[PATCH 09/13] PM / QoS: Decouple request alloc from dev_pm_qos_mtx

[Rob Clark]

From: Rob Clark <robdcl...@chromium.org>

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 <robdcl...@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