linux-kernel - [PATCH] cpuidle: psci: Iterate backwards over list in psci_pd

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Date:   Fri, 25 Feb 2022 16:24:20 +0800
From:   Shawn Guo <shawn.guo@...aro.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Ulf Hansson <ulf.hansson@...aro.org>, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Shawn Guo <shawn.guo@...aro.org>
Subject: [PATCH] cpuidle: psci: Iterate backwards over list in psci_pd_remove()

In case that psci_pd_init_topology() fails for some reason,
psci_pd_remove() will be responsible for deleting provider and removing
genpd from psci_pd_providers list.  There will be a failure when removing
the cluster PD, because the cpu (child) PDs haven't been removed.

[    0.050232] CPUidle PSCI: init PM domain cpu0
[    0.050278] CPUidle PSCI: init PM domain cpu1
[    0.050329] CPUidle PSCI: init PM domain cpu2
[    0.050370] CPUidle PSCI: init PM domain cpu3
[    0.050422] CPUidle PSCI: init PM domain cpu-cluster0
[    0.050475] PM: genpd_remove: unable to remove cpu-cluster0
[    0.051412] PM: genpd_remove: removed cpu3
[    0.051449] PM: genpd_remove: removed cpu2
[    0.051499] PM: genpd_remove: removed cpu1
[    0.051546] PM: genpd_remove: removed cpu0

Fix the problem by iterating the provider list in a reversely order, so
that parent PD gets removed before child's PDs.

Signed-off-by: Shawn Guo <shawn.guo@...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 ff2c3f8e4668..ce5c415fb04d 100644
--- a/drivers/cpuidle/cpuidle-psci-domain.c
+++ b/drivers/cpuidle/cpuidle-psci-domain.c
@@ -182,7 +182,8 @@ static void psci_pd_remove(void)
 	struct psci_pd_provider *pd_provider, *it;
 	struct generic_pm_domain *genpd;
 
-	list_for_each_entry_safe(pd_provider, it, &psci_pd_providers, link) {
+	list_for_each_entry_safe_reverse(pd_provider, it,
+					 &psci_pd_providers, link) {
 		of_genpd_del_provider(pd_provider->node);
 
 		genpd = of_genpd_remove_last(pd_provider->node);
-- 
2.25.1