[PATCH 1/6] PM_QOS to use handle based list implementation and exported functionname changes to be more descriptive of what is actually happening.

From: mgross
Date: Sat Mar 13 2010 - 11:18:36 EST

Signed-off-by: Mark Gross <mgross@xxxxxxxxxxxxxxx>

---
Documentation/power/pm_qos_interface.txt | 44 +++---
include/linux/pm_qos_params.h | 14 +-
kernel/pm_qos_params.c | 214 ++++++++++++++---------------
3 files changed, 134 insertions(+), 138 deletions(-)

diff --git a/Documentation/power/pm_qos_interface.txt b/Documentation/power/pm_qos_interface.txt
index c40866e..2138afb 100644
--- a/Documentation/power/pm_qos_interface.txt
+++ b/Documentation/power/pm_qos_interface.txt
@@ -18,44 +18,46 @@ and pm_qos_params.h. This is done because having the available parameters
being runtime configurable or changeable from a driver was seen as too easy to
abuse.

-For each parameter a list of performance requirements is maintained along with
+For each parameter a list of performance requests is maintained along with
an aggregated target value. The aggregated target value is updated with
-changes to the requirement list or elements of the list. Typically the
-aggregated target value is simply the max or min of the requirement values held
+changes to the request list or elements of the list. Typically the
+aggregated target value is simply the max or min of the request values held
in the parameter list elements.

From kernel mode the use of this interface is simple:
-pm_qos_add_requirement(param_id, name, target_value):
-Will insert a named element in the list for that identified PM_QOS parameter
-with the target value. Upon change to this list the new target is recomputed
-and any registered notifiers are called only if the target value is now
-different.

-pm_qos_update_requirement(param_id, name, new_target_value):
-Will search the list identified by the param_id for the named list element and
-then update its target value, calling the notification tree if the aggregated
-target is changed. with that name is already registered.
+handle = pm_qos_add_request(param_class, target_value):
+Will insert a element in the list for that identified PM_QOS class with the
+target value. Upon change to this list the new target is recomputed and any
+registered notifiers are called only if the target value is now different.
+Clients of pm_qos need to save the returned handle.

-pm_qos_remove_requirement(param_id, name):
-Will search the identified list for the named element and remove it, after
-removal it will update the aggregate target and call the notification tree if
-the target was changed as a result of removing the named requirement.
+void pm_qos_update_request(handle, new_target_value):
+Will update list element pointed to by the handle with the new target value.
+And recompute the new aggregated target, calling the notification tree if the
+target is changed.
+
+void pm_qos_remove_request(handle):
+Will remove the element, after removal it will update the aggregate target and
+call the notification tree if the target was changed as a result of removing
+the request.


From user mode:
-Only processes can register a pm_qos requirement. To provide for automatic
+Only processes can register a pm_qos request. To provide for automatic
cleanup for process the interface requires the process to register its
-parameter requirements in the following way:
+parameter requests in the following way:

To register the default pm_qos target for the specific parameter, the process
must open one of /dev/[cpu_dma_latency, network_latency, network_throughput]

As long as the device node is held open that process has a registered
-requirement on the parameter. The name of the requirement is "process_<PID>"
-derived from the current->pid from within the open system call.
+request on the parameter.

To change the requested target value the process needs to write a s32 value to
-the open device node. This translates to a pm_qos_update_requirement call.
+the open device node. Alternatively the user mode program could write a hex
+string for the value using 10 char long format e.g. "0x12345678". This
+translates to a pm_qos_update_request call.

To remove the user mode request for a target value simply close the device
node.
diff --git a/include/linux/pm_qos_params.h b/include/linux/pm_qos_params.h
index d74f75e..8ba440e 100644
--- a/include/linux/pm_qos_params.h
+++ b/include/linux/pm_qos_params.h
@@ -14,12 +14,14 @@
#define PM_QOS_NUM_CLASSES 4
#define PM_QOS_DEFAULT_VALUE -1

-int pm_qos_add_requirement(int qos, char *name, s32 value);
-int pm_qos_update_requirement(int qos, char *name, s32 new_value);
-void pm_qos_remove_requirement(int qos, char *name);
+struct pm_qos_request_list;

-int pm_qos_requirement(int qos);
+struct pm_qos_request_list *pm_qos_add_request(int pm_qos_class, s32 value);
+void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
+ s32 new_value);
+void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req);

