linux-kernel - [PATCH v2 2/5] cpuidle: psci: Mark as PREEMPT

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Message-Id: <20221219151503.385816-3-krzysztof.kozlowski@linaro.org>
Date:   Mon, 19 Dec 2022 16:15:00 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Adrien Thierry <athierry@...hat.com>,
        Brian Masney <bmasney@...hat.com>,
        linux-rt-users@...r.kernel.org
Subject: [PATCH v2 2/5] cpuidle: psci: Mark as PREEMPT_RT safe

The PSCI cpuidle power domain in power_off callback uses
__this_cpu_write() so it is PREEMPT_RT safe.  This allows to use it in
Realtime kernels and solves errors like:

  BUG: scheduling while atomic: swapper/2/0/0x00000002
  Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT)
  Call trace:
   dump_backtrace.part.0+0xe0/0xf0
   show_stack+0x18/0x40
   dump_stack_lvl+0x68/0x84
   dump_stack+0x18/0x34
   __schedule_bug+0x60/0x80
   __schedule+0x628/0x800
   schedule_rtlock+0x28/0x5c
   rtlock_slowlock_locked+0x360/0xd30
   rt_spin_lock+0x88/0xb0
   genpd_lock_nested_spin+0x1c/0x30
   genpd_power_off.part.0.isra.0+0x20c/0x2a0
   genpd_runtime_suspend+0x150/0x2bc
   __rpm_callback+0x48/0x170
   rpm_callback+0x6c/0x7c
   rpm_suspend+0x108/0x660
   __pm_runtime_suspend+0x4c/0x8c
   __psci_enter_domain_idle_state.constprop.0+0x54/0xe0
   psci_enter_domain_idle_state+0x18/0x2c
   cpuidle_enter_state+0x8c/0x4e0
   cpuidle_enter+0x38/0x50
   do_idle+0x248/0x2f0
   cpu_startup_entry+0x24/0x30
   secondary_start_kernel+0x130/0x154
   __secondary_switched+0xb0/0xb4

Cc: Adrien Thierry <athierry@...hat.com>
Cc: Brian Masney <bmasney@...hat.com>
Cc: linux-rt-users@...r.kernel.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
---
 drivers/cpuidle/cpuidle-psci-domain.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
index c80cf9ddabd8..d15a91fb7048 100644
--- a/drivers/cpuidle/cpuidle-psci-domain.c
+++ b/drivers/cpuidle/cpuidle-psci-domain.c
@@ -62,7 +62,8 @@ static int psci_pd_init(struct device_node *np, bool use_osi)
 	if (!pd_provider)
 		goto free_pd;

-	pd->flags |= GENPD_FLAG_IRQ_SAFE | GENPD_FLAG_CPU_DOMAIN;
+	pd->flags |= GENPD_FLAG_IRQ_SAFE | GENPD_FLAG_RT_SAFE | \
+		     GENPD_FLAG_CPU_DOMAIN;

 	/* Allow power off when OSI has been successfully enabled. */
 	if (use_osi)
-- 
2.34.1