From 3ad1c8ef083bef96ec922688966484be1039e6b5 Mon Sep 17 00:00:00 2001 From: Borislav Petkov 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 Suggested-by: Peter Zijlstra Signed-off-by: Borislav Petkov Reviewed-by: Paul E. McKenney Signed-off-by: Rafael J. Wysocki --- kernel/rcu/tree.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 8ce77d9ac716..f78ee759af9c 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 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 Signed-off-by: Ulf Hansson Acked-by: Paul E. McKenney Signed-off-by: Rafael J. Wysocki --- 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 74463841805f..d928b37718bd 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 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 Signed-off-by: Rafael J. Wysocki --- drivers/cpuidle/cpuidle.c | 10 ---------- 1 file changed, 10 deletions(-) diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 6c7e5621cf9a..29e84687f3c3 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" 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 Signed-off-by: Rafael J. Wysocki --- 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 7ecb90e90afd..f66236cff69b 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