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| author | Dmitry Torokhov <dmitry.torokhov@gmail.com> | 2012-10-21 17:57:19 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-10-22 08:50:37 +0300 |
| commit | 2f0157f13f42800aa3d9017ebb0fb80a65f7b2de (patch) | |
| tree | 7b2b3299b6ef785790336042ab28c0bffa37debb /fs/char_dev.c | |
| parent | 6f0c0580b70c89094b3422ba81118c7b959c7556 (diff) | |
| download | lwn-2f0157f13f42800aa3d9017ebb0fb80a65f7b2de.tar.gz lwn-2f0157f13f42800aa3d9017ebb0fb80a65f7b2de.zip | |
char_dev: pin parent kobject
In certain cases (for example when a cdev structure is embedded into
another object whose lifetime is controlled by a separate kobject) it is
beneficial to tie lifetime of another object to the lifetime of
character device so that related object is not freed until after
char_dev object is freed.
To achieve this let's pin kobject's parent when doing cdev_add() and
unpin when last reference to cdev structure is being released.
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/char_dev.c')
| -rw-r--r-- | fs/char_dev.c | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/fs/char_dev.c b/fs/char_dev.c index 3f152b92a94a..afc2bb691780 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; + + kobject_get(p->kobj.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 kobject *parent = kobj->parent; + cdev_purge(p); + kobject_put(parent); } static void cdev_dynamic_release(struct kobject *kobj) { struct cdev *p = container_of(kobj, struct cdev, kobj); + struct kobject *parent = kobj->parent; + cdev_purge(p); kfree(p); + kobject_put(parent); } static struct kobj_type ktype_cdev_default = { |