In certain cases (for example when a cdev structure is embedded into
another object whose lifetime is controlled by a separate device object)
it is beneficial to tie lifetime of another struct device to the lifetime
of character device so that related object is not freed until after
char_dev object is freed. To achieve this allow setting a "parent" device
for character devices and pin them when doing cdev_add() and unpin when
last reference to cdev structure is being released.
Signed-off-by: Dmitry Torokhov <dmitry.torok...@gmail.com>
---
Sorry, messed up the first attempt to send...
So, how about these 2? I enabled kmemleak and added some debug printks and
it looks like we dropping references and freeing object at right times and
in proper order.
Thanks!
fs/char_dev.c | 18 +++++++++++++++++-
include/linux/cdev.h | 1 +
2 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/fs/char_dev.c b/fs/char_dev.c
index 3f152b9..f8c44cc 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -471,9 +471,19 @@ static int exact_lock(dev_t dev, void *data)
*/
int cdev_add(struct cdev *p, dev_t dev, unsigned count)
{
+ int error;
+
p->dev = dev;
p->count = count;
- return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
+
+ error = kobj_map(cdev_map, dev, count, NULL,
+ exact_match, exact_lock, p);
+ if (error)
+ return error;
+
+ get_device(p->parent);
+
+ return 0;
}
static void cdev_unmap(dev_t dev, unsigned count)
@@ -498,14 +508,20 @@ void cdev_del(struct cdev *p)
static void cdev_default_release(struct kobject *kobj)
{
struct cdev *p = container_of(kobj, struct cdev, kobj);
+ struct device *parent = p->parent;
+
cdev_purge(p);
+ put_device(parent);
}
static void cdev_dynamic_release(struct kobject *kobj)
{
struct cdev *p = container_of(kobj, struct cdev, kobj);
+ struct device *parent = p->parent;
+
cdev_purge(p);
kfree(p);
+ put_device(parent);
}
static struct kobj_type ktype_cdev_default = {
diff --git a/include/linux/cdev.h b/include/linux/cdev.h
index fb45919..eba8251 100644
--- a/include/linux/cdev.h
+++ b/include/linux/cdev.h
@@ -12,6 +12,7 @@ struct module;
struct cdev {
struct kobject kobj;
struct module *owner;
+ struct device *parent;
const struct file_operations *ops;
struct list_head list;
dev_t dev;
--
1.7.11.7
--
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