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Date: Wed, 9 Jun 2010 11:15:14 +0200
From: florian@...kler.org
To: pm list <linux-pm@...ts.linux-foundation.org>
Cc: james.bottomley@...e.de, markgross@...gnar.org,
mgross@...ux.intel.com, Florian Mickler <florian@...kler.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Jonathan Corbet <corbet@....net>,
Thomas Gleixner <tglx@...utronix.de>,
linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] pm_qos: make update_request callable from interrupt context
The pm_qos framework has to guarantee atomic notifications so that
drivers can request and release constraints at all times while no races
occur.
In order to avoid implementing a secondary notification chain in which
listeners might sleep, we demand that every listener implements it's
notification so that it can run in interrupt context. The listener is in
a better position to know if races are harmful or not.
Signed-off-by: Florian Mickler <florian@...kler.org>
---
kernel/pm_qos_params.c | 50 ++++++++++++++++++++++++------------------------
1 files changed, 25 insertions(+), 25 deletions(-)
diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
index f42d3f7..d918605 100644
--- a/kernel/pm_qos_params.c
+++ b/kernel/pm_qos_params.c
@@ -63,7 +63,7 @@ static s32 min_compare(s32 v1, s32 v2);
struct pm_qos_object {
struct pm_qos_request_list requests;
- struct blocking_notifier_head *notifiers;
+ struct atomic_notifier_head *notifiers;
struct miscdevice pm_qos_power_miscdev;
char *name;
s32 default_value;
@@ -72,7 +72,7 @@ struct pm_qos_object {
};
static struct pm_qos_object null_pm_qos;
-static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
+static ATOMIC_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)},
.notifiers = &cpu_dma_lat_notifier,
@@ -82,7 +82,7 @@ static struct pm_qos_object cpu_dma_pm_qos = {
.comparitor = min_compare
};
-static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
+static ATOMIC_NOTIFIER_HEAD(network_lat_notifier);
static struct pm_qos_object network_lat_pm_qos = {
.requests = {LIST_HEAD_INIT(network_lat_pm_qos.requests.list)},
.notifiers = &network_lat_notifier,
@@ -93,7 +93,7 @@ static struct pm_qos_object network_lat_pm_qos = {
};
-static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
+static ATOMIC_NOTIFIER_HEAD(network_throughput_notifier);
static struct pm_qos_object network_throughput_pm_qos = {
.requests = {LIST_HEAD_INIT(network_throughput_pm_qos.requests.list)},
.notifiers = &network_throughput_notifier,
@@ -103,7 +103,6 @@ static struct pm_qos_object network_throughput_pm_qos = {
.comparitor = max_compare
};
-
static struct pm_qos_object *pm_qos_array[] = {
&null_pm_qos,
&cpu_dma_pm_qos,
@@ -135,35 +134,30 @@ static s32 min_compare(s32 v1, s32 v2)
return min(v1, v2);
}
-
static void update_target(int pm_qos_class)
{
s32 extreme_value;
+ struct pm_qos_object *obj = pm_qos_array[pm_qos_class];
struct pm_qos_request_list *node;
unsigned long flags;
int call_notifier = 0;
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);
+ extreme_value = obj->default_value;
+ list_for_each_entry(node, &obj->requests.list, list) {
+ extreme_value = obj->comparitor(extreme_value, node->value);
}
- if (atomic_read(&pm_qos_array[pm_qos_class]->target_value) !=
- extreme_value) {
+ if (atomic_read(&obj->target_value) != extreme_value) {
call_notifier = 1;
- atomic_set(&pm_qos_array[pm_qos_class]->target_value,
- extreme_value);
+ atomic_set(&obj->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));
+ atomic_read(&obj->target_value));
}
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);
+ atomic_notifier_call_chain(obj->notifiers,
+ (unsigned long) extreme_value, NULL);
}
static int register_pm_qos_misc(struct pm_qos_object *qos)
@@ -272,6 +266,7 @@ EXPORT_SYMBOL_GPL(pm_qos_update_request);
/**
* pm_qos_remove_request - modifies an existing qos request
+ *
* @pm_qos_req: handle to request list element
*
* Will remove pm qos request from the list of requests and
@@ -298,18 +293,21 @@ EXPORT_SYMBOL_GPL(pm_qos_remove_request);
/**
* pm_qos_add_notifier - sets notification entry for changes to target value
+ *
+ * Note: The notifier has to be callable from interrupt context.
+ *
* @pm_qos_class: identifies which qos target changes should be notified.
* @notifier: notifier block managed by caller.
*
- * will register the notifier into a notification chain that gets called
+ * Will register the notifier into a notification chain that gets called
* upon changes to the pm_qos_class target value.
*/
int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
{
int retval;
- retval = blocking_notifier_chain_register(
- pm_qos_array[pm_qos_class]->notifiers, notifier);
+ retval = atomic_notifier_chain_register(
+ pm_qos_array[pm_qos_class]->notifiers, notifier);
return retval;
}
@@ -317,18 +315,19 @@ EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
/**
* pm_qos_remove_notifier - deletes notification entry from chain.
+ *
* @pm_qos_class: identifies which qos target changes are notified.
* @notifier: notifier block to be removed.
*
- * will remove the notifier from the notification chain that gets called
+ * Will remove the notifier from the notification chain that gets called
* upon changes to the pm_qos_class target value.
*/
int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
{
int retval;
- retval = blocking_notifier_chain_unregister(
- pm_qos_array[pm_qos_class]->notifiers, notifier);
+ retval = atomic_notifier_chain_unregister(
+ pm_qos_array[pm_qos_class]->notifiers, notifier);
return retval;
}
@@ -381,6 +380,7 @@ static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
} else
return -EINVAL;
+
pm_qos_req = (struct pm_qos_request_list *)filp->private_data;
pm_qos_update_request(pm_qos_req, value);
--
1.7.1
--
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