[PATCH v2 18/23] PM / QoS: Decouple request alloc from dev_pm_qos_mtx

Rob Clark
2023-03-20T14:46:53Z

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 | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c
index f3e0c6b65635..9cba334b3729 100644
--- a/drivers/base/power/qos.c
+++ b/drivers/base/power/qos.c
@@ -922,12 +922,16 @@ 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_request *req = NULL;
int ret;

ret = dev_pm_qos_constraints_ensure_allocated(dev);
if (ret)
return ret;

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

if (!dev->power.qos->latency_tolerance_req) {
@@ -940,7 +944,6 @@ 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;
@@ -952,6 +955,13 @@ int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)
}
dev->power.qos->latency_tolerance_req = req;
} else {
+ /*
+ * If we raced with another thread to allocate the request,
+ * simply free the redundant allocation and move on.
+ */
+ if (req)
+ kfree(req);
+
if (val < 0) {
__dev_pm_qos_drop_user_request(dev, DEV_PM_QOS_LATENCY_TOLERANCE);
ret = 0;
--
2.39.2