device_del() should be called first and then called put_device() in
unregister path, becase if that the final reference count, the device
will be cleaned up via device_release() above. So use device_unregister()
instead.
Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling)
Signed-off-by: Yajun Deng <[email protected]>
---
drivers/pci/probe.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 0ec5c792c27d..abd481a15a17 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -994,9 +994,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
return 0;
unregister:
- put_device(&bridge->dev);
- device_del(&bridge->dev);
-
+ device_unregister(&bridge->dev);
free:
kfree(bus);
return err;
--
2.32.0
On Wed, Aug 25, 2021 at 3:34 AM Yajun Deng <[email protected]> wrote:
>
> device_del() should be called first and then called put_device() in
> unregister path, becase if that the final reference count, the device
> will be cleaned up via device_release() above. So use device_unregister()
> instead.
>
> Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling)
> Signed-off-by: Yajun Deng <[email protected]>
> ---
> drivers/pci/probe.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
NAK.
The current code is correct. Go read the comments for device_add/device_del.
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 0ec5c792c27d..abd481a15a17 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -994,9 +994,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
> return 0;
>
> unregister:
We get here if device_register() failed. Calling device_unregister()
in that case is never right.
> - put_device(&bridge->dev);
This is for the get_device() we do above, not the get the driver core does.
> - device_del(&bridge->dev);
This undoes the device_add() we do following the comment: "NOTE: this
should be called manually _iff_ device_add() was also called
manually."
> -
> + device_unregister(&bridge->dev);
> free:
> kfree(bus);
> return err;
> --
> 2.32.0
>
August 25, 2021 9:55 PM, "Rob Herring" <[email protected]> wrote:
> On Wed, Aug 25, 2021 at 3:34 AM Yajun Deng <[email protected]> wrote:
>
>> device_del() should be called first and then called put_device() in
>> unregister path, becase if that the final reference count, the device
>> will be cleaned up via device_release() above. So use device_unregister()
>> instead.
>>
>> Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling)
>> Signed-off-by: Yajun Deng <[email protected]>
>> ---
>> drivers/pci/probe.c | 4 +---
>> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> NAK.
>
> The current code is correct. Go read the comments for device_add/device_del.
But the device_unregister() is only contains device_del() and put_device(). It just put
device_del() before put_device().
>
>> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>> index 0ec5c792c27d..abd481a15a17 100644
>> --- a/drivers/pci/probe.c
>> +++ b/drivers/pci/probe.c
>> @@ -994,9 +994,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
>> return 0;
>>
>> unregister:
>
> We get here if device_register() failed. Calling device_unregister()
> in that case is never right.
>
>> - put_device(&bridge->dev);
>
> This is for the get_device() we do above, not the get the driver core does.
>
>> - device_del(&bridge->dev);
>
> This undoes the device_add() we do following the comment: "NOTE: this
> should be called manually _iff_ device_add() was also called
> manually."
>
>> -
>> + device_unregister(&bridge->dev);
>> free:
>> kfree(bus);
>> return err;
>> --
>> 2.32.0
On Wed, Aug 25, 2021 at 10:57 PM <[email protected]> wrote:
>
> August 25, 2021 9:55 PM, "Rob Herring" <[email protected]> wrote:
>
> > On Wed, Aug 25, 2021 at 3:34 AM Yajun Deng <[email protected]> wrote:
> >
> >> device_del() should be called first and then called put_device() in
> >> unregister path, becase if that the final reference count, the device
> >> will be cleaned up via device_release() above. So use device_unregister()
> >> instead.
> >>
> >> Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling)
> >> Signed-off-by: Yajun Deng <[email protected]>
> >> ---
> >> drivers/pci/probe.c | 4 +---
> >> 1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > NAK.
> >
> > The current code is correct. Go read the comments for device_add/device_del.
>
> But the device_unregister() is only contains device_del() and put_device(). It just put
> device_del() before put_device().
And that is the wrong order as we want to undo what the code above
did. The put_device here is for the get_device we did. The put_device
in device_unregister is for the get_device that device_register did
(on success only).
Logically, it is wrong too to call unregister if register failed. That
would be like doing this:
p = malloc(1);
if (!p)
free(p);
Rob
August 26, 2021 8:01 PM, "Rob Herring" <[email protected]> wrote:
> On Wed, Aug 25, 2021 at 10:57 PM <[email protected]> wrote:
>
>> August 25, 2021 9:55 PM, "Rob Herring" <[email protected]> wrote:
>>
>> On Wed, Aug 25, 2021 at 3:34 AM Yajun Deng <[email protected]> wrote:
>>
>> device_del() should be called first and then called put_device() in
>> unregister path, becase if that the final reference count, the device
>> will be cleaned up via device_release() above. So use device_unregister()
>> instead.
>>
>> Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling)
>> Signed-off-by: Yajun Deng <[email protected]>
>> ---
>> drivers/pci/probe.c | 4 +---
>> 1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> NAK.
>>
>> The current code is correct. Go read the comments for device_add/device_del.
>>
>> But the device_unregister() is only contains device_del() and put_device(). It just put
>> device_del() before put_device().
>
> And that is the wrong order as we want to undo what the code above
> did. The put_device here is for the get_device we did. The put_device
> in device_unregister is for the get_device that device_register did
> (on success only).
>
> Logically, it is wrong too to call unregister if register failed. That
> would be like doing this:
>
> p = malloc(1);
> if (!p)
> free(p);
>
This is the raw code:
err = device_register(&bus->dev);
if (err)
goto unregister;
unregister:
put_device(&bridge->dev);
device_del(&bridge->dev);
This is my code:
err = device_register(&bus->dev);
if (err)
goto unregister;
unregister:
device_unregister(&bridge->dev);
The parameter in device_register() is bus->dev, but the parameter in device_unregister() is bridge->dev.The are different.
