linux-kernel - [PATCH v2] cpuidle: psci: Iterate backwards over list in psci_pd

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Message-Id: <20220308082931.3385902-1-shawn.guo@linaro.org>
Date:   Tue,  8 Mar 2022 16:29:31 +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 v2] 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 reversely, so that parent
PD gets removed after child's PDs like below.

[    0.029052] CPUidle PSCI: init PM domain cpu0
[    0.029076] CPUidle PSCI: init PM domain cpu1
[    0.029103] CPUidle PSCI: init PM domain cpu2
[    0.029124] CPUidle PSCI: init PM domain cpu3
[    0.029151] CPUidle PSCI: init PM domain cpu-cluster0
[    0.029647] PM: genpd_remove: removed cpu0
[    0.029666] PM: genpd_remove: removed cpu1
[    0.029690] PM: genpd_remove: removed cpu2
[    0.029714] PM: genpd_remove: removed cpu3
[    0.029738] PM: genpd_remove: removed cpu-cluster0

Fixes: a65a397f2451 ("cpuidle: psci: Add support for PM domains by using genpd")
Reviewed-by: Sudeep Holla <sudeep.holla@....com>
Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Shawn Guo <shawn.guo@...aro.org>
---
Changes since v1:
- Fix commit log
- Pick up Reviewed-by tag from Sudeep and Ulf (Thanks!)
- Add Fixes tag as suggested by Ulf

 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