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PM QoS: Use spinlock in the per-device PM QoS constraints code
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The per-device PM QoS locking requires a spinlock to be used. The reasons
are:
 - an alignement with the PM QoS core code, which is used by the per-device
   PM QoS code for the constraints lists management. The PM QoS core code
   uses spinlocks to protect the constraints lists,
 - some drivers need to use the per-device PM QoS functionality from
   interrupt context or spinlock protected context.
   An example of such a driver is the OMAP HSI (high-speed synchronous serial
   interface) driver which needs to control the IP block idle state
   depending on the FIFO empty state, from interrupt context.

Reported-by: Djamil Elaidi <d-elaidi@ti.com>
Signed-off-by: Jean Pihet <j-pihet@ti.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
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Jean Pihet authored and Rafael J. Wysocki committed Sep 19, 2012
1 parent c6a57bf commit fc2fb3a
Showing 1 changed file with 41 additions and 26 deletions.
67 changes: 41 additions & 26 deletions drivers/base/power/qos.c
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Original file line number Diff line number Diff line change
Expand Up @@ -24,26 +24,32 @@
* . a system-wide notification callback using the dev_pm_qos_*_global_notifier
* API. The notification chain data is stored in a static variable.
*
* Note about the per-device constraint data struct allocation:
* . The per-device constraints data struct ptr is tored into the device
* Notes about the per-device constraint data struct allocation:
* . The per-device constraints data struct ptr is stored into the device
* dev_pm_info.
* . To minimize the data usage by the per-device constraints, the data struct
* is only allocated at the first call to dev_pm_qos_add_request.
* is only allocated at the first call to dev_pm_qos_add_request.
* . The data is later free'd when the device is removed from the system.
* . A global mutex protects the constraints users from the data being
* allocated and free'd.
*
* Notes about locking:
* . The dev->power.lock lock protects the constraints list
* (dev->power.constraints) allocation and free, as triggered by the
* driver core code at device insertion and removal,
* . A global lock dev_pm_qos_lock protects the constraints list entries
* from any modification and the notifiers registration and unregistration.
* . For both locks a spinlock is needed since this code can be called from
* interrupt context or spinlock protected context.
*/

#include <linux/pm_qos.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/export.h>

#include "power.h"

static DEFINE_MUTEX(dev_pm_qos_mtx);
static DEFINE_SPINLOCK(dev_pm_qos_lock);

static BLOCKING_NOTIFIER_HEAD(dev_pm_notifiers);

Expand Down Expand Up @@ -110,18 +116,19 @@ static int apply_constraint(struct dev_pm_qos_request *req,
* @dev: device to allocate data for
*
* Called at the first call to add_request, for constraint data allocation
* Must be called with the dev_pm_qos_mtx mutex held
* Must be called with the dev_pm_qos_lock lock held
*/
static int dev_pm_qos_constraints_allocate(struct device *dev)
{
struct pm_qos_constraints *c;
struct blocking_notifier_head *n;
unsigned long flags;

c = kzalloc(sizeof(*c), GFP_KERNEL);
c = kzalloc(sizeof(*c), GFP_ATOMIC);
if (!c)
return -ENOMEM;

n = kzalloc(sizeof(*n), GFP_KERNEL);
n = kzalloc(sizeof(*n), GFP_ATOMIC);
if (!n) {
kfree(c);
return -ENOMEM;
Expand All @@ -134,9 +141,9 @@ static int dev_pm_qos_constraints_allocate(struct device *dev)
c->type = PM_QOS_MIN;
c->notifiers = n;

spin_lock_irq(&dev->power.lock);
spin_lock_irqsave(&dev->power.lock, flags);
dev->power.constraints = c;
spin_unlock_irq(&dev->power.lock);
spin_unlock_irqrestore(&dev->power.lock, flags);

return 0;
}
Expand All @@ -150,10 +157,12 @@ static int dev_pm_qos_constraints_allocate(struct device *dev)
*/
void dev_pm_qos_constraints_init(struct device *dev)
{
mutex_lock(&dev_pm_qos_mtx);
unsigned long flags;

spin_lock_irqsave(&dev_pm_qos_lock, flags);
dev->power.constraints = NULL;
dev->power.power_state = PMSG_ON;
mutex_unlock(&dev_pm_qos_mtx);
spin_unlock_irqrestore(&dev_pm_qos_lock, flags);
}

/**
Expand All @@ -166,14 +175,15 @@ void dev_pm_qos_constraints_destroy(struct device *dev)
{
struct dev_pm_qos_request *req, *tmp;
struct pm_qos_constraints *c;
unsigned long flags;

/*
* If the device's PM QoS resume latency limit has been exposed to user
* space, it has to be hidden at this point.
*/
dev_pm_qos_hide_latency_limit(dev);

mutex_lock(&dev_pm_qos_mtx);
spin_lock_irqsave(&dev_pm_qos_lock, flags);

dev->power.power_state = PMSG_INVALID;
c = dev->power.constraints;
Expand All @@ -198,7 +208,7 @@ void dev_pm_qos_constraints_destroy(struct device *dev)
kfree(c);

out:
mutex_unlock(&dev_pm_qos_mtx);
spin_unlock_irqrestore(&dev_pm_qos_lock, flags);
}