-int pm_qos_add_notifier(int qos, struct notifier_block *notifier);
-int pm_qos_remove_notifier(int qos, struct notifier_block *notifier);
+int pm_qos_request(int pm_qos_class);
+int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier);
+int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier);

diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
index 3db49b9..a1aea04 100644
--- a/kernel/pm_qos_params.c
+++ b/kernel/pm_qos_params.c
@@ -2,7 +2,7 @@
* This module exposes the interface to kernel space for specifying
* QoS dependencies. It provides infrastructure for registration of:
*
- * Dependents on a QoS value : register requirements
+ * Dependents on a QoS value : register requests
* Watchers of QoS value : get notified when target QoS value changes
*
* This QoS design is best effort based. Dependents register their QoS needs.
@@ -14,19 +14,21 @@
* timeout: usec <-- currently not used.
* throughput: kbs (kilo byte / sec)
*
- * There are lists of pm_qos_objects each one wrapping requirements, notifiers
+ * There are lists of pm_qos_objects each one wrapping requests, notifiers
*
- * User mode requirements on a QOS parameter register themselves to the
+ * User mode requests on a QOS parameter register themselves to the
* subsystem by opening the device node /dev/... and writing there request to
* the node. As long as the process holds a file handle open to the node the
* client continues to be accounted for. Upon file release the usermode
- * requirement is removed and a new qos target is computed. This way when the
- * requirement that the application has is cleaned up when closes the file
+ * request is removed and a new qos target is computed. This way when the
+ * request that the application has is cleaned up when closes the file
* pointer or exits the pm_qos_object will get an opportunity to clean up.
*
* Mark Gross <mgross@xxxxxxxxxxxxxxx>
*/

+/*#define DEBUG*/
+
#include <linux/pm_qos_params.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
@@ -42,25 +44,25 @@
#include <linux/uaccess.h>

/*
- * locking rule: all changes to requirements or notifiers lists
+ * locking rule: all changes to requests or notifiers lists
* or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
* held, taken with _irqsave. One lock to rule them all
*/
-struct requirement_list {
+struct pm_qos_request_list {
struct list_head list;
union {
s32 value;
s32 usec;
s32 kbps;
};
- char *name;
+ int pm_qos_class;
};

static s32 max_compare(s32 v1, s32 v2);
static s32 min_compare(s32 v1, s32 v2);

struct pm_qos_object {
- struct requirement_list requirements;
+ struct pm_qos_request_list requests;
struct blocking_notifier_head *notifiers;
struct miscdevice pm_qos_power_miscdev;
char *name;
@@ -72,7 +74,7 @@ struct pm_qos_object {
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 = {
- .requirements = {LIST_HEAD_INIT(cpu_dma_pm_qos.requirements.list)},
+ .requests = {LIST_HEAD_INIT(cpu_dma_pm_qos.requests.list)},
.notifiers = &cpu_dma_lat_notifier,
.name = "cpu_dma_latency",
.default_value = 2000 * USEC_PER_SEC,
@@ -82,7 +84,7 @@ static struct pm_qos_object cpu_dma_pm_qos = {

static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
static struct pm_qos_object network_lat_pm_qos = {
- .requirements = {LIST_HEAD_INIT(network_lat_pm_qos.requirements.list)},
+ .requests = {LIST_HEAD_INIT(network_lat_pm_qos.requests.list)},
.notifiers = &network_lat_notifier,
.name = "network_latency",
.default_value = 2000 * USEC_PER_SEC,
@@ -93,8 +95,7 @@ static struct pm_qos_object network_lat_pm_qos = {

static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
static struct pm_qos_object network_throughput_pm_qos = {
- .requirements =
- {LIST_HEAD_INIT(network_throughput_pm_qos.requirements.list)},
+ .requests = {LIST_HEAD_INIT(network_throughput_pm_qos.requests.list)},
.notifiers = &network_throughput_notifier,
.name = "network_throughput",
.default_value = 0,
@@ -135,31 +136,34 @@ static s32 min_compare(s32 v1, s32 v2)
}


