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>

diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
index f42d3f737a3326a1a66751ba6589fb4d26b6c925..db8e51d7f392ec19c9902279259073c178322f05 100644 (file)
--- 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);