linux-kernel - [PATCH 2/6] pmdomain: core: Don't hold the genpd-lock when calling dev_pm_domain

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Message-Id: <20240429140531.210576-3-ulf.hansson@linaro.org>
Date: Mon, 29 Apr 2024 16:05:27 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: "Rafael J . Wysocki" <rafael@...nel.org>,
	Sudeep Holla <sudeep.holla@....com>,
	linux-pm@...r.kernel.org
Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Nikunj Kela <nkela@...cinc.com>,
	Prasad Sodagudi <psodagud@...cinc.com>,
	Maulik Shah <quic_mkshah@...cinc.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	linux-rt-users@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/6] pmdomain: core: Don't hold the genpd-lock when calling dev_pm_domain_set()

There is no need to hold the genpd-lock, while assigning the
dev->pm_domain. In fact, it becomes a problem on a PREEMPT_RT based
configuration as the genpd-lock may be a raw spinlock, while the lock
acquired through the call to dev_pm_domain_set() is a regular spinlock.

To fix the problem, let's simply move the calls to dev_pm_domain_set()
outside the genpd-lock.

Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
---
 drivers/pmdomain/core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
index abd3c069df8b..1e3f8dea4654 100644
--- a/drivers/pmdomain/core.c
+++ b/drivers/pmdomain/core.c
@@ -1726,7 +1726,6 @@ static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
 	genpd_lock(genpd);
 
 	genpd_set_cpumask(genpd, gpd_data->cpu);
-	dev_pm_domain_set(dev, &genpd->domain);
 
 	genpd->device_count++;
 	if (gd)
@@ -1735,6 +1734,7 @@ static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
 	list_add_tail(&gpd_data->base.list_node, &genpd->dev_list);
 
 	genpd_unlock(genpd);
+	dev_pm_domain_set(dev, &genpd->domain);
  out:
 	if (ret)
 		genpd_free_dev_data(dev, gpd_data);
@@ -1791,12 +1791,13 @@ static int genpd_remove_device(struct generic_pm_domain *genpd,
 		genpd->gd->max_off_time_changed = true;
 
 	genpd_clear_cpumask(genpd, gpd_data->cpu);
-	dev_pm_domain_set(dev, NULL);
 
 	list_del_init(&pdd->list_node);
 
 	genpd_unlock(genpd);
 
+	dev_pm_domain_set(dev, NULL);
+
 	if (genpd->detach_dev)
 		genpd->detach_dev(genpd, dev);
 
-- 
2.34.1