-static void update_target(int target)
+static void update_target(int pm_qos_class)
{
s32 extreme_value;
- struct requirement_list *node;
+ 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[target]->default_value;
+ extreme_value = pm_qos_array[pm_qos_class]->default_value;
list_for_each_entry(node,
- &pm_qos_array[target]->requirements.list, list) {
- extreme_value = pm_qos_array[target]->comparitor(
+ &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[target]->target_value) != extreme_value) {
+ if (atomic_read(&pm_qos_array[pm_qos_class]->target_value) !=
+ extreme_value) {
call_notifier = 1;
- atomic_set(&pm_qos_array[target]->target_value, extreme_value);
- pr_debug(KERN_ERR "new target for qos %d is %d\n", target,
- atomic_read(&pm_qos_array[target]->target_value));
+ 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));
}
spin_unlock_irqrestore(&pm_qos_lock, flags);

if (call_notifier)
- blocking_notifier_call_chain(pm_qos_array[target]->notifiers,
- (unsigned long) extreme_value, NULL);
+ blocking_notifier_call_chain(
+ pm_qos_array[pm_qos_class]->notifiers,
+ (unsigned long) extreme_value, NULL);
}

static int register_pm_qos_misc(struct pm_qos_object *qos)
@@ -185,125 +189,110 @@ static int find_pm_qos_object_by_minor(int minor)
}

/**
- * pm_qos_requirement - returns current system wide qos expectation
+ * 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.
*/
-int pm_qos_requirement(int pm_qos_class)
+int pm_qos_request(int pm_qos_class)
{
return atomic_read(&pm_qos_array[pm_qos_class]->target_value);
}
-EXPORT_SYMBOL_GPL(pm_qos_requirement);
+EXPORT_SYMBOL_GPL(pm_qos_request);

/**
- * pm_qos_add_requirement - inserts new qos request into the list
+ * pm_qos_add_request - inserts new qos request into the list
* @pm_qos_class: identifies which list of qos request to us
- * @name: identifies the request
* @value: defines the qos request
*
* This function inserts a new entry in the pm_qos_class list of requested qos
* performance characteristics. It recomputes the aggregate QoS expectations
- * for the pm_qos_class of parameters.
+ * for the pm_qos_class of parameters, and returns the pm_qos_request list
+ * element as a handle for use in updating and removal. Call needs to save
+ * this handle for later use.
*/
-int pm_qos_add_requirement(int pm_qos_class, char *name, s32 value)
+struct pm_qos_request_list *pm_qos_add_request(int pm_qos_class, s32 value)
{
- struct requirement_list *dep;
+ struct pm_qos_request_list *dep;
unsigned long flags;

- dep = kzalloc(sizeof(struct requirement_list), GFP_KERNEL);
+ dep = kzalloc(sizeof(struct pm_qos_request_list), GFP_KERNEL);
if (dep) {
if (value == PM_QOS_DEFAULT_VALUE)
dep->value = pm_qos_array[pm_qos_class]->default_value;
else
dep->value = value;
- dep->name = kstrdup(name, GFP_KERNEL);
- if (!dep->name)
- goto cleanup;
+ dep->pm_qos_class = pm_qos_class;

spin_lock_irqsave(&pm_qos_lock, flags);
list_add(&dep->list,
- &pm_qos_array[pm_qos_class]->requirements.list);
+ &pm_qos_array[pm_qos_class]->requests.list);
spin_unlock_irqrestore(&pm_qos_lock, flags);
update_target(pm_qos_class);
-
- return 0;
}

-cleanup:
- kfree(dep);
- return -ENOMEM;
+ return dep;
}
-EXPORT_SYMBOL_GPL(pm_qos_add_requirement);
+EXPORT_SYMBOL_GPL(pm_qos_add_request);

/**
- * pm_qos_update_requirement - modifies an existing qos request
- * @pm_qos_class: identifies which list of qos request to us
- * @name: identifies the request
+ * pm_qos_update_request - modifies an existing qos request
+ * @pm_qos_req : handle to list element holding a pm_qos request to use
* @value: defines the qos request
*
- * Updates an existing qos requirement for the pm_qos_class of parameters along
+ * Updates an existing qos request for the pm_qos_class of parameters along
* with updating the target pm_qos_class value.
*
- * If the named request isn't in the list then no change is made.
+ * Attempts are made to make this code callable on hot code paths.
*/
-int pm_qos_update_requirement(int pm_qos_class, char *name, s32 new_value)
+void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
+ s32 new_value)
{
unsigned long flags;
- struct requirement_list *node;
int pending_update = 0;
+ s32 temp;

spin_lock_irqsave(&pm_qos_lock, flags);
- list_for_each_entry(node,
- &pm_qos_array[pm_qos_class]->requirements.list, list) {
- if (strcmp(node->name, name) == 0) {
- if (new_value == PM_QOS_DEFAULT_VALUE)
- node->value =
- pm_qos_array[pm_qos_class]->default_value;
- else
- node->value = new_value;
- pending_update = 1;
- break;
- }
+ 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_class);
-
- return 0;
+ update_target(pm_qos_req->pm_qos_class);
}
-EXPORT_SYMBOL_GPL(pm_qos_update_requirement);
+EXPORT_SYMBOL_GPL(pm_qos_update_request);

