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@xxxxxx>
Signed-off-by: Jean Pihet <j-pihet@xxxxxx>
---
drivers/base/power/qos.c | 67 ++++++++++++++++++++++++++++------------------
1 files changed, 41 insertions(+), 26 deletions(-)
diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c
index 74a67e0..968a771 100644
--- a/drivers/base/power/qos.c
+++ b/drivers/base/power/qos.c
@@ -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);
@@ -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;
@@ -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;
}
@@ -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);
}
/**
@@ -166,6 +175,7 @@ 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
@@ -173,7 +183,7 @@ void dev_pm_qos_constraints_destroy(struct device *dev)
*/
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;
@@ -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);
}
/**
@@ -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;
@@ -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) {
@@ -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;
}
@@ -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;
@@ -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)
@@ -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);
@@ -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;
@@ -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,
@@ -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);
@@ -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 ?
@@ -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);
@@ -389,8 +403,9 @@ 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)
@@ -398,7 +413,7 @@ int dev_pm_qos_remove_notifier(struct device *dev,
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);
--
1.7.7.6
