pm_qos: Reimplement using plists

A lot of the pm_qos extremal value handling is really duplicating what a
priority ordered list does, just in a less efficient fashion.  Simply
redoing the implementation in terms of a plist gets rid of a lot of this
junk (although there are several other strange things that could do with
tidying up, like pm_qos_request_list has to carry the pm_qos_class with
every node, simply because it doesn't get passed in to
pm_qos_update_request even though every caller knows full well what
parameter it's updating).

I think this redo is a win independent of android, so we should do
something like this now.

Signed-off-by: James Bottomley <James.Bottomley@suse.de>
Signed-off-by: mark gross <markgross@thegnar.org>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 86 insertions, 86 deletions

diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
index f42d3f737a33..db8e51d7f392 100644
--- a/kernel/pm_qos_params.c
+++ b/kernel/pm_qos_params.c
@@ -30,6 +30,7 @@
 /*#define DEBUG*/
 
 #include <linux/pm_qos_params.h>
+#include <linux/plist.h>
 #include <linux/sched.h>
 #include <linux/spinlock.h>
 #include <linux/slab.h>
@@ -49,58 +50,53 @@
  * held, taken with _irqsave.  One lock to rule them all
  */
 struct pm_qos_request_list {
-        struct list_head list;
-        union {
-                s32 value;
-                s32 usec;
-                s32 kbps;
-        };
+        struct plist_node list;
         int pm_qos_class;
 };
 
-static s32 max_compare(s32 v1, s32 v2);
-static s32 min_compare(s32 v1, s32 v2);
+enum pm_qos_type {
+        PM_QOS_MAX,             /* return the largest value */
+        PM_QOS_MIN              /* return the smallest value */
+};
 
 struct pm_qos_object {
-        struct pm_qos_request_list requests;
+        struct plist_head requests;
         struct blocking_notifier_head *notifiers;
         struct miscdevice pm_qos_power_miscdev;
         char *name;
         s32 default_value;
-        atomic_t target_value;
-        s32 (*comparitor)(s32, s32);
+        enum pm_qos_type type;
 };
 
+static DEFINE_SPINLOCK(pm_qos_lock);
+
 static struct pm_qos_object null_pm_qos;
 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
 static struct pm_qos_object cpu_dma_pm_qos = {
-        .requests = {LIST_HEAD_INIT(cpu_dma_pm_qos.requests.list)},
+        .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 = ATOMIC_INIT(2000 * USEC_PER_SEC),
-        .comparitor = min_compare
+        .type = PM_QOS_MIN,
 };
 
 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
 static struct pm_qos_object network_lat_pm_qos = {
-        .requests = {LIST_HEAD_INIT(network_lat_pm_qos.requests.list)},
+        .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 = ATOMIC_INIT(2000 * USEC_PER_SEC),
-        .comparitor = min_compare
+        .type = PM_QOS_MIN
 };
 
 
 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
 static struct pm_qos_object network_throughput_pm_qos = {
-        .requests = {LIST_HEAD_INIT(network_throughput_pm_qos.requests.list)},
+        .requests = PLIST_HEAD_INIT(network_throughput_pm_qos.requests, pm_qos_lock),
         .notifiers = &network_throughput_notifier,
         .name = "network_throughput",
         .default_value = 0,
-        .target_value = ATOMIC_INIT(0),
-        .comparitor = max_compare
+        .type = PM_QOS_MAX,
 };
 
 
@@ -111,8 +107,6 @@ static struct pm_qos_object *pm_qos_array[] = {
         &network_throughput_pm_qos
 };
 
-static DEFINE_SPINLOCK(pm_qos_lock);
-
 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
                 size_t count, loff_t *f_pos);
 static int pm_qos_power_open(struct inode *inode, struct file *filp);
@@ -124,46 +118,55 @@ static const struct file_operations pm_qos_power_fops = {
         .release = pm_qos_power_release,
 };
 
-/* static helper functions */
-static s32 max_compare(s32 v1, s32 v2)
+/* unlocked internal variant */
+static inline int pm_qos_get_value(struct pm_qos_object *o)
 {
-        return max(v1, v2);
-}
+        if (plist_head_empty(&o->requests))
+                return o->default_value;
 
-static s32 min_compare(s32 v1, s32 v2)
-{
-        return min(v1, v2);
-}
+        switch (o->type) {
+        case PM_QOS_MIN:
+                return plist_last(&o->requests)->prio;
 
+        case PM_QOS_MAX:
+                return plist_first(&o->requests)->prio;
 
-static void update_target(int pm_qos_class)
+        default:
+                /* runtime check for not using enum */
+                BUG();
+        }
+}
+
+static void update_target(struct pm_qos_object *o, struct plist_node *node,
+                          int del, int value)
 {
-        s32 extreme_value;
-        struct pm_qos_request_list *node;
         unsigned long flags;
-        int call_notifier = 0;
+        int prev_value, curr_value;
 