/**
Expand All @@ -223,6 +233,7 @@ int dev_pm_qos_add_request(struct device *dev, struct dev_pm_qos_request *req,
s32 value)
{
int ret = 0;
unsigned long flags;

if (!dev || !req) /*guard against callers passing in null */
return -EINVAL;
Expand All @@ -233,7 +244,7 @@ int dev_pm_qos_add_request(struct device *dev, struct dev_pm_qos_request *req,

req->dev = dev;

mutex_lock(&dev_pm_qos_mtx);
spin_lock_irqsave(&dev_pm_qos_lock, flags);

if (!dev->power.constraints) {
if (dev->power.power_state.event == PM_EVENT_INVALID) {
Expand All @@ -255,7 +266,7 @@ int dev_pm_qos_add_request(struct device *dev, struct dev_pm_qos_request *req,
ret = apply_constraint(req, PM_QOS_ADD_REQ, value);

out:
mutex_unlock(&dev_pm_qos_mtx);
spin_unlock_irqrestore(&dev_pm_qos_lock, flags);

return ret;
}
Expand All @@ -280,6 +291,7 @@ int dev_pm_qos_update_request(struct dev_pm_qos_request *req,
s32 new_value)
{
int ret = 0;
unsigned long flags;

if (!req) /*guard against callers passing in null */
return -EINVAL;
Expand All @@ -288,7 +300,7 @@ int dev_pm_qos_update_request(struct dev_pm_qos_request *req,
"%s() called for unknown object\n", __func__))
return -EINVAL;

mutex_lock(&dev_pm_qos_mtx);
spin_lock_irqsave(&dev_pm_qos_lock, flags);

if (req->dev->power.constraints) {
if (new_value != req->node.prio)
Expand All @@ -299,7 +311,7 @@ int dev_pm_qos_update_request(struct dev_pm_qos_request *req,
ret = -ENODEV;
}

mutex_unlock(&dev_pm_qos_mtx);
spin_unlock_irqrestore(&dev_pm_qos_lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_update_request);
Expand All @@ -319,6 +331,7 @@ EXPORT_SYMBOL_GPL(dev_pm_qos_update_request);
int dev_pm_qos_remove_request(struct dev_pm_qos_request *req)
{
int ret = 0;
unsigned long flags;

if (!req) /*guard against callers passing in null */
return -EINVAL;
Expand All @@ -327,7 +340,7 @@ int dev_pm_qos_remove_request(struct dev_pm_qos_request *req)
"%s() called for unknown object\n", __func__))
return -EINVAL;

mutex_lock(&dev_pm_qos_mtx);
spin_lock_irqsave(&dev_pm_qos_lock, flags);

if (req->dev->power.constraints) {
ret = apply_constraint(req, PM_QOS_REMOVE_REQ,
Expand All @@ -338,7 +351,7 @@ int dev_pm_qos_remove_request(struct dev_pm_qos_request *req)
ret = -ENODEV;
}

mutex_unlock(&dev_pm_qos_mtx);
spin_unlock_irqrestore(&dev_pm_qos_lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_remove_request);
Expand All @@ -359,8 +372,9 @@ EXPORT_SYMBOL_GPL(dev_pm_qos_remove_request);
int dev_pm_qos_add_notifier(struct device *dev, struct notifier_block *notifier)
{
int ret = 0;
unsigned long flags;

mutex_lock(&dev_pm_qos_mtx);
spin_lock_irqsave(&dev_pm_qos_lock, flags);

if (!dev->power.constraints)
ret = dev->power.power_state.event != PM_EVENT_INVALID ?
Expand All @@ -370,7 +384,7 @@ int dev_pm_qos_add_notifier(struct device *dev, struct notifier_block *notifier)
ret = blocking_notifier_chain_register(
dev->power.constraints->notifiers, notifier);

mutex_unlock(&dev_pm_qos_mtx);
spin_unlock_irqrestore(&dev_pm_qos_lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_add_notifier);
Expand All @@ -389,16 +403,17 @@ int dev_pm_qos_remove_notifier(struct device *dev,
struct notifier_block *notifier)
{
int retval = 0;
unsigned long flags;

mutex_lock(&dev_pm_qos_mtx);
spin_lock_irqsave(&dev_pm_qos_lock, flags);

/* Silently return if the constraints object is not present. */
if (dev->power.constraints)
retval = blocking_notifier_chain_unregister(
dev->power.constraints->notifiers,
notifier);

mutex_unlock(&dev_pm_qos_mtx);
spin_unlock_irqrestore(&dev_pm_qos_lock, flags);
return retval;
}
EXPORT_SYMBOL_GPL(dev_pm_qos_remove_notifier);
Expand Down

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