PM: Reference counting of power.subsys_data

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>

diff --git a/drivers/base/power/Makefile b/drivers/base/power/Makefile
index 2639ae7..6488ce1 100644 (file)
--- a/drivers/base/power/Makefile
+++ b/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

diff --git a/drivers/base/power/clock_ops.c b/drivers/base/power/clock_ops.c
index b7f1db4..8383e24 100644 (file)
--- a/drivers/base/power/clock_ops.c
+++ b/drivers/base/power/clock_ops.c
@@ -140,12 +140,8 @@ void pm_clk_remove(struct device *dev, const char *con_id)
 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);
-       spin_lock_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;
-
        spin_lock_irq(&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)
 
        spin_unlock_irq(&psd->lock);
 
-       kfree(psd);
+       dev_pm_put_subsys_data(dev);
 }
 
 #endif /* CONFIG_PM */

diff --git a/drivers/base/power/common.c b/drivers/base/power/common.c
new file mode 100644 (file)
index 0000000..d398cf0
--- /dev/null
+++ b/drivers/base/power/common.c
@@ -0,0 +1,87 @@
+/*
+ * 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/module.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 {
+               spin_lock_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);

diff --git a/include/linux/pm.h b/include/linux/pm.h
index bf5ee37..c6b5a0a 100644 (file)
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -423,6 +423,7 @@ struct wakeup_source;
 
 struct pm_subsys_data {
        spinlock_t lock;
+       unsigned int refcount;
 #ifdef CONFIG_PM_CLK
        struct list_head clock_list;
 #endif
@@ -473,6 +474,8 @@ 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,