[PATCH AUTOSEL 5.8 23/29] cpuidle: psci: Fix suspicious RCU usage

Sasha Levin
2020-09-29T01:31:07Z

From: Ulf Hansson <ulf.hansson@linaro.org>

[ Upstream commit 36050d8984ab743f9990a2eb97a0062fdc3d7bbd ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 3806f911b61c0..915172e3ec906 100644
--- a/drivers/cpuidle/cpuidle-psci.c
+++ b/drivers/cpuidle/cpuidle-psci.c
@@ -64,7 +64,7 @@ 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)
@@ -72,7 +72,7 @@ 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();

--
2.25.1