[PATCH v4 4/9] PM / QoS: Decouple request alloc from dev_pm_qos_mtx

Rob Clark
2023-08-07T17:12:40Z

Similar to the previous patch, move the allocation out from under
dev_pm_qos_mtx, by speculatively doing the allocation and handle
any race after acquiring dev_pm_qos_mtx by freeing the redundant
allocation.

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
drivers/base/power/qos.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c
index 7e95760d16dc..5ec06585b6d1 100644
--- a/drivers/base/power/qos.c
+++ b/drivers/base/power/qos.c
@@ -930,8 +930,12 @@ s32 dev_pm_qos_get_user_latency_tolerance(struct device *dev)
int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)
{
struct dev_pm_qos *qos = dev_pm_qos_constraints_allocate(dev);
+ struct dev_pm_qos_request *req = NULL;
int ret = 0;

+ if (!dev->power.qos->latency_tolerance_req)
+ req = kzalloc(sizeof(*req), GFP_KERNEL);
+
mutex_lock(&dev_pm_qos_mtx);

dev_pm_qos_constraints_set(dev, qos);
@@ -945,8 +949,6 @@ int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)
goto out;

if (!dev->power.qos->latency_tolerance_req) {
- struct dev_pm_qos_request *req;
-
if (val < 0) {
if (val == PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT)
ret = 0;
@@ -954,17 +956,15 @@ int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)
ret = -EINVAL;
goto out;
}
- req = kzalloc(sizeof(*req), GFP_KERNEL);
if (!req) {
ret = -ENOMEM;
goto out;
}
ret = __dev_pm_qos_add_request(dev, req, DEV_PM_QOS_LATENCY_TOLERANCE, val);
- if (ret < 0) {
- kfree(req);
+ if (ret < 0)
goto out;
- }
dev->power.qos->latency_tolerance_req = req;
+ req = NULL;
} else {
if (val < 0) {
__dev_pm_qos_drop_user_request(dev, DEV_PM_QOS_LATENCY_TOLERANCE);
@@ -976,6 +976,7 @@ int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)

out:
mutex_unlock(&dev_pm_qos_mtx);
+ kfree(req);
return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_update_user_latency_tolerance);
--
2.41.0