9990a2eb97a0062fdc3d7bbd Mon Sep 17 00:00:00 2001
From: Ulf Hansson <ulf.hansson@linaro.org>
Date: Fri, 4 Sep 2020 08:47:05 +0200
Subject: [PATCH 2/4] cpuidle: psci: Fix suspicious RCU usage
The commit eb1f00237aca ("lockdep,trace: Expose tracepoints"), started to
expose us for tracepoints. This lead to the following RCU splat on an ARM64
Qcom board.
[ 5.529634] WARNING: suspicious RCU usage
[ 5.537307] sdhci-pltfm: SDHCI platform and OF driver helper
[ 5.541092] 5.9.0-rc3 #86 Not tainted
[ 5.541098] -----------------------------
[ 5.541105] ../include/trace/events/lock.h:37 suspicious rcu_dereference_check() usage!
[ 5.541110]
[ 5.541110] other info that might help us debug this:
[ 5.541110]
[ 5.541116]
[ 5.541116] rcu_scheduler_active = 2, debug_locks = 1
[ 5.541122] RCU used illegally from extended quiescent state!
[ 5.541129] no locks held by swapper/0/0.
[ 5.541134]
[ 5.541134] stack backtrace:
[ 5.541143] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.9.0-rc3 #86
[ 5.541149] Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT)
[ 5.541157] Call trace:
[ 5.568185] sdhci_msm 7864900.sdhci: Got CD GPIO
[ 5.574186] dump_backtrace+0x0/0x1c8
[ 5.574206] show_stack+0x14/0x20
[ 5.574229] dump_stack+0xe8/0x154
[ 5.574250] lockdep_rcu_suspicious+0xd4/0xf8
[ 5.574269] lock_acquire+0x3f0/0x460
[ 5.574292] _raw_spin_lock_irqsave+0x80/0xb0
[ 5.574314] __pm_runtime_suspend+0x4c/0x188
[ 5.574341] psci_enter_domain_idle_state+0x40/0xa0
[ 5.574362] cpuidle_enter_state+0xc0/0x610
[ 5.646487] cpuidle_enter+0x38/0x50
[ 5.650651] call_cpuidle+0x18/0x40
[ 5.654467] do_idle+0x228/0x278
[ 5.657678] cpu_startup_entry+0x24/0x70
[ 5.661153] rest_init+0x1a4/0x278
[ 5.665061] arch_call_rest_init+0xc/0x14
[ 5.668272] start_kernel+0x508/0x540
Following the path in pm_runtime_put_sync_suspend() from
psci_enter_domain_idle_state(), it seems like we end up using the RCU.
Therefore, let's simply silence the splat by informing the RCU about it
with RCU_NONIDLE.
Note that, this is a temporary solution. Instead we should strive to avoid
using RCU_NONIDLE (and similar), but rather push rcu_idle_enter|exit()
further down, closer to the arch specific code. However, as the CPU PM
notifiers are also using the RCU, additional rework is needed.
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/cpuidle/cpuidle-psci.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/cpuidle/cpuidle-psci.c b/drivers/cpuidle/cpuidle-psci.c
index 74463841805f2..d928b37718bde 100644
--- a/drivers/cpuidle/cpuidle-psci.c
+++ b/drivers/cpuidle/cpuidle-psci.c
@@ -66,7 +66,7 @@ static int psci_enter_domain_idle_state(struct cpuidle_device *dev,
return -1;
/* Do runtime PM to manage a hierarchical CPU toplogy. */
- pm_runtime_put_sync_suspend(pd_dev);
+ RCU_NONIDLE(pm_runtime_put_sync_suspend(pd_dev));
state = psci_get_domain_state();
if (!state)
@@ -74,7 +74,7 @@ static int psci_enter_domain_idle_state(struct cpuidle_device *dev,
ret = psci_cpu_suspend_enter(state) ? -1 : idx;
- pm_runtime_get_sync(pd_dev);
+ RCU_NONIDLE(pm_runtime_get_sync(pd_dev));
cpu_pm_exit();
From bd805274577457f301bf826f86543f550cf5c1ef Mon Sep 17 00:00:00 2001
From: Ulf Hansson <ulf.hansson@linaro.org>
Date: Tue, 22 Sep 2020 11:15:50 +0200
Subject: [PATCH 3/4] cpuidle: Drop misleading comments about RCU usage
The commit 1098582a0f6c ("sched,idle,rcu: Push rcu_idle deeper into the
idle path"), moved the calls rcu_idle_enter|exit() into the cpuidle core.
However, it forgot to remove a couple of comments in enter_s2idle_proper()
about why RCU_NONIDLE earlier was needed. So, let's drop them as they have
become a bit misleading.
Fixes: 1098582a0f6c ("sched,idle,rcu: Push rcu_idle deeper into the idle path")
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/cpuidle/cpuidle.c | 10 ----------
1 file changed, 10 deletions(-)
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 6c7e5621cf9a8..29e84687f3c39 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -142,11 +142,6 @@ static void enter_s2idle_proper(struct cpuidle_driver *drv,
time_start = ns_to_ktime(local_clock());
- /*
- * trace_suspend_resume() called by tick_freeze() for the last CPU
- * executing it contains RCU usage regarded as invalid in the idle
- * context, so tell RCU about that.
- */
tick_freeze();
/*
* The state used here cannot be a "coupled" one, because the "coupled"
@@ -159,11 +154,6 @@ static void enter_s2idle_proper(struct cpuidle_driver *drv,
target_state->enter_s2idle(dev, drv, index);
if (WARN_ON_ONCE(!irqs_disabled()))
local_irq_disable();
- /*
- * timekeeping_resume() that will be called by tick_unfreeze() for the
- * first CPU executing it calls functions containing RCU read-side
- * critical sections, so tell RCU about that.
- */
if (!(target_state->flags & CPUIDLE_FLAG_RCU_IDLE))
rcu_idle_exit();
tick_unfreeze();
From 955921289dcdbc49b46a731ec07978fb7d4e1fc7 Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Date: Wed, 23 Sep 2020 13:50:12 +0200
Subject: [PATCH 4/4] ACPI: processor: Fix build for ARCH_APICTIMER_STOPS_ON_C3
unset
Fix the lapic_timer_needs_broadcast() stub for
ARCH_APICTIMER_STOPS_ON_C3 unset to actually return
a value.
Fixes: aa6b43d57f99 ("ACPI: processor: Use CPUIDLE_FLAG_TIMER_STOP")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/acpi/processor_idle.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 7ecb90e90afde..f66236cff69b0 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -176,6 +176,7 @@ static void lapic_timer_propagate_broadcast(struct acpi_processor *pr) { }
static bool lapic_timer_needs_broadcast(struct acpi_processor *pr,
struct acpi_processor_cx *cx)
{
+ return false;
}
#endif