The bridge->dev is already success before called device_register().So it wouldn't be happen like your code.
> Rob
On Thu, Aug 26, 2021 at 9:39 PM <[email protected]> wrote:
>
> August 26, 2021 8:01 PM, "Rob Herring" <[email protected]> wrote:
>
> > On Wed, Aug 25, 2021 at 10:57 PM <[email protected]> wrote:
> >
> >> August 25, 2021 9:55 PM, "Rob Herring" <[email protected]> wrote:
> >>
> >> On Wed, Aug 25, 2021 at 3:34 AM Yajun Deng <[email protected]> wrote:
> >>
> >> device_del() should be called first and then called put_device() in
> >> unregister path, becase if that the final reference count, the device
> >> will be cleaned up via device_release() above. So use device_unregister()
> >> instead.
> >>
> >> Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling)
> >> Signed-off-by: Yajun Deng <[email protected]>
> >> ---
> >> drivers/pci/probe.c | 4 +---
> >> 1 file changed, 1 insertion(+), 3 deletions(-)
> >>
> >> NAK.
> >>
> >> The current code is correct. Go read the comments for device_add/device_del.
> >>
> >> But the device_unregister() is only contains device_del() and put_device(). It just put
> >> device_del() before put_device().
> >
> > And that is the wrong order as we want to undo what the code above
> > did. The put_device here is for the get_device we did. The put_device
> > in device_unregister is for the get_device that device_register did
> > (on success only).
> >
> > Logically, it is wrong too to call unregister if register failed. That
> > would be like doing this:
You are right that the register and unregister are different devices.
However, your change is still wrong. The device_register is actually
irrelevant.
> >
> > p = malloc(1);
> > if (!p)
> > free(p);
> >
> This is the raw code:
> err = device_register(&bus->dev);
> if (err)
> goto unregister;
> unregister:
> put_device(&bridge->dev);
> device_del(&bridge->dev);
The pertinent parts are this:
err = device_add(&bridge->dev); // which calls get_device() itself,
so there's the first ref
if (err) {
put_device(&bridge->dev);
goto free;
}
bus->bridge = get_device(&bridge->dev); // This is the 2nd ref which
the PCI core holds
...
unregister:
put_device(&bridge->dev); // This is the put for the get_device
just above here.
device_del(&bridge->dev); // Then this does the 2nd put.
The get_device and put_device are paired, and the device_add and
device_del are paired.
As I said earlier, go read the kerneldoc for device_add. For your
convenience, here's the important part:
device_add:
* Rule of thumb is: if device_add() succeeds, you should call
* device_del() when you want to get rid of it. If device_add() has
* *not* succeeded, use *only* put_device() to drop the reference
* count.
device_del:
* NOTE: this should be called manually _iff_ device_add() was
* also called manually.
Rob
August 30, 2021 10:55 PM, "Rob Herring" <[email protected]> wrote:
> On Thu, Aug 26, 2021 at 9:39 PM <[email protected]> wrote:
>
>> August 26, 2021 8:01 PM, "Rob Herring" <[email protected]> wrote:
>>
>> On Wed, Aug 25, 2021 at 10:57 PM <[email protected]> wrote:
>>
>> August 25, 2021 9:55 PM, "Rob Herring" <[email protected]> wrote:
>>
>> On Wed, Aug 25, 2021 at 3:34 AM Yajun Deng <[email protected]> wrote:
>>
>> device_del() should be called first and then called put_device() in
>> unregister path, becase if that the final reference count, the device
>> will be cleaned up via device_release() above. So use device_unregister()
>> instead.
>>
>> Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling)
>> Signed-off-by: Yajun Deng <[email protected]>
>> ---
>> drivers/pci/probe.c | 4 +---
>> 1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> NAK.
>>
>> The current code is correct. Go read the comments for device_add/device_del.
>>
>> But the device_unregister() is only contains device_del() and put_device(). It just put
>> device_del() before put_device().
>>
>> And that is the wrong order as we want to undo what the code above
>> did. The put_device here is for the get_device we did. The put_device
>> in device_unregister is for the get_device that device_register did
>> (on success only).
>>
>> Logically, it is wrong too to call unregister if register failed. That
>> would be like doing this:
>
> You are right that the register and unregister are different devices.
> However, your change is still wrong. The device_register is actually
> irrelevant.
>
OK, the original order is right, it was my mistake.
>> p = malloc(1);
>> if (!p)
>> free(p);
>>
>> This is the raw code:
>> err = device_register(&bus->dev);
>> if (err)
>> goto unregister;
>> unregister:
>> put_device(&bridge->dev);
>> device_del(&bridge->dev);
>
> The pertinent parts are this:
>
> err = device_add(&bridge->dev); // which calls get_device() itself,
> so there's the first ref
> if (err) {
> put_device(&bridge->dev);
> goto free;
> }
> bus->bridge = get_device(&bridge->dev); // This is the 2nd ref which
> the PCI core holds
> ...
> unregister:
> put_device(&bridge->dev); // This is the put for the get_device
> just above here.
> device_del(&bridge->dev); // Then this does the 2nd put.
>
> The get_device and put_device are paired, and the device_add and
> device_del are paired.
>
> As I said earlier, go read the kerneldoc for device_add. For your
> convenience, here's the important part:
>
> device_add:
> * Rule of thumb is: if device_add() succeeds, you should call
> * device_del() when you want to get rid of it. If device_add() has
> * *not* succeeded, use *only* put_device() to drop the reference
> * count.
>
> device_del:
> * NOTE: this should be called manually _iff_ device_add() was
> * also called manually.
>
> Rob