         spin_lock_irqsave(&pm_qos_lock, flags);
-        extreme_value = pm_qos_array[pm_qos_class]->default_value;
-        list_for_each_entry(node,
-                        &pm_qos_array[pm_qos_class]->requests.list, list) {
-                extreme_value = pm_qos_array[pm_qos_class]->comparitor(
-                                extreme_value, node->value);
-        }
-        if (atomic_read(&pm_qos_array[pm_qos_class]->target_value) !=
-                        extreme_value) {
-                call_notifier = 1;
-                atomic_set(&pm_qos_array[pm_qos_class]->target_value,
-                                extreme_value);
-                pr_debug(KERN_ERR "new target for qos %d is %d\n", pm_qos_class,
-                        atomic_read(&pm_qos_array[pm_qos_class]->target_value));
+        prev_value = pm_qos_get_value(o);
+        /* PM_QOS_DEFAULT_VALUE is a signal that the value is unchanged */
+        if (value != PM_QOS_DEFAULT_VALUE) {
+                /*
+                 * to change the list, we atomically remove, reinit
+                 * with new value and add, then see if the extremal
+                 * changed
+                 */
+                plist_del(node, &o->requests);
+                plist_node_init(node, value);
+                plist_add(node, &o->requests);
+        } else if (del) {
+                plist_del(node, &o->requests);
+        } else {
+                plist_add(node, &o->requests);
         }
+        curr_value = pm_qos_get_value(o);
         spin_unlock_irqrestore(&pm_qos_lock, flags);
 
-        if (call_notifier)
-                blocking_notifier_call_chain(
-                                pm_qos_array[pm_qos_class]->notifiers,
-                                        (unsigned long) extreme_value, NULL);
+        if (prev_value != curr_value)
+                blocking_notifier_call_chain(o->notifiers,
+                                             (unsigned long)curr_value,
+                                             NULL);
 }
 
 static int register_pm_qos_misc(struct pm_qos_object *qos)
@@ -196,7 +199,14 @@ static int find_pm_qos_object_by_minor(int minor)
  */
 int pm_qos_request(int pm_qos_class)
 {
-        return atomic_read(&pm_qos_array[pm_qos_class]->target_value);
+        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;
 }
 EXPORT_SYMBOL_GPL(pm_qos_request);
 
@@ -214,21 +224,19 @@ EXPORT_SYMBOL_GPL(pm_qos_request);
 struct pm_qos_request_list *pm_qos_add_request(int pm_qos_class, s32 value)
 {
         struct pm_qos_request_list *dep;
-        unsigned long flags;
 
         dep = kzalloc(sizeof(struct pm_qos_request_list), GFP_KERNEL);
         if (dep) {
+                struct pm_qos_object *o =  pm_qos_array[pm_qos_class];
+                int new_value;
+
                 if (value == PM_QOS_DEFAULT_VALUE)
-                        dep->value = pm_qos_array[pm_qos_class]->default_value;
+                        new_value = o->default_value;
                 else
-                        dep->value = value;
+                        new_value = value;
+                plist_node_init(&dep->list, new_value);
                 dep->pm_qos_class = pm_qos_class;
-
-                spin_lock_irqsave(&pm_qos_lock, flags);
-                list_add(&dep->list,
-                        &pm_qos_array[pm_qos_class]->requests.list);
-                spin_unlock_irqrestore(&pm_qos_lock, flags);
-                update_target(pm_qos_class);
+                update_target(o, &dep->list, 0, PM_QOS_DEFAULT_VALUE);
         }
 
         return dep;
@@ -246,27 +254,23 @@ EXPORT_SYMBOL_GPL(pm_qos_add_request);
  * Attempts are made to make this code callable on hot code paths.
  */
 void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
-                s32 new_value)
+                           s32 new_value)
 {
-        unsigned long flags;
-        int pending_update = 0;
         s32 temp;
+        struct pm_qos_object *o;
 
-        if (pm_qos_req) { /*guard against callers passing in null */
-                spin_lock_irqsave(&pm_qos_lock, flags);
-                if (new_value == PM_QOS_DEFAULT_VALUE)
-                        temp = pm_qos_array[pm_qos_req->pm_qos_class]->default_value;
-                else
-                        temp = new_value;
-
-                if (temp != pm_qos_req->value) {
-                        pending_update = 1;
-                        pm_qos_req->value = temp;
-                }
-                spin_unlock_irqrestore(&pm_qos_lock, flags);
-                if (pending_update)
-                        update_target(pm_qos_req->pm_qos_class);
-        }
+        if (!pm_qos_req) /*guard against callers passing in null */
+                return;
+
+        o = pm_qos_array[pm_qos_req->pm_qos_class];
+
+        if (new_value == PM_QOS_DEFAULT_VALUE)
+                temp = o->default_value;
+        else
+                temp = new_value;
+
+        if (temp != pm_qos_req->list.prio)
+                update_target(o, &pm_qos_req->list, 0, temp);
 }
 EXPORT_SYMBOL_GPL(pm_qos_update_request);
 
@@ -280,19 +284,15 @@ EXPORT_SYMBOL_GPL(pm_qos_update_request);
  */
 void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req)
 {
-        unsigned long flags;
-        int qos_class;
+        struct pm_qos_object *o;
 
         if (pm_qos_req == NULL)
                 return;
                 /* silent return to keep pcm code cleaner */
 
-        qos_class = pm_qos_req->pm_qos_class;
-        spin_lock_irqsave(&pm_qos_lock, flags);
-        list_del(&pm_qos_req->list);
+        o = pm_qos_array[pm_qos_req->pm_qos_class];
+        update_target(o, &pm_qos_req->list, 1, PM_QOS_DEFAULT_VALUE);
         kfree(pm_qos_req);
-        spin_unlock_irqrestore(&pm_qos_lock, flags);
-        update_target(qos_class);
 }
 EXPORT_SYMBOL_GPL(pm_qos_remove_request);