| Message ID | 1350804271-2449-1-git-send-email-dmitry.torokhov@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, Oct 21, 2012 at 12:24:30AM -0700, Dmitry Torokhov wrote: > 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. Why struct device and not simply struct kobject? -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sun, Oct 21, 2012 at 08:39:28AM +0100, Al Viro wrote: > On Sun, Oct 21, 2012 at 12:24:30AM -0700, Dmitry Torokhov wrote: > > 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. > > Why struct device and not simply struct kobject? It was more convenient for my uses and I also think that parents of character devices will be struct devices... I however will not insist and if you prefer using more generic kobject I can change it, Thanks.
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;
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.torokhov@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(-)