/**
- * pm_qos_remove_requirement - modifies an existing qos request
- * @pm_qos_class: identifies which list of qos request to us
- * @name: identifies the request
+ * pm_qos_remove_request - modifies an existing qos request
+ * @pm_qos_req: handle to request list element
*
- * Will remove named qos request from pm_qos_class list of parameters and
- * recompute the current target value for the pm_qos_class.
+ * Will remove pm qos request from the list of requests and
+ * recompute the current target value for the pm_qos_class. Call this
+ * on slow code paths.
*/
-void pm_qos_remove_requirement(int pm_qos_class, char *name)
+void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req)
{
unsigned long flags;
- struct requirement_list *node;
- int pending_update = 0;
+ int qos_class;
+
+ 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_for_each_entry(node,
- &pm_qos_array[pm_qos_class]->requirements.list, list) {
- if (strcmp(node->name, name) == 0) {
- kfree(node->name);
- list_del(&node->list);
- kfree(node);
- pending_update = 1;
- break;
- }
- }
+ list_del(&pm_qos_req->list);
+ kfree(pm_qos_req);
spin_unlock_irqrestore(&pm_qos_lock, flags);
- if (pending_update)
- update_target(pm_qos_class);
+ update_target(qos_class);
}
-EXPORT_SYMBOL_GPL(pm_qos_remove_requirement);
+EXPORT_SYMBOL_GPL(pm_qos_remove_request);

/**
* pm_qos_add_notifier - sets notification entry for changes to target value
@@ -313,7 +302,7 @@ EXPORT_SYMBOL_GPL(pm_qos_remove_requirement);
* 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 pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
{
int retval;

@@ -343,21 +332,16 @@ int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
}
EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);

-#define PID_NAME_LEN 32
-
static int pm_qos_power_open(struct inode *inode, struct file *filp)
{
- int ret;
long pm_qos_class;
- char name[PID_NAME_LEN];

pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
if (pm_qos_class >= 0) {
- filp->private_data = (void *)pm_qos_class;
- snprintf(name, PID_NAME_LEN, "process_%d", current->pid);
- ret = pm_qos_add_requirement(pm_qos_class, name,
- PM_QOS_DEFAULT_VALUE);
- if (ret >= 0)
+ filp->private_data = (void *) pm_qos_add_request(pm_qos_class,
+ PM_QOS_DEFAULT_VALUE);
+
+ if (filp->private_data)
return 0;
}
return -EPERM;
@@ -365,32 +349,40 @@ static int pm_qos_power_open(struct inode *inode, struct file *filp)

static int pm_qos_power_release(struct inode *inode, struct file *filp)
{
- int pm_qos_class;
- char name[PID_NAME_LEN];
+ struct pm_qos_request_list *req;

- pm_qos_class = (long)filp->private_data;
- snprintf(name, PID_NAME_LEN, "process_%d", current->pid);
- pm_qos_remove_requirement(pm_qos_class, name);
+ req = (struct pm_qos_request_list *)filp->private_data;
+ pm_qos_remove_request(req);

return 0;
}

+
static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
size_t count, loff_t *f_pos)
{
s32 value;
- int pm_qos_class;
- char name[PID_NAME_LEN];
-
- pm_qos_class = (long)filp->private_data;
- if (count != sizeof(s32))
+ int x;
+ char ascii_value[11];
+ struct pm_qos_request_list *pm_qos_req;
+
+ if (count == sizeof(s32)) {
+ if (copy_from_user(&value, buf, sizeof(s32)))
+ return -EFAULT;
+ } else if (count == 11) { /* len('0x12345678/0') */
+ if (copy_from_user(ascii_value, buf, 11))
+ return -EFAULT;
+ x = sscanf(ascii_value, "%x", &value);
+ if (x != 1)
+ return -EINVAL;
+ pr_debug(KERN_ERR "%s, %d, 0x%x\n", ascii_value, x, value);
+ } else
return -EINVAL;
- if (copy_from_user(&value, buf, sizeof(s32)))
- return -EFAULT;
- snprintf(name, PID_NAME_LEN, "process_%d", current->pid);
- pm_qos_update_requirement(pm_qos_class, name, value);

- return sizeof(s32);
+ pm_qos_req = (struct pm_qos_request_list *)filp->private_data;
+ pm_qos_update_request(pm_qos_req, value);
+
+ return count;
}


--
1.6.3.3

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