idle governor: Avoid lock acquisition to read pm_qos before entering idle

[linux-flexiantxendom0-natty.git] / kernel / pm_qos_params.c

diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
index aeaa7f8..6a8fad8 100644 (file)
--- a/kernel/pm_qos_params.c
+++ b/kernel/pm_qos_params.c
@@ -53,11 +53,17 @@ enum pm_qos_type {
        PM_QOS_MIN              /* return the smallest value */
 };
 
+/*
+ * Note: The lockless read path depends on the CPU accessing
+ * target_value atomically.  Atomic access is only guaranteed on all CPU
+ * types linux supports for 32 bit quantites
+ */
 struct pm_qos_object {
        struct plist_head requests;
        struct blocking_notifier_head *notifiers;
        struct miscdevice pm_qos_power_miscdev;
        char *name;
+       s32 target_value;       /* Do not change to 64 bit */
        s32 default_value;
        enum pm_qos_type type;
 };
@@ -70,7 +76,8 @@ static struct pm_qos_object cpu_dma_pm_qos = {
        .requests = PLIST_HEAD_INIT(cpu_dma_pm_qos.requests, pm_qos_lock),
        .notifiers = &cpu_dma_lat_notifier,
        .name = "cpu_dma_latency",
-       .default_value = 2000 * USEC_PER_SEC,
+       .target_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
+       .default_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
        .type = PM_QOS_MIN,
 };
 
@@ -79,7 +86,8 @@ static struct pm_qos_object network_lat_pm_qos = {
        .requests = PLIST_HEAD_INIT(network_lat_pm_qos.requests, pm_qos_lock),
        .notifiers = &network_lat_notifier,
        .name = "network_latency",
-       .default_value = 2000 * USEC_PER_SEC,
+       .target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
+       .default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
        .type = PM_QOS_MIN
 };
 
@@ -89,7 +97,8 @@ static struct pm_qos_object network_throughput_pm_qos = {
        .requests = PLIST_HEAD_INIT(network_throughput_pm_qos.requests, pm_qos_lock),
        .notifiers = &network_throughput_notifier,
        .name = "network_throughput",
-       .default_value = 0,
+       .target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
+       .default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
        .type = PM_QOS_MAX,
 };
 
@@ -132,6 +141,16 @@ static inline int pm_qos_get_value(struct pm_qos_object *o)
        }
 }
 
+static inline s32 pm_qos_read_value(struct pm_qos_object *o)
+{
+       return o->target_value;
+}
+
+static inline void pm_qos_set_value(struct pm_qos_object *o, s32 value)
+{
+       o->target_value = value;
+}
+
 static void update_target(struct pm_qos_object *o, struct plist_node *node,
                          int del, int value)
 {
@@ -156,6 +175,7 @@ static void update_target(struct pm_qos_object *o, struct plist_node *node,
                plist_add(node, &o->requests);
        }
        curr_value = pm_qos_get_value(o);
+       pm_qos_set_value(o, curr_value);
        spin_unlock_irqrestore(&pm_qos_lock, flags);
 
        if (prev_value != curr_value)
@@ -190,18 +210,11 @@ static int find_pm_qos_object_by_minor(int minor)
  * pm_qos_request - returns current system wide qos expectation
  * @pm_qos_class: identification of which qos value is requested
  *
- * This function returns the current target value in an atomic manner.
+ * This function returns the current target value.
  */
 int pm_qos_request(int pm_qos_class)
 {
-       unsigned long flags;
-       int value;
-
-       spin_lock_irqsave(&pm_qos_lock, flags);
-       value = pm_qos_get_value(pm_qos_array[pm_qos_class]);
-       spin_unlock_irqrestore(&pm_qos_lock, flags);
-
-       return value;
+       return pm_qos_read_value(pm_qos_array[pm_qos_class]);
 }
 EXPORT_SYMBOL_GPL(pm_qos_request);