[PATCH 2/4] PM: Reference counting of power.subsys_data

Rafael J. Wysocki
2011-08-08T22:32:53Z

Since the power.subsys_data device field will be used by multiple
filesystems, introduce a reference counting mechanism for it to avoid
freeing it prematurely or changing its value at a wrong time.

Make the PM clocks management code that currently is the only user of
power.subsys_data use the new reference counting.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
drivers/base/power/Makefile | 2
drivers/base/power/clock_ops.c | 24 ++---------
drivers/base/power/common.c | 86 +++++++++++++++++++++++++++++++++++++++++
include/linux/pm.h | 3 +
4 files changed, 95 insertions(+), 20 deletions(-)

Index: linux-2.6/drivers/base/power/common.c
===================================================================
--- /dev/null
+++ linux-2.6/drivers/base/power/common.c
@@ -0,0 +1,86 @@
+/*
+ * drivers/base/power/common.c - Common device power management code.
+ *
+ * Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/pm_runtime.h>
+
+/**
+ * dev_pm_get_subsys_data - Create or refcount power.subsys_data for device.
+ * @dev: Device to handle.
+ *
+ * If power.subsys_data is NULL, point it to a new object, otherwise increment
+ * its reference counter. Return 1 if a new object has been created, otherwise
+ * return 0 or error code.
+ */
+int dev_pm_get_subsys_data(struct device *dev)
+{
+ struct pm_subsys_data *psd;
+ int ret = 0;
+
+ psd = kzalloc(sizeof(*psd), GFP_KERNEL);
+ if (!psd)
+ return -ENOMEM;
+
+ spin_lock_irq(&dev->power.lock);
+
+ if (dev->power.subsys_data) {
+ dev->power.subsys_data->refcount++;
+ } else {
+ mutex_init(&psd->lock);
+ psd->refcount = 1;
+ dev->power.subsys_data = psd;
+ pm_clk_init(dev);
+ psd = NULL;
+ ret = 1;
+ }
+
+ spin_unlock_irq(&dev->power.lock);
+
+ /* kfree() verifies that its argument is nonzero. */
+ kfree(psd);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dev_pm_get_subsys_data);
+
+/**
+ * dev_pm_put_subsys_data - Drop reference to power.subsys_data.
+ * @dev: Device to handle.
+ *
+ * If the reference counter of power.subsys_data is zero after dropping the
+ * reference, power.subsys_data is removed. Return 1 if that happens or 0
+ * otherwise.
+ */
+int dev_pm_put_subsys_data(struct device *dev)
+{
+ struct pm_subsys_data *psd;
+ int ret = 0;
+
+ spin_lock_irq(&dev->power.lock);
+
+ psd = dev_to_psd(dev);
+ if (!psd) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ if (--psd->refcount == 0) {
+ dev->power.subsys_data = NULL;
+ kfree(psd);
+ ret = 1;
+ }
+
+ out:
+ spin_unlock_irq(&dev->power.lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(dev_pm_put_subsys_data);
Index: linux-2.6/include/linux/pm.h
===================================================================
--- linux-2.6.orig/include/linux/pm.h
+++ linux-2.6/include/linux/pm.h
@@ -424,6 +424,7 @@ struct wakeup_source;

struct pm_subsys_data {
struct mutex lock;
+ unsigned int refcount;
#ifdef CONFIG_PM_CLK
struct list_head clock_list;
#endif
@@ -474,6 +475,8 @@ struct dev_pm_info {
};

extern void update_pm_runtime_accounting(struct device *dev);
+extern int dev_pm_get_subsys_data(struct device *dev);
+extern int dev_pm_put_subsys_data(struct device *dev);

/*
* Power domains provide callbacks that are executed during system suspend,
Index: linux-2.6/drivers/base/power/Makefile
===================================================================
--- linux-2.6.orig/drivers/base/power/Makefile
+++ linux-2.6/drivers/base/power/Makefile
@@ -1,4 +1,4 @@
-obj-$(CONFIG_PM) += sysfs.o generic_ops.o
+obj-$(CONFIG_PM) += sysfs.o generic_ops.o common.o
obj-$(CONFIG_PM_SLEEP) += main.o wakeup.o
obj-$(CONFIG_PM_RUNTIME) += runtime.o
obj-$(CONFIG_PM_TRACE_RTC) += trace.o
Index: linux-2.6/drivers/base/power/clock_ops.c
===================================================================
--- linux-2.6.orig/drivers/base/power/clock_ops.c
+++ linux-2.6/drivers/base/power/clock_ops.c
@@ -140,12 +140,8 @@ void pm_clk_remove(struct device *dev, c
void pm_clk_init(struct device *dev)
{
struct pm_subsys_data *psd = dev_to_psd(dev);
-
- if (!psd)
- return;
-
- INIT_LIST_HEAD(&psd->clock_list);
- mutex_init(&psd->lock);
+ if (psd)
+ INIT_LIST_HEAD(&psd->clock_list);
}

/**
@@ -157,16 +153,8 @@ void pm_clk_init(struct device *dev)
*/
int pm_clk_create(struct device *dev)
{
- struct pm_subsys_data *psd;
-
- psd = kzalloc(sizeof(*psd), GFP_KERNEL);
- if (!psd) {
- dev_err(dev, "Not enough memory for PM clock data.\n");
- return -ENOMEM;
- }
- dev->power.subsys_data = psd;
- pm_clk_init(dev);
- return 0;
+ int ret = dev_pm_get_subsys_data(dev);
+ return ret < 0 ? ret : 0;
}

/**
@@ -185,8 +173,6 @@ void pm_clk_destroy(struct device *dev)
if (!psd)
return;

- dev->power.subsys_data = NULL;
-
mutex_lock(&psd->lock);

list_for_each_entry_safe_reverse(ce, c, &psd->clock_list, node)
@@ -194,7 +180,7 @@ void pm_clk_destroy(struct device *dev)

mutex_unlock(&psd->lock);

- kfree(psd);
+ dev_pm_put_subsys_data(dev);
}

#endif /* CONFIG_PM */