[PATCH 3/4] PM / Domains: Search for the CPU device outside the genpd lock

[Ulf Hansson]

While attaching/detaching a device to a PM domain (genpd) that has the
GENPD_FLAG_CPU_DOMAIN set, genpd iterates the cpu_possible_mask to check
whether the device corresponds to a CPU. This iteration is done while
holding the genpd's lock, which is unnecessary. Let's avoid the locking,
by restructuring the corresponding code a bit.

Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
---
 drivers/base/power/domain.c | 52 +++++++++++++++++++------------------
 1 file changed, 27 insertions(+), 25 deletions(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 93298b7db408..da1c99178943 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1450,8 +1450,8 @@ static void genpd_free_dev_data(struct device *dev,
 	dev_pm_put_subsys_data(dev);
 }
 
-static void __genpd_update_cpumask(struct generic_pm_domain *genpd,
-				   int cpu, bool set, unsigned int depth)
+static void genpd_update_cpumask(struct generic_pm_domain *genpd,
+				 int cpu, bool set, unsigned int depth)
 {
 	struct gpd_link *link;
 
@@ -1462,7 +1462,7 @@ static void __genpd_update_cpumask(struct generic_pm_domain *genpd,
 		struct generic_pm_domain *master = link->master;
 
 		genpd_lock_nested(master, depth + 1);
-		__genpd_update_cpumask(master, cpu, set, depth + 1);
+		genpd_update_cpumask(master, cpu, set, depth + 1);
 		genpd_unlock(master);
 	}
 
@@ -1472,38 +1472,37 @@ static void __genpd_update_cpumask(struct generic_pm_domain *genpd,
 		cpumask_clear_cpu(cpu, genpd->cpus);
 }
 
-static void genpd_update_cpumask(struct generic_pm_domain *genpd,
-				 struct device *dev, bool set)
+static void genpd_set_cpumask(struct generic_pm_domain *genpd, int cpu)
+{
+	if (cpu >= 0)
+		genpd_update_cpumask(genpd, cpu, true, 0);
+}
+
+static void genpd_clear_cpumask(struct generic_pm_domain *genpd, int cpu)
+{
+	if (cpu >= 0)
+		genpd_update_cpumask(genpd, cpu, false, 0);
+}
+
+static int genpd_get_cpu(struct generic_pm_domain *genpd, struct device *dev)
 {
 	int cpu;
 
 	if (!genpd_is_cpu_domain(genpd))
-		return;
+		return -1;
 
 	for_each_possible_cpu(cpu) {
-		if (get_cpu_device(cpu) == dev) {
-			__genpd_update_cpumask(genpd, cpu, set, 0);
-			return;
-		}
+		if (get_cpu_device(cpu) == dev)
+			return cpu;
 	}
-}
 
-static void genpd_set_cpumask(struct generic_pm_domain *genpd,
-			      struct device *dev)
-{
-	genpd_update_cpumask(genpd, dev, true);
-}
-
-static void genpd_clear_cpumask(struct generic_pm_domain *genpd,
-				struct device *dev)
-{
-	genpd_update_cpumask(genpd, dev, false);
+	return -1;
 }
 
 static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev)
 {
 	struct generic_pm_domain_data *gpd_data;
-	int ret;
+	int ret, cpu;
 
 	dev_dbg(dev, "%s()\n", __func__);
 
@@ -1514,13 +1513,15 @@ static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev)
 	if (IS_ERR(gpd_data))
 		return PTR_ERR(gpd_data);
 
+	cpu = genpd_get_cpu(genpd, dev);
+
 	ret = genpd->attach_dev ? genpd->attach_dev(genpd, dev) : 0;
 	if (ret)
 		goto out;
 
 	genpd_lock(genpd);
 
-	genpd_set_cpumask(genpd, dev);
+	genpd_set_cpumask(genpd, cpu);
 	dev_pm_domain_set(dev, &genpd->domain);
 
 	genpd->device_count++;
@@ -1560,13 +1561,14 @@ static int genpd_remove_device(struct generic_pm_domain *genpd,
 {
 	struct generic_pm_domain_data *gpd_data;
 	struct pm_domain_data *pdd;
-	int ret = 0;
+	int cpu, ret = 0;
 
 	dev_dbg(dev, "%s()\n", __func__);
 
 	pdd = dev->power.subsys_data->domain_data;
 	gpd_data = to_gpd_data(pdd);
 	dev_pm_qos_remove_notifier(dev, &gpd_data->nb);
+	cpu = genpd_get_cpu(genpd, dev);
 
 	genpd_lock(genpd);
 
@@ -1578,7 +1580,7 @@ static int genpd_remove_device(struct generic_pm_domain *genpd,
 	genpd->device_count--;
 	genpd->max_off_time_changed = true;
 
-	genpd_clear_cpumask(genpd, dev);
+	genpd_clear_cpumask(genpd, cpu);
 	dev_pm_domain_set(dev, NULL);
 
 	list_del_init(&pdd->list_node);
-- 
2.17.1